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IP Packet Sampling and Filtering Techniques Update

This document provides updates on sampling and filtering techniques for IP packets, including recommended hash functions and selection criteria. Issues such as hash function recommendations, selection methods, and digest functions are discussed.

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IP Packet Sampling and Filtering Techniques Update

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  1. Sampling and Filtering Techniques for IP Packet Selection- Update - draft-ietf-psamp-sample-tech-05.txt Tanja Zseby, FhG FOKUS Maurizio Molina, DANTE Nick Duffield, AT&T Labs Saverio Niccolini, NEC Europe Ltd. Fredric Raspall, EPSC-UPC

  2. Changed • Associations • If no IPFIX process specified, packet selector applies to all processes on observation point • Only AND for router state filters • Use of correct terminology in 7.2. • e.g. Hash Selection Range instead of Selection Interval Specification • Address changes • 3 of the 5 authors changed affiliation… • Some clarifications that came up from MIB definition • Some re-wording proposed by Stewart draft-ietf-psamp-sample-tech-05.txt

  3. Not Changed • Some proposed changes not addressed: • Simplicity of filter model was criticized • But: substitution of complex by simple model (limitied to AND) was result of last IETF discussion • Terminology remains in both documents • Nothing changed regarding recommended hash function because ongoing discussion • Small TODOs • Change references to documents if titles of other documents change (as proposed by Benoit, e.g. MIB) • Some terminology re-wording proposed by Stewart that need to be consistent with FW draft • Benoit has corrected some typos on his paper version  already done for 07 version draft-ietf-psamp-sample-tech-05.txt

  4. Open Issue: Recommended Hash-Function • Some clarification: • PSAMP compliance: MUST implement at least one of the selection method (sampling or filtering) •  Its not mandatory to implement a hash-based selection • But: we want to give a recommendation which hash function to use in case someone decided to use hash-based selection •  IF hash-based selection is chosen, [function] SHOULD be implemented • Current recommendation • IPSX for packet selection • CRC for packet digest • New Proposal: • Recommend BOB for both • IPSX and CRC optional draft-ietf-psamp-sample-tech-05.txt

  5. Open Issue: Recommended Hash-Function • Selection Function • Speed important (process each packet) • Collisions not relevant • Pro IPSX • IPSX is 7 times faster than BOB • IPSX is simple • Pro BOB • IPSX limited to 16 bytes input • problem with IPv6 packets • poor uniformity • For all hash functions with 16 bit input • Improvement for BOB and CRC if larger input • Couldn’t be checked with IPSX draft-ietf-psamp-sample-tech-05.txt

  6. Open Issue: Recommended Hash-Function • Digest Function • Collisions relevant • Speed less important (only operate on selected packets) • Pro CRC • Faster in hardware ? • But existing implementations cannot be used ? • Pro BOB • BOB is faster than CRC on software implementation • BOB achieves similar good collision probability as CRC • Approaches: • 1. BOB for digest, IPSX for IPv4 selection, BOB for IPv6 selection, others optional • 2. BOB for digest and selection, others optional •  Still ongoing discussion on list draft-ietf-psamp-sample-tech-05.txt

  7. Other Issues • Which hash function to recommend for IPv6  depends on hash discussion • Better reference for IPSX ? • Allow NOT operation for filters ? • Seems not difficult to implement • Allow for all or only for some filter types ? draft-ietf-psamp-sample-tech-05.txt

  8. Research Topics for IMRG ? • Extend work on hash-based sampling ? • More tests on uniformity and speed • Hash-functions for IPv6 • Flow-state and router-state methods ? • Suitability for PSAMP (criteria ?) • Investigate/Compare different methods • … • Volunteers ? draft-ietf-psamp-sample-tech-05.txt

  9. Thank you for your attention ! Questions ?

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