Internet Draft J. Quittek Document: draft-quittek-psamp-ipfix-01.txt NEC Europe Ltd. Expires: August 2003 B. Claise Cisco Systems February 2003 On the Relationship between PSAMP and IPFIX Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. 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 Distribution of this document is unlimited. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This memo discusses the relationship between the packet sampling (PSAMP) Working Group and the IP flow information export (IPFIX) Working Group. The goals of writing this memo are: avoiding duplication of work, increase mutual benefits between the groups, and harmonize the documents and standards developed by the groups. Quittek et. al. Expires - August 2003 [Page 1] February 2003 Therefore, potential overlap of both group's activities is analyzed, activities in both groups that potentially complement each other are pointed out, and common issues are listed that should be harmonized between the groups. Table of Contents 1. Introduction...................................................2 2. Working Group Goals............................................3 2.1 IPFIX Goals................................................3 2.2 PSAMP Goals................................................4 3. Architecture...................................................5 3.1 IPFIX Architecture.........................................5 3.2 PSAMP Architecture.........................................6 4. PSAMP and IPFIX Comparison.....................................7 4.1 Architectural Comparison...................................7 4.2 Conceptual Comparison......................................8 5. Potential Overlap, Complement, and Harmonization...............9 5.1 Terminology................................................9 5.2 Packet selection and sampling model........................9 5.2.1 PSAMP as an IPFIX component: packet sampling.........9 5.2.2 PSAMP as an IPFIX component: packet selection.......10 5.3 IPFIX export for PSAMP....................................10 5.3.1 Information Model...................................11 5.3.2 Export Protocol.....................................11 5.4 Configuration.............................................11 6. Security Considerations.......................................12 7. References....................................................12 8. Acknwoldgements...............................................13 9. AuthorÆs Addresses............................................13 1. Introduction The packet sampling (PSAMP) Working Group and the IP flow information export (IPFIX) Working Group both aim at standardizing technology for observing traffic from network devices and for exporting some part of the observation. Also, both Working Groups consider packet sampling as a component of their technology. While for the IPFIX Working Group packet sampling is just one out of many components considered, it is the focus of the PSAMP Working Group. This memo discusses the relationship between the two Working Groups. The goals of writing this memo are: Quittek et. al. Expires - August 2003 [Page 2] February 2003 - avoiding duplication of work, - increase mutual benefits between the groups, - harmonize the documents and standards developed by the groups. In order to achieve this, the following issues are analyzed: - potential overlap of both group's activities, - potential mutual complements between the groups, - common issues that should be harmonized. The analysis start with brief summaries of each Working Group's goal and a comparison of the respective architectures. 2. Working Group Goals The following is a brief summary of the goals of the two Working Groups. A more detailed description can be found in the respective Working Group charters at http://www.ietf.org/html.charters/psamp- charter.html and http://www.ietf.org/html.charters/ipfix- charter.html. 2.1 IPFIX Goals The IP flow information export (IPFIX) Working Group was established in October 2001 with the goal to select a protocol for IP flow information export out of devices measuring network traffic. The Working Group's charter lists the following steps: - Define the notion of a "standard IP flow". - Devise data encodings for IP flows. - Consider the notion of IP flow information export based upon packet sampling. - Identify and address any security privacy concerns affecting flow data. - Specify the transport mapping for carrying IP flow information Quittek et. al. Expires - August 2003 [Page 3] February 2003 (IETF approved congestion-aware transport protocol) - Ensure that the flow export system is reliable and efficient (in that it will minimize the likelihood of flow data being lost due to resource constraints in the exporter or receiver and to accurately report such loss if it occurs) The output of the group will be structured into four documents: o Requirements for IP flow information export o IP flow information architecture o IP flow information export information model o IP flow information export applicability The protocol itself should not be developed by the Working Group but selected out of already existing protocols or protocols developed for this purpose externally of the IETF. Once the protocol will be selected out, small modifications will be brought to it to make it fully compliant to the IPFIX requirement draft. The focus of the Working Group is on improving and standardizing existing state-of-the-art technology and common practice. 2.2 PSAMP Goals The packet sampling (PSAMP) Working Group was established in August 2002 with the goals of - specifying a set of selection operations by which packets are sampled. - specifying the information that is to be made available for reporting on sampled packets. - describing protocols by which information on sampled packets is reported to applications. - describing protocols by which packet selection and reporting configured. Quittek et. al. Expires - August 2003 [Page 4] February 2003 In contrast to IPFIX, the PSAMP Working Group is chartered to develop new technology that is not already widely available and for which a common practice does not exist, so far. The output of the group will be structured into five documents: o Framework document o Packet selector and packet information document o Report format and report stream format document o Export and requirements for collectors document o MIB document 3. Architecture For both Working Groups, architectures are still under definition. This memo tries to sketch the basic architectures as they are currently being discussed in [IPFIX-REQ],[IPFIX-ARCH],[PSAMP-FRM], and [PSAMP-PSS]. These architecture snapshots are used in the discussion of potential overlaps and complements further below. It should be noted that during architecture development, both architectures might evolve such that some of the arguments stated below in this memo do not hold anymore. 3.1 IPFIX Architecture Please note that the [IPFIX-ARCH] draft has been put ôon holdö until the [IPFIX-REQ] is finalized and the base IPFIX protocol has been chosen amongst the candidate protocols. As a consequence, the IPIFX architecture paragraph below is not based on [IPFIX-ARCH] but on [IPFIX-REQ]. The IPFIX architecture contains six main components: observation point, metering process, flow records, exporting process, export protocol, and collecting process [IPFIX-REQ]. At the observation point, IP packets are observed. Observed packets are metered by the metering process. Metering results are stored in Quittek et. al. Expires - August 2003 [Page 5] February 2003 flow records. The exporting process exports information stored in flow records to the collecting process. +------+ packet +-------+ flow +-------+ flow +-------+ |obser-| headers|meter- | records|export-| records |collec-| |vation+------->|ing +------->|ing +-------->|ting | |point | |process| |process| IPFIX |process| +------+ +-------+ +-------+ protocol+-------+ Figure 1: Sketch of the basic IPFIX architecture Possible entity relationships between these components are not completely defined, yet. However, in general the assumption holds that each component may have several instances. According to [IPFIX-REQ], the metering process can be divided into packet header capturing, timestamping, classifying, and maintaining flow records. Before any of these functions, sampling may be applied. packet header capturing | timestamping | v +----->+ | | | classifying | | +------+ | maintaining flow records | v Figure 2: Functions of the metering process, from [IPFIX-REQ] 3.2 PSAMP Architecture PSAMP architecture development is even at an earlier stage than the IPFIX architecture. Therefore, the potential changes until completion are potentially more significant. Quittek et. al. Expires - August 2003 [Page 6] February 2003 Basically, the PSAMP architecture contains 6 main components, as defined in [PSAMP-FRM]: observation point, selection process, the reporting process (packet reports and report information), the export process and the collector. On the top of these components, the configuration management is clearly indicated as one of the charter goals. +------------------------------------------+ ---->| Configuration +<-----------+ +----+-----------------+---------------+---+ | | | | | v v v | +------+ +-------+ +-------+ packet +-------+ packet +---+---+ |obser-| packet |select-| packet |report-| report |export | report |collec-| |vation+------->|ion +------->|ing +------->|process|------->|tor | |point | header |process| header |process| report | | report | | +------+ +-------+ +-------+ info. +-------+ info. +-------+ Figure 3: Sketch of the basic PSAMP architecture Packets headers (and some subsequent bytes of the packet, and encapsulating headers if present) are observed at the observation point and selected and/or sampled by the selection process. The selection process can be based on filtering, sampling, and/or hashing functions and for selecting packets. The generated per packet information, composed of the packet report and report information is reported by the reporting process before being exported by an export process to a collecting process. The selection, reporting process and export process are configured either based on external input or by feedback from the collector. Again, entity relationships between these components are not clear, yet, but it can be assumed that each component may have multiple instances. 4. PSAMP and IPFIX Comparison 4.1 Architectural Comparison The basic structure of both architectures is quite similar, but there are three significant architectural differences that can be observed. Quittek et. al. Expires - August 2003 [Page 7] February 2003 The first one contains the information that is gathered and exported. IPFIX produces and exports flow records containing information per flow. This information is created based on the observation of a potentially large number of packets. In contrast, PSAMP generates and exports information per packet. Consequently, the PSAMP architecture contains a selecting and sampling process where the IPFIX architecture uses a more complex metering process. The second difference concerns configuration. It is an explicit goal of the PSAMP Working Group to define ways of configuring the packet selecting and sampling process and the exporting process. For IPFIX, configuration of metering process and exporting process is mentioned in the requirements document, but there are no plans yet for standardizing IPFIX configuration. The next difference concerns the export(ing) process. The PSAMP charter specifices ôNetwork elements shall support multiple parallel packet samplers, each with independently configurable packet selectors, reports, report streams, and export.ö. There is one exporting process for all the metering process in most of the IPFIX, cases: the exception comes the ôSpecial Device Considerations sectionö. Anyway, this implies that a global congestion avoiding protocol is sufficient per metering process for IPFIX, while PSAMP requires this congestion avoiding protocol per packet sampler. 4.2 Conceptual Comparison The basic concept of IPFIX and PSAMP are quite similar: observing traffic from network devices and exporting some part of this observation. But there are three differences that can be observed. Both IPFIX metering process and PSAMP selection process can select observed packets based on packet header content and packet treatement. Nevertheless, the difference is that the PSAMP selection process can compute some values out of the observed packet, i.e a hash value. This hash value can be used as a selector by the selection process. Another difference between IPFIX and PSAMP is that PSAMP might report information about "subsequent bytes of the packet and Quittek et. al. Expires - August 2003 [Page 8] February 2003 encapsulation headers if present" while IPFIX concentrates on reporting information on the IP packet header only. 5. Potential Overlap, Complement, and Harmonization 5.1 Terminology As the architecture sketches in Figures 1 and 3 show that there are several similarities between PSAMP and IPFIX. Both Working Groups address the same general subject of observing IP traffic, processing the observation, and exporting the obtained information. Therefore, it is desirable and appears to be quite feasible to agree on a common terminology to be used by both Working Groups. 5.2 Packet selection and sampling model The PSAMP Working Group already started developing a model for packet selection and packet sampling [PSAMP-PSS]. In the IPFIX Working Group this issue will probably not be specified in detail in any of the documents. They are mentioned implicitly or explicitly as functions of the IPFIX metering process, but the goal of IPFIX being to standardize the Flow Information eXport, the metering process is only briefly discussed; and only the metering process features that could influence the export protocol or information model are discussed (for example: metering process reliability or sampling). The IPFIX Working Group should consider using the PSAMP model when discussing packet selection and sampling. The PSAMP Working Group specification of sampling functions [PSAMP-PSS] should be re-used by the IPFIX Working Group for defining the sampling function of the metering process. 5.2.1 PSAMP as an IPFIX component: packet sampling The metering process of IPFIX (shown in Figure 2) contains capturing packet headers as first step. In case sampling is required, this function could be provided by a component implementing the PSAMP architecture. sampled +------+ packet +-------+ flow +-------+ flow +-------+ | | headers |meter- | records|export-| records |collec-| Quittek et. al. Expires - August 2003 [Page 9] February 2003 |PSAMP +-------->|ing +------->|ing +-------->|ting | | | |process| |process| IPFIX |process| +------+ +-------+ +-------+ protocol+-------+ So the PSAMP architecture could be used as input for the IPFIX metering process, the IPFIX metering process serving as PSAMP collecting process. Whether we would use the export protocol itself to send the sampled packets headers to the IPFIX metering process or not (API for example), should be discussed. In both cases, the PSAMP component would perform the packet header capturing function and the sampling function of the IPFIX metering process, and potentially also the timestamping function. 5.2.2 PSAMP as an IPFIX component: packet selection The IPFIX architecture does not explicitly talk about packet selection, but the packet header classification function (for example filtering) of the IPFIX metering process implicitly includes the option of packet selection: for packet headers that cannot be matched to already existing flow records, a decision need to be made on whether or not to create a new flow record for this packet. An explicit packet selection performed by a PSAMP component could contribute to this function of the IPFIX metering process, for example by already filtering all packets for which no flow record would be generated. filtered +------+ packet +-------+ flow +-------+ flow +-------+ | | headers |meter- | records|export-| records |collec-| |PSAMP +-------->|ing +------->|ing +-------->|ting | | | |process| |process| IPFIX |process| +------+ +-------+ +-------+ protocol+-------+ The PSAMP component would also potentially perform the timestamping function. 5.3 IPFIX export for PSAMP Quittek et. al. Expires - August 2003 [Page 10] February 2003 PSAMP needs to specify an information model, a data model, and a protocol for exporting packet information. This is similar to the task of IPFIX, where the same kind of specifications is required for the export of flow records. IPFIX already made good progress in specifying an information model [IPFIX-INFO] and the selection of a protocol is progressing. 5.3.1 Information Model Therefore, the PSAMP Working Group should discuss, whether or not output of the IPFIX Working Group can be used. The IPFIX flow information model may already include all information required for modeling packet information. The PSAMP Working Group could perform data modeling by just selecting a subset of the IPFIX data model to be used. If the IPFIX model would be fine in general for PSAMP, but a few packet attributes are missing, then it should be preferred to the IPFIX Working Group should be asked to extend their information model by the missing attributes instead of defining PSAMP extensions of the model (for example a new data type for the hash key, if a hash key is defined in the PSAMP Working Group). 5.3.2 Export Protocol If the IPFIX information model can be adopted by PSAMP, then there is potential to also use the IPFIX data model and protocol for PSAMP. In general, this should be possible, because an extreme case of a flow is a flow containing just a single packet. This is supported by IPFIX. Furthermore, [IPFIX-REQ] requests the IPFIX protocol to be flexible and extensible. The PSAMP Working Group should study the protocol selected as IPFIX protocol and discuss using it also as PSAMP protocol. Of course, it should be investigated carefully, whether or not there are PSAMP requirements not met by the IPFIX protocol. 5.4 Configuration For the IPFIX Working Group, a configuration protocol or a MIB module definition is out of scope for now. But for PSAMP, this is explicitly mentioned by the charter. It is not clear, whether in the Quittek et. al. Expires - August 2003 [Page 11] February 2003 future there will be a desire to standardize IPFIX configuration, as a second phase of the Working Group work. There might be reason not to so, for example allowing implementors to have differentiators for their products. However, if the IPFIX Working Group ever considers standardizing consideration, it should make sure, that IPFIX configuration will be consistent with PSAMP configuration. This applies to the configuration of sampling and packet selection as well as to the selection of attributes to be exported, the specification of data collectors to export information to, the export transmission rate, and the method of congestion handling (if configurable). 6. Security Considerations If the PSAMP Working Group discusses to use the IPFIX protocol also for PSAMP, it should study carefully, whether or not the PSAMP security requirements are stricter than the IPFIX security requirements and whether all PSAMP security requirements are covered by the IPFIX protocol. 7. References [IPFIX-REQ] Quittek, J., Zseby, T., Claise, B., Zander, S., Carle, G., Norseth, K.C., "Requirements for IP Flow Information Export", work in progress, , February 2003. [IPFIX-ARCH] Norseth, K.C., Sadasivan, G., "Architecture Model for IP Flow Information Export", work in progress, , June 2002. [IPFIX-INFO] Norseth, K.C., Calato, P., "Data Model for IP Flow Information Export", work in progress, , February 2002. [PSAMP-FRM] Duffield, N., Grossglauser, M., Rexford, J., Chiou, D., Marimuthu, P., Sadasivan, G. "A Framework for Passive Packet Measurement", work in progress, , November 2002. Quittek et. al. Expires - August 2003 [Page 12] February 2003 [PSAMP-PSS] Zseby, T., Molina, M., Raspall, F., "Sampling and Filtering Techniques for IP Packet Selection", work in progress, , October 2002. 8. Acknowledgements We would like to thank Tanja Zseby for her valuable technical feedback. 9. AuthorÆs Addresses Juergen Quittek NEC Europe Ltd. Network Laboratories Adenauerplatz 6 69115 Heidelberg Germany Phone: +49 6221 90511-15 Email: quittek@ccrle.nec.de Benoit Claise Cisco Systems De Kleetlaan 6a b1 1831 Diegem Belgium Phone: +32 2 704 5622 Email: bclaise@cisco.com Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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