IPFIX Working Group B. Trammell Internet-Draft CERT/NetSA Intended status: Informational E. Boschi Expires: March 3, 2007 Hitachi Europe August 30, 2006 Bidirectional Flow Export using IPFIX draft-ietf-ipfix-biflow-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 3, 2007. Copyright Notice Copyright (C) The Internet Society (2006). 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. Trammell & Boschi Expires March 3, 2007 [Page 1] Internet-Draft IPFIX Biflow Export August 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Rationale and History . . . . . . . . . . . . . . . . . . . . 4 4. Biflow Semantics . . . . . . . . . . . . . . . . . . . . . . . 5 5. Direction Assignment . . . . . . . . . . . . . . . . . . . . . 7 6. Record Representation . . . . . . . . . . . . . . . . . . . . 8 6.1. Reverse Information Element Private Enterprise Number . . 8 6.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 12 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . . . 15 Trammell & Boschi Expires March 3, 2007 [Page 2] Internet-Draft IPFIX Biflow Export August 2006 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 within a single Observation Domain 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 Metering Process as opposed to the Collecting Process. IPFIX 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. This method requires additional Information Elements to represent the reverse direction of each biflow. This method is motivated by an exploration of other possible methods of Biflow export using IPFIX; however, these methods have important drawbacks, as discussed in the Rationale and History section. 2. Terminology Capitalized terms used in this document that are defined in the Terminology section of the IPFIX Protocol draft [I-D.ietf-ipfix-protocol] are to be interpreted as defined there. The following additional terms are defined in terms of the protocol document terminology. Directional Key Field: A Directional Key Field is a single field in a Flow Key as defined in the IPFIX Protocol draft [I-D.ietf-ipfix-protocol] that is specifically associated with a single endpoint of the flow. sourceIPv4Address and destinationTransportPort are example common 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 draft [I-D.ietf-ipfix-protocol] that is not specifically associated with either endpoint of the flow. protocolIdentifier is an example common non-directional key field. Uniflow (Unidirectional Flow): A Uniflow is a Flow as defined in the IPFIX Protocol draft [I-D.ietf-ipfix-protocol], restricted such that the Flow is composed only of packets sent from a single endpoint to another single endpoint. Trammell & Boschi Expires March 3, 2007 [Page 3] Internet-Draft IPFIX Biflow Export August 2006 Biflow (Bidirectional Flow): A Biflow is a Flow as defined in the IPFIX Protocol draft [I-D.ietf-ipfix-protocol], composed of packets sent in both directions between two endpoints. A Biflow is composed from two Uniflows such that: 1. each Non-directional Key Field of each Uniflow is identical to its counterpart in the other, and 2. each Directional Key Field of each Uniflow is identical to its reverse direction counterpart in the other 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 source of a Biflow is the endpoint identified by the source Directional Key Fields in the biflow. Biflow Destination: The destination of a Biflow 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 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. Trammell & Boschi Expires March 3, 2007 [Page 4] Internet-Draft IPFIX Biflow Export August 2006 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 PSAMP Reports [I-D.boschi-ipfix-reducing-redundancy] for reducing this bandwidth inefficiency. This would also formally link 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 Process. 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 Element 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 was as such 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 Uniflow halves) 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. First, 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 Trammell & Boschi Expires March 3, 2007 [Page 5] Internet-Draft IPFIX Biflow Export August 2006 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 [I-D.ietf-ipfix-info], Source Key Fields are represented by Information Elements whose names begin with "source", and Destination Key Fields are represented by Information Elements whose names begin with "destination"; it is recommended that vendor-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 Uniflow halves that were matched to compose the Biflow. A Biflow record, then, contains each Flow Key record once, and both forward and reverse direction information elements for each non-key field. 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, and MUST be dropped by the Collecting Process. The Collecting Process SHOULD log the receipt of illegal Biflow Flow Records. Note that since the IPFIX information model makes no distinction between zeroes and null values, if a given flow has no reverse direction, it may only be unambiguously represented as a Biflow Flow Record if all its Reverse Information Elements are counters. Exporting Processes SHOULD switch to a Template containing no Reverse Information Elements when exporting flows without a reverse direction. Trammell & Boschi Expires March 3, 2007 [Page 6] Internet-Draft IPFIX Biflow Export August 2006 By the definition of Observation Domain in section 2 of the IPFIX Protocol draft [I-D.ietf-ipfix-protocol], Biflows may be composed only of packets observed within the same Observation Domain. This implies that Metering Processes that build Biflows out of Uniflow halves must ensure that the two Uniflow halves were observed within the same Observation Domain. 5. Direction Assignment Metering Processes, where possible, SHOULD define the Biflow Source to be the initiator of the Biflow, subject to the best effort of the Metering Process. This can be roughly approximated by a Metering Process observing packets in both directions simply assuming the first packet seen in a given Biflow is the packet initiating the flow. 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. There are circumstances in which initiator direction assignment is unavailable. For instance, when building flow records from sampled or particularly lossy packet sources, the correlation between the first packet seen and the first packet sent is broken. Also, when assembling Biflows from Uniflows generated by Metering Processes only capable of observing a single direction of traffic, for example a Observation Point on a router line card in an asymmetric routing infrastructure, the timestamp information available at biflow assembly time may not be of sufficiently high precision or synchronization to positively identify the first packet. In such cases, the Metering Process MAY assign direction arbitrarily, though it SHOULD be consistent in its choice of direction. Arbitrary direction assignment MAY use Flow Key fields, for example the interface number or source address, in order to maintain this consistency. No facility is provided for the Metering Process or Exporting Process to communicate whether arbitrary direction assignment is in effect for a given Biflow or Observation Domain. Regardless of the method used to assign direction, the Exporting Process MAY export additional information about each Biflow (e.g., TCP flags information, high-precision timestamps) in order to assist the Collecting Process in determining the flow initiator or revising the Metering Process' estimate of the flow initiator. Trammell & Boschi Expires March 3, 2007 [Page 7] Internet-Draft IPFIX Biflow Export August 2006 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 and reverse direction 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, by having IANA assign a single Private Enterprise Number (PEN) to this draft, and to define that PEN to signify "IPFIX Reverse Information Element" (the Reverse PEN). This reverse PEN would serve as a "reverse direction flag" in the template; each Information Element number within this PEN space would be 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 the figure below. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| flowStartSeconds 150 | Field Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ forward | | reverse V +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| (rev) flowStartSeconds 150 | Field Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reverse PEN TBA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Example Mapping between Forward and Reverse IEs using Reverse PEN 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 element should also be added. Aside from the initial allocation of an enterprise number for this purpose, there is no additional maintenance overhead for supporting reverse information elements in the information model. Trammell & Boschi Expires March 3, 2007 [Page 8] Internet-Draft IPFIX Biflow Export August 2006 Note that certain Information Elements in the IPFIX Information Model [I-D.ietf-ipfix-info] are not reversible; that is, they are semantically meaningless as reverse Information Elements. A Collecting Process MUST note the Information Element identifier of any Information Element so used as a Reverse Information Element, and MAY discard that Information Element from the Flow Record, as with unassigned Information Elements as in section 9 of the IPFIX Protocol draft [I-D.ietf-ipfix-protocol]. 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. They therefore cannot by definition 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 the Information Model which 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 the Information Model. 3. Process statistics elements defined in section 5.3 of the Information Model. 4. paddingOctets (5.12.1). Any future addition to the Information Element Registry by IANA which 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 not necessarily non-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. Example The following example describes a biflow record as specified above. The "IPFIX Reverse Information Element" PEN is assigned for the purpose of differentiating forward from reverse information elements. This private enterprise number is denoted as TBA, as it has not yet been assigned by IANA (Cf. section 7). The information exported in this case is: Trammell & Boschi Expires March 3, 2007 [Page 9] Internet-Draft IPFIX Biflow Export August 2006 o The start time of the flow: flowStartSeconds in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets o The reverse start time of the flow: flowStartSeconds in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets, and the enterprise bit set to 1. The following PEN is the Reverse PEN (not yet assigned, indicated with TBA in the draft) o The IPv4 source IP address: sourceIPv4Address in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets o The IPv4 destination IP address:destinationIPv4Address in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets o The source port: sourceTransportPort in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 2 octets o The destination port: destinationTransportPort in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 2 octets o The protocol identifier: protocolIdentifier in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 1 octet o The number of octets of the Flow: octetTotalCount in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets o The reverse number of octets of the Flow: octetTotalCount in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets, and the enterprise bit set to 1. The following PEN is the Reverse PEN (not yet assigned, indicated with TBA in the draft) o The number of packets of the Flow: octetTotalCount in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets o The reverse number of packets of the Flow: octetTotalCount in the IPFIX Information Model [I-D.ietf-ipfix-info], with a length of 4 octets, and the enterprise bit set to 1. The following PEN is the Reverse PEN (not yet assigned, indicated with TBA in the draft) and the resulting template would look like the diagram below: Trammell & Boschi Expires March 3, 2007 [Page 10] Internet-Draft IPFIX Biflow Export August 2006 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 TBA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |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 TBA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| packetTotalCount 86 | Field Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| packetTotalCount 86 | Field Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reverse PEN TBA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Single Record Biflow Template Set The following example data record represents a typical HTTP transaction. Its format is defined by the example template, above. Trammell & Boschi Expires March 3, 2007 [Page 11] Internet-Draft IPFIX Biflow Export August 2006 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 3: Single Record Biflow Data Set 7. IANA Considerations This document specifies the creation of a new dimension in the information element space defined by the IPFIX Information Model [I-D.ietf-ipfix-info]. This new dimension is defined by the allocation of a new Private Enterprise Number (PEN). The Internet Assigned Numbers Authority (IANA) is requested to allocate this PEN and to assign it to this draft, with the draft authors as the point of contact. 8. Security Considerations The same security considerations as for the IPFIX Protocol [I-D.ietf-ipfix-protocol] apply. 9. Open Issues 1. Consider adding deployment examples, showing where biflow assembly would happen for single-metering process architectures Trammell & Boschi Expires March 3, 2007 [Page 12] Internet-Draft IPFIX Biflow Export August 2006 as well as for multiple-metering process architectures. Clarify language about the benefits of assembling biflows as close to the metering interface as possible. 2. Do we need a way to annotate how direction assignment was done? That is, does the Collecting Process need a new IE saying "flows from this odId have direction assigned by initiator", or the like? 3. The arbitrary direction assignment method is not satisfactory as a backup for initiator direction assignment. We must address how to do direction assignment for biflows assembled from sampled or lossy packet sources in a consistent way, that is compatible with the realities of traffic on backbone links and routing across transit ASs. This is a point for wider discussion within the IPFIX Working Group. 10. 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. 11. References 11.1. Normative References [I-D.ietf-ipfix-protocol] Claise, B., "IPFIX Protocol Specification", draft-ietf-ipfix-protocol-22 (work in progress), June 2006. [I-D.ietf-ipfix-info] Quittek, J., "Information Model for IP Flow Information Export", draft-ietf-ipfix-info-12 (work in progress), June 2006. 11.2. Informative References [RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander, "Requirements for IP Flow Information Export (IPFIX)", RFC 3917, October 2004. [I-D.ietf-ipfix-as] Trammell & Boschi Expires March 3, 2007 [Page 13] Internet-Draft IPFIX Biflow Export August 2006 Zseby, T., "IPFIX Applicability", draft-ietf-ipfix-as-10 (work in progress), August 2006. [I-D.boschi-ipfix-reducing-redundancy] Boschi, E., "Reducing redundancy in IPFIX and PSAMP reports", draft-boschi-ipfix-reducing-redundancy-02 (work in progress), June 2006. [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Authors' Addresses Brian H. Trammell CERT Network Situational Awareness Software Engineering Institute 4500 Fifth Avenue Pittsburgh, PA 15213 US Phone: +1 412 268 9748 Email: bht@cert.org Elisa Boschi Hitachi Europe SAS Immeuble Le Theleme 1503 Route les Dolines 06560 Valbonne France Phone: +33 4 89874100 Email: elisa.boschi@hitachi-eu.com Trammell & Boschi Expires March 3, 2007 [Page 14] Internet-Draft IPFIX Biflow Export August 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). 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. 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Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Trammell & Boschi Expires March 3, 2007 [Page 15]