Internet Engineering Task Force (IETF)                         B. Claise
Request for Comments: 6313                                 G. Dhandapani
Updates: 5102                                                  P. Aitken
Category: Standards Track                                       S. Yates
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                              July 2011


   Export of Structured Data in IP Flow Information Export (IPFIX)

Abstract

  This document specifies an extension to the IP Flow Information
  Export (IPFIX) protocol specification in RFC 5101 and the IPFIX
  information model specified in RFC 5102 to support hierarchical
  structured data and lists (sequences) of Information Elements in data
  records.  This extension allows definition of complex data structures
  such as variable-length lists and specification of hierarchical
  containment relationships between Templates.  Finally, the semantics
  are provided in order to express the relationship among multiple list
  elements in a structured data record.

Status of This Memo

  This is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 5741.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  http://www.rfc-editor.org/info/rfc6313.

Copyright Notice

  Copyright (c) 2011 IETF Trust and the persons identified as the
  document authors.  All rights reserved.

  This document is subject to BCP 78 and the IETF Trust's Legal
  Provisions Relating to IETF Documents
  (http://trustee.ietf.org/license-info) in effect on the date of
  publication of this document.  Please review these documents
  carefully, as they describe your rights and restrictions with respect
  to this document.  Code Components extracted from this document must
  include Simplified BSD License text as described in Section 4.e of



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  the Trust Legal Provisions and are provided without warranty as
  described in the Simplified BSD License.

Table of Contents

  1. Overview ........................................................5
     1.1. IPFIX Documents Overview ...................................5
     1.2. Relationship between IPFIX and PSAMP .......................6
  2. Introduction ....................................................6
     2.1. The IPFIX Track ............................................7
     2.2. The IPFIX Limitations ......................................8
     2.3. Structured Data Use Cases ..................................8
     2.4. Specifications Summary ....................................11
  3. Terminology ....................................................11
     3.1. New Terminology ...........................................12
     3.2. Conventions Used in This Document .........................12
  4. Linkage with the IPFIX Information Model .......................12
     4.1. New Abstract Data Types ...................................12
          4.1.1. basicList ..........................................12
          4.1.2. subTemplateList ....................................12
          4.1.3. subTemplateMultiList ...............................12
     4.2. New Data Type Semantic ....................................13
          4.2.1. List ...............................................13
     4.3. New Information Elements ..................................13
          4.3.1. basicList ..........................................13
          4.3.2. subTemplateList ....................................13
          4.3.3. subTemplateMultiList ...............................13
     4.4. New Structured Data Type Semantics ........................13
          4.4.1. undefined ..........................................14
          4.4.2. noneOf .............................................14
          4.4.3. exactlyOneOf .......................................14
          4.4.4. oneOrMoreOf ........................................15
          4.4.5. allOf ..............................................16
          4.4.6. ordered ............................................16
     4.5. Encoding of IPFIX Data Types ..............................16
          4.5.1. basicList ..........................................17
          4.5.2. subTemplateList ....................................19
          4.5.3. subTemplateMultiList ...............................21
  5. Structured Data Format .........................................25
     5.1. Length Encoding Considerations ............................25
     5.2. Recursive Structured Data .................................26
     5.3. Structured Data Information Elements Applicability
          in Options Template Sets ..................................26
     5.4. Usage Guidelines for Equivalent Data Representations ......27
     5.5. Padding ...................................................29
     5.6. Semantic ..................................................29
  6. Template Management ............................................33
  7. The Collecting Process's Side ..................................33



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  8. Defining New Information Elements Based on the New
     Abstract Data Types ............................................34
  9. Structured Data Encoding Examples ..............................34
     9.1. Encoding a Multicast Data Record with basicList ...........35
     9.2. Encoding a Load-Balanced Data Record with a basicList .....37
     9.3. Encoding subTemplateList ..................................38
     9.4. Encoding subTemplateMultiList .............................41
     9.5. Encoding an Options Template Set Using Structured Data ....46
  10. Relationship with the Other IPFIX Documents ...................51
     10.1. Relationship with Reducing Redundancy ....................51
          10.1.1. Encoding Structured Data Element Using
                  Common Properties .................................51
          10.1.2. Encoding Common Properties Elements with
                  Structured Data Information Element ...............51
     10.2. Relationship with Guidelines for IPFIX Testing ...........53
     10.3. Relationship with IPFIX Mediation Function ...............54
  11. IANA Considerations ...........................................54
     11.1. New Abstract Data Types ..................................54
          11.1.1. basicList .........................................54
          11.1.2. subTemplateList ...................................54
          11.1.3. subTemplateMultiList ..............................55
     11.2. New Data Type Semantics ..................................55
          11.2.1. list ..............................................55
     11.3. New Information Elements .................................55
          11.3.1. basicList .........................................55
          11.3.2. subTemplateList ...................................56
          11.3.3. subTemplateMultiList ..............................56
     11.4. New Structured Data Semantics ............................56
          11.4.1. undefined .........................................56
          11.4.2. noneOf ............................................57
          11.4.3. exactlyOneOf ......................................57
          11.4.4. oneOrMoreOf .......................................57
          11.4.5. allOf .............................................57
          11.4.6. ordered ...........................................58
  12. Security Considerations .......................................58
  13. References ....................................................58
     13.1. Normative References .....................................58
     13.2. Informative References ...................................58
  14. Acknowledgements ..............................................59
  Appendix A. Additions to XML Specification of IPFIX
              Information Elements and Abstract Data Types ..........60
  Appendix B. Encoding IPS Alert Using Structured Data
              Information Elements ..................................65








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Table of Figures

 Figure 1:  basicList Encoding ......................................17
 Figure 2:  basicList Encoding with Enterprise Number ...............18
 Figure 3:  Variable-Length basicList Encoding (Length < 255 Octets) 18
 Figure 4:  Variable-Length basicList Encoding (Length 0 to 65535
            Octets) .................................................19
 Figure 5:  subTemplateList Encoding ................................19
 Figure 6:  Variable-Length subTemplateList Encoding
            (Length < 255 Octets) ...................................20
 Figure 7:  Variable-Length subTemplateList Encoding
            (Length 0 to 65535 Octets) ..............................21
 Figure 8:  subTemplateMultiList Encoding ...........................21
 Figure 9:  Variable-Length subTemplateMultiList Encoding
            (Length < 255 Octets) ...................................23
 Figure 10: Variable-Length subTemplateMultiList Encoding
            (Length 0 to 65535 Octets) ..............................24
 Figure 11: Encoding basicList, Template Record .....................35
 Figure 12: Encoding basicList, Data Record, Semantic allOf .........36
 Figure 13: Encoding basicList, Data Record with Variable-Length
            Elements, Semantic allOf ................................37
 Figure 14: Encoding basicList, Data Record, Semantic exactlyOneOf ..38
 Figure 15: Encoding subTemplateList, Template for One-Way Delay
            Metrics .................................................39
 Figure 16: Encoding subTemplateList, Template Record ...............40
 Figure 17: Encoding subTemplateList, Data Set ......................40
 Figure 18: Encoding subTemplateMultiList, Template for Filtering
            Attributes ..............................................44
 Figure 19: Encoding subTemplateMultiList, Template for Sampling
            Attributes ..............................................44
 Figure 20: Encoding subTemplateMultiList, Template for Flow Record .45
 Figure 21: Encoding subTemplateMultiList, Data Set .................45
 Figure 22: PSAMP SSRI to Be encoded ................................48
 Figure 23: Options Template Record for PSAMP SSRI Using
            subTemplateMultiList ....................................48
 Figure 24: PSAMP SSRI, Template Record for interface ...............49
 Figure 25: PSAMP SSRI, Template Record for linecard ................49
 Figure 26: PSAMP SSRI, Template Record for linecard and interface ..49
 Figure 27: Example of a PSAMP SSRI Data Record, Encoded Using a
            subTemplateMultiList ...................................50
 Figure 28: Common and Specific Properties Exported Together
            [RFC5473] ..............................................51
 Figure 29: Common and Specific Properties Exported Separately
            According to [RFC5473] .................................52
 Figure 30: Common and Specific Properties Exported with Structured
            Data Information Element ...............................52
 Figure 31: Encoding IPS Alert, Template for Target ................67
 Figure 32: Encoding IPS Alert, Template for Attacker ..............68



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 Figure 33: Encoding IPS Alert, Template for Participant ...........68
 Figure 34: Encoding IPS Alert, Template for IPS Alert .............69
 Figure 35: Encoding IPS Alert, Data Set ...........................69

1.  Overview

1.1.  IPFIX Documents Overview

  The IPFIX protocol [RFC5101] provides network administrators with
  access to IP Flow information.

  The architecture for the export of measured IP Flow information out
  of an IPFIX Exporting Process to a Collecting Process is defined in
  the IPFIX architecture [RFC5470], per the requirements defined in RFC
  3917 [RFC3917].

  The IPFIX architecture [RFC5470] specifies how IPFIX Data Records and
  Templates are carried via a congestion-aware transport protocol from
  IPFIX Exporting Processes to IPFIX Collecting Processes.

  IPFIX has a formal description of IPFIX Information Elements, their
  name, type, and additional semantic information, as specified in the
  IPFIX information model [RFC5102].

  In order to gain a level of confidence in the IPFIX implementation,
  probe the conformity and robustness, and allow interoperability, the
  guidelines for IPFIX testing [RFC5471] present a list of tests for
  implementers of compliant Exporting Processes and Collecting
  Processes.

  The Bidirectional Flow Export [RFC5103] specifies a method for
  exporting bidirectional flow (biflow) information using the IP Flow
  Information Export (IPFIX) protocol, representing each biflow using a
  single Flow Record.

  "Reducing Redundancy in IP Flow Information Export (IPFIX) and Packet
  Sampling (PSAMP) Reports" [RFC5473] specifies a bandwidth-saving
  method for exporting Flow or packet information, by separating
  information common to several Flow Records from information specific
  to an individual Flow Record: common Flow information is exported
  only once.










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1.2.  Relationship between IPFIX and PSAMP

  The specification in this document applies to the IPFIX protocol
  specifications [RFC5101].  All specifications from [RFC5101] apply
  unless specified otherwise in this document.

  The Packet Sampling (PSAMP) protocol [RFC5476] specifies the export
  of packet information from a PSAMP Exporting Process to a PSAMP
  Collecting Process.  Like IPFIX, PSAMP has a formal description of
  its information elements, their name, type, and additional semantic
  information.  The PSAMP information model is defined in [RFC5477].

  As the PSAMP protocol specifications [RFC5476] are based on the IPFIX
  protocol specifications, the specifications in this document are also
  valid for the PSAMP protocol.

  Indeed, the major difference between IPFIX and PSAMP is that the
  IPFIX protocol exports Flow Records while the PSAMP protocol exports
  Packet Reports.  From a pure export point of view, IPFIX will not
  distinguish a Flow Record composed of several packets aggregated
  together from a Flow Record composed of a single packet.  So the
  PSAMP export can be seen as a special IPFIX Flow Record containing
  information about a single packet.

2.  Introduction

  While collecting the interface counters every five minutes has proven
  to be useful in the past, more and more granular information is
  required from network elements for a series of applications:
  performance assurance, capacity planning, security, billing, or
  simply monitoring.  However, the amount of information has become so
  large that, when dealing with highly granular information such as
  Flow information, a push mechanism (as opposed to a pull mechanism,
  such as Simple Network Management Protocol (SNMP)) is the only
  solution for routers whose primary function is to route packets.
  Indeed, polling short-lived Flows via SNMP is not an option: high-end
  routers can support hundreds of thousands of Flows simultaneously.
  Furthermore, in order to reduce the export bandwidth requirements,
  the network elements have to integrate mediation functions to
  aggregate the collected information, both in space (typically, from
  different linecards or different Exporters) and in time.

  Typically, it would be beneficial if access routers could export Flow
  Records, composed of the counters before and after an optimization
  mechanism on the egress interface, instead of exporting two Flow
  Records with identical tuple information.





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  In terms of aggregation in time, let us imagine that, for performance
  assurance, the network management application must receive the
  performance metrics associated with a specific Flow, every
  millisecond.  Since the performance metrics will be constantly
  changing, there is a new dimension to the Flow definition: we are not
  dealing anymore with a single Flow lasting a few seconds or a few
  minutes, but with a multitude of one millisecond sub-flows for which
  the performance metrics are reported.

  Which current protocol is suitable for these requirements: push
  mechanism, highly granular information, and huge number of similar
  records? IPFIX, as specified in RFC 5101 would give part of the
  solution.

2.1.  The IPFIX Track

  The IPFIX working group has specified a protocol to export Flow
  information [RFC5101].  This protocol is designed to export
  information about IP traffic Flows and related measurement data,
  where a Flow is defined by a set of key attributes (e.g., source and
  destination IP address, source and destination port).

  The IPFIX protocol specification [RFC5101] specifies that traffic
  measurements for Flows are exported using a TLV (type, length, value)
  format.  The information is exported using a Template Record that is
  sent once to export the {type, length} pairs that define the data
  format for the Information Elements in a Flow.  The Data Records
  specify values for each Flow.

  Based on the requirements for IP Flow Information Export (IPFIX)
  [RFC3917], the IPFIX protocol has been optimized to export Flow-
  related information.  However, thanks to its Template mechanism, the
  IPFIX protocol can export any type of information, as long as the
  relevant Information Element is specified in the IPFIX information
  model [RFC5102], registered with IANA [IANA-IPFIX], or specified as
  an enterprise-specific Information Element.  For each Information
  Element, the IPFIX information model [RFC5102] defines a numeric
  identifier, an abstract data type, an encoding mechanism for the data
  type, and any semantic constraints.  Only basic, single-valued data
  types, e.g., numbers, strings, and network addresses, are currently
  supported.










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2.2.  The IPFIX Limitations

  The IPFIX protocol specification [RFC5101] does not support the
  encoding of hierarchical structured data and arbitrary-length lists
  (sequences) of Information Elements as fields within a Template
  Record.  As it is currently specified, a Data Record is a "flat" list
  of single-valued attributes.  However, it is a common data modeling
  requirement to compose complex hierarchies of data types, with
  multiple occurrences, e.g., 0..* cardinality allowed for instances of
  each Information Element in the hierarchy.

  A typical example is the MPLS label stack entries model.  An early
  NetFlow implementation used two Information Elements to represent the
  MPLS label stack entry: a "label stack entry position" followed by a
  "label stack value".  However, several drawbacks were discovered.
  Firstly, the Information Elements in the Template Record had to be
  imposed so that the position would always precede the value.
  However, some encoding optimizations are based on the permutation of
  Information Element order.  Secondly, a new semantic intelligence,
  not described in the information model, had to be hard-coded in the
  Collecting Process: the label value at the position "X" in the stack
  is contained in the "label stack value" Information Element following
  by a "label stack entry position" Information Element containing the
  value "X".  Therefore, this model was abandoned.

  The selected solution in the IPFIX information model [RFC5102] is a
  long series of Information Elements: mplsTopLabelStackSection,
  mplsLabelStackSection2, mplsLabelStackSection3,
  mplsLabelStackSection4, mplsLabelStackSection5,
  mplsLabelStackSection6, mplsLabelStackSection7,
  mplsLabelStackSection8, mplsLabelStackSection9,
  mplsLabelStackSection10.  While this model removes any ambiguity, it
  overloads the IPFIX information model with repetitive information.
  Furthermore, if mplsLabelStackSection11 is required, IANA
  [IANA-IPFIX] will not be able to assign the new Information Element
  next to the other ones in the registry, which might cause some
  confusion.

2.3.  Structured Data Use Cases

  Clearly, the MPLS label stack entries issue can best be solved by
  using a real structured data type composed of ("label stack entry
  position", "label stack value") pairs, potentially repeated multiple
  times in Flow Records, since this would be the most efficient from an
  information model point of view.






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  Some more examples enter the same category: how to encode the list of
  output interfaces in a multicast Flow, how to encode the list of BGP
  Autonomous Systems (AS) in a BGP Flow, how to encode the BGP
  communities in a BGP Flow, etc.

  The one-way delay passive measurement, which is described in the
  IPFIX applicability [RFC5472], is yet another example that would
  benefit from a structured data encoding.  Assuming synchronized
  clocks, the Collector can deduce the one-way delay between two
  Observation Points from the following two Information Elements,
  collected from two different Observation Points:

      - Packet arrival time: observationTimeMicroseconds [RFC5477]
      - Packet ID: digestHashValue [RFC5477]

  In practice, this implies that many pairs of
  (observationTimeMicroseconds, digestHashValue) must be exported for
  each Observation Point, even if Hash-Based Filtering [RFC5475] is
  used.  On top of that information, if the requirement is to
  understand the one-way delay per application type, the 5-tuple
  (source IP address, destination IP address, protocol, source port,
  destination port) would need to be added to every Flow Record.
  Instead of exporting this repetitive 5-tuple, as part of every single
  Flow Record a Flow Record composed of a structured data type such as
  the following would save a lot of bandwidth:

     5-tuple
               { observationTimeMicroseconds 1, digestHashValue 1 }
               { observationTimeMicroseconds 2, digestHashValue 2 }
               { observationTimeMicroseconds 3, digestHashValue 3 }
               { ...  , ... }




















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  As a last example, here is a more complex case of hierarchical
  structured data encoding.  Consider the example scenario of an IPS
  (Intrusion Prevention System) alert data structure containing
  multiple participants, where each participant contains multiple
  attackers and multiple targets, with each target potentially composed
  of multiple applications, as depicted below:

     alert
         signatureId
         protocolIdentifier
         riskRating
         participant 1
             attacker 1
                 sourceIPv4Address
                 applicationId
             ...
             attacker N
                 sourceIPv4Address
                 applicationId
             target 1
                 destinationIPv4Address
                 applicationId 1
                 ...
                 applicationId n
             ...
             target N
                 destinationIPv4Address
                 applicationId 1
                 ...
                 applicationId n
         participant 2
             ...

  To export this information in IPFIX, the data would need to be
  flattened (thus, losing the hierarchical relationships) and a new
  IPFIX Template created for each alert, according to the number of
  applicationId elements in each target, the number of targets and
  attackers in each participant, and the number of participants in each
  alert.  Clearly, each Template will be unique to each alert, and a
  large amount of CPU, memory, and export bandwidth will be wasted
  creating, exporting, maintaining, and withdrawing the Templates.  See
  Appendix B for a specific example related to this case study.









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2.4.  Specifications Summary

  This document specifies an IPFIX extension to support hierarchical
  structured data and variable-length lists by defining three new
  Information Elements and three corresponding new abstract data types
  called basicList, subTemplateList, and subTemplateMultiList.  These
  are defined in Sections 4.1 and 4.3.

  The three Structured Data Information Elements carry some semantic
  information so that the Collecting Process can understand the
  relationship between the different list elements.  The semantic in
  the Structured Data Information Elements is provided in order to
  express the relationship among the multiple top-level list elements.
  As an example, if a list is composed of the elements (A,B,C), the
  semantic expresses the relationship among A, B, and C, regardless of
  whether A, B, and C are individual elements or a list of elements.

  It is important to note that whereas the Information Elements and
  abstract data types defined in the IPFIX information model [RFC5102]
  represent single values, these new abstract data types are structural
  in nature and primarily contain references to other Information
  Elements and to Templates.  By referencing other Information Elements
  and Templates from an Information Element's data content, it is
  possible to define complex data structures such as variable-length
  lists and to specify hierarchical containment relationships between
  Templates.  Therefore, this document prefers the more generic "Data
  Record" term to the "Flow Record" term.

  This document specifies three new abstract data types, which are
  basic blocks to represent structured data.  However, this document
  does not comment on all possible combinations of basicList,
  subTemplateList, and subTemplateMultiList.  Neither does it limit the
  possible combinations.

3.  Terminology

  IPFIX-specific terminology used in this document is defined in
  Section 2 of the IPFIX protocol specification [RFC5101] and Section 3
  of the PSAMP protocol specification [RFC5476].  As in [RFC5101],
  these IPFIX-specific terms have the first letter of a word
  capitalized when used in this document.










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3.1.  New Terminology

  Structured Data Information Element

     One of the Information Elements supporting structured data, i.e.,
     the basicList, subTemplateList, or subTemplateMultiList
     Information Elements specified in Section 4.3.

3.2.  Conventions Used in This Document

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
  document are to be interpreted as described in RFC 2119 [RFC2119].

4.  Linkage with the IPFIX Information Model

  As in the IPFIX protocol specification [RFC5101], the new Information
  Elements specified in Section 4.3 MUST be sent in canonical format in
  network-byte order (also known as the big-endian byte ordering).

4.1.  New Abstract Data Types

  This document specifies three new abstract data types, as described
  below.

4.1.1.  basicList

  The type "basicList" represents a list of zero or more instances of
  any Information Element, primarily used for single-valued data types.
  Examples include a list of port numbers, a list of interface indexes,
  a list of AS in a BGP AS-PATH, etc.

4.1.2.  subTemplateList

  The type "subTemplateList" represents a list of zero or more
  instances of a structured data type, where the data type of each list
  element is the same and corresponds with a single Template Record.
  Examples include a structured data type composed of multiple pairs of
  ("MPLS label stack entry position", "MPLS label stack value"), a
  structured data type composed of performance metrics, and a
  structured data type composed of multiple pairs of IP address, etc.

4.1.3.  subTemplateMultiList

  The type "subTemplateMultiList" represents a list of zero or more
  instances of a structured data type, where the data type of each list
  element can be different and corresponds with different Template
  definitions.  Examples include a structured data type composed of



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  multiple access-list entries, where entries can be composed of
  different criteria types.

4.2.  New Data Type Semantic

  This document specifies a new data type semantic, in addition to the
  ones specified in Section 3.2 of the IPFIX information model
  [RFC5102], as described below.

4.2.1.  List

  A list represents an arbitrary-length sequence of zero or more
  structured data Information Elements, either composed of regular
  Information Elements or composed of data conforming to a Template
  Record.

4.3.  New Information Elements

  This document specifies three new Information Elements, as described
  below.

4.3.1.  basicList

  A basicList specifies a generic Information Element with a basicList
  abstract data type as defined in Section 4.1.1 and list semantics as
  defined in Section 4.2.1.  Examples include a list of port numbers, a
  list of interface indexes, etc.

4.3.2.  subTemplateList

  A subTemplateList specifies a generic Information Element with a
  subTemplateList abstract data type as defined in Section 4.1.2 and
  list semantics as defined in Section 4.2.1.

4.3.3.  subTemplateMultiList

  A subTemplateMultiList specifies a generic Information Element with a
  subTemplateMultiList abstract data type as defined in Section 4.1.3
  and list semantics as defined in Section 4.2.1.

4.4.  New Structured Data Type Semantics

  Structured data type semantics are provided in order to express the
  relationship among multiple list elements in a Structured Data
  Information Element.  These structured data type semantics require a
  new IPFIX subregistry, as specified in the "IANA Considerations"
  section.  The semantics are specified in the following subsections.




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4.4.1.  undefined

  The "undefined" structured data type semantic specifies that the
  semantic of list elements is not specified and that, if a semantic
  exists, then it is up to the Collecting Process to draw its own
  conclusions.  The "undefined" structured data type semantic, which is
  the default value, is used when no other structured data type
  semantic applies.

  For example, a mediator that wants to translate IPFIX [RFC5101] into
  the export of structured data according to the specifications in this
  document doesn't know what the semantic is; it can only guess, as the
  IPFIX specifications [RFC5101] does not contain any semantic.
  Therefore, the mediator should use the "undefined" semantic.

4.4.2.  noneOf

  The "noneOf" structured data type semantic specifies that none of the
  elements are actual properties of the Data Record.

  For example, a mediator might want to report to a Collector that a
  specific Flow is suspicious, but that it checked already that this
  Flow does not belong to the attack type 1, attack type 2, or attack
  type 3.  So this Flow might need some further inspection.  In such a
  case, the mediator would report the Flow Record with a basicList
  composed of (attack type 1, attack type 2, attack type 3) and the
  respective structured data type semantic of "noneOf".

  Another example is a router that monitors some specific BGP AS-PATHs
  and reports if a Flow belongs to any of them.  If the router wants to
  export that a Flow does not belong to any of the monitored BGP AS-
  PATHs, the router reports a Data Record with a basicList composed of
  (BGP AS-PATH 1, BGP AS-PATH 2, BGP AS-PATH 3) and the respective
  structured data type semantic of "noneOf".

4.4.3. exactlyOneOf

  The "exactlyOneOf" structured data type semantic specifies that only
  a single element from the structured data is an actual property of
  the Data Record.  This is equivalent to a logical XOR operation.

  For example, if a Flow record contains a basicList of outgoing
  interfaces with the "exactlyOneOf" semantic, then it implies that the
  reported Flow only egressed from a single interface, although the
  Flow Record lists all of the possible outgoing interfaces.  This is a
  typical example of a per destination load-balancing.





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  Another example is a mediator that must aggregate Data Records from
  different Observation Points and report an aggregated Observation
  Point.  However, the different Observation Points can be specified by
  different Information Element types depending on the Exporter.  For
  example:

     Exporter1 Observation Point is characterized by the
     exporterIPv4Address, so a specific Exporter can be represented.

     Exporter2 Observation Point is characterized by the
     exporterIPv4Address and a basicList of ingressInterface, so the
     Exporting Process can express that the observations were made on a
     series of input interfaces.

     Exporter3 Observation Point is characterized by the
     exporterIPv4Address and a specific lineCardId, so the Exporting
     Process can express that the observation was made on a specific
     linecard.

  If the mediator models the three different types of Observation
  Points with the three Template Records below:

     Template Record 1: exporterIPv4Address
     Template Record 2: exporterIPv4Address, basicList of
                        ingressInterface
     Template Record 3: exporterIPv4Address, lineCardId

  then it can represent the aggregated Observation Point with a
  subTemplateMultiList and the semantic "exactlyOneOf".  The aggregated
  Observation Point is modeled with the Data Records corresponding to
  either Template Record 1, Template Record 2, or Template Record 3 but
  not more than one of these.  This implies that the Flow was observed
  at exactly one of the Observation Points reported.

4.4.4.  oneOrMoreOf

  The "oneOrMoreOf" structured data type semantic specifies that one or
  more elements from the list in the structured data are actual
  properties of the Data Record.  This is equivalent to a logical OR
  operation.

  Consider an example where a mediator must report an aggregated Flow
  (e.g., by aggregating IP addresses from IP prefixes), with an
  aggregated Observation Point.  However, the different Observation
  Points can be specified by different Information Element types as
  described in Section 4.4.2.





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  If the mediator models the three different types of Observation
  Points with the three Template Records below:

         Template Record 1: exporterIPv4Address
         Template Record 2: exporterIPv4Address, basicList of
                            ingressInterface
         Template Record 3: exporterIPv4Address, lineCardId

  then it can represent the aggregated Observation Point with a
  subTemplateMultiList and the semantic "oneOrMoreOf".  The aggregated
  Observation Point is modeled with the Data Records corresponding to
  either Template Record 1, Template Record 2, or Template Record 3.
  This implies that the Flow was observed on at least one of the
  Observation Points reported, and potentially on multiple Observation
  Points.

4.4.5.  allOf

  The "allOf" structured data type semantic specifies that all of the
  list elements from the structured data are actual properties of the
  Data Record.

  For example, if a Record contains a basicList of outgoing interfaces
  with the "allOf" semantic, then the observed Flow is typically a
  multicast Flow where each packet in the Flow has been replicated to
  each outgoing interface in the basicList.

4.4.6.  ordered

  The "ordered" structured data type semantic specifies that elements
  from the list in the structured data are ordered.

  For example, an Exporter might want to export the AS10 AS20 AS30 AS40
  BGP AS-PATH.  In such a case, the Exporter would report a basicList
  composed of (AS10, AS20, AS30, AS40) and the respective structured
  data type semantic of "ordered".

4.5.  Encoding of IPFIX Data Types

  The following subsections define the encoding of the abstract data
  types defined in Section 4.1.  These data types may be encoded using
  either fixed- or variable-length Information Elements, as discussed
  in Section 5.1.  Like in the IPFIX specifications [RFC5101], all
  lengths are specified in octets.







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4.5.1.  basicList

  The basicList Information Element defined in Section 4.3.1 represents
  a list of zero or more instances of an Information Element and is
  encoded as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Semantic    |0|          Field ID           |   Element...  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | ...Length     |           basicList Content ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: basicList Encoding

  Semantic

     The Semantic field indicates the relationship among the different
     Information Element values within this Structured Data Information
     Element.  Refer to IANA's "IPFIX Structured Data Types Semantics"
     registry.

  Field ID

     Field ID is the Information Element identifier of the Information
     Element(s) contained in the list.

  Element Length

     Per Section 7 of [RFC5101], the Element Length field indicates the
     length, in octets, of each list element specified by Field ID, or
     contains the value 0xFFFF if the length is encoded as a variable-
     length Information Element at the start of the basicList Content.

     Effectively, the Element Length field is part of the header, so
     even in the case of a zero-element list, it MUST NOT be omitted.

  basicList Content

     A Collecting Process decodes list elements from the basicList
     Content until no further data remains.  A field count is not
     included but can be derived when the Information Element is
     decoded.



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  Note that in the diagram above, Field ID is shown with the Enterprise
  bit (most significant bit) set to 0.  Instead, if the Enterprise bit
  is set to 1, a four-byte Enterprise Number MUST be encoded
  immediately after the Element Length as shown below.  See the "Field
  Specifier Format" section in the IPFIX protocol [RFC5101] for
  additional information.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Semantic   |1|         Field ID            |   Element...  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | ...Length     |               Enterprise Number ...           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |              basicList Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 2: basicList Encoding with Enterprise Number

  Also, note that if a basicList has zero elements, the encoded data
  contains the Semantic field, Field ID, the Element Length field, and
  the four-byte Enterprise Number (if present), while the basicList
  Content is empty.

  If the basicList is encoded as a variable-length Information Element
  in less than 255 octets, it MAY be encoded with the Length field per
  Section 7 of [RFC5101] as shown in Figure 3.  However, the three-byte
  length encoding, as shown in Figure 4, is RECOMMENDED (see Section
  5.1).

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length (< 255)|   Semantic    |0|          Field ID           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Element Length        | basicList Content ...         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 3: Variable-Length basicList Encoding
                     (Length < 255 Octets)





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  If the basicList is encoded as a variable-length Information Element
  in 255 or more octets, it MUST be encoded with the Length field per
  Section 7 of [RFC5101] as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      |      Length (0 to 65535)      |   Semantic    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|          Field ID           |        Element Length         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      basicList Content ...                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 4: Variable-Length basicList Encoding
                 (Length 0 to 65535 Octets)

4.5.2.  subTemplateList

  The subTemplateList Information Element represents a list of zero or
  more Data Records corresponding to a specific Template.  Because the
  Template Record referenced by a subTemplateList Information Element
  can itself contain other subTemplateList Information Elements, and
  because these Template Record references are part of the Information
  Elements content in the Data Record, it is possible to represent
  complex hierarchical data structures.  The following diagram shows
  how a subTemplateList Information Element is encoded within a Data
  Record:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Semantic    |         Template ID           |     ...       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                subTemplateList Content    ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 5: subTemplateList Encoding







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  Semantic

     The Semantic field indicates the relationship among the different
     Data Records within this Structured Data Information Element.

  Template ID

     The Template ID field contains the ID of the Template used to
     encode and decode the subTemplateList Content.

  subTemplateList Content

     subTemplateList Content consists of zero or more instances of Data
     Records corresponding to the Template ID specified in the Template
     ID field.  A Collecting Process decodes the subTemplateList
     Content until no further data remains.  A record count is not
     included but can be derived when the subTemplateList is decoded.
     Encoding and decoding are performed recursively if the specified
     Template itself contains Structured Data Information Elements as
     described here.

  Note that, if a subTemplateList has zero elements, the encoded data
  contains only the Semantic field and the Template ID field, while the
  subTemplateList Content is empty.

  If the subTemplateList is encoded as a variable-length Information
  Element in less than 255 octets, it MAY be encoded with the Length
  field per Section 7 of [RFC5101] as shown in Figure 6.  However, the
  three-byte length encoding, as shown in Figure 7, is RECOMMENDED (see
  Section 5.1).

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length (< 255)|   Semantic    |         Template ID           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                subTemplateList Content    ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 6: Variable-Length subTemplateList Encoding
                      (Length < 255 Octets)








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  If the subTemplateList is encoded as a variable-length Information
  Element in 255 or more octets, it MUST be encoded with the Length
  field per Section 7 of [RFC5101] as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      |      Length (0 to 65535)      |   Semantic    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID           | subTemplateList Content ...   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 7: Variable-Length subTemplateList Encoding
                   (Length 0 to 65535 Octets)

4.5.3.  subTemplateMultiList

  Whereas each element in a subTemplateList Information Element
  corresponds to a single Template, it is sometimes useful for a list
  to contain elements corresponding to different Templates.  To support
  this case, each top-level element in a subTemplateMultiList
  Information Element carries a Template ID, Length, and zero or more
  Data Records corresponding to the Template ID.  The following diagram
  shows how a subTemplateMultiList Information Element is encoded
  within a Data Record.  Note that the encoding following the Semantic
  field is consistent with the Set Header specified in [RFC5101].

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Semantic   |         Template ID X         |Data Records...|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | ... Length X  |        Data Record X.1 Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |        Data Record X.2 Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |        Data Record X.L Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |         Template ID Y         |Data Records...|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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  | ... Length Y  |        Data Record  Y.1 Content ...           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |        Data Record Y.2 Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |        Data Record Y.M Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |         Template ID Z         |Data Records...|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | ... Length Z  |        Data Record Z.1 Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |        Data Record Z.2 Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |        Data Record Z.N Content ...            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      ...      |
  +-+-+-+-+-+-+-+-+

               Figure 8: subTemplateMultiList Encoding

  Semantic

     The Semantic field indicates the top-level relationship among the
     series of Data Records corresponding to the different Template
     Records within this Structured Data Information Element.

  Template ID

     Unlike the subTemplateList Information Element, each element of
     the subTemplateMultiList contains a Template ID that specifies the
     encoding of the following Data Records.









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  Data Records Length

     This is the total length of the Data Records encoding for the
     Template ID previously specified, including the two bytes for the
     Template ID and the two bytes for the Data Records Length field
     itself.

  Data Record X.M

     The Data Record X.M consists of the Mth Data Record of the
     Template Record X.  A Collecting Process decodes the Data Records
     according to Template Record X until no further data remains,
     according to the Data Records Length X.  Further Template IDs and
     Data Records may then be decoded according to the overall
     subTemplateMultiList length.  A record count is not included but
     can be derived when the Element Content is decoded.  Encoding and
     decoding are performed recursively if the specified Template
     itself contains Structured Data Information Elements as described
     here.

  In the exceptional case of zero instances in the
  subTemplateMultiList, no data is encoded, only the Semantic field and
  Template ID field(s), and the Data Record Length field is set to
  zero.

  If the subTemplateMultiList is encoded as a variable-length
  Information Element in less than 255 octets, it MAY be encoded with
  the Length field per Section 7 of [RFC5101] as shown in Figure 9.
  However, the three-byte length encoding, as shown in Figure 10, is
  RECOMMENDED (see Section 5.1).

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length (< 255)|    Semantic   |         Template ID X         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Data Records Length X    |  Data Record X.1 Content ...  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |   Data Record X.2 Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |   Data Record X.L Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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  |             ...               |         Template ID Y         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Data Records Length Y    |   Data Record Y.1 Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |   Data Record Y.2 Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |   Data Record Y.M Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |         Template ID Z         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Data Records Length Z    |   Data Record Z.1 Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |   Data Record Z.2 Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |   Data Record Z.N Content ... |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 9: Variable-Length subTemplateMultiList Encoding
                     (Length < 255 Octets)

  If the subTemplateMultiList is encoded as a variable-length
  Information Element in 255 or more octets, it MUST be encoded with
  the Length field per Section 7 of [RFC5101] as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      |      Length (0 to 65535)      |   Semantic    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID X         |    Data Records Length X      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Data Record X.1 Content ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |



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  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Data Record X.2 Content ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Data Record X.L Content ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID Y         |    Data Records Length Y      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Data Record  Y.1 Content ...                |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Data Record Y.2 Content ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Data Record Y.M Content ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID Z         |    Data Records Length Z      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Data Record Z.1 Content ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Data Record Z.2 Content ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Data Record Z.N Content ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 10: Variable-Length subTemplateMultiList Encoding
                       (Length 0 to 65535 Octets)

5.  Structured Data Format

5.1.  Length Encoding Considerations

  The new Structured Data Information Elements represent a list that
  potentially carries complex hierarchical and repeated data.




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  When the encoding of a Structured Data Information Element has a
  fixed length (because, for example, it contains the same number of
  fixed-length elements, or if the permutations of elements in the list
  always produces the same total length), the element length can be
  encoded in the corresponding Template Record.

  However, when representing variable-length data, hierarchical data,
  and repeated data with variable element counts, where the number and
  length of elements can vary from record to record, we RECOMMEND that
  the Information Elements are encoded using the variable-length
  encoding described in Section 7 of [RFC5101], with the length carried
  before the Structured Data Information Element encoding.

  Because of the complex and repeated nature of the data, it is
  potentially difficult for the Exporting Process to efficiently know
  in advance the exact encoding size.  In this case, the Exporting
  Process may encode the available data starting at a fixed offset and
  fill in the final length afterwards.  Therefore, the three-byte
  length encoding is RECOMMENDED for variable-length Information
  Elements in all Template Records containing a Structured Data
  Information Element, even if the encoded length can be less than 255
  bytes, because the starting offset of the data is known in advance.

  When encoding such data, an Exporting Process MUST take care to not
  exceed the maximum allowed IPFIX message length of 65535 bytes as
  specified in [RFC5101].

5.2.  Recursive Structured Data

  It is possible to define recursive relationships between IPFIX
  structured data instances, for example, when representing a tree
  structure.  The simplest case of this might be a basicList, where
  each element is itself a basicList, or a subTemplateList where one of
  the fields of the referenced Template is itself a subTemplateList
  referencing the same Template.  Also, the Exporting Process MUST take
  care when encoding recursively-defined structured data not to exceed
  the maximum allowed length of an IPFIX Message (as noted in Length
  Encoding Considerations).

5.3.  Structured Data Information Elements Applicability in Options
     Template Sets

  Structured Data Information Elements MAY be used in Options Template
  Sets.

  As an example, consider a mediation function that must aggregate Data
  Records from multiple Observation Point types:




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     Router 1, (interface 1)
     Router 2, (linecard A)
     Router 3, (linecard B)
     Router 4, (linecard C, interface 2)

  In order to encode the PSAMP Selection Sequence Report Interpretation
  [RFC5476], the mediation function must express this combination of
  Observation Points as a single new Observation Point.  Recall from
  [RFC5476] that the PSAMP Selection Sequence Report Interpretation
  consists of the following fields:

    Scope:     selectionSequenceId
    Non-Scope: one Information Element mapping the Observation Point
               selectorId (one or more)

  Without structured data, there is clearly no way to express the
  complex aggregated Observation Point as "one Information Element
  mapping the Observation Point".  However, the desired result may be
  easily achieved using the structured data types.  Refer to Section
  9.5. for an encoding example related to this case study.

  Regarding the scope in the Options Template Record, the IPFIX
  specification [RFC5101] mentions that "the IPFIX protocol doesn't
  prevent the use of any Information Elements for scope".  Therefore, a
  Structured Data Information Element MAY be used as scope in an
  Options Template Set.

  Extending the previous example, the mediation function could export a
  given name for this complex aggregated Observation Point:

     Scope: Aggregated Observation Point (structured data)
     Non-Scope: a new Information Element containing the name

5.4.  Usage Guidelines for Equivalent Data Representations

  Because basicList, subTemplateList, and subTemplateMultiList are all
  lists, in several cases, there is more than one way to represent what
  is effectively the same data structure.  However, in some cases, one
  approach has an advantage over the other, e.g., more compact, uses
  fewer resources, and is therefore preferred over an alternate
  representation.

  A subTemplateList can represent the same simple list of single-valued
  Information Elements as a basicList, if the Template referenced by
  the subTemplateList contains only one single-valued Information
  Element.  Although the encoding is more compact than a basicList by
  two bytes, using a subTemplateList, in this case, requires a new




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  Template per Information Element.  The basicList requires no
  additional Template and is therefore RECOMMENDED in this case.

  Although a subTemplateMultiList with one Element can represent the
  contents of a subTemplateList, the subTemplateMultiList carries two
  additional bytes (Element Length).  It is also potentially useful to
  a Collecting Process to know in advance that a subTemplateList
  directly indicates that list element types are consistent.  The
  subTemplateList Information Element is therefore RECOMMENDED in this
  case.

  The Semantic field in a subTemplateMultiList indicates the top-level
  relationship among the series of Data Records corresponding to the
  different Template Records, within this Structured Data Information
  Element.  If a semantic is required to describe the relationship
  among the different Data Records corresponding to a single Template
  ID within the subTemplateMultiList, then an encoding based on a
  basicList of subTemplateLists should be used; refer to Section 5.6
  for more information.  Alternatively, if a semantic is required to
  describe the relationship among all Data Records within a
  subTemplateMultiList (regardless of the Template Record), an encoding
  based on a subTemplateMultiList with one Data Record corresponding to
  a single Template ID can be used.

  Note that the referenced Information Element(s) in the Structured
  Data Information Elements can be taken from the IPFIX information
  model [RFC5102], the PSAMP information model [RFC5477], any of the
  Information Elements defined in the IANA IPFIX registry [IANA-IPFIX],
  or enterprise-specific Information Elements.

  If a Template Record contains a subTemplateList as the only field, a
  Set encoding as specified in the IPFIX protocol specifications
  [RFC5101] should be considered, unless:

  - A relationship among multiple list elements must be exported, in
    which case, the semantic from the IPFIX Structured Data Information
    Element can convey this relationship.

  - The Exporting Process wants to convey the number of elements in the
    list, even in the special cases of zero or one element in the list.
    Indeed, the case of an empty list cannot be represented with the
    IPFIX protocol specifications [RFC5101].  In the case of a single
    element list, the Template Record specified in the IPFIX protocol
    specification [RFC5101] could be used.  However, on the top of the
    Template Record with the subTemplateList to export multiple list
    elements, this supplementary Template would impose some extra





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    management, both on the Exporting Process and on the Collecting
    Process, which might have to correlate the information from two
    Template Records.

  Similarly, if a Template Record contains a subTemplateMultiList as
  the only field, an IPFIX Message as described in the IPFIX protocol
  specification [RFC5101] should be considered, unless:

  - A relationship among top-level list elements must be exported, in
    which case, the semantic from the IPFIX Structured Data Information
    Element can convey this relationship.

  - The Exporting Process wants to convey the number of Data Records
    corresponding to every Template in the subTemplateMultiList.

5.5.  Padding

  The Exporting Process MAY insert some padding octets in structured
  data field values in a Data Record by including the 'paddingOctets'
  Information Element as described in [RFC5101], Section 3.3.1.  The
  paddingOctets Information Element can be included in a Template
  Record referenced by a structured data Information Element for this
  purpose.

5.6.  Semantic

  Semantic interpretations of received Data Records at or beyond the
  Collecting Process remain explicitly undefined, unless that data is
  transmitted using this extension with explicit structured data type
  semantic information.

  It is not the Exporter's role to check the validity of the semantic
  representation of Data Records.

  More complex semantics can be expressed as a combination of the
  Semantic Data Information Elements specified in this document.

  For example, the export of the AS10 AS20 AS30 AS40 {AS50,AS60} BGP
  AS-PATH would be reported as a basicList of two elements, each
  element being a basicList of BGP AS, with the top-level structured
  data type semantic of "ordered".  The first element would contain a
  basicList composed of (AS10,AS20,AS30,AS40) and the respective
  structured data type semantic of "ordered", while the second element
  would contain a basicList composed of (AS50, AS60) and the respective
  structured data type semantic of "exactlyOneOf".  A high-level Data
  Record diagram would be represented as:





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       BGP AS-PATH = (basicList, ordered,

           (basicList, ordered, AS10,AS20,AS30,AS40),

           (basicList, exactlyOneOf, AS50, AS60)

       )

  If a semantic is required to describe the relationship among the
  different Data Records corresponding to a single Template ID within
  the subTemplateMultiList, then an encoding based on a basicList of
  subTemplateLists should be used, as shown in the next case study.

   Case study 1:

  In this example, an Exporter monitoring security attacks must export
  a list of security events consisting of attackers and targets.  For
  the sake of the example, assume that the Collector can differentiate
  the attacker (which is expressed using source fields) from the target
  (which is expressed using destination fields).  Imagine that
  attackers A1 or A2 may attack targets T1 and T2.

  The first case uses a subTemplateMultiList composed of two Template
  Records, one representing the attacker and one representing the
  target, each of them containing an IP address and a port.

       Attacker Template Record = (src IP address, src port)

       Target Template Record = (dst IP address, dst port)

  A high-level Data Record diagram would be represented as:

        Alert = (subTemplateMultiList, allOf,

           (Attacker Template Record, A1, A2),

           (Target Template Record, T1, T2)

        )

  The Collecting Process can only conclude that the list of attackers
  (A1, A2) and the list of targets (T1, T2) are present, without
  knowing the relationship amongst attackers and targets.  The
  Exporting Process would have to explicitly call out the relationship
  amongst attackers and targets as the top-level semantic offered by
  the subTemplateMultiList isn't sufficient.





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  The only proper encoding for the previous semantic (i.e., attacker A1
  or A2 may attack target T1 and T2) uses a basicList of
  subTemplateLists and is represented as follows:

       Attacker Template Record = (src IP address, src port)

       Target Template Record = (dst IP address, dst port)

       Alert = (basicList, allOf,

             (subTemplateList, exactlyOneOf, attacker A1, A2)

             (subTemplateList, allOf, target T1, T2)

       )

   Case study 2:

  In this example, an Exporter monitoring security attacks must export
  a list of attackers and targets.  For the sake of the example, assume
  that the Collector can differentiate the attacker (which is expressed
  using source fields) from the target (which is expressed using
  destination fields).  Imagine that attacker A1 or A2 is attacking
  target T1, while attacker A3 is attacking targets T2 and T3.  The
  first case uses a subTemplateMultiList that contains Data Records
  corresponding to two Template Records, one representing the attacker
  and one representing the target, each of them containing an IP
  address and a port.

       Attacker Template Record = (src IP address, src port)
       Target Template Record = (dst IP address, dst port)

  A high-level Data Record diagram would be represented as:

        Alert = (subTemplateMultiList, allOf,

           (Attacker Template Record, A1, A2, A3),

           (Target Template Record, T1, T2, T3)

        )

  The Collecting Process can only conclude that the list of attackers
  (A1, A2, A3), and the list of targets (T1, T2, T3) are present,
  without knowing the relationship amongst attackers and targets.






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  The second case could use a Data Record definition composed of the
  following:

        Alert = (subTemplateMultiList, allOf,

           (Attacker Template Record, A1, A2),

           (Target Template Record, T1),

           (Attacker Template Record, A3),

           (Target Template Record, T2, T3)

        )

  With the above representation, the Collecting Process can infer that
  the alert consists of the list of attackers (A1, A2), target (T1),
  attacker (A3), and list of targets (T2, T3).  From the sequence in
  which attackers and targets are encoded, the Collector can possibly
  deduce that some relationship exists among (A1, A2, T1) and (A2, T1,
  T2) but cannot understand what it is exactly.  So, there is a need
  for the Exporting Process to explicitly define the relationship
  between the attackers, and targets and the top-level semantic of the
  subTemplateMultiList is not sufficient.

  The only proper encoding for the previous semantic (i.e., attacker A1
  or A2 attacks target T1, attacker A3 attacks targets T2 and T3) uses
  a basicList of subTemplateLists and is represented as follows:

       Participant P1 =

       (basicList, allOf,

             (subTemplateList, exactlyOneOf, attacker A1, A2)

             (subTemplateList, undefined, target T1)

       )

       Participant P2 =

       (basicList, allOf,

             (subTemplateList, undefined, attacker A3,

             (subTemplateList, allOf, targets T2, T3)

       )



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  The security alert is represented as a subTemplateList of
  participants.

       Alert =

          (subTemplateList, allOf, Participant P1, Participant P2)

  Note that, in the particular case of a single element in a Structured
  Data Information Element, the Semantic field is actually not very
  useful since it specifies the relationship among multiple elements.
  Any choice of allOf, exactlyOneOf, or OneOrMoreOf would provide the
  same result semantically.  Therefore, in case of a single element in
  a Structured Data Information Element, the default "undefined"
  semantic SHOULD be used.

6.  Template Management

  This section introduces some more specific Template management and
  Template Withdrawal Message-related specifications compared to the
  IPFIX protocol specification [RFC5101].

  First of all, the Template ID uniqueness is unchanged compared to
  [RFC5101]; the uniqueness is local to the Transport Session and
  Observation Domain that generated the Template ID.  In other words,
  the Set ID used to export the Template Record does not influence the
  Template ID uniqueness.

  While [RFC5101] mentions that "if an Information Element is required
  more than once in a Template, the different occurrences of this
  Information Element SHOULD follow the logical order of their
  treatments by the Metering Process", this rule MAY be ignored within
  Structured Data Information Elements.

  As specified in [RFC5101], Templates that are not used anymore SHOULD
  be deleted.  Deleting a Template implies that it MUST NOT be used
  within subTemplateList and subTemplateMultiList anymore.  Before
  reusing a Template ID, the Template MUST be deleted.  In order to
  delete an allocated Template, the Template is withdrawn through the
  use of a Template Withdrawal Message.

7.  The Collecting Process's Side

  This section introduces some more specific specifications to the
  Collection Process compared to Section 9 in the IPFIX protocol
  [RFC5101].

  As opposed to the IPFIX specification in [RFC5101], IPFIX Messages
  with IPFIX Structured Data Information Elements change the IPFIX



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  concept from the Collector's point of view as the data types are
  present in the Data Records rather than in the Template Records.  For
  example, a basicList Information Element in a Template Record doesn't
  specify the list element data type; this information is contained in
  the Data Record.  For example, in case of a subTemplateMultiList, the
  Collecting Process must refer to the included Template Records in the
  middle of the Data Record decode.

  As described in [RFC5101], a Collecting Process MUST note the
  Information Element identifier of any Information Element that it
  does not understand and MAY discard that Information Element from the
  Flow Record.  Therefore, a Collection Process that does not support
  the extension specified in this document can ignore the Structured
  Data Information Elements in a Data Record, or it can ignore Data
  Records containing these new Structured Data Information Elements
  while continuing to process other Data Records.

  If the structured data contains the "undefined" structured data type
  semantic, the Collecting Process MAY attempt to draw its own
  conclusion in terms of the semantic contained in the Data Record.

8.  Defining New Information Elements Based on the New Abstract Data
   Types

  This document specifies three new abstract data types: basicList,
  subTemplateList, and subTemplateMultiList.  As specified in
  [RFC5102], the specification of new IPFIX Information Elements uses
  the Template specified in Section 2.1 of [RFC5102].  This Template
  mentioned existing and future the data types: "One of the types
  listed in Section 3.1 of this document or in a future extension of
  the information model".  So new Information Elements can be specified
  based on the three new abstract data types.

  The authors anticipate the creation of both enterprise-specific and
  IANA Information Elements based on the IPFIX structured data types.
  For example, bgpPathList, bgpSequenceList, and bgpSetList, of
  abstract types and semantics basicList/ordered, basicList/ordered,
  and basicList/exactlyOneOf respectively, would define the complete
  semantic of the list.  This specification doesn't specify any new
  Information Elements beyond the ones in Section 4.3.

9.  Structured Data Encoding Examples

  The following examples are created solely for the purpose of
  illustrating how the extensions proposed in this document are
  encoded.





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9.1.  Encoding a Multicast Data Record with basicList

  Consider encoding a multicast Data Record containing the following
  data:

  ---------------------------------------------------------------
   Ingress If | Source IP   | Destination IP  | Egress Interfaces
  ---------------------------------------------------------------
        9       192.0.2.201      233.252.0.1         1, 4, 8
  ---------------------------------------------------------------

  Template Record for the multicast Flows, with the Template ID 256:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Set ID = 2            |      Length = 24 octets       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Template ID = 256       |       Field Count = 4         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|    ingressInterface = 10    |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   sourceIPv4Address = 8     |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| DestinationIPv4Address = 12 |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|       basicList = 291       |     Field Length = 0xFFFF     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 11: Encoding basicList, Template Record

  The list of outgoing interfaces is represented as a basicList with
  semantic allOf, and the Length of the list is chosen to be encoded in
  three bytes even though it may be less than 255 octets.

















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  The Data Set is represented as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 256         |          Length = 36          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     ingressInterface = 9                      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |               sourceIPv4Address = 192.0.2.201                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             DestinationIPv4Address = 233.252.0.1              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      |        List Length = 17       | semantic=allOf|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | egressInterface FieldId = 14  |egressInterface Field Length=4 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                egressInterface value 1 = 1                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                egressInterface value 2 = 4                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                egressInterface value 3 = 8                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 12: Encoding basicList, Data Record, Semantic allOf

  In the example above, the basicList contains fixed-length elements.
  To illustrate how variable-length elements would be encoded, the same
  example is shown below with variable-length interface names in the
  basicList instead:





















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   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 256         |          Length = 44          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     ingressInterface = 9                      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |               sourceIPv4Address = 192.0.2.201                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             DestinationIPv4Address = 233.252.0.1              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      |        List Length = 25       | semantic=allOf|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| InterfaceName FieldId = 82  | InterfaceName Field Len=0xFFFF|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Length = 5   |      'F'      |      'E'      |      '0'      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     '/'       |      '0'      |  Length = 7   |      'F'      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     'E'       |      '1'      |      '0'      |      '/'      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     '1'       |      '0'      |  Length = 5   |      'F'      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     'E'       |      '2'      |     '/'       |      '2'      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 13: Encoding basicList, Data Record with Variable-Length
                      Elements, Semantic allOf

9.2.  Encoding a Load-Balanced Data Record with a basicList

  Consider encoding a load-balanced Data Record containing the
  following data:

  ---------------------------------------------------------------
   Ingress If | Source IP   | Destination IP  | Egress Interfaces
  ---------------------------------------------------------------
        9       192.0.2.201      233.252.0.1         1, 4, 8
  ---------------------------------------------------------------












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  So the Data Record egressed from either interface 1, 4, or 8.  The
  Data Set is represented as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 256         |          Length = 36          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     ingressInterface = 9                      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |               sourceIPv4Address = 192.0.2.201                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             DestinationIPv4Address = 233.252.0.1              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      |        List Length = 17       |sem=exactlyOne |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | egressInterface FieldId = 14  |egressInterface Field Length=4 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                egressInterface value 1 = 1                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                egressInterface value 2 = 4                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                egressInterface value 3 = 8                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Note: sem=exactlyOne represents semantic=exactlyOneOf

    Figure 14: Encoding basicList, Data Record, Semantic exactlyOneOf

9.3.  Encoding subTemplateList

  As explained in Section 2.2, multiple pairs of
  (observationTimeMicroseconds, digestHashValue) must be collected from
  two different Observation Points to passively compute the one-way
  delay across the network.  This data can be exported with an
  optimized Data Record that consists of the following attributes:

      5-tuple
                { observationTimeMicroseconds 1, digestHashValue 1 }
                { observationTimeMicroseconds 2, digestHashValue 2 }
                { observationTimeMicroseconds 3, digestHashValue 3 }
                { ...  , ... }

  A subTemplateList is best suited for exporting the list of
  (observationTimeMicroseconds, digestHashValue).  For illustration
  purposes, the number of elements in the list is 5; in practice, it
  could be more.




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  ------------------------------------------------------------------
  srcIP     | dstIP      | src   | dst  |proto| one-way delay
            |            | Port  | Port |     |   metrics
  ------------------------------------------------------------------
  192.0.2.1  192.0.2.105   1025     80     6    Time1, 0x0x91230613
                                                Time2, 0x0x91230650
                                                Time3, 0x0x91230725
                                                Time4, 0x0x91230844
                                                Time5, 0x0x91230978
  ------------------------------------------------------------------

  The following Template is defined for exporting the one-way delay
  metrics:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Set ID = 2             |      Length = 16 octets       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Template ID = 257       |       Field Count = 2         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| observationTimeMicroSec=324 |       Field Length = 8        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   digestHashValue = 326     |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 15: Encoding subTemplateList, Template for One-Way Delay
                                Metrics























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  The Template Record for the Optimized Data Record is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Set ID = 2            |      Length = 32 octets       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Template ID = 258       |       Field Count = 6         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   sourceIPv4Address = 8     |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| destinationIPv4Address = 12 |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|  sourceTransportPort = 7    |       Field Length = 2        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| destinationTransportPort= 11|       Field Length = 2        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| protocolIdentifier = 4      |       Field Length = 1        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|  subTemplateList = 292      |     Field Length = 0xFFFF     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 16: Encoding subTemplateList, Template Record

  The list of (observationTimeMicroseconds, digestHashValue) is
  exported as a subTemplateList with semantic allOf.  The Length of the
  subTemplateList is chosen to be encoded in three bytes even though it
  may be less than 255 octets.

  The Data Record is represented as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Set ID = 258          |      Length = 83 octets       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                sourceIPv4Address = 192.0.2.1                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              destinationIPv4Address = 192.0.2.105             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | sourceTransportPort = 1025    | destinationTransportPort = 80 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Protocol = 6  |      255      | one-way metrics list len = 63 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | semantic=allOf|       TemplateID = 257        | TimeValue1    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                 ... octets 2-5 of TimeValue1                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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  |          ... octets 6-8 of TimeValue1         |digestHashVal1=|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                ... 0x0x91230613               | TimeValue2    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                 ... octets 2-5 of TimeValue2                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          ... octets 6-8 of TimeValue2         |digestHashVal2=|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                ... 0x0x91230650               | TimeValue3    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                 ... octets 2-5 of TimeValue3                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          ... octets 6-8 of TimeValue3         |digestHashVal3=|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                ... 0x0x91230725               | TimeValue4    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                 ... octets 2-5 of TimeValue4                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          ... octets 6-8 of TimeValue4         |digestHashVal4=|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                ... 0x0x91230844               | TimeValue5    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                 ... octets 2-5 of TimeValue5                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          ... octets 6-8 of TimeValue5         |digestHashVal5=|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                ... 0x0x91230978               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 17: Encoding subTemplateList, Data Set

9.4.  Encoding subTemplateMultiList

  As explained in Section 4.5.3, a subTemplateMultiList is used to
  export a list of mixed-type content where each top-level element
  corresponds to a different Template Record.

  To illustrate this, consider the Data Record with the following
  attributes:












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       5-tuple (Flow Keys), octetCount, packetCount
                 attributes for filtering
                      selectorId,
                      selectorAlgorithm
                 attributes for sampling
                      selectorId,
                      selectorAlgorithm,
                      samplingPacketInterval,
                      samplingPacketSpace

  This example demonstrates that the Selector Report Interpretation
  [RFC5476] can be encoded with the subTemplateMultiList.  More
  specifically, the example describes Property Match Filtering Selector
  Report Interpretation [RFC5476] used for filtering purposes, and the
  Systemic Count-Based Sampling as described in Section 6.5.2.1 of
  [RFC5476].  Some traffic will be filtered according to match
  properties configured, some will be sampled, some will be filtered
  and sampled, and some will not be filtered or sampled.

  A subTemplateMultiList is best suited for exporting this variable
  data.  A Template is defined for filtering attributes and another
  Template is defined for sampling attributes.  A Data Record can
  contain data corresponding to either of the Templates, both of them,
  or neither of them.

  Consider the example below where the following Data Record contains
  both filtering and sampling attributes.

  Key attributes of the Data Record:

  ------------------------------------------------------------------
  srcIP      | dstIP     | src  | dst  | proto | octetCount | packet
             |           | Port | Port |       |            | Count
  ------------------------------------------------------------------
  2001:DB8::1 2001:DB8::2  1025    80      6       108000      120
  ------------------------------------------------------------------

  Filtering attributes:

  -------------------------------------------
  selectorId  | selectorAlgorithm
  -------------------------------------------
     100         5 (Property Match Filtering)
  -------------------------------------------







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  Sampling attributes:

  For Systemic Count-Based Sampling as defined in Section 6.5.2.1 of
  [RFC5476] the required algorithm-specific Information Elements are:

        samplingPacketInterval: number of packets selected in a row
        samplingPacketSpace:    number of packets between selections

  Example of a simple 1-out-of-100 systematic count-based Selector
  definition, where the samplingPacketInterval is 1 and the
  samplingPacketSpace is 99.

  --------------------------------------------------------------
  selectorId | selectorAlgorithm        | sampling | sampling
             |                          | Packet   | Packet
             |                          | Interval | Space
  --------------------------------------------------------------
     15        1 (Count-Based Sampling)      1         99
  --------------------------------------------------------------

  To represent the Data Record, the following Template Records are
  defined:

      Template for filtering attributes: 259
       Template for sampling attributes: 260
       Template for Flow Record: 261

       Flow record (261)
           |  (sourceIPv6Address)
           |  (destinationIPv6Address)
           |  (sourceTransportPort)
           |  (destinationTransportPort)
           |  (protocolIdentifier)
           |  (octetTotalCount)
           |  (packetTotalCount)
           |
           +------ filtering attributes (259)
           |          (selectorId)
           |          (selectorAlgorithm)
           |
           +------ sampling attributes (260)
           |          (selectorId)
           |          (selectorAlgorithm)
           |          (samplingPacketInterval)
           |          (samplingPacketSpace)






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  The following Template Record is defined for filtering attributes:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 2           |          Length = 16          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Template ID = 259        |        Field Count = 2        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|    selectorId = 302         |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| selectorAlgorithm = 304     |        Field Length = 1       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 18: Encoding subTemplateMultiList, Template for Filtering
                              Attributes

  The Template for sampling attributes is defined as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 2           |          Length = 24          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Template ID = 260        |        Field Count = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|    selectorId = 302         |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|  selectorAlgorithm = 304    |        Field Length = 1       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| samplingPacketInterval = 305|        Field Length = 1       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| samplingPacketSpace = 306   |        Field Length = 1       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 19: Encoding subTemplateMultiList, Template for Sampling
                              Attributes

  Note that while selectorAlgorithm is defined as unsigned16, and
  samplingPacketInterval and samplingPacketSpace are defined as
  unsigned32, they are compressed down to 1 octet here as allowed by
  Reduced Size Encoding in Section 6.2 of the IPFIX protocol
  specifications [RFC5101].








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  Template for the Flow Record is defined as shown below:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 2           |          Length = 40          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Template ID = 261        |        Field Count = 8        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   sourceIPv6Address = 27    |       Field Length = 16       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| destinationIPv6Address = 28 |       Field Length = 16       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| sourceTransportPort = 7     |       Field Length = 2        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| destinationTransportPort=11 |       Field Length = 2        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| protocolIdentifier = 4      |       Field Length = 1        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   octetTotalCount = 85      |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   packetTotalCount = 86     |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| subTemplateMultiList = 293  |     Field Length = 0XFFFF     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure 20: Encoding subTemplateMultiList, Template for Flow Record

  A subTemplateMultiList with semantic allOf is used to export the
  filtering and sampling attributes.  The Length field of the
  subTemplateMultiList is chosen to be encoded in three bytes even
  though it may be less than 255 octets.

  The Data Record is encoded as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Set ID = 261            |          Length = 73          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      sourceIPv6Address =        ...           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          2001:DB8::1                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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  |                   destinationIPv6Address =      ...           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              ...                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          2001:DB8::2                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  sourceTransportPort = 1025   | destinationTransportPort = 80 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | protocol = 6  |        octetTotalCount = 108000               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     ...       |        packetTotalCount = 120                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     ...       |      255      | Attributes List Length = 21   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |semantic=allOf | Filtering Template ID = 259   |Filtering Attr |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | ...Length = 9 |              selectorId = ...                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | ...  100      |selectorAlg = 5|  Sampling Template ID = 260   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Sampling Attributes Length=11 |         selectorId = ...      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  ...         15               |selectorAlg = 1|  Interval = 1 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Space = 99    |
  +-+-+-+-+-+-+-+-+

          Figure 21: Encoding subTemplateMultiList, Data Set

9.5.  Encoding an Options Template Set Using Structured Data

  As described in Section 5.3, consider a mediation function that must
  aggregate Data Records from different Observation Points.

  Say Observation Point 1 consists of one or more interfaces,
  Observation Points 2 and 3 consist of one or more linecards, and
  Observation Point 4 consists of one or more interfaces and one or
  more linecards.  Without structured data, a Template would have to be
  defined for every possible combination to interpret the data
  corresponding to each of the Observation Points.  However, with
  structured data, a basicList can be used to encode the list of
  interfaces and another basicList can be used to encode the list of
  linecards.






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  For the sake of simplicity, each Observation Point shown below has
  the IP address corresponding to the Router and an <interface> or
  <linecard> or <linecard and interface>.  This can very well be
  extended to include a list of interfaces and a list of linecards
  using basicLists as explained above.

     Observation Point 1: Router 1, (interface 1)
     Observation Point 2: Router 2, (linecard A)
     Observation Point 3: Router 3, (linecard B)
     Observation Point 4: Router 4, (linecard C, interface 2)

  The mediation function wishes to express this as a single Observation
  Point, in order to encode the PSAMP Selection Sequence Report
  Interpretation (SSRI).  Recall from [RFC5476] that the PSAMP
  Selection Sequence Report Interpretation consists of the following
  fields:

    Scope:     selectionSequenceId
    Non-Scope: one Information Element mapping the
               Observation Point
               selectorId (one or more)

  For example, the Observation Point detailed above may be encoded in a
  PSAMP Selection Sequence Report Interpretation as shown below:

   Selection Sequence 7 (Filter->Sampling):
    Observation Point: subTemplateMultiList.
     Router 1 (IP address = 192.0.2.11), (interface 1)
     Router 2 (IP address = 192.0.2.12), (linecard A)
     Router 3 (IP address = 192.0.2.13), (linecard B)
     Router 4 (IP address = 192.0.2.14), (linecard C, interface 2)
     selectorId: 5 (Filter, match IPv4SourceAddress 192.0.2.1)
     selectorId: 10 (Sampler, Random 1 out-of ten)

  The following Templates are defined to represent the PSAMP SSRI:
  Template for representing PSAMP SSRI: 262
  Template for representing interface: 263
  Template for representing linecard: 264
  Template for representing linecard and interface: 265












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      PSAMP SSRI (262)
          | (SelectionSequenceId)
          |
          +--- Observation Point 1 (263)
          |      (exporterIPv4Address)
          |      (Interface Id)
          |
          +--- Observation Point 2 and 3 (264)
          |      (exporterIPv4Address)
          |      (linecard)
          |
          +--- Observation Point 4 (265)
          |      (exporterIPv4Address)
          |      (linecard)
          |      (Interface Id)
          |
          | (selectorId 1)
          | (selectorId 2)

  Note that the example could further be improved with a basicList
  of selectorId if many Selector IDs have to be reported.

                   Figure 22: PSAMP SSRI to Be Encoded

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 3           |          Length = 26          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Template ID = 262      |         Field Count = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Scope Field Count =  1    |0|  selectionSequenceId = 301  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Scope 1 Length = 4      |0| subTemplateMultiList =  293 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Field Length = 0xFFFF     |0|      selectorId = 302       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Field Length = 4       |0|      selectorId = 302       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 23: Options Template Record for PSAMP SSRI Using
                         subTemplateMultiList

  A subTemplateMultiList with semantic allOf is used to encode the
  list of Observation Points.




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   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 2           |          Length = 16          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Template ID = 263      |         Field Count = 2       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   exporterIPv4Address = 8   |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   ingressInterface = 10     |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 24: PSAMP SSRI, Template Record for interface


   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 2           |          Length = 16          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Template ID = 264      |         Field Count = 2       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   exporterIPv4Address = 8   |         Field Length = 4      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|      lineCardId = 141       |         Field Length = 4      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 25: PSAMP SSRI, Template Record for linecard


   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 2           |          Length = 20          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Template ID = 265      |         Field Count = 3       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   exporterIPv4Address = 8   |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|      lineCardId = 141       |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|    ingressInterface = 10    |        Field Length = 4       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure 26: PSAMP SSRI, Template Record for linecard and interface






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  The PSAMP SSRI Data Set is represented as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Set ID = 262         |           Length = 68         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    selectionSequenceId = 7                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      255      | Observation Point List Len=49 |semantic=allOf |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     OP1 Template ID = 263     |        OP1 Length = 12        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Router 1 exporterIPv4Address = 192.0.2.11             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  OP1 ingressInterface = 1                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   OP2&OP3 Template ID = 264   |    OP2 & OP3 Length = 20      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Router 2 exporterIPv4Address = 192.0.2.12             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      OP2 lineCardId = A                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Router 3 exporterIPv4Address = 192.0.2.13             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      OP3 lineCardId = B                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     OP4 Template ID = 265     |         OP4 Length = 16       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Router 4 exporterIPv4Address = 192.0.2.14             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      OP4 lineCardId = C                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   OP4 ingressInterface = 2                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         selectorId = 5                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         selectorId = 10                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure 27: Example of a PSAMP SSRI Data Record, Encoded Using a
                        subTemplateMultiList

  Note that the Data Record above contains multiple instances of
  Template 264 to represent Observation Point 2 (Router2, linecard A)
  and Observation Point 3 (Router3, linecard B).  Instead, if a single
  Observation Point had both linecard A and linecard B, a basicList
  would be used to represent the list of linecards.



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10.  Relationship with the Other IPFIX Documents

10.1.  Relationship with Reducing Redundancy

  "Reducing Redundancy in IP Flow Information Export (IPFIX) and Packet
  Sampling (PSAMP) Reports" [RFC5473] describes a bandwidth saving
  method for exporting Flow or packet information using the IP Flow
  Information Export (IPFIX) protocol.

  It defines the commonPropertiesID Information Element for exporting
  Common Properties.

10.1.1.  Encoding Structured Data Element Using Common Properties

  When Structured Data Information Elements contain repeated elements,
  these elements may be replaced with a commonPropertiesID Information
  Element as specified in [RFC5473].  The replaced elements may include
  the basicList, subTemplateList, and subTemplateMultiList Information
  Elements.

  This technique might help reducing the bandwidth requirements for the
  export.  However, a detailed analysis of the gain has not been done;
  refer to Section 8.3 of [RFC5473] for further considerations.

10.1.2. Encoding Common Properties Elements with Structured Data
       Information Element

  Structured Data Information Element MAY be used to define a list of
  commonPropertiesID, as a replacement for the specifications in
  [RFC5473].

  Indeed, the example in Figures 1 and 2 of [RFC5473] can be encoded
  with the specifications in this document.

  +----------------+-------------+---------------------------+
  | sourceAddressA | sourcePortA |     <Flow1 information>   |
  +----------------+-------------+---------------------------+
  | sourceAddressA | sourcePortA |     <Flow2 information>   |
  +----------------+-------------+---------------------------+
  | sourceAddressA | sourcePortA |     <Flow3 information>   |
  +----------------+-------------+---------------------------+
  | sourceAddressA | sourcePortA |     <Flow4 information>   |
  +----------------+-------------+---------------------------+
  |      ...       |     ...     |            ...            |
  +----------------+-------------+---------------------------+

  Figure 28: Common and Specific Properties Exported Together
                             [RFC5473]



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  +------------------------+-----------------+-------------+
  | index for properties A | sourceAddressA  | sourcePortA |
  +------------------------+-----------------+-------------+
  |          ...           |      ...        |     ...     |
  +------------------------+-----------------+-------------+

  +------------------------+---------------------------+
  | index for properties A |     <Flow1 information>   |
  +------------------------+---------------------------+
  | index for properties A |     <Flow2 information>   |
  +------------------------+---------------------------+
  | index for properties A |     <Flow3 information>   |
  +------------------------+---------------------------+
  | index for properties A |     <Flow4 information>   |
  +------------------------+---------------------------+

  Figure 29: Common and Specific Properties Exported Separately
                    According to [RFC5473]


  +----------------+-------------+---------------------------+
  | sourceAddressA | sourcePortA |     <Flow1 information>   |
  +----------------+-------------+---------------------------+
                                 |     <Flow2 information>   |
                                 +---------------------------+
                                 |     <Flow3 information>   |
                                 +---------------------------+
                                 |     <Flow4 information>   |
                                 +---------------------------+
                                 |            ...            |
                                 +---------------------------+

   Figure 30: Common and Specific Properties Exported with
                Structured Data Information Element

  The example in Figure 28 could be encoded with a basicList if the
  <Flow information> represents a single Information Element, with a
  subTemplateList if the <Flow information> represents a Template
  Record, or with a subTemplateMultiList if the <Flow information> is
  composed of different Template Records.

  Using Structured Data Information Elements as a replacement for the
  techniques specified in "Reducing Redundancy in IP Flow Information
  Export (IPFIX) and Packet Sampling (PSAMP) Reports" [RFC5473] offers
  the advantage that a single Template Record is defined.  Hence, the
  Collector's job is simplified in terms of Template management and
  combining Template/Options Template Records.




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  However, it must be noted that using Structured Data Information
  Elements as a replacement for the techniques specified in "Reducing
  Redundancy in IP Flow Information Export (IPFIX) and Packet Sampling
  (PSAMP) Reports" only applies to simplified cases.  For example, the
  "Multiple Data Reduction" (Section 7.1 [RFC5473]) might be too
  complex to encode with Structured Data Information Elements.

10.2.  Relationship with Guidelines for IPFIX Testing

  [RFC5471] presents a list of tests for implementers of IP Flow
  Information Export (IPFIX) compliant Exporting Processes and
  Collecting Processes.

  Although [RFC5471] doesn't define any structured data element
  specific tests, the Structured Data Information Elements can be used
  in many of the [RFC5471] tests.

  The [RFC5471] series of test could be useful because the document
  specifies that every Information Element type should be tested.
  However, not all cases from this document are tested in [RFC5471].

  The following sections are especially noteworthy:

     3.2.1.  Transmission of Template with Fixed-Size Information
             Elements

        - each data type should be used in at least one test.  The new
          data types specified in Section 4.1 should be included in
          this test.

     3.2.2.  Transmission of Template with Variable-Length Information
             Elements

        - this test should be expanded to include Data Records
          containing variable length basicList, subTemplateList, and
          subTemplateMultiList Information Elements.

     3.3.1.  Enterprise-Specific Information Elements

        - this test should include the export of basicList,
          subTemplateList, and subTemplateMultiList Information
          Elements containing Enterprise-specific Information Elements,
          e.g., see the example in Figure 2.








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     3.3.3.  Multiple Instances of the Same Information Element in One
             Template

        - this test should verify that multiple instances of the
          basicList, subTemplateList, and subTemplateMultiList
          Information Elements are accepted.

     3.5.  Stress/Load Tests

        - since the structured data types defined here allow modeling
          of complex data structures, they may be useful for stress
          testing both Exporting Processes and Collecting Processes.

10.3.  Relationship with IPFIX Mediation Function

  The Structured Data Information Elements would be beneficial for the
  export of aggregated Data Records in mediation function, as was
  demonstrated with the example of the aggregated Observation Point in
  Section 5.3.

11.  IANA Considerations

  This document specifies several new IPFIX abstract data types, a new
  IPFIX Data Type Semantic, and several new Information Elements.

  Two new IPFIX registries have been created, and the existing IPFIX
  Information Element registry has been updated as detailed below.

11.1.  New Abstract Data Types

  Section 4.1 of this document specifies several new IPFIX abstract
  data types.  Per Section 6 of the IPFIX information model [RFC5102],
  new abstract data types can be added to the IPFIX information model
  in the IPFIX Information Element Data Types registry.

  Abstract data types that have been added to the IPFIX Information
  Element Data Types registry are listed below.

11.1.1.  basicList

  The type "basicList" represents a list of any Information Element
  used for single-valued data types.

11.1.2.  subTemplateList

  The type "subTemplateList" represents a list of a structured data
  type, where the data type of each list element is the same and
  corresponds with a single Template Record.



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11.1.3.  subTemplateMultiList

  The type "subTemplateMultiList" represents a list of structured data
  types, where the data types of the list elements can be different and
  correspond with different Template definitions.

11.2.  New Data Type Semantics

  Section 4.2 of this document specifies a new IPFIX Data Type
  Semantic.  Per Section 3.2 of the IPFIX information model [RFC5102],
  new data type semantics can be added to the IPFIX information model.
  Therefore, the IANA IPFIX informationElementSemantics registry
  [IANA-IPFIX], which contains all the data type semantics from Section
  3.2 of [RFC5102], has been augmented with the "list" value below.

11.2.1.  list

  A list is a structured data type, being composed of a sequence of
  elements, e.g., Information Element, Template Record.

11.3.  New Information Elements

  Section 4.3 of this document specifies several new Information
  Elements that have been created in the IPFIX Information Element
  registry [IANA-IPFIX].

  New Information Elements that have been added to the IPFIX
  Information Element registry are listed below.

11.3.1.  basicList

  Name: basicList
  Description:
  Specifies a generic Information Element with a basicList abstract
  data type.  Examples include a list of port numbers, and a list of
  interface indexes.
  Abstract Data Type: basicList
  Data Type Semantics: list
  ElementId: 291
  Status: current











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11.3.2. subTemplateList

  Name: subTemplateList
  Description:
  Specifies a generic Information Element with a subTemplateList
  abstract data type.
  Abstract Data Type: subTemplateList
  Data Type Semantics: list
  ElementId: 292
  Status: current

11.3.3. subTemplateMultiList

  Name: subTemplateMultiList
  Description:
  Specifies a generic Information Element with a
  subTemplateMultiList abstract data type.
  Abstract Data Type: subTemplateMultiList
  Data Type Semantics: list
  ElementId: 293
  Status: current

11.4.  New Structured Data Semantics

  Section 4.4 of this document specifies a series of new IPFIX
  structured data type semantics, which is expressed as an 8-bit value.
  This requires the creation of a new "IPFIX Structured Data Types
  Semantics" IPFIX subregistry [IANA-IPFIX].

  Entries may be added to this subregistry subject to a Standards
  Action [RFC5226].  Initially, this registry includes all the
  structured data type semantics listed below.

11.4.1.  undefined

  Name: undefined

  Description: The "undefined" structured data type semantic specifies
  that the semantic of list elements is not specified and that, if a
  semantic exists, then it is up to the Collecting Process to draw its
  own conclusions.  The "undefined" structured data type semantic is
  the default structured data type semantic.

  Value: 0xFF

  Reference: RFC 6313





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11.4.2.  noneOf

  Name: noneOf

  Description: The "noneOf" structured data type semantic specifies
  that none of the elements are actual properties of the Data Record.

  Value: 0x00

  Reference: RFC 6313

11.4.3.  exactlyOneOf

  Name: exactlyOneOf

  Description: The "exactlyOneOf" structured data type semantic
  specifies that only a single element from the structured data is an
  actual property of the Data Record.  This is equivalent to a logical
  XOR operation.

  Value: 0x01

  Reference: RFC 6313

11.4.4.  oneOrMoreOf

  Name: oneOrMoreOf

  Description: The "oneOrMoreOf" structured data type semantic
  specifies that one or more elements from the list in the structured
  data are actual properties of the Data Record.  This is equivalent to
  a logical OR operation.

  Value: 0x02

  Reference: RFC 6313

11.4.5.  allOf

  Name: allOf

  Description: The "allOf" structured data type semantic specifies that
  all of the list elements from the structured data are actual
  properties of the Data Record.

  Value: 0x03

  Reference: RFC 6313



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11.4.6.  ordered

  Name: ordered Description: The "ordered" structured data type
  semantic specifies that elements from the list in the structured data
  are ordered.

  Value: 0x04

  Reference: RFC 6313

12.  Security Considerations

  The addition of complex data types necessarily complicates the
  implementation of the Collector.  This could easily result in new
  security vulnerabilities (e.g., buffer overflows); this creates
  additional risk in cases where either Datagram Transport Layer
  Security (DTLS) is not used or if the Observation Point and Collector
  belong to different trust domains.  Otherwise, the same security
  considerations as for the IPFIX protocol [RFC5101] and the IPFIX
  information model [RFC5102] apply.

13.  References

13.1.  Normative References

  [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

  [RFC5101]    Claise, B., Ed., "Specification of the IP Flow
               Information Export (IPFIX) Protocol for the Exchange of
               IP Traffic Flow Information", RFC 5101, January 2008.

  [RFC5102]    Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
               Meyer, "Information Model for IP Flow Information
               Export", RFC 5102, January 2008.

  [RFC5226]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
               IANA Considerations Section in RFCs", BCP 26, RFC 5226,
               May 2008.

13.2.  Informative References

  [RFC3917]    Quittek, J., Zseby, T., Claise, B., and S. Zander,
               "Requirements for IP Flow Information Export (IPFIX)",
               RFC 3917, October 2004.






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  [RFC5103]    Trammell, B. and E. Boschi, "Bidirectional Flow Export
               Using IP Flow Information Export (IPFIX)", RFC 5103,
               January 2008.

  [RFC5470]    Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
               "Architecture for IP Flow Information Export", RFC 5470,
               March 2009.

  [RFC5471]    Schmoll, C., Aitken, P., and B. Claise, "Guidelines for
               IP Flow Information Export (IPFIX) Testing", RFC 5471,
               March 2009.

  [RFC5472]    Zseby, T., Boschi, E., Brownlee, N., and B. Claise, "IP
               Flow Information Export (IPFIX) Applicability", RFC
               5472, March 2009.

  [RFC5473]    Boschi, E., Mark, L., and B. Claise, "Reducing
               Redundancy in IP Flow Information Export (IPFIX) and
               Packet Sampling (PSAMP) Reports", RFC 5473, March 2009.

  [RFC5475]    Zseby, T., Molina, M., Duffield, N., Niccolini, S., and
               F. Raspall, "Sampling and Filtering Techniques for IP
               Packet Selection", RFC 5475, March 2009.

  [RFC5476]    Claise, B., Ed., Johnson, A., and J. Quittek, "Packet
               Sampling (PSAMP) Protocol Specifications", RFC 5476,
               March 2009.

  [RFC5477]    Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
               Carle, "Information Model for Packet Sampling Exports",
               RFC 5477, March 2009.

  [IANA-IPFIX] IANA, "IP Flow Information Export (IPFIX) Entities",
               <http://www.iana.org/>.

14.  Acknowledgements

  The authors would like to thank Zhipu Jin, Nagaraj Varadharajan,
  Brian Trammel, Atsushi Kobayashi, and Rahul Patel for their feedback,
  and Gerhard Muenz, for proofreading the document.











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Appendix A.  Additions to XML Specification of IPFIX Information
            Elements and Abstract Data Types

  This appendix contains additions to the machine-readable description
  of the IPFIX information model coded in XML in Appendices A and B in
  [RFC5102].  Note that this appendix is of informational nature, while
  the text in Section 4 (generated from this appendix) is normative.

  The following field definitions are appended to the IPFIX information
  model in Appendix A of [RFC5102].

  <field name="basicList"
          dataType="basicList"
          group="structured-data"
          dataTypeSemantics="List"
          elementId="291" applicability="all" status="current">
     <description>
       <paragraph>
          Represents a list of zero or more instances of
          any Information Element, primarily used for
          single-valued data types.  Examples include a list of port
          numbers, list of interface indexes, and a list of AS in a
          BGP AS-PATH.
       </paragraph>
     </description>
   </field>

   <field name="subTemplateList"
          dataType="subTemplateList"
          group="structured-data"
          dataTypeSemantics="List"
          elementId="292" applicability="all" status="current">
     <description>
       <paragraph>
          Represents a list of zero or more instances of a
          structured data type, where the data type of each list
          element is the same and corresponds with a single
          Template Record.  Examples include a structured data type
          composed of multiple pairs of ("MPLS label stack entry
          position", "MPLS label stack value"), a structured data
          type composed of performance metrics, and a structured data
          type composed of multiple pairs of IP address.
       </paragraph>
     </description>
   </field>






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   <field name="subTemplateMultiList"
          dataType="subTemplateMultiList"
          group="structured-data"
          dataTypeSemantics="List"
          elementId="293" applicability="all" status="current">
     <description>
       <paragraph>
         Represents a list of zero or more instances of
         structured data types, where the data type of each list
         element can be different and corresponds with
         different Template definitions.  Examples include, a
         structured data type composed of multiple access-list
         entries, where entries can be composed of different
         criteria types.
       </paragraph>
     </description>
   </field>

  The following structured data type semantic definitions are appended
  to the IPFIX information model in Appendix A of [RFC5102].

  <structuredDataTypeSemantics>
    <structuredDataTypeSemantic name="undefined" value="255">
      <description>
        <paragraph>
         The "undefined" structured data type semantic specifies
         that the semantic of list elements is not specified and
         that, if a semantic exists, then it is up to the
         Collecting Process to draw its own conclusions.  The
         "undefined" structured data type semantic is the default
         structured data type semantic.
        </paragraph>
      </description>
    </structuredDataTypeSemantic>

    <structuredDataTypeSemantic name="noneOf" value="0">
      <description>
        <paragraph>
         The "noneOf" structured data type semantic specifies
         that none of the elements are actual properties of the
         Data Record.
        </paragraph>
      </description>
    </structuredDataTypeSemantic>







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    <structuredDataTypeSemantic name="exactlyOneOf" value="1">
      <description>
        <paragraph>
         The "exactlyOneOf" structured data type semantic
         specifies that only a single element from the structured
         data is an actual property of the Data Record.  This is
         equivalent to a logical XOR operation.
        </paragraph>
      </description>
    </structuredDataTypeSemantic>

    <structuredDataTypeSemantic name="oneOrMoreOf" value="2">
      <description>
        <paragraph>
         The "oneOrMoreOf" structured data type semantic
         specifies that one or more elements from the list in the
         structured data are actual properties of the Data
         Record.  This is equivalent to a logical OR operation.
        </paragraph>
      </description>
    </structuredDataTypeSemantic>

    <structuredDataTypeSemantic name="allOf" value="3">
      <description>
        <paragraph>
         The "allOf" structured data type semantic specifies that
         all of the list elements from the structured data are
         actual properties of the Data Record.
        </paragraph>
      </description>
    </structuredDataTypeSemantic>

    <structuredDataTypeSemantic name="ordered" value="4">
      <description>
        <paragraph>
         The "ordered" structured data type semantic specifies
         that elements from the list in the structured data are
         ordered.
        </paragraph>
      </description>
    </structuredDataTypeSemantic>
  </structuredDataTypeSemantics>

  The following schema definitions are appended to the abstract data
  types defined in Appendix B of [RFC5102].  This schema and its
  namespace are registered by IANA at
  http://www.iana.org/assignments/xml-registry/schema/ipfix.xsd.




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<simpleType name="dataType">
  <restriction base="string">
    <enumeration value="basicList">
      <annotation>
        <documentation>
          Represents a list of zero or more instances of
          any Information Element, primarily used for
          single-valued data types.  Examples include a list of port
          numbers, a list of interface indexes, and a list of AS in a
          BGP AS-PATH.
        </documentation>
      </annotation>
    </enumeration>
    <enumeration value="subTemplateList">
      <annotation>
        <documentation>
          Represents a list of zero or more instances of a
          structured data type, where the data type of each list
          element is the same and corresponds with a single
          Template Record.  Examples include a structured data type
          composed of multiple pairs of ("MPLS label stack entry
          position", "MPLS label stack value"), a structured
          data type composed of performance metrics, and a
          structured data type composed of multiple pairs of IP
          address.
        </documentation>
      </annotation>
    </enumeration>
    <enumeration value="subTemplateMultiList">
      <annotation>
        <documentation>
          Represents a list of zero or more instances of
          structured data types, where the data type of each
          list element can be different and corresponds with
          different Template definitions.  An example is a
          structured data type composed of multiple
          access-list entries, where entries can be
          composed of different criteria types.
        </documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>








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<simpleType name="dataTypeSemantics">
  <restriction base="string">
    <enumeration value="List">
      <annotation>
        <documentation>
          Represents an arbitrary-length sequence of structured
          data elements, either composed of regular Information
          Elements or composed of data conforming to a Template
          Record.
        </documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>

<complexType name="structuredDataTypeSemantics">
  <sequence>
    <element name="structuredDataTypeSemantic"
             minOccurs="1" maxOccurs="unbounded">
      <complexType>
        <sequence>
          <element name="description" type="text"/>
        </sequence>
        <attribute name="name" type="string" use="required"/>
        <attribute name="value" type="unsignedByte" use="required"/>
      </complexType>
    </element>
  </sequence>
</complexType>

<element name="structuredDataTypeSemantics"
         type="structuredDataTypeSemantics">
  <annotation>
    <documentation>
      Structured data type semantics express the relationship
      among multiple list elements in a structured data
      Information Element.
    </documentation>
  </annotation>
</element>











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Appendix B.  Encoding IPS Alert Using Structured Data Information
            Elements

  In this section, an IPS alert example is used to demonstrate how
  complex data and multiple levels of hierarchy can be encoded using
  Structured Data Information Elements.  Also, this example
  demonstrates how a basicList of subTemplateLists can be used to
  represent semantics at multiple levels in the hierarchy.

  An IPS alert consists of the following mandatory attributes:
  signatureId, protocolIdentifier, and riskRating.  It can also contain
  zero or more participants, and each participant can contain zero or
  more attackers and zero or more targets.  An attacker contains the
  attributes sourceIPv4Address and applicationId, and a target contains
  the attributes destinationIPv4Address and applicationId.

  Note that the signatureId and riskRating Information Element fields
  are created for these examples only; the Field IDs are shown as N/A.
  The signatureId helps to uniquely identify the IPS signature that
  triggered the alert.  The riskRating identifies the potential risk,
  on a scale of 0-100 (100 being most serious), of the traffic that
  triggered the alert.

  Consider the example described in case study 2 of Section 5.6. The
  IPS alert contains participants encoded as a subTemplateList with
  semantic allOf.  Each participant uses a basicList of
  subTemplateLists to represent attackers and targets.  For the sake of
  simplicity, the alert has two participants P1 and P2.  In participant
  P1, attacker A1 or A2 attacks target T1.  In participant P2, attacker
  A3 attacks targets T2 and T3.





















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  Participant P1:

       (basicList, allOf,

             (subTemplateList, exactlyOneOf, attacker A1, A2)

             (subTemplateList, undefined, target T1)

       )

  Participant P2:

       (basicList, allOf,

             (subTemplateList, undefined, attacker A3,
             (subTemplateList, allOf, targets T2, T3)

       )

  Alert :

          (subTemplateList, allOf, Participant P1, Participant P2)

   ------------------------------------------------------------------
         |        |        |             participant
   sigId |protocol| risk   |      attacker   |      target
         |   Id   | Rating |    IP   | appId |    IP      | appId
   ------------------------------------------------------------------
   1003     17      10      192.0.2.3  103    192.0.2.103    3001
                            192.0.2.4  104

                            192.0.2.5  105    192.0.2.104    4001
                                              192.0.2.105    5001
   ------------------------------------------------------------------

   Participant P1 contains:
   Attacker A1: (IP, appId)=(192.0.2.3, 103)
   Attacker A2: (IP, appId)=(192.0.2.4, 104)
   Target T1: (IP, appId)= (192.0.2.103, 3001)

   Participant P2 contains:
   Attacker A3: (IP, appId) = (192.0.2.5, 105)
   Target T2: (IP, appId)= (192.0.2.104, 4001)
   Target T3: (IP, appId)= (192.0.2.105, 5001)

   To represent an alert, the following Templates are defined:
   Template for target (268)
   Template for attacker (269)



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   Template for participant (270)
   Template for alert (271)

        alert (271)
        |  (signatureId)
        |  (protocolIdentifier)
        |  (riskRating)
        |
        +------- participant (270)
                 |
                 +------- attacker (269)
                 |           (sourceIPv4Address)
                 |           (applicationId)
                 |
                 +------- target (268)
                          |  (destinationIPv4Address)
                          |  (applicationId)

  Note that the attackers are always composed of a single
  applicationId, while the targets typically have multiple
  applicationIds; for the sake of simplicity, this example shows only
  one applicationId in the target.

  Template Record for target, with the Template ID 268:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Set ID = 2             |      Length = 16 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 268       |       Field Count = 2         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| destinationIPv4Address = 12 |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|       applicationId = 95    |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 31: Encoding IPS Alert, Template for Target













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   Template Record for attacker, with the Template ID 269:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 2            |      Length = 16 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 269       |       Field Count = 2         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    sourceIPv4Address = 8    |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     applicationId = 95      |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 32: Encoding IPS Alert, Template for Attacker

   Template Record for participant, with the Template ID 270:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 2            |      Length = 12 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 270       |       Field Count = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|       basicList = 291       |     Field Length = 0xFFFF     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 33: Encoding IPS Alert, Template for Participant

  The Template Record for the participant has one basicList Information
  Element, which is a list of subTemplateLists of attackers and
  targets.


















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  Template Record for IPS alert, with the Template ID 271:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 2            |      Length = 24 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 271       |       Field Count = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    signatureId = N/A        |       Field Length = 2        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   protocolIdentifier = 4    |       Field Length = 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     riskRating = N/A        |       Field Length = 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     subTemplateList = 292   |     Field Length = 0xFFFF     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 34: Encoding IPS Alert, Template for IPS Alert

  The subTemplateList in the alert Template Record contains a list of
  participants.

  The Length of basicList and subTemplateList are encoded in three
  bytes even though they may be less than 255 octets.

  The Data Set is represented as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Set ID = 271         |         Length = 102          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      signatureId = 1003       | protocolId=17 | riskRating=10 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      255      |participant List Length  = 91  |semantic=allOf |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | participant Template ID = 270 |     255       | P1 List Len = |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      41       | semantic=allOf|    P1 List Field ID = 292     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | P1 List Field ID Len = 0xFFFF |      255      |P1 attacker ...|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | List Len = 19 |sem=exactlyOne | P1 attacker Template ID = 269 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          P1 attacker A1 sourceIPv4Address = 192.0.2.3         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               P1 attacker A1 applicationId = 103              |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          P1 attacker A2 sourceIPv4Address = 192.0.2.4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               P1 attacker A2 applicationId = 104              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      255      | P1 target List Len = 11       | sem=undefined |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  P1 target Template ID = 268  | P1 target T1 destinationIPv4  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ... Address = 192.0.2.103     |P1 target T1 applicationId =...|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ...       3001                |      255      | P2 List Len = |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ...  41       | semantic=allOf|    P2 List Field ID = 292     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | P2 List Field ID Len = 0xFFFF |      255      |P2 attacker ...|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | List Len = 11 | sem=undefined | P2 attacker Template ID = 269 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          P2 attacker A3 sourceIPv4Address = 192.0.2.5         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               P2 attacker A3 applicationId = 105              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      255      |    P2 target List Len = 19    |semantic=allOf |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  P2 target Template ID = 268  | P2 target T2 destinationIPv4  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ... Address = 192.0.2.104     |P2 target T2 applicationId =...|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ...       4001                | P2 target T3 destinationIPv4  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ... Address = 192.0.2.105     |P2 target T3 applicationId =...|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ...       5001                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Note: sem=exactlyOne represents semantic=exactlyOneOf

                 Figure 35: Encoding IPS Alert, Data Set












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Authors' Addresses

  Benoit Claise
  Cisco Systems, Inc.
  De Kleetlaan 6a b1
  Diegem 1813
  Belgium

  Phone: +32 2 704 5622
  EMail: [email protected]


  Gowri Dhandapani
  Cisco Systems, Inc.
  13615 Dulles Technology Drive
  Herndon, Virginia 20171
  United States

  Phone: +1 408 853 0480
  EMail: [email protected]


  Paul Aitken
  Cisco Systems, Inc.
  96 Commercial Quay
  Commercial Street
  Edinburgh, EH6 6LX
  United Kingdom

  Phone: +44 131 561 3616
  EMail: [email protected]


  Stan Yates
  Cisco Systems, Inc.
  7100-8 Kit Creek Road
  PO Box 14987
  Research Triangle Park, North Carolina 27709-4987
  United States

  Phone: +1 919 392 8044
  EMail: [email protected]









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