Network Working Group                                     B. Claise, Ed.
Request for Comments: 5101                           Cisco Systems, Inc.
Category: Standards Track                                   January 2008


  Specification of the IP Flow Information Export (IPFIX) Protocol
           for the Exchange of IP Traffic Flow Information

Status of This Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Abstract

  This document specifies the IP Flow Information Export (IPFIX)
  protocol that serves for transmitting IP Traffic Flow information
  over the network.  In order to transmit IP Traffic Flow information
  from an Exporting Process to an information Collecting Process, a
  common representation of flow data and a standard means of
  communicating them is required.  This document describes how the
  IPFIX Data and Template Records are carried over a number of
  transport protocols from an IPFIX Exporting Process to an IPFIX
  Collecting Process.

Table of Contents

  1. Introduction ....................................................3
     1.1. IPFIX Documents Overview ...................................4
  2. Terminology .....................................................4
     2.1. Terminology Summary Table ..................................9
  3. IPFIX Message Format ...........................................10
     3.1. Message Header Format .....................................11
     3.2. Field Specifier Format ....................................13
     3.3. Set and Set Header Format .................................14
          3.3.1. Set Format .........................................14
          3.3.2. Set Header Format ..................................15
     3.4. Record Format .............................................16
          3.4.1. Template Record Format .............................16
          3.4.2. Options Template Record Format .....................18
                 3.4.2.1. Scope .....................................19
                 3.4.2.2. Options Template Record Format ............20
          3.4.3. Data Record Format .................................22
  4. Specific Reporting Requirements ................................23
     4.1. The Metering Process Statistics Option Template ...........23



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     4.2. The Metering Process Reliability Statistics Option
          Template ..................................................24
     4.3. The Exporting Process Reliability Statistics
          Option Template ...........................................25
     4.4. The Flow Keys Option Template .............................26
  5. IPFIX Message Header "Export Time" and Flow Record Time ........27
  6. Linkage with the Information Model .............................28
     6.1. Encoding of IPFIX Data Types ..............................28
          6.1.1. Integral Data Types ................................28
          6.1.2. Address Types ......................................28
          6.1.3. float32 ............................................28
          6.1.4. float64 ............................................28
          6.1.5. boolean ............................................28
          6.1.6. string and octetarray ..............................28
          6.1.7. dateTimeSeconds ....................................29
          6.1.8. dateTimeMilliseconds ...............................29
          6.1.9. dateTimeMicroseconds ...............................29
          6.1.10.dateTimeNanoseconds.................................29
     6.2. Reduced Size Encoding of Integer and Float Types ..........29
  7. Variable-Length Information Element ............................30
  8. Template Management ............................................31
  9. The Collecting Process's Side ..................................34
  10. Transport Protocol ............................................36
     10.1. Transport Compliance and Transport Usage .................36
     10.2. SCTP .....................................................37
          10.2.1. Congestion Avoidance ..............................37
          10.2.2. Reliability .......................................37
          10.2.3. MTU ...............................................37
          10.2.4. Exporting Process .................................38
                 10.2.4.1. Association Establishment ................38
                 10.2.4.2. Association Shutdown .....................38
                 10.2.4.3. Stream ...................................38
                 10.2.4.4. Template Management ......................39
          10.2.5. Collecting Process ................................39
          10.2.6. Failover ..........................................39
     10.3. UDP ......................................................39
          10.3.1. Congestion Avoidance ..............................39
          10.3.2. Reliability .......................................40
          10.3.3. MTU ...............................................40
          10.3.4. Port Numbers ......................................40
          10.3.5. Exporting Process .................................40
          10.3.6. Template Management ...............................40
          10.3.7. Collecting Process ................................41
          10.3.8. Failover ..........................................42
     10.4. TCP ......................................................42
          10.4.1. Connection Management .............................42
                 10.4.1.1. Connection Establishment .................42
                 10.4.1.2. Graceful Connection Release ..............43



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                 10.4.1.3. Restarting Interrupted Connections .......43
                 10.4.1.4. Failover .................................43
          10.4.2. Data Transmission .................................43
                 10.4.2.1. IPFIX Message Encoding ...................43
                 10.4.2.2. Template Management ......................44
                 10.4.2.3. Congestion Handling and Reliability ......44
          10.4.3. Collecting Process ................................45
  11. Security Considerations .......................................46
     11.1. Applicability of TLS and DTLS ............................47
     11.2. Usage ....................................................48
     11.3. Authentication ...........................................48
     11.4. Protection against DoS Attacks ...........................48
     11.5. When DTLS or TLS Is Not an Option ........................50
     11.6. Logging an IPFIX Attack ..................................50
     11.7. Securing the Collector ...................................51
  12. IANA Considerations ...........................................51
  Appendix A. IPFIX Encoding Examples ...............................52
     A.1. Message Header Example.....................................52
     A.2. Template Set Examples......................................53
          A.2.1. Template Set Using IETF-Specified Information
                 Elements ...........................................53
          A.2.2. Template Set Using Enterprise-Specific Information
                 Elements ...........................................53
     A.3. Data Set Example ..........................................55
     A.4. Options Template Set Examples .............................56
          A.4.1. Options Template Set Using IETF-Specified
                 Information Elements ...............................56
          A.4.2. Options Template Set Using Enterprise-Specific
                 Information Elements ...............................56
          A.4.3. Options Template Set Using an Enterprise-Specific
                 Scope ..............................................57
          A.4.4. Data Set Using an Enterprise-Specific Scope ........58
     A.5. Variable-Length Information Element Examples ..............59
          A.5.1. Example of Variable-Length Information Element
                 with Length Inferior to 255 Octets .................59
          A.5.2. Example of Variable-Length Information Element
                 with Length 255 to 65535 Octets ....................59
  References ........................................................59
     Normative References ...........................................59
     Informative References .........................................60
  Acknowledgments ...................................................61

1.  Introduction

  A data network with IP traffic primarily consists of IP flows passing
  through the network elements.  It is often interesting, useful, or
  even required to have access to information about these flows that
  pass through the network elements for administrative or other



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  purposes.  The IPFIX Collecting Process should be able to receive the
  flow information passing through multiple network elements within the
  data network.  This requires uniformity in the method of representing
  the flow information and the means of communicating the flows from
  the network elements to the collection point.  This document
  specifies the protocol to achieve these aforementioned requirements.
  This document specifies in detail the representation of different
  flows, the additional data required for flow interpretation, packet
  format, transport mechanisms used, security concerns, etc.

1.1.  IPFIX Documents Overview

  The IPFIX protocol 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 [IPFIX-ARCH], per the requirements defined in
  [RFC3917].  This document specifies how IPFIX data records and
  templates are carried via a number of transport protocols 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 [RFC5102].
  Finally, [IPFIX-AS] describes what type of applications can use the
  IPFIX protocol and how they can use the information provided.  It
  furthermore shows how the IPFIX framework relates to other
  architectures and frameworks.

2.  Terminology

  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].

  The definitions of the basic terms like IP Traffic Flow, Exporting
  Process, Collecting Process, Observation Points, etc.  are
  semantically identical to those found in the IPFIX requirements
  document [RFC3917].  Some of the terms have been expanded for more
  clarity when defining the protocol.  Additional terms required for
  the protocol have also been defined.  Definitions in this document
  and in [IPFIX-ARCH] are equivalent, except that definitions that are
  only relevant to the IPFIX protocol only appear here.

  The terminology summary table in Section 2.1 gives a quick overview
  of the relationships between some of the different terms defined.








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  Observation Point

     An Observation Point is a location in the network where IP packets
     can be observed.  Examples include: a line to which a probe is
     attached, a shared medium, such as an Ethernet-based LAN, a single
     port of a router, or a set of interfaces (physical or logical) of
     a router.

     Note that every Observation Point is associated with an
     Observation Domain (defined below), and that one Observation Point
     may be a superset of several other Observation Points.  For
     example, one Observation Point can be an entire line card.  That
     would be the superset of the individual Observation Points at the
     line card's interfaces.

  Observation Domain

     An Observation Domain is the largest set of Observation Points for
     which Flow information can be aggregated by a Metering Process.
     For example, a router line card may be an Observation Domain if it
     is composed of several interfaces, each of which is an Observation
     Point.  In the IPFIX Message it generates, the Observation Domain
     includes its Observation Domain ID, which is unique per Exporting
     Process.  That way, the Collecting Process can identify the
     specific Observation Domain from the Exporter that sends the IPFIX
     Messages.  Every Observation Point is associated with an
     Observation Domain.  It is RECOMMENDED that Observation Domain IDs
     also be unique per IPFIX Device.

  IP Traffic Flow or Flow

     There are several definitions of the term 'flow' being used by the
     Internet community.  Within the context of IPFIX we use the
     following definition:

     A Flow is defined as a set of IP packets passing an Observation
     Point in the network during a certain time interval.  All packets
     belonging to a particular Flow have a set of common properties.
     Each property is defined as the result of applying a function to
     the values of:

        1. one or more packet header fields (e.g., destination IP
           address), transport header fields (e.g., destination port
           number), or application header fields (e.g., RTP header
           fields [RFC3550]).

        2. one or more characteristics of the packet itself (e.g.,
           number of MPLS labels, etc...).



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        3. one or more of fields derived from packet treatment (e.g.,
           next hop IP address, the output interface, etc...).

     A packet is defined as belonging to a Flow if it completely
     satisfies all the defined properties of the Flow.

     This definition covers the range from a Flow containing all
     packets observed at a network interface to a Flow consisting of
     just a single packet between two applications.  It includes
     packets selected by a sampling mechanism.

  Flow Key

     Each of the fields that:

     1.  belong to the packet header (e.g., destination IP address),

     2.  are a property of the packet itself (e.g., packet length),

     3.  are derived from packet treatment (e.g., Autonomous System
         (AS) number),

     and that are used to define a Flow are termed Flow Keys.

  Flow Record

     A Flow Record contains information about a specific Flow that was
     observed at an Observation Point.  A Flow Record contains measured
     properties of the Flow (e.g., the total number of bytes for all
     the Flow's packets) and usually characteristic properties of the
     Flow (e.g., source IP address).

  Metering Process

     The Metering Process generates Flow Records.  Inputs to the
     process are packet headers and characteristics observed at an
     Observation Point, and packet treatment at the Observation Point
     (for example, the selected output interface).

     The Metering Process consists of a set of functions that includes
     packet header capturing, timestamping, sampling, classifying, and
     maintaining Flow Records.

     The maintenance of Flow Records may include creating new records,
     updating existing ones, computing Flow statistics, deriving
     further Flow properties, detecting Flow expiration, passing Flow
     Records to the Exporting Process, and deleting Flow Records.




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  Exporting Process

     The Exporting Process sends Flow Records to one or more Collecting
     Processes.  The Flow Records are generated by one or more Metering
     Processes.

  Exporter

     A device that hosts one or more Exporting Processes is termed an
     Exporter.

  IPFIX Device

     An IPFIX Device hosts at least one Exporting Process.  It may host
     further Exporting Processes and arbitrary numbers of Observation
     Points and Metering Processes.

  Collecting Process

     A Collecting Process receives Flow Records from one or more
     Exporting Processes.  The Collecting Process might process or
     store received Flow Records, but such actions are out of scope for
     this document.

  Collector

     A device that hosts one or more Collecting Processes is termed a
     Collector.

  Template

     A Template is an ordered sequence of <type, length> pairs used to
     completely specify the structure and semantics of a particular set
     of information that needs to be communicated from an IPFIX Device
     to a Collector.  Each Template is uniquely identifiable by means
     of a Template ID.

  IPFIX Message

     An IPFIX Message is a message originating at the Exporting Process
     that carries the IPFIX records of this Exporting Process and whose
     destination is a Collecting Process.  An IPFIX Message is
     encapsulated at the transport layer.








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  Message Header

     The Message Header is the first part of an IPFIX Message, which
     provides basic information about the message, such as the IPFIX
     version, length of the message, message sequence number, etc.

  Template Record

     A Template Record defines the structure and interpretation of
     fields in a Data Record.

  Data Record

     A Data Record is a record that contains values of the parameters
     corresponding to a Template Record.

  Options Template Record

     An Options Template Record is a Template Record that defines the
     structure and interpretation of fields in a Data Record, including
     defining how to scope the applicability of the Data Record.

  Set

     Set is a generic term for a collection of records that have a
     similar structure.  In an IPFIX Message, one or more Sets follow
     the Message Header.

     There are three different types of Sets: Template Set, Options
     Template Set, and Data Set.

  Template Set

     A Template Set is a collection of one or more Template Records
     that have been grouped together in an IPFIX Message.

  Options Template Set

     An Options Template Set is a collection of one or more Options
     Template Records that have been grouped together in an IPFIX
     Message.

  Data Set

     A Data Set is one or more Data Records, of the same type, that are
     grouped together in an IPFIX Message.  Each Data Record is
     previously defined by a Template Record or an Options Template
     Record.



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  Information Element

     An Information Element is a protocol and encoding-independent
     description of an attribute that may appear in an IPFIX Record.
     The IPFIX information model [RFC5102] defines the base set of
     Information Elements for IPFIX.  The type associated with an
     Information Element indicates constraints on what it may contain
     and also determines the valid encoding mechanisms for use in
     IPFIX.

  Transport Session

     In Stream Control Transmission Protocol (SCTP), the transport
     session is known as the SCTP association, which is uniquely
     identified by the SCTP endpoints [RFC4960]; in TCP, the transport
     session is known as the TCP connection, which is uniquely
     identified by the combination of IP addresses and TCP ports used.
     In UDP, the transport session is known as the UDP session, which
     is uniquely identified by the combination of IP addresses and UDP
     ports used.

2.1.  Terminology Summary Table

  +------------------+---------------------------------------------+
  |                  |                 contents                    |
  |                  +--------------------+------------------------+
  |       Set        |      Template      |         record         |
  +------------------+--------------------+------------------------+
  |     Data Set     |          /         |     Data Record(s)     |
  +------------------+--------------------+------------------------+
  |   Template Set   | Template Record(s) |           /            |
  +------------------+--------------------+------------------------+
  | Options Template | Options Template   |           /            |
  |       Set        | Record(s)          |                        |
  +------------------+--------------------+------------------------+

  Figure A: Terminology Summary Table

  A Data Set is composed of Data Record(s).  No Template Record is
  included.  A Template Record or an Options Template Record defines
  the Data Record.

  A Template Set contains only Template Record(s).

  An Options Template Set contains only Options Template Record(s).






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3.  IPFIX Message Format

  An IPFIX Message consists of a Message Header, followed by one or
  more Sets.  The Sets can be any of the possible three types: Data
  Set, Template Set, or Options Template Set.

  The format of the IPFIX Message is shown in Figure B.

  +----------------------------------------------------+
  | Message Header                                     |
  +----------------------------------------------------+
  | Set                                                |
  +----------------------------------------------------+
  | Set                                                |
  +----------------------------------------------------+
    ...
  +----------------------------------------------------+
  | Set                                                |
  +----------------------------------------------------+

  Figure B: IPFIX Message Format

  The Exporter MUST code all binary integers of the Message Header and
  the different Sets in network-byte order (also known as the
  big-endian byte ordering).

  Following are some examples of IPFIX Messages:

  1. An IPFIX Message consisting of interleaved Template, Data, and
     Options Template Sets -- A newly created Template is exported as
     soon as possible.  So, if there is already an IPFIX Message with a
     Data Set that is being prepared for export, the Template and
     Option Template Sets are interleaved with this information,
     subject to availability of space.

  +--------+--------------------------------------------------------+
  |        | +----------+ +---------+     +-----------+ +---------+ |
  |Message | | Template | | Data    |     | Options   | | Data    | |
  | Header | | Set      | | Set     | ... | Template  | | Set     | |
  |        | |          | |         |     | Set       | |         | |
  |        | +----------+ +---------+     +-----------+ +---------+ |
  +--------+--------------------------------------------------------+

  Figure C: IPFIX Message, Example 1







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  2. An IPFIX Message consisting entirely of Data Sets -- After the
     appropriate Template Records have been defined and transmitted to
     the Collecting Process, the majority of IPFIX Messages consist
     solely of Data Sets.

  +--------+----------------------------------------------+
  |        | +---------+     +---------+      +---------+ |
  |Message | | Data    |     | Data    |      | Data    | |
  | Header | | Set     | ... | Set     | ...  | Set     | |
  |        | +---------+     +---------+      +---------+ |
  +--------+----------------------------------------------+

  Figure D: IPFIX Message, Example 2

  3. An IPFIX Message consisting entirely of Template and Options
     Template Sets.

  +--------+-------------------------------------------------+
  |        | +----------+     +----------+      +----------+ |
  |Message | | Template |     | Template |      | Options  | |
  | Header | | Set      | ... | Set      | ...  | Template | |
  |        | |          |     |          |      | Set      | |
  |        | +----------+     +----------+      +----------+ |
  +--------+-------------------------------------------------+

  Figure E: IPFIX Message, Example 3

3.1.  Message Header Format

  The format of the IPFIX Message Header is shown in Figure F.

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Version Number          |            Length             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           Export Time                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                       Sequence Number                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Observation Domain ID                      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure F: IPFIX Message Header Format







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  Message Header Field Descriptions:

  Version

     Version of Flow Record format exported in this message.  The value
     of this field is 0x000a for the current version, incrementing by
     one the version used in the NetFlow services export version 9
     [RFC3954].

  Length

     Total length of the IPFIX Message, measured in octets, including
     Message Header and Set(s).

  Export Time

     Time, in seconds, since 0000 UTC Jan 1, 1970, at which the IPFIX
     Message Header leaves the Exporter.

  Sequence Number

     Incremental sequence counter modulo 2^32 of all IPFIX Data Records
     sent on this PR-SCTP stream from the current Observation Domain by
     the Exporting Process.  Check the specific meaning of this field
     in the subsections of Section 10 when UDP or TCP is selected as
     the transport protocol.  This value SHOULD be used by the
     Collecting Process to identify whether any IPFIX Data Records have
     been missed.  Template and Options Template Records do not
     increase the Sequence Number.

  Observation Domain ID

     A 32-bit identifier of the Observation Domain that is locally
     unique to the Exporting Process.  The Exporting Process uses the
     Observation Domain ID to uniquely identify to the Collecting
     Process the Observation Domain that metered the Flows.  It is
     RECOMMENDED that this identifier also be unique per IPFIX Device.
     Collecting Processes SHOULD use the Transport Session and the
     Observation Domain ID field to separate different export streams
     originating from the same Exporting Process.  The Observation
     Domain ID SHOULD be 0 when no specific Observation Domain ID is
     relevant for the entire IPFIX Message, for example, when exporting
     the Exporting Process Statistics, or in case of a hierarchy of
     Collectors when aggregated Data Records are exported.







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3.2.  Field Specifier Format

  Vendors need the ability to define proprietary Information Elements,
  because, for example, they are delivering a pre-standards product, or
  the Information Element is, in some way, commercially sensitive.
  This section describes the Field Specifier format for both
  IETF-specified Information Elements [RFC5102] and enterprise-specific
  Information Elements.

  The Information Elements are identified by the Information Element
  identifier.  When the Enterprise bit is set to 0, the corresponding
  Information Element identifier will report an IETF-specified
  Information Element, and the Enterprise Number MUST NOT be present.
  When the Enterprise bit is set to 1, the corresponding Information
  Element identifier will report an enterprise-specific Information
  Element; the Enterprise Number MUST be present.  An example of this
  is shown in Section A.4.2.

  The Field Specifier format is shown in Figure G.

  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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |E|  Information Element ident. |        Field Length           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      Enterprise Number                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure G: Field Specifier Format

  Where:

  E

     Enterprise bit.  This is the first bit of the Field Specifier.  If
     this bit is zero, the Information Element Identifier identifies an
     IETF-specified Information Element, and the four-octet Enterprise
     Number field MUST NOT be present.  If this bit is one, the
     Information Element identifier identifies an enterprise-specific
     Information Element, and the Enterprise Number filed MUST be
     present.

  Information Element identifier

     A numeric value that represents the type of Information Element.
     Refer to [RFC5102].





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  Field Length

     The length of the corresponding encoded Information Element, in
     octets.  Refer to [RFC5102].  The field length may be smaller than
     the definition in [RFC5102] if the reduced size encoding is used
     (see Section 6.2).  The value 65535 is reserved for variable-
     length Information Elements (see Section 7).

  Enterprise Number

     IANA enterprise number [PEN] of the authority defining the
     Information Element identifier in this Template Record.

3.3.  Set and Set Header Format

  A Set is a generic term for a collection of records that have a
  similar structure.  There are three different types of Sets: Template
  Sets, Options Template Sets, and Data Sets.  Each of these Sets
  consists of a Set Header and one or more records.  The Set Format and
  the Set Header Format are defined in the following sections.

3.3.1.  Set Format

  A Set has the format shown in Figure H.  The record types can be
  either Template Records, Options Template Records, or Data Records.
  The record types MUST NOT be mixed within a Set.

  +--------------------------------------------------+
  | Set Header                                       |
  +--------------------------------------------------+
  | record                                           |
  +--------------------------------------------------+
  | record                                           |
  +--------------------------------------------------+
   ...
  +--------------------------------------------------+
  | record                                           |
  +--------------------------------------------------+
  | Padding (opt.)                                   |
  +--------------------------------------------------+

  Figure H: Set Format

  The Set Field Definitions are as follows:

  Set Header

     The Set Header Format is defined in Section 3.3.2.



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  Record

     One of the record Formats: Template Record, Options Template
     Record, or Data Record Format.

  Padding

     The Exporting Process MAY insert some padding octets, so that the
     subsequent Set starts at an aligned boundary.  For security
     reasons, the padding octet(s) MUST be composed of zero (0) valued
     octets.  The padding length MUST be shorter than any allowable
     record in this Set.  If padding of the IPFIX Message is desired in
     combination with very short records, then the padding Information
     Element 'paddingOctets' [RFC5102] can be used for padding records
     such that their length is increased to a multiple of 4 or 8
     octets.  Because Template Sets are always 4-octet aligned by
     definition, padding is only needed in case of other alignments
     e.g., on 8-octet boundaries.

3.3.2.  Set Header Format

  Every Set contains a common header.  This header is defined in Figure
  I.

   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               |          Length               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure I: Set Header Format

  The Set Header Field Definitions are as follows:

  Set ID

     Set ID value identifies the Set.  A value of 2 is reserved for the
     Template Set.  A value of 3 is reserved for the Option Template
     Set.  All other values from 4 to 255 are reserved for future use.
     Values above 255 are used for Data Sets.  The Set ID values of 0
     and 1 are not used for historical reasons [RFC3954].

  Length

     Total length of the Set, in octets, including the Set Header, all
     records, and the optional padding.  Because an individual Set MAY
     contain multiple records, the Length value MUST be used to
     determine the position of the next Set.



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3.4.   Record Format

  IPFIX defines three record formats, defined in the next sections: the
  Template Record Format, the Options Template Record Format, and the
  Data Record Format.

3.4.1.  Template Record Format

  One of the essential elements in the IPFIX record format is the
  Template Record.  Templates greatly enhance the flexibility of the
  record format because they allow the Collecting Process to process
  IPFIX Messages without necessarily knowing the interpretation of all
  Data Records.  A Template Record contains any combination of
  IANA-assigned and/or enterprise-specific Information Elements
  identifiers.

  The format of the Template Record is shown in Figure J.  It consists
  of a Template Record Header and one or more Field Specifiers.  The
  definition of the Field Specifiers is given in Figure G above.

  +--------------------------------------------------+
  | Template Record Header                           |
  +--------------------------------------------------+
  | Field Specifier                                  |
  +--------------------------------------------------+
  | Field Specifier                                  |
  +--------------------------------------------------+
   ...
  +--------------------------------------------------+
  | Field Specifier                                  |
  +--------------------------------------------------+

  Figure J: Template Record Format

  The format of the Template Record Header is shown in Figure K.

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Template ID (> 255)      |         Field Count           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure K: Template Record Header Format








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  The Template Record Header Field Definitions are as follows:

  Template ID

     Each of the newly generated Template Records is given a unique
     Template ID.  This uniqueness is local to the Transport Session
     and Observation Domain that generated the Template ID.  Template
     IDs 0-255 are reserved for Template Sets, Options Template Sets,
     and other reserved Sets yet to be created.  Template IDs of Data
     Sets are numbered from 256 to 65535.  There are no constraints
     regarding the order of the Template ID allocation.

  Field Count

     Number of fields in this Template Record.

  The example in Figure L shows a Template Set with mixed standard and
  enterprise-specific Information Elements.  It consists of a Set
  Header, a Template Header, and several Field Specifiers.
































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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               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Template ID = 256        |         Field Count = N       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |1| Information Element id. 1.1 |        Field Length 1.1       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Enterprise Number  1.1                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| Information Element id. 1.2 |        Field Length 1.2       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |              ...              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |1| Information Element id. 1.N |        Field Length 1.N       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Enterprise Number  1.N                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Template ID = 257        |         Field Count = M       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| Information Element id. 2.1 |        Field Length 2.1       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |1| Information Element id. 2.2 |        Field Length 2.2       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Enterprise Number  2.2                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |              ...              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |1| Information Element id. 2.M |        Field Length 2.M       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Enterprise Number  2.M                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          Padding (opt)                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure L: Template Set Example

  Information Element Identifiers 1.2 and 2.1 are defined by the IETF
  (Enterprise bit = 0) and, therefore, do not need an Enterprise Number
  to identify them.

3.4.2.  Options Template Record Format

  Thanks to the notion of scope, The Options Template Record gives the
  Exporter the ability to provide additional information to the
  Collector that would not be possible with Flow Records alone.




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  One Options Template Record example is the "Flow Keys", which reports
  the Flow Keys for a Template, which is defined as the scope.  Another
  example is the "Template configuration", which reports the
  configuration sampling parameter(s) for the Template, which is
  defined as the scope.

3.4.2.1.  Scope

  The scope, which is only available in the Options Template Set, gives
  the context of the reported Information Elements in the Data Records.
  Note that the IPFIX Message Header already contains the Observation
  Domain ID (the identifier of the Observation Domain).  If not zero,
  this Observation Domain ID can be considered as an implicit scope for
  the Data Records in the IPFIX Message.  The Observation Domain ID
  MUST be zero when the IPFIX Message contains Data Records with
  different Observation Domain ID values defined as scopes.

  Multiple Scope Fields MAY be present in the Options Template Record,
  in which case, the composite scope is the combination of the scopes.
  For example, if the two scopes are defined as "metering process" and
  "template", the combined scope is this Template for this Metering
  Process.  The order of the Scope Fields, as defined in the Options
  Template Record, is irrelevant in this case.  However, if the order
  of the Scope Fields in the Options Template Record is relevant, the
  order of the Scope Fields MUST be used.  For example, if the first
  scope defines the filtering function, while the second scope defines
  the sampling function, the order of the scope is important.  Applying
  the sampling function first, followed by the filtering function,
  would lead to potentially different Data Records than applying the
  filtering function first, followed by the sampling function.  In this
  case, the Collector deduces the function order by looking at the
  order of the scope in the Options Template Record.

  The scope is an Information Element specified in the IPFIX
  Information Model [RFC5102].  An IPFIX-compliant implementation of
  the Collecting Process SHOULD support this minimum set of Information
  Elements as scope: LineCardId, TemplateId, exporterIPv4Address,
  exporterIPv6Address, and ingressInterface.  Note that other
  Information Elements, such as meteringProcessId, exportingProcessId,
  observationDomainId, etc. are also valid scopes.  The IPFIX protocol
  doesn't prevent the use of any Information Elements for scope.
  However, some Information Element types don't make sense if specified
  as scope; for example, the counter Information Elements.

  Finally, note that the Scope Field Count MUST NOT be zero.






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3.4.2.2.  Options Template Record Format

  An Options Template Record contains any combination of IANA-assigned
  and/or enterprise-specific Information Elements identifiers.

  The format of the Options Template Record is shown in Figure M.  It
  consists of an Options Template Record Header and one or more Field
  Specifiers.  The definition of the Field Specifiers is given in
  Figure G above.

  +--------------------------------------------------+
  | Options Template Record Header                   |
  +--------------------------------------------------+
  | Field Specifier                                  |
  +--------------------------------------------------+
  | Field Specifier                                  |
  +--------------------------------------------------+
   ...
  +--------------------------------------------------+
  | Field Specifier                                  |
  +--------------------------------------------------+

  Figure M: Options Template Record Format

  The format of the Options Template Record Header is shown in Figure
  N.

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID (> 255)   |         Field Count           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      Scope Field Count        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure N: Options Template Record Header Format

  The Options Template Record Header Field Definitions are as follows:

  Template ID

  Template ID of this Options Template Record.  This value is greater
  than 255.








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  Field Count

  Number of all fields in this Options Template Record, including the
  Scope Fields.

  Scope Field Count

  Number of scope fields in this Options Template Record.  The Scope
  Fields are normal Fields except that they are interpreted as scope at
  the Collector.  The Scope Field Count MUST NOT be zero.

  The example in Figure O shows an Option Template Set with mixed IETF
  and enterprise-specific Information Elements.  It consists of a Set
  Header, an Option Template Header, and several Field Specifiers.

   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               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID = 258     |         Field Count = N + M   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Scope Field Count = N     |0|  Scope 1 Infor. Element Id. |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Scope 1 Field Length      |0|  Scope 2 Infor. Element Id. |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Scope 2 Field Length      |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            ...                |1|  Scope N Infor. Element Id. |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Scope N Field Length      |   Scope N Enterprise Number ...
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ...  Scope N Enterprise Number   |1| Option 1 Infor. Element Id. |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Option 1 Field Length      |  Option 1 Enterprise Number ...
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ... Option 1 Enterprise Number   |              ...              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ...               |0| Option M Infor. Element Id. |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Option M Field Length     |      Padding (optional)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure O: Option Template Set Example







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3.4.3.  Data Record Format

  The Data Records are sent in Data Sets.  The format of the Data
  Record is shown in Figure P.  It consists only of one or more Field
  Values.  The Template ID to which the Field Values belong is encoded
  in the Set Header field "Set ID", i.e., "Set ID" = "Template ID".

  +--------------------------------------------------+
  | Field Value                                      |
  +--------------------------------------------------+
  | Field Value                                      |
  +--------------------------------------------------+
   ...
  +--------------------------------------------------+
  | Field Value                                      |
  +--------------------------------------------------+

  Figure P: Data Record Format

  Note that Field Values do not necessarily have a length of 16 bits.
  Field Values are encoded according to their data type specified in
  [RFC5102].

  Interpretation of the Data Record format can be done only if the
  Template Record corresponding to the Template ID is available at the
  Collecting Process.

  The example in Figure Q shows a Data Set. It consists of a Set Header
  and several Field Values.






















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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 = Template ID        |          Length               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Record 1 - Field Value 1    |   Record 1 - Field Value 2    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Record 1 - Field Value 3    |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Record 2 - Field Value 1    |   Record 2 - Field Value 2    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Record 2 - Field Value 3    |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Record 3 - Field Value 1    |   Record 3 - Field Value 2    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Record 3 - Field Value 3    |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              ...              |      Padding (optional)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure Q: Data Set, Containing Data Records

4.  Specific Reporting Requirements

  Some specific Options Templates and Options Template Records are
  necessary to provide extra information about the Flow Records and
  about the Metering Process.

  The Option Template and Options Template Records defined in these
  subsections, which impose some constraints on the Metering Process
  and Exporting Process implementations, MAY be implemented.  If
  implemented, the specific Option Templates SHOULD be implemented as
  specified in these subsections.

  The minimum set of Information Elements is always specified in these
  Specific IPFIX Options Templates.  Nevertheless, extra Information
  Elements may be used in these specific Options Templates.

4.1.  The Metering Process Statistics Option Template

  The Metering Process Statistics Option Template specifies the
  structure of a Data Record for reporting Metering Process statistics.
  It SHOULD contain the following Information Elements that are defined
  in [RFC5102]:







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  observationDomainId
                          An identifier of an Observation Domain that
                          is locally unique to the Exporting Process.
                          This Information Element MUST be defined as a
                          Scope Field.

  exportedMessageTotalCount
                          The total number of IPFIX Messages that the
                          Exporting Process successfully sent to the
                          Collecting Process since the Exporting
                          Process re-initialization.

  exportedFlowTotalCount
                          The total number of Flow Records that the
                          Exporting Process successfully sent to the
                          Collecting Process since the Exporting
                          Process re-initialization.

  exportedOctetTotalCount
                          The total number of octets that the Exporting
                          Process successfully sent to the Collecting
                          Process since the Exporting Process re-
                          initialization.

  The Exporting Process SHOULD export the Data Record specified by the
  Metering Process Statistics Option Template on a regular basis or
  based on some export policy.  This periodicity or export policy
  SHOULD be configurable.

  Note that if several Metering Processes are available on the Exporter
  Observation Domain, the Information Element meteringProcessId MUST be
  specified as an additional Scope Field.

4.2.  The Metering Process Reliability Statistics Option Template

  The Metering Process Reliability Option Template specifies the
  structure of a Data Record for reporting lack of reliability in the
  Metering Process.  It SHOULD contain the following Information
  Elements that are defined in [RFC5102]:

  observationDomainId
                          An identifier of an Observation Domain that
                          is locally unique to the Exporting Process.
                          This Information Element MUST be defined as a
                          Scope Field.






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  ignoredPacketTotalCount
                          The total number of IP packets that the
                          Metering Process did not process.

  ignoredOctetTotalCount
                          The total number of octets in observed IP
                          packets that the Metering Process did not
                          process.

  time first ignored
                          The timestamp of the first IP packet that was
                          ignored by the Metering Process.  For this
                          timestamp, any of the "flowStart" timestamp
                          Information Elements flowStartMilliseconds,
                          flowStartMicroseconds, flowStartNanoseconds,
                          and flowStartDeltaMicroseconds can be used.

  time last ignored
                          The timestamp of the last IP packet that was
                          ignored by the Metering Process.  For this
                          timestamp, any of the "flowEnd" timestamp
                          Information Elements flowEndMilliseconds,
                          flowEndMicroseconds, flowEndNanoseconds, and
                          flowEndDeltaMicroseconds can be used.

  The Exporting Process SHOULD export the Data Record specified by the
  Metering Process Reliability Statistics Option Template on a regular
  basis or based on some export policy.  This periodicity or export
  policy SHOULD be configurable.

  Note that if several Metering Processes are available on the Exporter
  Observation Domain, the Information Element meteringProcessId MUST be
  specified as an additional Scope Field.

4.3.  The Exporting Process Reliability Statistics Option Template

  The Exporting Process Reliability Option Template specifies the
  structure of a Data Record for reporting lack of reliability in the
  Exporting process.  It SHOULD contain the following Information
  Elements that are defined in [RFC5102]:

  Exporting Process ID
                       The identifier of the Exporting Process for
                       which lack of reliability is reported.  There
                       are three Information Elements specified in
                       [RFC5102] that can be used for this purpose:
                       exporterIPv4Address, exporterIPv6Address, or




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                       exportingProcessId.  This Information Element
                       MUST be defined as a Scope Field.

  notSentFlowTotalCount
                       The total number of Flows that were generated by
                       the Metering Process and dropped by the Metering
                       Process or by the Exporting Process instead of
                       being sent to the Collecting Process.

  notSentPacketTotalCount
                       The total number of packets in Flow Records that
                       were generated by the Metering Process and
                       dropped by the Metering Process or by the
                       Exporting Process instead of being sent to the
                       Collecting Process.

  notSentOctetTotalCount
                       The total number of octets in packets in Flow
                       Records that were generated by the Metering
                       Process and dropped by the Metering Process or
                       by the Exporting Process instead of being sent
                       to the Collecting Process.

  time first flow dropped
                       The timestamp of the first Flow was dropped by
                       the Metering Process.  For this timestamp, any
                       of the "flowStart" timestamp Information
                       Elements flowStartMilliseconds,
                       flowStartMicroseconds, flowStartNanoseconds, and
                       flowStartDeltaMicroseconds can be used.

  time last flow dropped
                       The timestamp of the last IP packet that was
                       ignored by the Metering Process.  For this
                       timestamp, any of the "flowEnd" timestamp
                       Information Elements flowEndMilliseconds,
                       flowEndMicroseconds, flowEndNanoseconds, and
                       flowEndDeltaMicroseconds can be used.

  The Exporting Process SHOULD export the Data Record specified by the
  Exporting Process Reliability Statistics Option Template on a regular
  basis or based on some export policy.  This periodicity or export
  policy SHOULD be configurable.

4.4.  The Flow Keys Option Template

  The Flow Keys Option Template specifies the structure of a Data
  Record for reporting the Flow Keys of reported Flows.  A Flow Keys



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  Data Record extends a particular Template Record that is referenced
  by its templateId identifier.  The Template Record is extended by
  specifying which of the Information Elements contained in the
  corresponding Data Records describe Flow properties that serve as
  Flow Keys of the reported Flow.

  The Flow Keys Option Template SHOULD contain the following
  Information Elements that are defined in [RFC5102]:

  templateId              An identifier of a Template.  This
                          Information Element MUST be defined as a
                          Scope Field.

  flowKeyIndicator        Bitmap with the positions of the Flow Keys in
                          the Data Records.

5.  IPFIX Message Header "Export Time" and Flow Record Time

  The IPFIX Message Header "Export Time" field is the time in seconds
  since 0000 UTC Jan 1, 1970, at which the IPFIX Message Header leaves
  the Exporter.  The time-related Information Elements specified in
  [RFC5102] MAY use this "Export Time" as base time and specify an
  offset relative to it, instead of using a common base time, such as
  0000 UTC Jan 1, 1970.  All Information Elements that do not have
  their base time defined by their data type MUST have the base time
  clearly specified in their description.

  For example, Data Records requiring a microsecond precision can
  export the flow start and end times with the flowStartMicroseconds
  and flowEndMicroseconds Information Elements [RFC5102], containing
  the time since 0000 UTC Jan 1, 1970.  An alternate solution is to
  export the flowStartDeltaMicroseconds and flowEndDeltaMicroseconds
  Information Elements [RFC5102] in the Data Record, which respectively
  report the flow start and end time offsets compared to the IPFIX
  Message Header "Export Time".  The latter solution lowers the export
  bandwidth requirement while it increases the load on the Exporter, as
  the Exporting Process must calculate the flowStartDeltaMicroseconds
  and flowEndDeltaMicroseconds of every single Data Record before
  exporting the IPFIX Message.

  It must be noted that using time-related Information Elements with
  offset times, compared to the IPFIX Message Header "Export Time",
  imposes some time constraints on the Data Records contained in the
  IPFIX Message.  In the example of flowStartDeltaMicroseconds and
  flowEndDeltaMicroseconds Information Elements [RFC5102], the Data
  Record must be exported within a maximum of 71 minutes after its
  creation.  Otherwise, the 32-bit counter would not be sufficient to
  contain the flow start time offset.



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6.  Linkage with the Information Model

  The Information Elements [RFC5102] MUST be sent in canonical format
  in network-byte order (also known as the big-endian byte ordering).

6.1.  Encoding of IPFIX Data Types

  The following sections will define the encoding of the data types
  specified in [RFC5102].

6.1.1.  Integral Data Types

  Integral data types -- octet, signed8, unsigned16, signed16,
  unsigned32, signed32, signed64, and unsigned64 -- MUST be encoded
  using the default canonical format in network-byte order.  Signed
  Integral data types are represented in two's complement notation.

6.1.2.  Address Types

  Address types -- macAddress, ipv4Address, and ipv6Address -- MUST be
  encoded the same way as the integral data types.  The macAddress is
  treated as a 6-octet integer, the ipv4Address as a 4-octet integer,
  and the ipv6Address as a 16-octet integer.

6.1.3.  float32

  The float32 data type MUST be encoded as an IEEE single-precision
  32-bit floating point-type, as specified in [IEEE.754.1985].

6.1.4.  float64

  The float64 data type MUST be encoded as an IEEE double-precision
  64-bit floating point-type, as specified in [IEEE.754.1985].

6.1.5.  boolean

  The boolean data type is specified according to the TruthValue in
  [RFC2579]: it is an integer with the value 1 for true and a value 2
  for false.  Every other value is undefined.  The boolean data type
  MUST be encoded in a single octet.

6.1.6.  string and octetarray

  The data type string represents a finite length string of valid
  characters of the Unicode character encoding set.  The string data
  type MUST be encoded in UTF-8 format.  The string is sent as an array
  of octets using an Information Element of fixed or variable length.




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  The length of the Information Element specifies the length of the
  octetarray.

6.1.7.  dateTimeSeconds

  The data type dateTimeseconds represents a time value in units of
  seconds normalized to the GMT timezone.  It MUST be encoded in a
  32-bit integer containing the number of seconds since 0000 UTC Jan 1,
  1970.  The 32-bit integer allows the time encoding up to 136 years.

6.1.8.  dateTimeMilliseconds

  The data type dateTimeMilliseconds represents a time value in units
  of milliseconds normalized to the GMT timezone.  It MUST be encoded
  in a 64-bit integer containing the number of milliseconds since 0000
  UTC Jan 1, 1970.

6.1.9.  dateTimeMicroseconds

  The data type dateTimeMicroseconds represents a time value in units
  of microseconds normalized to the GMT timezone.  It MUST be encoded
  in a 64-bit integer, according to the NTP format given in [RFC1305].

6.1.10.  dateTimeNanoseconds

  The data type of dateTimeNanoseconds represents a time value in units
  of nanoseconds normalized to the GMT time zone.  It MUST be encoded
  in a 64-bit integer, according to the NTP format given in [RFC1305].

6.2.  Reduced Size Encoding of Integer and Float Types

  Information Elements containing integer, string, float, and
  octetarray types in the information model MAY be encoded using fewer
  octets than those implied by their type in the information model
  definition [RFC5102], based on the assumption that the smaller size
  is sufficient to carry any value the Exporter may need to deliver.
  This reduces the network bandwidth requirement between the Exporter
  and the Collector.  Note that the Information Element definitions
  [RFC5102] will always define the maximum encoding size.

  For instance, the information model [RFC5102] defines byteCount as an
  unsigned64 type, which would require 64 bits.  However, if the
  Exporter will never locally encounter the need to send a value larger
  than 4294967295, it may chose to send the value instead as an
  unsigned32.  For example, a core router would require an unsigned64
  byteCount, while an unsigned32 might be sufficient for an access
  router.




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  This behavior is indicated by the Exporter by specifying a type size
  with a smaller length than that associated with the assigned type of
  the Information Element.  In the example above, the Exporter would
  place a length of 4 versus 8 in the Template.

  If reduced sizing is used, it MUST only be applied to the following
  integer types: unsigned64, signed64, unsigned32, signed32,
  unsigned16, and signed16.  The signed versus unsigned property of the
  reported value MUST be preserved.  The reduction in size can be to
  any number of octets smaller than the original type if the data value
  still fits, i.e., so that only leading zeroes are dropped.  For
  example, an unsigned64 can be reduced in size to 7, 6, 5, 4, 3, 2, or
  1 octet(s).

  Reduced sizing can also be used to reduce float64 to float32.  The
  float32 not only has a reduced number range, but due to the smaller
  mantissa, is also less precise.

  The reduced size encoding MUST NOT be applied to dateTimeMicroseconds
  or to dateTimeNanoseconds because these represent an inherent
  structure that would be destroyed by using less than the original
  number of bytes.

7.  Variable-Length Information Element

  The IPFIX Template mechanism is optimized for fixed-length
  Information Elements [RFC5102].  Where an Information Element has a
  variable length, the following mechanism MUST be used to carry the
  length information for both the IETF and proprietary Information
  Elements.

  In the Template Set, the Information Element Field Length is recorded
  as 65535.  This reserved length value notifies the Collecting Process
  that length of the Information Element will be carried in the
  Information Element content itself.

  In most cases, the length of the Information Element will be less
  than 255 octets.  The following length-encoding mechanism optimizes
  the overhead of carrying the Information Element length in this
  majority case.  The length is carried in the octet before the
  Information Element, as shown in Figure R.










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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length (< 255)|          Information Element                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      ... continuing as needed                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure R: Variable-Length Information Element (length < 255 octets)

  If the length of the Information Element is greater than or equal to
  255 octets, the length is encoded into 3 octets before the
  Information Element.  The first octet is 255, and the length is
  carried in the second and third octets, as shown in Figure S.

   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)      |       IE      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      ... continuing as needed                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure S: Variable-Length Information Element (length 0 to 65535
  octets)

  The octets carrying the length (either the first or the first three
  octets) MUST NOT be included in the length of the Information
  Element.

8.  Template Management

  This section describes Template Management when using SCTP and
  PR-SCTP as the transport protocol.  Any necessary changes to Template
  Management specifically related to TCP or UDP transport protocols are
  specified in Section 10.

  The Exporting Process assigns and maintains the Template IDs per SCTP
  association for the Exporter's Observation Domains.  A newly created
  Template Record is assigned an unused Template ID by the Exporting
  Process.

  If a specific Information Element is required by a Template, but is
  not available in observed packets, the Exporting Process MAY choose
  to export Flow Records without this Information Element in a Data
  Record defined by a new Template.





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  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.  For
  example, if a selected packet goes through two hash functions, and if
  the two hash values are sent within a single Template, the first
  occurrence of the hash value should belong to the first hash function
  in the Metering Process.  For example, when exporting the two source
  IP addresses of an IPv4 in IPv4 packets, the first sourceIPv4Address
  Information Element occurrence should be the IPv4 address of the
  outer header, while the second occurrence should be the inner header
  one.

  Template Sets and Options Template Sets may be sent on any SCTP
  stream.  Template Sets and Options Template Sets MUST be sent
  reliably, using SCTP-ordered delivery.  As such, the Collecting
  Process MUST store the Template Record information for the duration
  of the SCTP association so that it can interpret the corresponding
  Data Records that are received in subsequent Data Sets.

  The Exporting Process SHOULD transmit the Template Set and Options
  Template Set in advance of any Data Sets that use that (Options)
  Template ID, to help ensure that the Collector has the Template
  Record before receiving the first Data Record.  Data Records that
  correspond to a Template Record MAY appear in the same and/or
  subsequent IPFIX Message(s).

  Different Observation Domains from the same SCTP association may use
  the same Template ID value to refer to different Templates.

  The Templates that are not used anymore SHOULD be deleted.  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.

  The Template Withdrawal Message MUST NOT be sent until sufficient
  time has elapsed to allow the Collecting Process to receive and
  process the last Data Record using this Template information.  This
  time MUST be configurable.  A suitable default value is 5 seconds
  after the last Data Record has been sent.

  The Template ID from a withdrawn Template MUST NOT be reused until
  sufficient time has elapsed to allow for the Collecting Process to
  receive and process the Template Withdrawal Message.

  A Template Withdrawal Message is a Template Record for that Template
  ID with a Field Count of 0.  The format of the Template Withdrawal
  Message is shown in Figure T.




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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 or 3)       |          Length = 16          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Template ID N        |        Field Count = 0        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Template ID ...      |        Field Count = 0        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Template ID M        |        Field Count = 0        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure T: Template Withdrawal Message Format

  The Set ID field MUST contain the value 2 for Template Set Withdrawal
  and the value 3 for Options Template Set Withdrawal.  Multiple
  Template IDs MAY be withdrawn with a single Template Withdrawal
  Message, in that case, padding MAY be used.

  The Template Withdrawal Message withdraws the Template IDs for the
  Observation Domain ID specified in the IPFIX Message Header.

  The Template Withdrawal Message may be sent on any SCTP stream.  The
  Template Withdrawal Message MUST be sent reliably, using SCTP-ordered
  delivery.

  The Template Withdrawal Message MUST NOT contain new Template or
  Options Template Records.

  If the measurement parameters change such that a new Template is
  required, the Template MUST be withdrawn (using a Template Withdraw
  Message and a new Template definition) or an unused Template ID MUST
  be used.  Examples of the measurement changes are: a new sampling
  rate, a new Flow expiration process, a new filtering definition, etc.

  When the SCTP association shuts down or the Exporting Process
  restarts, all Template assignments are lost and Template IDs MUST be
  reassigned.

  If the Metering Process restarts, the Exporting Process MUST either
  reuse the previously assigned Template ID for each Template, or it
  MUST withdraw the previously issued Template IDs by sending Template
  Withdraw Message(s) before reusing them.

  A Template Withdrawal Message to withdraw all Templates for the
  Observation Domain ID specified in the IPFIX Message Header MAY be
  used.  Its format is shown in Figure U.




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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 = 8           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID = 2       |        Field Count = 0        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure U: All Data Templates Withdrawal Message Format

  A Template Withdrawal Message to withdraw all Options Templates for
  the Observation Domain ID specified in the IPFIX Message Header MAY
  be used.  Its format is shown in Figure V.

   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 = 8           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Template ID = 3       |        Field Count = 0        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure V: All Options Templates Withdrawal Message Format

  When the SCTP association restarts, the Exporting Process MUST resend
  all the Template Records.

9.  The Collecting Process's Side

  This section describes the Collecting Process when using SCTP and
  PR-SCTP as the transport protocol.  Any necessary changes to the
  Collecting Process specifically related to TCP or UDP transport
  protocols are specified in Section 10.

  The Collecting Process SHOULD listen for a new association request
  from the Exporting Process.  The Exporting Process will request a
  number of streams to use for export.  An Exporting Process MAY
  request and support more than one stream per SCTP association.

  If the Collecting Process receives a malformed IPFIX Message, it MUST
  reset the SCTP association, discard the IPFIX Message, and SHOULD log
  the error.  Note that non-zero Set padding does not constitute a
  malformed IPFIX Message.

  Template Sets and Option Template Sets are only sent once.  The
  Collecting Process MUST store the Template Record information for the
  duration of the association so that it can interpret the
  corresponding Data Records that are received in subsequent Data Sets.



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  Template IDs are unique per SCTP association and per Observation
  Domain.  If the Collecting Process receives a Template that has
  already been received but that has not previously been withdrawn
  (i.e., a Template Record from the same Exporter Observation Domain
  with the same Template ID received on the SCTP association), then the
  Collecting Process MUST shut down the association.

  When an SCTP association is closed, the Collecting Process MUST
  discard all Templates received over that association and stop
  decoding IPFIX Messages that use those Templates.

  The Collecting Process normally receives Template Records from the
  Exporting Process before receiving Data Records.  The Data Records
  are then decoded and stored by the Collector.  If the Template
  Records have not been received at the time Data Records are received,
  the Collecting Process MAY store the Data Records for a short period
  of time and decode them after the Template Records are received.  A
  Collecting Process MUST NOT assume that the Data Set and the
  associated Template Set (or Options Template Set) are exported in the
  same IPFIX Message.

  The 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.

  The Collector MUST accept padding in Data Records and Template
  Records.  The padding size is the Set Length minus the size of the
  Set Header (4 octets for the Set ID and the Set Length), modulo the
  Record size deduced from the Template Record.

  The IPFIX protocol has a Sequence Number field in the Export header
  that increases with the number of IPFIX Data Records in the IPFIX
  Message.  A Collector may detect out-of-sequence, dropped, or
  duplicate IPFIX Messages by tracking the Sequence Number.  A
  Collector SHOULD provide a logging mechanism for tracking
  out-of-sequence IPFIX Messages.  Such out-of-sequence IPFIX Messages
  may be due to Exporter resource exhaustion where it cannot transmit
  messages at their creation rate, an Exporting Process reset,
  congestion on the network link between the Exporter and Collector,
  Collector resource exhaustion where it cannot process the IPFIX
  Messages at their arrival rate, out-of-order packet reception,
  duplicate packet reception, or an attacker injecting false messages.

  If a Collecting Process receives a Template Withdrawal Message, the
  Collecting Process MUST delete the corresponding Template Records
  associated with the specific SCTP association and specific
  Observation Domain, and stop decoding IPFIX Messages that use the
  withdrawn Templates.



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  If the Collecting Process receives a Template Withdraw message for a
  Template Record it has not received before on this SCTP association,
  it MUST reset the SCTP association, discard the IPFIX Message, and
  SHOULD log the error as it does for malformed IPFIX Messages.

  A Collecting Process that receives IPFIX Messages from several
  Observation Domains on the same Transport Session MUST be aware that
  the uniqueness of the Template ID is not guaranteed across
  Observation Domains.

  The Collector MUST support the use of Templates containing multiple
  occurrences of the similar Information Elements.

10.  Transport Protocol

  The IPFIX Protocol Specification has been designed to be transport
  protocol independent.  Note that the Exporter can export to multiple
  Collecting Processes using independent transport protocols.

  The IPFIX Message Header 16-bit Length field limits the length of an
  IPFIX Message to 65535 octets, including the header.  A Collecting
  Process MUST be able to handle IPFIX Message lengths of up to 65535
  octets.

10.1.  Transport Compliance and Transport Usage

  We need to differentiate between what must be implemented (so that
  operators can interoperably deploy compliant implementations from
  different vendors) and what should or could be used in various
  operational environments.  We must also make sure that ALL
  implementations can operate in a congestion-aware and
  congestion-avoidance mode.

  SCTP [RFC4960] using the PR-SCTP extension specified in [RFC3758]
  MUST be implemented by all compliant implementations.  UDP [UDP] MAY
  also be implemented by compliant implementations.  TCP [TCP] MAY also
  be implemented by compliant implementations.

  PR-SCTP SHOULD be used in deployments where Exporters and Collectors
  are communicating over links that are susceptible to congestion.
  PR-SCTP is capable of providing any required degree of reliability.

  TCP MAY be used in deployments where Exporters and Collectors
  communicate over links that are susceptible to congestion, but
  PR-SCTP is preferred due to its ability to limit back pressure on
  Exporters and its message versus stream orientation.





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  UDP MAY be used, although it is not a congestion-aware protocol.
  However, the IPFIX traffic between Exporter and Collector MUST run in
  an environment where IPFIX traffic has been provisioned for, or is
  contained through some other means.

10.2.  SCTP

  This section describes how IPFIX can be transported over SCTP
  [RFC4960] using the PR-SCTP [RFC3758] extension.

10.2.1.  Congestion Avoidance

  The SCTP transport protocol provides the required level of congestion
  avoidance by design.

  SCTP will detect congestion in the end-to-end path between the IPFIX
  Exporting Process and the IPFIX Collecting Process, and limit the
  transfer rate accordingly.  When an IPFIX Exporting Process has
  records to export, but detects that transmission by SCTP is
  temporarily impossible, it can either wait until sending is possible
  again, or it can decide to drop the record.  In the latter case, the
  dropped export data MUST be accounted for, so that the amount of
  dropped export data can be reported.

10.2.2.  Reliability

  The SCTP transport protocol is by default reliable, but has the
  capability to deliver messages with partial reliability  [RFC3758].

  Using reliable SCTP messages for the IPFIX export is not in itself a
  guarantee that all Data Records will be delivered.  If there is
  congestion on the link from the Exporting Process to the Collecting
  Process, or if a significant number of retransmissions are required,
  the send queues on the Exporting Process may fill up; the Exporting
  Process MAY either suspend, export, or discard the IPFIX Messages.
  If Data Records are discarded the IPFIX Sequence Numbers used for
  export MUST reflect the loss of data.

10.2.3.  MTU

  SCTP provides the required IPFIX Message fragmentation service based
  on path MTU discovery.









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10.2.4.  Exporting Process

10.2.4.1.  Association Establishment

  The IPFIX Exporting Process SHOULD initiate an SCTP association with
  the IPFIX Collecting Process.  By default, the Collecting Process
  listens for connections on SCTP port 4739.  By default, the
  Collecting Process listens for secure connections on SCTP port 4740
  (refer to the Security Considerations section).  By default, the
  Exporting Process tries to connect to one of these ports.  It MUST be
  possible to configure both the Exporting and Collecting Processes to
  use a different SCTP port.

  The Exporting Process MAY establish more than one association
  (connection "bundle" in SCTP terminology) to the Collecting Process.

  An Exporting Process MAY support more than one active association to
  different Collecting Processes (including the case of different
  Collecting Processes on the same host).

10.2.4.2.   Association Shutdown

  When an Exporting Process is shut down, it SHOULD shut down the SCTP
  association.

  When a Collecting Process no longer wants to receive IPFIX Messages,
  it SHOULD shut down its end of the association.  The Collecting
  Process SHOULD continue to receive and process IPFIX Messages until
  the Exporting Process has closed its end of the association.

  When a Collecting Process detects that the SCTP association has been
  abnormally terminated, it MUST continue to listen for a new
  association establishment.

  When an Exporting Process detects that the SCTP association to the
  Collecting Process is abnormally terminated, it SHOULD try to
  re-establish the association.

  Association timeouts SHOULD be configurable.

10.2.4.3.  Stream

  An Exporting Process MAY request more than one SCTP stream per
  association.  Each of these streams may be used for the transmission
  of IPFIX Messages containing Data Sets, Template Sets, and/or Options
  Template Sets.





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  Depending on the requirements of the application, the Exporting
  Process may send Data Sets with full or partial reliability, using
  ordered or out-of-order delivery, over any SCTP stream established
  during SCTP Association setup.

  An IPFIX Exporting Process MAY use any PR-SCTP Service Definition as
  per Section 4 of the PR-SCTP [RFC3758] specification when using
  partial reliability to transmit IPFIX Messages containing only Data
  Sets.

  However, Exporting Processes SHOULD mark such IPFIX Messages for
  retransmission for as long as resource or other constraints allow.

10.2.4.4.  Template Management

  When the transport protocol is SCTP, the default Template Management
  described in Section 8 is used.

10.2.5.  Collecting Process

  When the transport protocol is SCTP, the default Collector processing
  described in Section 9 is used.

10.2.6.  Failover

  If the Collecting Process does not acknowledge the attempt by the
  Exporting Process to establish an association, the Exporting Process
  should retry using the SCTP exponential backoff feature.  The
  Exporter MAY log an alarm if the time to establish the association
  exceeds a specified threshold, configurable on the Exporter.

  If Collecting Process failover is supported by the Exporting Process,
  a second SCTP association MAY be opened in advance.

10.3.  UDP

  This section describes how IPFIX can be transported over UDP [UDP].

10.3.1.  Congestion Avoidance

  UDP has no integral congestion-avoidance mechanism.  Its use over
  congestion-sensitive network paths is therefore not recommended.  UDP
  MAY be used in deployments where Exporters and Collectors always
  communicate over dedicated links that are not susceptible to
  congestion, i.e., over provisioned links compared to the maximum
  export rate from the Exporters.





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10.3.2.  Reliability

  UDP is not a reliable transport protocol, and cannot guarantee
  delivery of messages.  IPFIX Messages sent from the Exporting Process
  to the Collecting Process using UDP may therefore be lost.  UDP MUST
  NOT be used unless the application can tolerate some loss of IPFIX
  Messages.

  The Collecting Process SHOULD deduce the loss and reordering of IPFIX
  Data Records by looking at the discontinuities in the IPFIX Sequence
  Number.  In the case of UDP, the IPFIX Sequence Number contains the
  total number of IPFIX Data Records sent for the UDP Transport Session
  prior to the receipt of this IPFIX Message, modulo 2^32.  A Collector
  SHOULD detect out-of-sequence, dropped, or duplicate IPFIX Messages
  by tracking the Sequence Number.  Templates sent from the Exporting
  Process to the Collecting Process using UDP as a transport MUST be
  re-sent at regular intervals, in case previous copies were lost.

10.3.3.  MTU

  The maximum size of exported messages MUST be configured such that
  the total packet size does not exceed the path MTU.  If the path MTU
  is unknown, a maximum packet size of 512 octets SHOULD be used.

10.3.4.  Port Numbers

  By default, the Collecting Process listens on the UDP port 4739.  By
  default, the Collecting Process listens for secure connections on UDP
  port 4740 (refer to the "Security Considerations" section).  By
  default, the Exporting Process tries to connect to one of these
  ports.  It MUST be possible to configure both the Exporting and
  Collecting Processes to use a different UDP port.

10.3.5.  Exporting Process

  The Exporting Process MAY duplicate the IPFIX Message to the several
  Collecting Processes.

10.3.6.  Template Management

  When IPFIX uses UDP as the transport protocol, Template Sets and
  Option Template Sets MUST be re-sent at regular intervals.  The
  frequency of the (Options) Template transmission MUST be
  configurable.  The default value for the frequency of the (Options)
  Template transmission is 10 minutes.  The Exporting Process SHOULD
  transmit the Template Set and Options Template Set in advance of any
  Data Sets that use that (Options) Template ID to help ensure that the




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  Collector has the Template Record before receiving the first Data
  Record.

  In the event of configuration changes, the Exporting Process SHOULD
  send multiple copies of the new Template definitions, in different
  IPFIX Messages, at an accelerated rate.  In such a case, it SHOULD
  transmit the changed Template Record(s) and Options Template
  Record(s), without any data, in advance to help ensure that the
  Collector will have the correct Template information before receiving
  the first data.

  If the Option Template scope is defined in another Template, then
  both Templates SHOULD be sent in the same IPFIX Message.  For
  example, if a Flow Key Option Template (see Section 4.4) is sent in
  an Option Template, then the associated Template SHOULD be sent in
  the same IPFIX Message.

  Following a configuration change that can modify the interpretation
  of the Data Records (for example, a sampling rate change) a new
  Template ID MUST be used, and the old Template ID MUST NOT be reused
  until its lifetime (see Section 10.3.7) has expired.

  If UDP is selected as the transport protocol, the Template Withdraw
  Messages MUST NOT be used, as this method is inefficient due to the
  unreliable nature of UDP.

10.3.7.  Collecting Process

  The Collecting Process MUST associate a lifetime with each Template
  (or another definition of an identifier considered unique within the
  Transport Session) received via UDP.  Templates (and similar
  definitions) not refreshed by the Exporting Process within the
  lifetime are expired at the Collecting Process.  If the Template (or
  other definition) is not refreshed before that lifetime has expired,
  the Collecting Process MUST discard that definition and any current
  and future associated Data Records.  In which case, an alarm MUST be
  logged.  The Collecting Process MUST NOT decode any further Data
  Records that are associated with the expired Template.  If a Template
  is refreshed with a Template Record that differs from the previously
  received Template Record, the Collecting Process SHOULD log a warning
  and replace the previously received Template Record with the new one.
  The Template lifetime at the Collecting Process MUST be at least 3
  times higher than the Template refresh timeout configured on the
  Exporting Process.

  Template IDs are unique per UDP session and per Observation Domain.
  At any given time, the Collecting Process SHOULD maintain the
  following for all the current Template Records and Options Template



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  Records: <IPFIX Device, Exporter source UDP port, Observation Domain
  ID, Template ID, Template Definition, Last Received>.

  The Collecting Process SHOULD accept Data Records without the
  associated Template Record (or other definitions) required to decode
  the Data Record.  If the Template Records (or other definitions such
  as Common Properties) have not been received at the time Data Records
  are received, the Collecting Process SHOULD store the Data Records
  for a short period of time and decode them after the Template Records
  (or other definitions) are received.  The short period of time MUST
  be lower than the lifetime of definitions associated with identifiers
  considered unique within the UDP session.

  If the Collecting Process receives a malformed IPFIX Message, it MUST
  discard the IPFIX Message and SHOULD log the error.

10.3.8.  Failover

  Because UDP is not a connection-oriented protocol, the Exporting
  Process is unable to determine from the transport protocol that the
  Collecting Process is no longer able to receive the IPFIX Messages.
  Therefore, it cannot invoke a failover mechanism.  However, the
  Exporting Process MAY duplicate the IPFIX Message to several
  Collecting Processes.

10.4.  TCP

  This section describes how IPFIX can be transported over TCP [TCP].

10.4.1.  Connection Management

10.4.1.1.  Connection Establishment

  The IPFIX Exporting Process initiates a TCP connection to the
  Collecting Process.  By default, the Collecting Process listens for
  connections on TCP port 4739.  By default, the Collecting Process
  listens for secure connections on TCP port 4740 (refer to the
  Security Considerations section).  By default, the Exporting Process
  tries to connect to one of these ports.  It MUST be possible to
  configure both the Exporting Process and the Collecting Process to
  use a different TCP port.

  An Exporting Process MAY support more than one active connection to
  different Collecting Processes (including the case of different
  Collecting Processes on the same host).

  The Exporter MAY log an alarm if the time to establish the connection
  exceeds a specified threshold, configurable on the Exporter.



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10.4.1.2.  Graceful Connection Release

  When an Exporting Process is shut down, it SHOULD shut down the TCP
  connection.

  When a Collecting Process no longer wants to receive IPFIX Messages,
  it SHOULD close its end of the connection.  The Collecting Process
  SHOULD continue to read IPFIX Messages until the Exporting Process
  has closed its end.

10.4.1.3.  Restarting Interrupted Connections

  When a Collecting Process detects that the TCP connection to the
  Exporting Process has terminated abnormally, it MUST continue to
  listen for a new connection.

  When an Exporting Process detects that the TCP connection to the
  Collecting Process has terminated abnormally, it SHOULD try to
  re-establish the connection.  Connection timeouts and retry schedules
  SHOULD be configurable.  In the default configuration, an Exporting
  Process MUST NOT attempt to establish a connection more frequently
  than once per minute.

10.4.1.4.  Failover

  If the Collecting Process does not acknowledge the attempt by the
  Exporting Process to establish a connection, it will retry using the
  TCP exponential backoff feature.

  If Collecting Process failover is supported by the Exporting Process,
  a second TCP connection MAY be opened in advance.

10.4.2.  Data Transmission

  Once a TCP connection is established, the Exporting Process starts
  sending IPFIX Messages to the Collecting Process.

10.4.2.1.  IPFIX Message Encoding

  IPFIX Messages are sent over the TCP connection without any special
  encoding.  The Length field in the IPFIX Message Header defines the
  end of each IPFIX Message and thus the start of the next IPFIX
  Message.  This means that IPFIX Messages cannot be interleaved.

  In the case of TCP, the IPFIX Sequence Number contains the total
  number of IPFIX Data Records sent from this TCP connection, from the
  current Observation Domain by the Exporting Process, prior to the
  receipt of this IPFIX Message, modulo 2^32.



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  If an Exporting Process exports data from multiple Observation
  Domains, it should be careful to choose IPFIX Message lengths
  appropriately to minimize head-of-line blocking between different
  Observation Domains.  Multiple TCP connections MAY be used to avoid
  head-of-line between different Observation Domains.

10.4.2.2.  Template Management

  For each Template, the Exporting Process MUST send the Template
  Record before exporting Data Records that refer to that Template.

  Template IDs are unique per TCP connection and per Observation
  Domain.  A Collecting Process MUST record all Template and Options
  Template Records for the duration of the connection, as an Exporting
  Process is not required to re-export Template Records.

  When the TCP connection restarts, the Exporting Process MUST resend
  all the Template Records.

  When a TCP connection is closed, the Collecting Process MUST discard
  all Templates received over that connection and stop decoding IPFIX
  Messages that use those Templates.

  The Templates that are not used anymore SHOULD be deleted.  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 over the TCP connection.

  If the Collecting Process receives a malformed IPFIX Message, it MUST
  reset the TCP connection, discard the IPFIX Message, and SHOULD log
  the error.

10.4.2.3.  Congestion Handling and Reliability

  TCP ensures reliable delivery of data from the Exporting Process to
  the Collecting Process.  TCP also controls the rate at which data can
  be sent from the Exporting Process to the Collecting Process, using a
  mechanism that takes into account both congestion in the network and
  the capabilities of the receiver.

  Therefore, an IPFIX Exporting Process may not be able to send IPFIX
  Messages at the rate that the Metering Process generates it, either
  because of congestion in the network or because the Collecting
  Process cannot handle IPFIX Messages fast enough.  As long as
  congestion is transient, the Exporting Process can buffer IPFIX
  Messages for transmission.  But such buffering is necessarily
  limited, both because of resource limitations and because of




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  timeliness requirements, so ongoing and/or severe congestion may lead
  to a situation where the Exporting Process is blocked.

  When an Exporting Process has Data Records to export but the
  transmission buffer is full, and it wants to avoid blocking, it can
  decide to drop some Data Records.  The dropped Data Records MUST be
  accounted for, so that the amount can later be exported.

  When an Exporting Process finds that the rate at which records should
  be exported is consistently higher than the rate at which TCP sending
  permits, it should provide back pressure to the Metering Processes.
  The Metering Process could then adapt by temporarily reducing the
  amount of data it generates, for example, using sampling or
  aggregation.

10.4.3.  Collecting Process

  The Collecting Process SHOULD listen for a new TCP connection from
  the Exporting Process.

  If the Collecting Process receives a malformed IPFIX Message, it MUST
  reset the TCP connection, discard the IPFIX Message, and SHOULD log
  the error.  Note that non-zero Set padding does not constitute a
  malformed IPFIX Message.

  Template Sets and Option Template Sets are only sent once.  The
  Collecting Process MUST store the Template Record information for the
  duration of the connection so that it can interpret the corresponding
  Data Records that are received in subsequent Data Sets.

  Template IDs are unique per TCP connection and per Observation
  Domain.  If the Collecting Process receives a Template that has
  already been received but that has not previously been withdrawn
  (i.e., a Template Record from the same Exporter Observation Domain
  with the same Template ID received on the TCP connection), then the
  Collecting Process MUST shut down the connection.

  When a TCP connection is closed, the Collecting Process MUST discard
  all Templates received over that connection and stop decoding IPFIX
  Messages that use those Templates.

  If a Collecting Process receives a Template Withdrawal Message, the
  Collecting Process MUST delete the corresponding Template Records
  associated with the specific TCP connection and specific Observation
  Domain, and stop decoding IPFIX Messages that use the withdrawn
  Templates.





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  If the Collecting Process receives a Template Withdrawal Message for
  a Template Record it has not received before on this TCP connection,
  it MUST reset the TCP association, discard the IPFIX Message, and
  SHOULD log the error as it does for malformed IPFIX Messages.

11.  Security Considerations

  The security considerations for the IPFIX protocol have been derived
  from an analysis of potential security threats, as discussed in the
  "Security Considerations" section of IPFIX requirements [RFC3917].
  The requirements for IPFIX security are as follows:

  1. IPFIX must provide a mechanism to ensure the confidentiality of
     IPFIX data transferred from an Exporting Process to a Collecting
     Process, in order to prevent disclosure of Flow Records
     transported via IPFIX.

  2. IPFIX must provide a mechanism to ensure the integrity of IPFIX
     data transferred from an Exporting Process to a Collecting
     Process, in order to prevent the injection of incorrect data or
     control information (e.g., Templates) into an IPFIX Message
     stream.

  3. IPFIX must provide a mechanism to authenticate IPFIX Collecting
     and Exporting Processes, to prevent the collection of data from an
     unauthorized Exporting Process or the export of data to an
     unauthorized Collecting Process.

  Because IPFIX can be used to collect information for network
  forensics and billing purposes, attacks designed to confuse, disable,
  or take information from an IPFIX collection system may be seen as a
  prime objective during a sophisticated network attack.

  An attacker in a position to inject false messages into an IPFIX
  Message stream can either affect the application using IPFIX (by
  falsifying data), or the IPFIX Collecting Process itself (by
  modifying or revoking Templates, or changing options); for this
  reason, IPFIX Message integrity is important.

  The IPFIX Messages themselves may also contain information of value
  to an attacker, including information about the configuration of the
  network as well as end-user traffic and payload data, so care must be
  taken to confine their visibility to authorized users.  When an
  Information Element containing end-user payload information is
  exported, it SHOULD be transmitted to the Collecting Process using a
  means that secures its contents against eavesdropping.  Suitable
  mechanisms include the use of either a direct point-to-point
  connection or the use of an encryption mechanism.  It is the



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  responsibility of the Collecting Process to provide a satisfactory
  degree of security for this collected data, including, if necessary,
  anonymization of any reported data.

11.1.  Applicability of TLS and DTLS

  Transport Layer Security (TLS) [RFC4346] and Datagram Transport Layer
  Security (DTLS) [RFC4347] were designed to provide the
  confidentiality, integrity, and authentication assurances required by
  the IPFIX protocol, without the need for pre-shared keys.

  With the mandatory SCTP and PR-SCTP transport protocols for IPFIX,
  DTLS [RFC4347] MUST be implemented.  If UDP is selected as the IPFIX
  transport protocol, DTLS [RFC4347] MUST be implemented.  If TCP is
  selected as the IPFIX transport protocol, TLS [RFC4346] MUST be
  implemented.

  Note that DTLS is selected as the security mechanism for SCTP and
  PR-SCTP.  Though TLS bindings to SCTP are defined in [RFC3436], they
  require all communication to be over reliable, bidirectional streams,
  and require one TLS connection per stream.  This arrangement is not
  compatible with the rationale behind the choice of SCTP as an IPFIX
  transport protocol.

  Note that using DTLS [RFC4347] has a vulnerability, i.e., a true man
  in the middle may attempt to take data out of an association and fool
  the sender into thinking that the data was actually received by the
  peer.  In generic TLS for SCTP (and/or TCP), this is not possible.
  This means that the removal of a message may become hidden from the
  sender or receiver.  Another vulnerability of using PR-SCTP with DTLS
  is that someone could inject SCTP control information to shut down
  the SCTP association, effectively generating a loss of IPFIX Messages
  if those are buffered outside of the SCTP association.  In the
  future, techniques such as [dtls-for-sctp] could be used to overcome
  these vulnerabilities.

  When using DTLS over SCTP, the Exporting Process MUST ensure that
  each IPFIX Message is sent over the same SCTP stream that would be
  used when sending the same IPFIX Message directly over SCTP.  Note
  that DTLS may send its own control messages on stream 0 with full
  reliability; however, this will not interfere with the processing of
  stream 0 IPFIX Messages at the Collecting Process, because DTLS
  consumes its own control messages before passing IPFIX Messages up to
  the application layer.







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11.2.  Usage

  The IPFIX Exporting Process initiates the communication to the IPFIX
  Collecting Process, and acts as a TLS or DTLS client according to
  [RFC4346] and [RFC4347], while the IPFIX Collecting Process acts as a
  TLS or DTLS server.  The DTLS client opens a secure connection on the
  SCTP port 4740 of the DTLS server if SCTP or PR-SCTP is selected as
  the transport protocol.  The TLS client opens a secure connection on
  the TCP port 4740 of the TLS server if TCP is selected as the
  transport protocol.  The DTLS client opens a secure connection on the
  UDP port 4740 of the DTLS server if UDP is selected as the transport
  protocol.

11.3.  Authentication

  IPFIX Exporting Processes and IPFIX Collecting Processes are
  identified by the fully qualified domain name of the interface on
  which IPFIX Messages are sent or received, for purposes of X.509
  client and server certificates as in [RFC3280].

  To prevent man-in-the-middle attacks from impostor Exporting or
  Collecting Processes, the acceptance of data from an unauthorized
  Exporting Process, or the export of data to an unauthorized
  Collecting Process, strong mutual authentication via asymmetric keys
  MUST be used for both TLS and DTLS.  Each of the IPFIX Exporting and
  Collecting Processes MUST verify the identity of its peer against its
  authorized certificates, and MUST verify that the peer's certificate
  matches its fully qualified domain name, or, in the case of SCTP, the
  fully qualified domain name of one of its endpoints.

  The fully qualified domain name used to identify an IPFIX Collecting
  Process or Exporting Process may be stored either in a subjectAltName
  extension of type dNSName, or in the most specific Common Name field
  of the Subject field of the X.509 certificate.  If both are present,
  the subjectAltName extension is given preference.

  Internationalized domain names (IDN) in either the subjectAltName
  extension of type dNSName or the most specific Common Name field of
  the Subject field of the X.509 certificate MUST be encoded using
  Punycode [RFC3492] as described in Section 4 of [RFC3490],
  "Conversion Operations".

11.4.  Protection against DoS Attacks

  An attacker may mount a denial-of-service (DoS) attack against an
  IPFIX collection system either directly, by sending large amounts of
  traffic to a Collecting Process, or indirectly, by generating large
  amounts of traffic to be measured by a Metering Process.



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  Direct denial-of-service attacks can also involve state exhaustion,
  whether at the transport layer (e.g., by creating a large number of
  pending connections), or within the IPFIX Collecting Process itself
  (e.g., by sending Flow Records pending Template or scope information,
  a large amount of Options Template Records, etc.).

  SCTP mandates a cookie-exchange mechanism designed to defend against
  SCTP state exhaustion denial-of-service attacks.  Similarly, TCP
  provides the "SYN cookie" mechanism to mitigate state exhaustion; SYN
  cookies SHOULD be used by any Collecting Process accepting TCP
  connections.  DTLS also provides cookie exchange to protect against
  DTLS server state exhaustion.

  The reader should note that there is no way to prevent fake IPFIX
  Message processing (and state creation) for UDP & SCTP communication.
  The use of TLS and DTLS can obviously prevent the creation of fake
  states, but they are themselves prone to state exhaustion attacks.
  Therefore, Collector rate limiting SHOULD be used to protect TLS &
  DTLS (like limiting the number of new TLS or DTLS session per second
  to a sensible number).

  IPFIX state exhaustion attacks can be mitigated by limiting the rate
  at which new connections or associations will be opened by the
  Collecting Process, the rate at which IPFIX Messages will be accepted
  by the Collecting Process, and adaptively limiting the amount of
  state kept, particularly records waiting on Templates.  These rate
  and state limits MAY be provided by a Collecting Process; if
  provided, the limits SHOULD be user configurable.

  Additionally, an IPFIX Collecting Process can eliminate the risk of
  state exhaustion attacks from untrusted nodes by requiring TLS or
  DTLS mutual authentication, causing the Collecting Process to accept
  IPFIX Messages only from trusted sources.

  With respect to indirect denial of service, the behavior of IPFIX
  under overload conditions depends on the transport protocol in use.
  For IPFIX over TCP, TCP congestion control would cause the flow of
  IPFIX Messages to back off and eventually stall, blinding the IPFIX
  system.  PR-SCTP improves upon this situation somewhat, as some IPFIX
  Messages would continue to be received by the Collecting Process due
  to the avoidance of head-of-line blocking by SCTP's multiple streams
  and partial reliability features, possibly affording some visibility
  of the attack.  The situation is similar with UDP, as some datagrams
  may continue to be received at the Collecting Process, effectively
  applying sampling to the IPFIX Message stream, implying that some
  forensics may be left.





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  To minimize IPFIX Message loss under overload conditions, some
  mechanism for service differentiation could be used to prioritize
  IPFIX traffic over other traffic on the same link.  Alternatively,
  IPFIX Messages can be transported over a dedicated network.  In this
  case, care must be taken to ensure that the dedicated network can
  handle the expected peak IPFIX Message traffic.

11.5.  When DTLS or TLS Is Not an Option

  The use of DTLS or TLS might not be possible in some cases due to
  performance issues or other operational concerns.

  Without TLS or DTLS mutual authentication, IPFIX Exporting Processes
  and Collecting Processes can fall back on using IP source addresses
  to authenticate their peers.  A policy of allocating Exporting
  Process and Collecting Process IP addresses from specified address
  ranges, and using ingress filtering to prevent spoofing, can improve
  the usefulness of this approach.  Again, completely segregating IPFIX
  traffic on a dedicated network, where possible, can improve security
  even further.  In any case, the use of open Collecting Processes
  (those that will accept IPFIX Messages from any Exporting Process
  regardless of IP address or identity) is discouraged.

  Modern TCP and SCTP implementations are resistant to blind insertion
  attacks (see [RFC1948], [RFC4960]); however, UDP offers no such
  protection.  For this reason, IPFIX Message traffic transported via
  UDP and not secured via DTLS SHOULD be protected via segregation to a
  dedicated network.

11.6.  Logging an IPFIX Attack

  IPFIX Collecting Processes MUST detect potential IPFIX Message
  insertion or loss conditions by tracking the IPFIX Sequence Number,
  and SHOULD provide a logging mechanism for reporting out-of-sequence
  messages.  Note that an attacker may be able to exploit the handling
  of out-of-sequence messages at the Collecting Process, so care should
  be taken in handling these conditions.  For example, a Collecting
  Process that simply resets the expected Sequence Number upon receipt
  of a later Sequence Number could be temporarily blinded by deliberate
  injection of later Sequence Numbers.

  IPFIX Exporting and Collecting Processes SHOULD log any connection
  attempt that fails due to authentication failure, whether due to
  being presented an unauthorized or mismatched certificate during TLS
  or DTLS mutual authentication, or due to a connection attempt from an
  unauthorized IP address when TLS or DTLS is not in use.





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  IPFIX Exporting and Collecting Processes SHOULD detect and log any
  SCTP association reset or TCP connection reset.

11.7.  Securing the Collector

  The security of the Collector and its implementation is important to
  achieve overall security.  However, it is outside the scope of this
  document.

12.  IANA Considerations

  IPFIX Messages use two fields with assigned values.  These are the
  IPFIX Version Number, indicating which version of the IPFIX Protocol
  was used to export an IPFIX Message, and the IPFIX Set ID, indicating
  the type for each set of information within an IPFIX Message.

  The IPFIX Version Number value of 10 is reserved for the IPFIX
  protocol specified in this document.  Set ID values of 0 and 1 are
  not used for historical reasons [RFC3954].  The Set ID value of 2 is
  reserved for the Template Set.  The Set ID value of 3 is reserved for
  the Option Template Set.  All other Set ID values from 4 to 255 are
  reserved for future use.  Set ID values above 255 are used for Data
  Sets.

  New assignments in either IPFIX Version Number or IPFIX Set ID
  assignments require a Standards Action [RFC2434], i.e., they are to
  be made via Standards Track RFCs approved by the IESG.
























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RFC 5101              IPFIX Protocol Specification          January 2008


Appendix A.  IPFIX Encoding Examples

  This appendix, which is a not a normative reference, contains IPFIX
  encoding examples.

  Let's consider the example of an IPFIX Message composed of a Template
  Set, a Data Set (which contains three Data Records), an Options
  Template Set and a Data Set (which contains 2 Data Records related to
  the previous Options Template Record).

  IPFIX Message:

  +--------+------------------------------------------. . .
  |        | +--------------+ +------------------+
  |Message | | Template     | | Data             |
  | Header | | Set          | | Set              |   . . .
  |        | | (1 Template) | | (3 Data Records) |
  |        | +--------------+ +------------------+
  +--------+------------------------------------------. . .

       . . .-------------------------------------------+
             +------------------+ +------------------+ |
             | Options          | | Data             | |
      . . .  | Template Set     | | Set              | |
             | (1 Template)     | | (2 Data Records) | |
             +------------------+ +------------------+ |
       . . .-------------------------------------------+

A.1.  Message Header Example

  The Message Header is composed of:
   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Version = 0x000a          |         Length = 152          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          Export Time                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        Sequence Number                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Observation Domain ID                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+









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A.2.  Template Set Examples

A.2.1.  Template Set Using IETF-Specified Information Elements


  We want to report the following Information Elements:

  - The IPv4 source IP address: sourceIPv4Address in [RFC5102],
    with a length of 4 octets

  - The IPv4 destination IP address: destinationIPv4Address in
    [RFC5102], with a length of 4 octets

  - The next-hop IP address (IPv4): ipNextHopIPv4Address in
    [RFC5102], with a length of 4 octets

  - The number of packets of the Flow: inPacketDeltaCount in
    [RFC5102], with a length of 4 octets

  - The number of octets of the Flow: inOctetDeltaCount in
    [RFC5102], with a length of 4 octets

  Therefore, the Template Set will be composed of the following:

   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 = 28 octets       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Template ID 256         |       Field Count = 5         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|    sourceIPv4Address = 8    |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| destinationIPv4Address = 12 |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|  ipNextHopIPv4Address = 15  |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   inPacketDeltaCount = 2    |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   inOctetDeltaCount =  1    |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.2.2.  Template Set Using Enterprise-Specific Information Elements

  We want to report the following Information Elements:

  - The IPv4 source IP address: sourceIPv4Address in [RFC5102], with a
    length of 4 octets



Claise, et al.              Standards Track                    [Page 53]

RFC 5101              IPFIX Protocol Specification          January 2008


  - The IPv4 destination IP address: destinationIPv4Address in
    [RFC5102], with a length of 4 octets

  - An enterprise-specific Information Element representing proprietary
    information, with a type of 15 and a length of 4

  - The number of packets of the Flow: inPacketDeltaCount in [RFC5102],
    with a length of 4 octets

  - The number of octets of the Flow: inOctetDeltaCount in [RFC5102],
    with a length of 4 octets

  Therefore, the Template Set will be composed of the following:

   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 257         |       Field Count = 5         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|    sourceIPv4Address = 8    |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0| destinationIPv4Address = 12 |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |1| Information Element Id. = 15|       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                       Enterprise number                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   inPacketDeltaCount = 2    |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0|   inOctetDeltaCount = 1     |       Field Length = 4        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


















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A.3.  Data Set Example

  In this example, we report the following three Flow Records:

  Src IP addr. | Dst IP addr.  | Next Hop addr. | Packet | Octets
               |               |                | Number | Number
  ------------------------------------------------------------------
  192.0.2.12   | 192.0.2.254   | 192.0.2.1      | 5009   | 5344385
  192.0.2.27   | 192.0.2.23    | 192.0.2.2      | 748    | 388934
  192.0.2.56   | 192.0.2.65    | 192.0.2.3      | 5      | 6534

   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 = 64          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.12                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.254                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.1                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                             5009                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                            5344385                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.27                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.23                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.2                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              748                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                             388934                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.56                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.65                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          192.0.2.3                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               5                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                              6534                             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Note that padding is not necessary in this example.



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RFC 5101              IPFIX Protocol Specification          January 2008


A.4.  Options Template Set Examples

A.4.1.  Options Template Set Using IETF-Specified Information Elements

  Per line card (the router being composed of two line cards), we want
  to report the following Information Elements:

  - Total number of IPFIX Messages: exportedPacketCount [RFC5102], with
    a length of 2 octets

  - Total number of exported Flows: exportedFlowCount [RFC5102], with a
    length of 2 octets

  The line card, which is represented by the lineCardId Information
  Element [RFC5102], is used as the Scope Field.

  Therefore, the Options Template Set will be:

   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 = 24          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Template ID 258         |        Field Count = 3        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Scope Field Count = 1     |0|     lineCardId = 141        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Scope 1 Field Length = 4    |0|  exportedPacketCount = 41   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Field Length = 2        |0|   exportedFlowCount = 42    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       Field Length = 2        |           Padding             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.4.2.  Options Template Set Using Enterprise-Specific Information
       Elements

  Per line card (the router being composed of two line cards), we want
  to report the following Information Elements:

     - Total number of IPFIX Messages: exportedPacketCount [RFC5102],
       with a length of 2 octets

     - An enterprise-specific number of exported Flows, with a type of
       42 and a length of 4 octets

  The line card, which is represented by the lineCardId Information
  Element [RFC5102], is used as the Scope Field.



Claise, et al.              Standards Track                    [Page 56]

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  The format of the Options Template Set 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 = 3            |          Length = 28          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 259         |        Field Count = 3        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scope Field Count = 1     |0|     lineCardId = 141        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Scope 1 Field Length = 4    |0|  exportedPacketCount = 41   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |1|Information Element Id. = 42 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 4        |       Enterprise number     ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...      Enterprise number      |           Padding             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.4.3.  Options Template Set Using an Enterprise-Specific Scope

  In this example, we want to export the same information as in the
  example in Section A.4.1:

     - Total number of IPFIX Messages: exportedPacketCount [RFC5102],
       with a length of 2 octets

     - Total number of exported Flows: exportedFlowCount [RFC5102],
       with a length of 2 octets

  But this time, the information pertains to a proprietary scope,
  identified by enterprise-specific Information Element number 123.


















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RFC 5101              IPFIX Protocol Specification          January 2008


  The format of the Options Template Set is now 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 = 3            |          Length = 28          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 260         |        Field Count = 3        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scope Field Count = 1     |1|Scope 1 Infor. El. Id. = 123 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Scope 1 Field Length = 4   |       Enterprise Number      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ...       Enterprise Number      |0|  exportedPacketCount = 41   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |0|   exportedFlowCount = 42    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |           Padding             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.4.4.  Data Set Using an Enterprise-Specific Scope

  In this example, we report the following two Data Records:

  Line Card ID               | IPFIX Message  | Exported Flow Records
  -------------------------------------------------------------------
  Line Card 1 (lineCardId=1) | 345            | 10201
  Line Card 2 (lineCardId=2) | 690            | 20402

   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 = 260             |         Length = 20           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               1                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             345               |            10201              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               2                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             690               |            20402              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+









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A.5.  Variable-Length Information Element Examples

A.5.1.  Example of Variable-Length Information Element with Length
       Inferior to 255 Octets

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       5       |          5 octet Information Element          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.5.2.  Example of Variable-Length Information Element with Length 255
       to 65535 Octets

   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      |             1000              |    IE ...     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                1000 octet Information Element                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  :                              ...                              :
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                             ... IE            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

References

Normative References

  [RFC1305]       Mills, D., "Network Time Protocol (Version 3)
                  Specification, Implementation and Analysis", RFC
                  1305, March 1992.

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

  [RFC2434]       Narten, T. and H. Alvestrand, "Guidelines for Writing
                  an IANA Considerations Section in RFCs", BCP 26, RFC
                  2434, October 1998.

  [RFC3280]       Housley, R., Polk, W., Ford, W., and D. Solo,
                  "Internet X.509 Public Key Infrastructure Certificate
                  and Certificate Revocation List (CRL) Profile", RFC
                  3280, April 2002.




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RFC 5101              IPFIX Protocol Specification          January 2008


  [RFC3436]       Jungmaier, A., Rescorla, E., and M. Tuexen,
                  "Transport Layer Security over Stream Control
                  Transmission Protocol", RFC 3436, December 2002.

  [RFC3758]       Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
                  Conrad, "Stream Control Transmission Protocol (SCTP)
                  Partial Reliability Extension", RFC 3758, May 2004.

  [RFC4346]       Dierks, T. and E. Rescorla, "The Transport Layer
                  Security (TLS) Protocol Version 1.1", RFC 4346, April
                  2006.

  [RFC4347]       Rescorla, E. and N. Modadugu, "Datagram Transport
                  Layer Security", RFC 4347, April 2006.

  [RFC3490]       Faltstrom, P., Hoffman, P., and A. Costello,
                  "Internationalizing Domain Names in Applications
                  (IDNA)", RFC 3490, March 2003.

  [RFC3492]       Costello, A., "Punycode: A Bootstring encoding of
                  Unicode for Internationalized Domain Names in
                  Applications (IDNA)", RFC 3492, March 2003.

  [RFC4960]       Stewart, R., Ed., "Stream Control Transmission
                  Protocol", RFC 4960, September 2007.

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

  [TCP]           Postel, J., "Transmission Control Protocol", STD 7,
                  RFC 793, September 1981.

  [UDP]           Postel, J., "User Datagram Protocol", STD 6, RFC 768,
                  August 1980.

Informative References

  [IPFIX-ARCH]    Sadasivan, G., Brownlee, N., Claise, B., and J.
                  Quittek, "Architecture Model for IP Flow Information
                  Export", Work in Progress, September 2006.

  [IPFIX-AS]      Zseby, T., Boschi, E., Brownlee, N., and B. Claise,
                  "IPFIX Applicability", Work in Progress, June 2007.

  [PEN]           IANA Private Enterprise Numbers registry
                  http://www.iana.org/assignments/enterprise-numbers.




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RFC 5101              IPFIX Protocol Specification          January 2008


  [RFC1948]       Bellovin, S., "Defending Against Sequence Number
                  Attacks", RFC 1948, May 1996.

  [RFC2579]       McCloghrie, K., Perkins, D., and J. Schoenwaelder,
                  "Textual Conventions for SMIv2", STD 58, RFC 2579,
                  April 1999.

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

  [RFC3550]       Schulzrinne, H., Casner, S., Frederick, R., and V.
                  Jacobson, "RTP: A Transport Protocol for Real-Time
                  Applications", STD 64, RFC 3550, July 2003.

  [RFC3954]       Claise, B., Ed., "Cisco Systems NetFlow Services
                  Export Version 9", RFC 3954, October 2004.

  [IEEE.754.1985] Institute of Electrical and Electronics Engineers,
                  "Standard for Binary Floating-Point Arithmetic", IEEE
                  Standard 754, August 1985.

  [dtls-for-sctp] Tuexen, M. and E. Rescola, "Datagram Transport Layer
                  Security for Stream Control Transmission Protocol",
                  Work in Progress, November 2007.

Acknowledgments

  We would like to thank the following persons: Ganesh Sadasivan for
  his significant contribution during the initial phases of the
  protocol specification; Juergen Quittek for the coordination job
  within IPFIX and PSAMP; Nevil Brownlee, Dave Plonka, Paul Aitken, and
  Andrew Johnson for the thorough reviews; Randall Stewart and Peter
  Lei for their SCTP expertise and contributions; Martin Djernaes for
  the first essay on the SCTP section; Michael Behringer and Eric
  Vyncke for their advice and knowledge in security; Michael Tuexen for
  his help regarding the DTLS section; Elisa Boschi for her
  contribution regarding the improvement of SCTP sections; Mark
  Fullmer, Sebastian Zander, Jeff Meyer, Maurizio Molina, Carter
  Bullard, Tal Givoly, Lutz Mark, David Moore, Robert Lowe, Paul
  Calato, and many more, for the technical reviews and feedback.










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Authors' Addresses

  Benoit Claise
  Cisco Systems
  De Kleetlaan 6a b1
  1831 Diegem
  Belgium
  Phone: +32 2 704 5622
  EMail: [email protected]

  Stewart Bryant
  Cisco Systems, Inc.
  250, Longwater,
  Green Park,
  Reading, RG2 6GB,
  United Kingdom
  Phone: +44 (0)20 8824-8828
  EMail: [email protected]

  Simon Leinen
  SWITCH
  Werdstrasse 2
  P.O. Box
  CH-8021 Zurich
  Switzerland
  Phone: +41 44 268 1536
  EMail: [email protected]

  Thomas Dietz
  NEC Europe Ltd.
  NEC Laboratories Europe
  Network Research Division
  Kurfuersten-Anlage 36
  69115 Heidelberg
  Germany
  Phone: +49 6221 4342-128
  EMail: [email protected]

  Brian H. Trammell
  CERT Network Situational Awareness
  Software Engineering Institute
  4500 Fifth Avenue
  Pittsburgh, PA 15213
  United States
  Phone: +1 412 268 9748
  EMail: [email protected]





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Full Copyright Statement

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  contained in BCP 78, and except as set forth therein, the authors
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