Network Working Group B. Trammell
Request for Comments: 5103 CERT/NetSA
Category: Standards Track E. Boschi
Hitachi Europe
January 2008
Bidirectional Flow Export Using IP Flow Information Export (IPFIX)
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 describes an efficient method for exporting
bidirectional flow (Biflow) information using the IP Flow Information
Export (IPFIX) protocol, representing each Biflow using a single Flow
Record.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. IPFIX Documents Overview . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Rationale and History . . . . . . . . . . . . . . . . . . . . 5
4. Biflow Semantics . . . . . . . . . . . . . . . . . . . . . . . 6
5. Direction Assignment . . . . . . . . . . . . . . . . . . . . . 8
5.1. Direction by Initiator . . . . . . . . . . . . . . . . . . 9
5.2. Direction by Perimeter . . . . . . . . . . . . . . . . . . 10
5.3. Arbitrary Direction . . . . . . . . . . . . . . . . . . . 10
6. Record Representation . . . . . . . . . . . . . . . . . . . . 11
6.1. Reverse Information Element Private Enterprise Number . . 11
6.2. Enterprise-Specific Reverse Information Elements . . . . . 13
6.3. biflowDirection Information Element . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 17
Appendix B. XML Specification of biflowDirection Information
Element . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
Many flow analysis tasks benefit from association of the upstream and
downstream flows of a bidirectional communication, e.g., separating
answered and unanswered TCP requests, calculating round trip times,
etc. Metering processes that are not part of an asymmetric routing
infrastructure, especially those deployed at a single point through
which bidirectional traffic flows, are well positioned to observe
bidirectional flows (Biflows). In such topologies, the total
resource requirements for Biflow assembly are often lower if the
Biflows are assembled at the measurement interface as opposed to the
Collector. The IPFIX Protocol requires only information model
extensions to be complete as a solution for exporting Biflow data.
To that end, we propose a Biflow export method using a single Flow
Record per Biflow in this document. We explore the semantics of
bidirectional flow data in Section 4, "Biflow Semantics"; examine the
various possibilities for determining the direction of Biflows in
Section 5, "Direction Assignment"; then define the Biflow export
method in Section 6, "Record Representation".
This export method requires additional Information Elements to
represent data values for the reverse direction of each Biflow, and a
single additional Information Element to represent direction
assignment information, as described in Sections 6.1 through 6.3.
The selection of this method was motivated by an exploration of other
possible methods of Biflow export using IPFIX; however, these methods
have important drawbacks, as discussed in Section 3, "Rationale and
History".
1.1. IPFIX Documents Overview
"Specification of the IPFIX Protocol for the Exchange of IP Traffic
Flow Information" [RFC5101] (informally, the IPFIX Protocol document)
and its associated documents define the IPFIX Protocol, which
provides network engineers and administrators with access to IP
traffic flow information.
"Architecture for IP Flow Information Export" [IPFIX-ARCH] (the IPFIX
Architecture document) defines the architecture for the export of
measured IP flow information out of an IPFIX Exporting Process to an
IPFIX Collecting Process, and the basic terminology used to describe
the elements of this architecture, per the requirements defined in
"Requirements for IP Flow Information Export" [RFC3917]. The IPFIX
Protocol document [RFC5101] then covers the details of the method for
transporting IPFIX Data Records and Templates via a congestion-aware
transport protocol from an IPFIX Exporting Process to an IPFIX
Collecting Process.
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"Information Model for IP Flow Information Export" [RFC5102]
(informally, the IPFIX Information Model document) describes the
Information Elements used by IPFIX, including details on Information
Element naming, numbering, and data type encoding. Finally, "IPFIX
Applicability" [IPFIX-AS] describes the various applications of the
IPFIX protocol and their use of information exported via IPFIX, and
relates the IPFIX architecture to other measurement architectures and
frameworks.
This document references the Protocol and Architecture documents for
terminology, uses the IPFIX Protocol to define a bidirectional flow
export method, and proposes additions to the information model
defined in the IPFIX Information Model document.
2. Terminology
Capitalized terms used in this document that are defined in the
Terminology section of the IPFIX Protocol document [RFC5101] are to
be interpreted as defined there. The following additional terms are
defined in terms of the IPFIX Protocol document terminology.
Directional Key Field: A Directional Key Field is a single field in
a Flow Key as defined in the IPFIX Protocol document [RFC5101]
that is specifically associated with a single endpoint of the
Flow. sourceIPv4Address and destinationTransportPort are example
Directional Key Fields.
Non-directional Key Field: A Non-directional Key Field is a single
field within a Flow Key as defined in the IPFIX Protocol document
[RFC5101] that is not specifically associated with either endpoint
of the Flow. protocolIdentifier is an example Non-directional Key
Field.
Uniflow (Unidirectional Flow): A Uniflow is a Flow as defined in the
IPFIX Protocol document [RFC5101], restricted such that the Flow
is composed only of packets sent from a single endpoint to another
single endpoint.
Biflow (Bidirectional Flow): A Biflow is a Flow as defined in the
IPFIX Protocol document [RFC5101], composed of packets sent in
both directions between two endpoints. A Biflow is composed from
two Uniflows such that:
1. the value of each Non-directional Key Field of each Uniflow is
identical to its counterpart in the other, and
2. the value of each Directional Key Field of each Uniflow is
identical to its reverse direction counterpart in the other.
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A Biflow contains two non-key fields for each value it represents
associated with a single direction or endpoint: one for the
forward direction and one for the reverse direction, as defined
below.
Biflow Source: The Biflow Source is the endpoint identified by the
source Directional Key Fields in the Biflow.
Biflow Destination: The Biflow Destination is the endpoint
identified by the destination Directional Key Fields in the
Biflow.
forward direction (of a Biflow): The direction of a Biflow composed
of packets sent by the Biflow Source. Values associated with the
forward direction of a Biflow are represented using normal
Information Elements. In other words, a Uniflow may be defined as
a Biflow having only a forward direction.
reverse direction (of a Biflow): The direction of a Biflow composed
of packets sent by the Biflow Destination. Values associated with
the reverse direction of a Biflow are represented using Reverse
Information Elements, as defined below.
Reverse Information Element: An Information Element defined as
corresponding to a normal (or forward) Information Element, but
associated with the reverse direction of a Biflow.
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].
3. Rationale and History
In selecting the Single Record Biflow export method described in this
document as the recommendation for bidirectional flow export using
IPFIX, we considered several other possible methods.
The first and most obvious would be simply to export Biflows as two
Uniflows adjacent in the record stream; a Collecting Process could
then reassemble them with minimal state requirements. However, this
has the drawbacks that it is merely an informal arrangement the
Collecting Process cannot rely upon, and that it is not bandwidth-
efficient, duplicating the export of Flow Key data in each Uniflow
record.
We then considered the method outlined in Reducing Redundancy in
IPFIX and Packet Sampling (PSAMP) Reports [IPFIX-REDUCING] for
reducing this bandwidth inefficiency. This would also formally link
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the two Uniflows into a single construct, by exporting the Flow Key
as Common Properties then exporting each direction's information as
Specific Properties. However, it would do so at the expense of
additional overhead to transmit the commonPropertiesId, and
additional state management requirements at both the Collecting and
Exporting Processes.
A proposal was made on the IPFIX mailing list to use the Multiple
Information Element feature of the protocol to export forward and
reverse counters using identical Information Elements in the same
Flow Record. In this approach, the first instance of a counter would
represent the forward direction, and the second instance of the same
counter would represent the reverse. This had the disadvantage of
conflicting with the presently defined semantics for these counters,
and, as such, was abandoned.
4. Biflow Semantics
As stated in the Terminology section above, a Biflow is simply a Flow
representing packets flowing in both directions between two endpoints
on a network. There are compelling reasons to treat Biflows as
single entities (as opposed to merely ad-hoc combinations of
Uniflows) within IPFIX. First, as most application-layer network
protocols are inherently bidirectional, a Biflow-based data model
more accurately represents the behavior of the network, and enables
easier application of flow data to answering interesting questions
about network behavior. Second, exporting Biflow data can result in
improved export efficiency by eliminating the duplication of Flow Key
data in an IPFIX message stream, and improve collection efficiency by
removing the burden of Biflow matching from the Collecting Process
where possible.
Biflows are somewhat more semantically complicated than Uniflows.
When handling Uniflows, the semantics of source and destination
Information Elements are clearly defined by the semantics of the
underlying packet header data: the source Information Elements
represent the source header fields, and the destination Information
Elements represent the destination header fields. When representing
Biflows with single IPFIX Data Records, the definitions of source and
destination must be chosen more carefully.
As in the Terminology section above, we define the Source of a Biflow
to be that identified by the source Directional Key Field(s), and the
Destination of the Biflow to be that identified by the destination
Directional Key Field(s). Note that, for IANA-registered Information
Elements, or those defined by the IPFIX Information Model [RFC5102],
Directional Key Fields associated with the Biflow Source are
represented by Information Elements whose names begin with "source",
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and Directional Key Fields associated with the Biflow Destination are
represented by Information Elements whose names begin with
"destination"; it is recommended that enterprise-specific Information
Elements follow these conventions, as well.
Methods for assignment of Source and Destination by the Metering and
Exporting Processes are described in the following section.
As the Source and Destination of a Biflow are defined in terms of its
Directional Keys, Biflow values are also split info forward and
reverse directions. As in the Terminology section above, the forward
direction of a Biflow is composed of packets sent by the Biflow
Source, and the reverse direction of a Biflow is composed of packets
sent by the Destination. In other words, the two directions of a
Biflow may be roughly thought of as the two Uniflows that were
matched to compose the Biflow. A Biflow record, then, contains each
Flow Key record once, and both forward Information Elements and
Reverse Information Elements for each non-key field. See Figure 1
for an illustration of the composition of Biflows from Uniflows.
Uniflow Uniflow
+-------+-------+-----------------+ +-------+-------+-----------------+
| src A | dst B | counters/values | | src B | dst A | counters/values |
+-------+-------+-----------------+ +-------+-------+-----------------+
| | | |
V V V V
+-------+-------+---------------------+---------------------+
| src A | dst B | fwd counters/values | rev counters/values |
+-------+-------+---------------------+---------------------+
Biflow
Figure 1: Bidirectional Flow Conceptual Diagram
The reverse direction values are represented by Reverse Information
Elements. The representation of these Reverse Information Elements
within Templates is detailed in Section 5. A Flow Record may be
considered to be a Biflow record by the Collecting Process if it
contains at least one Reverse Information Element AND at least one
Directional Key Field. Flow Records containing Reverse Information
Elements but no Directional Key Fields are illegal, MUST NOT be sent
by the Exporting Process, and SHOULD be dropped by the Collecting
Process. The Collecting Process SHOULD log the receipt of such
illegal Flow Records.
When exporting Uniflows, Exporting Processes SHOULD use a Template
containing no Reverse Information Elements. Note that a Template
whose only Reverse Information Elements are counters MAY be used to
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export Uniflows, as counters with values of 0 are semantically
equivalent to no reverse direction. However, this approach is not
possible for Reverse Information Elements whose zero values have a
distinct meaning (e.g., tcpControlBits).
Note that a Biflow traversing a middlebox [RFC3234] may show
different flow properties on each side of the middlebox due to
changes to the packet header or payload performed by the middlebox
itself. Therefore, it MUST be clear at a Collecting Process whether
packets were observed and metered before or after modification. The
Observation Process SHOULD be located on one side of a middlebox, and
the Exporting Process SHOULD communicate to the Collecting Process
both the incoming value of the flow property changed within the
middlebox and the changed value on the "other side". The IPFIX
Information Model [RFC5102] provides Information Elements with prefix
"post" for this purpose. The location of the Observation Point(s)
with respect to the middlebox can be communicated using Options with
Observation Point as Scope and elements such as lineCardID or
samplerID.
For further information on the effect of middleboxes within the IPFIX
architecture, refer to Section 7 of the IPFIX Implementation
Guidelines [IPFIX-IMPLEMENTATION].
By the definition of Observation Domain in Section 2 of the IPFIX
Protocol document [RFC5101], Biflows may be composed only of packets
observed within the same Observation Domain. This implies that
Metering Processes that build Biflows out of Uniflows must ensure
that the two Uniflows were observed within the same Observation
Domain.
5. Direction Assignment
Due to the variety of flow measurement applications and restrictions
on Metering Process deployment, one single method of assigning the
directions of a Biflow will not apply in all cases. This section
describes three methods of direction assignment, and recommends them
based upon Metering Process position and measurement application
requirements. In each of the figures in this section, the "MP" box
represents the Metering Process.
As the method selection is dependent on Metering Process position, it
is sufficient to configure the direction assignment method at the
Collecting and/or the Exporting Process out-of-band. For example, a
Collecting Process might be configured that a specific Exporting
Process identified by exporterIPv4Address is assigning direction by
initiator; or both a Collecting Process and an Exporting Process
could be simultaneously configured with a specific direction
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assignment perimeter. However, for Exporting Processes that use
multiple direction selection methods, or for Collecting Processes
accepting data from Exporting Processes using a variety of methods, a
biflowDirection Information Element is provided for optional
representation of direction assignment information.
5.1. Direction by Initiator
If the measurement application requires the determination of the
initiator and responder of a given communication, the Metering
Process SHOULD define the Biflow Source to be the initiator of the
Biflow, where possible. This can be roughly approximated by a
Metering Process observing packets in both directions simply assuming
that the first packet seen in a given Biflow is the packet initiating
the Biflow. A Metering Process may improve upon this method by using
knowledge of the transport or application protocols (e.g., TCP flags,
DNS question/answer counts) to better approximate the flow-initiating
packet.
Note that direction assignment by initiator is most easily done by a
single Metering Process positioned on a local link layer, as in
Figure 2, or a single Metering Process observing bidirectional packet
flows at a symmetric perimeter routing point, as in Figure 3.
Note also that many Metering Processes have an "active" timeout, such
that any flow with a duration longer than the active timeout is
expired and any further packets belonging to that flow are accounted
for as part of a new flow. This mechanism may cause issues with the
assumption that a first packet seen is from the flow initiator, if
the "first" packet is a middle packet in a long-duration flow.
+-------+ +-------+
| node | | node |
+---+---+ +---+---+
| | +---------+
<===+=====+=====+======>+ +<===> Internet
| | router |
+---+---+ +---------+
| MP |
+---+---+
Figure 2: Local Link Metering Process Position
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+-------+ +-------+
| node | | node |
+---+---+ +---+---+
| | +---------+
<===+===========+======>+ +<===> Internet
| router |
| +----+--+
+----+ MP |
+-------+
Figure 3: Symmetric Routing Point Metering Process Position
5.2. Direction by Perimeter
If the measurement application is deployed at a network perimeter, as
illustrated in Figure 4, such that there is a stable set of addresses
that can be defined as "inside" that perimeter, and there is no
measurement application requirement to determine the initiator and
responder of a given communication, then the Metering Process SHOULD
assign the Biflow Source to be the endpoint outside the perimeter.
No facility is provided for exporting the address set defining the
interior of a perimeter; this set may be deduced by the Collecting
Process observing the set of Biflow Source and Biflow Destination
addresses, or configured out-of-band.
+---------+ +---------+
====>+ access +====> ====>+ access +====>
Internet | router | Local Net | router | Internet
(link A) <====+ A +<==== <====+ B +<==== (link B)
+----+----+ +---------+
|
+---+---+
| MP |
+-------+
Figure 4: Perimeter Metering Process Position
5.3. Arbitrary Direction
If the measurement application is deployed in a network core, such
that there is no stable set of addresses defining a perimeter (e.g.,
due to BGP updates), as in Figure 5, and no requirement or ability to
determine the initiator or responder of a given communication, then
the Metering Process MAY assign the Biflow Source and Biflow
Destination endpoints arbitrarily.
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In this case, the Metering Process SHOULD be consistent in its choice
of direction. Once assigned, direction SHOULD be maintained for the
lifetime of the Biflow, even in the case of active timeout of a
long-lived Biflow.
|
V
+----+----+ +---------+
<===+ core | | core +===>
| router +<========>+ router |
===>+ | | +<===
+----+----+ +----+----+
| |
+---+---+ V
| MP |
+-------+
Figure 5: Transit/Core Metering Process Position
6. Record Representation
As noted above, Biflows are exported using a single Flow Record, each
of which contains the Flow Key fields once, and both forward
Information Elements and Reverse Information Elements for each non-
key field. The IPFIX Information Model is extended to provide a
Reverse Information Element counterpart to each presently defined
forward Information Element, as required by any Information Element
that may be a non-key field in a Biflow.
6.1. Reverse Information Element Private Enterprise Number
Reverse Information Elements are specified as a separate "dimension"
in the Information Element space, assigning Private Enterprise Number
(PEN) 29305 to this document, and defining that PEN to signify "IPFIX
Reverse Information Element" (the Reverse PEN). This Reverse PEN
serves as a "reverse direction flag" in the Template; each
Information Element number within this PEN space is assigned to the
reverse counterpart of the corresponding IANA-assigned public
Information Element number. In other words, to generate a Reverse
Information Element in a Template corresponding to a given forward
Information Element, simply set the enterprise bit and define the
Information Element within the Reverse PEN space, as in Figure 6
below.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| flowStartSeconds 150 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
forward |
|
reverse V
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| (rev) flowStartSeconds 150 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reverse PEN 29305 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Example Mapping between Forward and Reverse IEs
As the Reverse Information Element dimension is treated explicitly as
such, new Information Elements can be added freely to the IANA-
managed space without concern for whether a Reverse Information
Element should also be added. Aside from the initial allocation of a
Private Enterprise Number for this purpose, there is no additional
maintenance overhead for supporting Reverse Information Elements in
the IPFIX Information Model.
Note that certain Information Elements in the IPFIX Information Model
[RFC5102] are not reversible; that is, they are semantically
meaningless as Reverse Information Elements. An Exporting Process
MUST NOT export a Template containing the reverse counterpart of a
non-reversible Information Element. A Collecting Process receiving
the reverse counterpart of a non-reversible Information Element MAY
discard that Information Element from the Flow Record. Non-
reversible Information Elements represent properties of the Biflow
record as a whole, or are intended for internal the use of the IPFIX
Protocol itself. Therefore, by definition, they cannot be associated
with a single direction or endpoint of the Flow.
The following specific Information Elements are not reversible:
1. Identifiers defined in Section 5.1 of [RFC5102] that cannot be
associated with a single direction of Uniflow collection: flowId
(5.1.7), templateId (5.1.8), observationDomainId (5.1.9), and
commonPropertiesId (5.1.11).
2. Process configuration elements defined in Section 5.2 of
[RFC5102].
3. Process statistics elements defined in Section 5.3 of [RFC5102].
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4. paddingOctets defined in Section 5.12.1 of [RFC5102].
5. biflowDirection (defined in Section 6.3 of this document).
Any future addition to the Information Element Registry by IANA that
meets the criteria defined above SHOULD also be considered to be non-
reversible by the Collecting Process.
Note that Information Elements commonly used as Flow Keys (e.g.,
header fields defined in Sections 5.4 and 5.5 of the Information
Model) are reversible, as they may be used as value fields in certain
contexts, as when associating ICMP error messages with the flows that
caused them.
6.2. Enterprise-Specific Reverse Information Elements
Note that the Reverse PEN defined above is only available for
allocating reverse counterparts of IANA-registered IPFIX Information
Elements. No facility is provided for allocating reverse
counterparts of enterprise-specific Information Elements.
The allocation of enterprise-specific Information Elements for IPFIX
is left to the discretion of the organization allocating them. Note
that, as enterprise-specific Information Elements are designed for
the internal use of private enterprises, the lack of any guidance or
standard on Information Element allocation policies poses no
interoperability issues. However, if a private enterprise's own
Information Element registry anticipates the allocation of reversible
Information Elements, and the use of this specification for the
export of Biflow data, that registry MAY reserve one of the fifteen
available bits in the Information Element ID to signify the reverse
direction. For example, if the most significant bit were selected,
this would reserve Information Element IDs 0x4000 to 0x7FFF for the
reverse direction of Information Element IDs 0x0000 to 0x3FFF.
6.3. biflowDirection Information Element
Description: A description of the direction assignment method used
to assign the Biflow Source and Destination. This Information
Element MAY be present in a Flow Record, or applied to all flows
exported from an Exporting Process or Observation Domain using
IPFIX Options. If this Information Element is not present in a
Flow Record or associated with a Biflow via scope, it is assumed
that the configuration of the direction assignment method is done
out-of-band. Note that when using IPFIX Options to apply this
Information Element to all flows within an Observation Domain or
from an Exporting Process, the Option SHOULD be sent reliably. If
reliable transport is not available (i.e., when using UDP), this
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Information Element SHOULD appear in each Flow Record. This field
may take the following values:
+-------+------------------+----------------------------------------+
| Value | Name | Description |
+-------+------------------+----------------------------------------+
| 0x00 | arbitrary | Direction was assigned arbitrarily. |
| 0x01 | initiator | The Biflow Source is the flow |
| | | initiator, as determined by the |
| | | Metering Process' best effort to |
| | | detect the initiator. |
| 0x02 | reverseInitiator | The Biflow Destination is the flow |
| | | initiator, as determined by the |
| | | Metering Process' best effort to |
| | | detect the initiator. This value is |
| | | provided for the convenience of |
| | | Exporting Processes to revise an |
| | | initiator estimate without re-encoding |
| | | the Biflow Record. |
| 0x03 | perimeter | The Biflow Source is the endpoint |
| | | outside of a defined perimeter. The |
| | | perimeter's definition is implicit in |
| | | the set of Biflow Source and Biflow |
| | | Destination addresses exported in the |
| | | Biflow Records. |
+-------+------------------+----------------------------------------+
Abstract Data Type: unsigned8
Data Type Semantics: identifier
ElementId: 239
Status: current
7. IANA Considerations
This document specifies the creation of a new dimension in the
Information Element space defined by the IPFIX Information Model
[RFC5102]. This new dimension is defined by the allocation of a new
Private Enterprise Number (PEN). The Internet Assigned Numbers
Authority (IANA) has assigned Private Enterprise Number 29305 to this
document as the "IPFIX Reverse Information Element Private
Enterprise", with this document's authors as point of contact.
This document specifies the creation of a new IPFIX Information
Element, biflowDirection, as defined in Section 6.3. IANA has
assigned Information Element number 239 in the IPFIX Information
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Element registry for the biflowDirection Information Element. The
values defined for this Information Element are static, and as such
do not need to be maintained by IANA in a sub-registry.
8. Security Considerations
The same security considerations as for the IPFIX Protocol [RFC5101]
apply.
9. Acknowledgments
We would like to thank Lutz Mark, Juergen Quittek, Andrew Johnson,
Paul Aitken, Benoit Claise, and Carsten Schmoll for their
contributions and comments. Special thanks to Michelle Cotton for
her assistance in navigating the IANA process for Enterprise Number
assignment, and for the IANA pre-review of the document.
10. References
10.1. Normative References
[RFC5101] Claise, B., Ed., "Specification of the IP
Flow Information Export (IPFIX) Protocol for
the Exchange of IP Traffic Flow Information",
RFC 5101, January 2008.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken,
P., and J. Meyer, "Information Model for IP
Flow Information Export", RFC 5102, January
2008.
10.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes:
Taxonomy and Issues", RFC 3234,
February 2002.
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S.
Zander, "Requirements for IP Flow Information
Export (IPFIX)", RFC 3917, October 2004.
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RFC 5103 IPFIX Biflow Export January 2008
[IPFIX-ARCH] Sadasivan, G., Brownlee, N., Claise, B., and
J. Quittek, "Architecture 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, July 2007.
[IPFIX-IMPLEMENTATION] Boschi, E., Mark, L., Quittek, j.,
Stiemerling, M., and P. Aitken, "IPFIX
Implementation Guidelines", Work in Progress,
September 2007.
[IPFIX-REDUCING] Boschi, E., Mark, L., and B. Claise,
"Reducing Redundancy in IP Flow Information
Export (IPFIX) and Packet Sampling (PSAMP)
Reports", Work in Progress, May 2007.
Trammell & Boschi Standards Track [Page 16]
RFC 5103 IPFIX Biflow Export January 2008
Appendix A. Examples
The following example describes a Biflow record as specified in
Section 6, above. The Reverse PEN is assigned for the purpose of
differentiating forward from Reverse Information Elements.
The information exported in this case is:
o The start time of the flow: flowStartSeconds in the IPFIX
Information Model [RFC5102], with a length of 4 octets.
o The reverse start time of the flow: flowStartSeconds in the IPFIX
Information Model [RFC5102], with a length of 4 octets, and the
enterprise bit set to 1. The following PEN is the Reverse PEN.
o The IPv4 source IP address: sourceIPv4Address in the IPFIX
Information Model [RFC5102], with a length of 4 octets.
o The IPv4 destination IP address: destinationIPv4Address in the
IPFIX Information Model [RFC5102], with a length of 4 octets.
o The source port: sourceTransportPort in the IPFIX Information
Model [RFC5102], with a length of 2 octets.
o The destination port: destinationTransportPort in the IPFIX
Information Model [RFC5102], with a length of 2 octets.
o The protocol identifier: protocolIdentifier in the IPFIX
Information Model [RFC5102], with a length of 1 octet.
o The number of octets of the Flow: octetTotalCount in the IPFIX
Information Model [RFC5102], with a length of 4 octets.
o The reverse number of octets of the Flow: octetTotalCount in the
IPFIX Information Model [RFC5102], with a length of 4 octets, and
the enterprise bit set to 1. The following PEN is the Reverse
PEN.
o The number of packets of the Flow: packetTotalCount in the IPFIX
Information Model [RFC5102], with a length of 4 octets.
o The reverse number of packets of the Flow: packetTotalCount in the
IPFIX Information Model [RFC5102], with a length of 4 octets, and
the enterprise bit set to 1. The following PEN is the Reverse
PEN.
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RFC 5103 IPFIX Biflow Export January 2008
and the resulting Template Set would look like the diagram below:
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 = 64 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID >= 256 | Field Count = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| flowStartSeconds 150 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| flowStartSeconds 150 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reverse PEN 29305 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| sourceIPv4Address 8 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| destinationIPv4Address 12 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| sourceTransportPort 7 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| destinationTransportPort 11 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| protocolIdentifier 4 | Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| octetTotalCount 85 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| octetTotalCount 85 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reverse PEN 29305 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| packetTotalCount 86 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| packetTotalCount 86 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reverse PEN 29305 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Single Record Biflow Template Set
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RFC 5103 IPFIX Biflow Export January 2008
The following example Data Set represents a typical HTTP transaction.
Its format is defined by the example Template, above.
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 = 41 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2006-02-01 17:00:00 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2006-02-01 17:00:01 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.0.2.2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.0.2.3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 32770 | 80 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 | 18000 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . | 128000 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . | 65 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . | 110 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . |
+-+-+-+-+-+-+-+-+
Figure 8: Single Record Biflow Data Set
The following example demonstrates the use of the biflowDirection
Information Element, as specified in Section 6.2, using the IPFIX
Options mechanism to specify that perimeter direction selection is in
effect for a given Observation Domain.
The information exported in this case is:
o The Observation Domain: observationDomainId in the IPFIX
Information Model [RFC5102], with a length of 4 octets.
o The direction assignment method: biflowDirection as defined in
Section 6.2, above, with a length of 1 octet.
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RFC 5103 IPFIX Biflow Export January 2008
and the resulting Options Template Set would look like the diagram
below:
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 = 18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID >= 256 | Field Count = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Count = 1 |0| observationDomainId 149 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| biflowDirection 239 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Biflow Direction Options Template Set
The following example Data Set would specify that perimeter direction
selection is in effect for the Observation Domain with ID 33. Its
format is defined by the example Options Template, above. Note that
this example data set would be sent reliably, as specified in the
description of the biflowDirection Information Element.
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 = 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 33 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |
+-+-+-+-+-+-+-+-+
Figure 10: Biflow Direction Options Data Set
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RFC 5103 IPFIX Biflow Export January 2008
Appendix B. XML Specification of biflowDirection Information Element
This appendix contains a machine-readable description of the
biflowDirection information element defined in this document, coded
in XML. Note that this appendix is of informational nature, while
the text in Section 6.3 is normative.
The format in which this specification is given is described by the
XML Schema in Appendix B of the IPFIX Information Model [RFC5102].
<?xml version="1.0" encoding="UTF-8"?>
<fieldDefinitions xmlns="urn:ietf:params:xml:ns:ipfix-info"
xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:ipfix-info
ipfix-info.xsd">
<field name="biflowDirection" dataType="unsigned8"
dataTypeSemantics="identifier" group="misc"
elementId="239" applicability="all" status="current">
<description>
<paragraph>
A description of the direction assignment method used to
assign the Biflow Source and Destination. This
Information Element MAY be present in a Flow Data Record, or
applied to all flows exported from an Exporting Process or
Observation Domain using IPFIX Options. If this Information
Element is not present in a Flow Record or associated with a
Biflow via scope, it is assumed that the configuration of
the direction assignment method is done out-of-band. Note
that when using IPFIX Options to apply this Information
Element to all flows within an Observation Domain or from an
Exporting Process, the Option SHOULD be sent reliably. If
reliable transport is not available (i.e., when using UDP),
this Information Element SHOULD appear in each Flow
Record. This field may take the following values:
</paragraph>
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RFC 5103 IPFIX Biflow Export January 2008
<artwork>
+-------+------------------+----------------------------------------+
| Value | Name | Description |
+-------+------------------+----------------------------------------+
| 0x00 | arbitrary | Direction was assigned arbitrarily. |
| 0x01 | initiator | The Biflow Source is the flow |
| | | initiator, as determined by the |
| | | Metering Process' best effort to |
| | | detect the initiator. |
| 0x02 | reverseInitiator | The Biflow Destination is the flow |
| | | initiator, as determined by the |
| | | Metering Process' best effort to |
| | | detect the initiator. This value is |
| | | provided for the convenience of |
| | | Exporting Processes to revise an |
| | | initiator estimate without re-encoding |
| | | the Biflow Record. |
| 0x03 | perimeter | The Biflow Source is the endpoint |
| | | outside of a defined perimeter. The |
| | | perimeter's definition is implicit in |
| | | the set of Biflow Source and Biflow |
| | | Destination addresses exported in the |
| | | Biflow Records. |
+-------+------------------+----------------------------------------+
</artwork>
</description>
</field>
</fieldDefinitions>
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RFC 5103 IPFIX Biflow Export January 2008
Authors' Addresses
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]
Elisa Boschi
Hitachi Europe
c/o ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 6327057
EMail:
[email protected]
Trammell & Boschi Standards Track [Page 23]
RFC 5103 IPFIX Biflow Export January 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Trammell & Boschi Standards Track [Page 24]
