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Updated IPv4 ID Specification

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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  1. Updated IPv4 ID Specification IETF 77 Joe Touch, USC/ISI

  2. 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

  3. -03 / intarea mods • Issued as inarea doc • Text mods • Reformatted pseudocode fragments • Clarified requirements text • Mathis ack’d only

  4. IPv4 vs. IPv6 IDs ID MSL uniqueness already ignored

  5. 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

  6. 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)

  7. 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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