Updated ipv4 id specification
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Updated IPv4 ID Specification. IETF 77 Joe Touch, USC/ISI. Quick review. Current hosts don’t ensure ID uniqueness within 2MSL Recognize existing practice Explicitly limit ID to fragmentation Align IPv4 and IPv6 ID and fragmentation. -03 / intarea mods. Issued as inarea doc Text mods

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Updated IPv4 ID Specification

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Updated ipv4 id specification

Updated IPv4 ID Specification

IETF 77

Joe Touch, USC/ISI


Quick review

Quick review

  • Current hosts don’t ensure ID uniqueness within 2MSL

    • Recognize existing practice

  • Explicitly limit ID to fragmentation

    • Align IPv4 and IPv6 ID and fragmentation


03 intarea mods

-03 / intarea mods

  • Issued as inarea doc

  • Text mods

    • Reformatted pseudocode fragments

    • Clarified requirements text

    • Mathis ack’d only


Ipv4 vs ipv6 ids

IPv4 vs. IPv6 IDs

ID MSL uniqueness already ignored


Summary of changes

Summary of changes

  • SHOULD limit fragmentation in IPv4

    • Only at source (DF=1)

    • Only where use is safe (ID unique or integrity check)

  • MUST NOT fragment if ID not unique

  • MUST NOT reuse ID if fragmented/ableMUST NOT use for duplicate detection

  • MUST ignore overlap fragments

    • Now possible only by net duplication as transient


Remaining issues

Remaining issues

  • Clarify ‘maximum jitter’

    • “time during which reordering is expected & tolerated.”

  • Clarify IPv6 examples

    • IPv6 ID also in PTB ICMP, only for v6 talking to v4

    • May update RFC 2460 (?)

  • Clarify why overlaps are prohibited

    • Never retransmit with same ID

    • Now impacts only in-net replication (transient impact)


More issues

More issues

  • Impact on NATs

    • NATs act as hosts; SHOULD set DF, not fragment

  • Note that there are boxes that ignore DF

    • With predictable results ;-)

  • Transition plan

    • Do we need one? – it might help with ignore-DF case

    • When to cease?


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