Shoichi just talked to me and made me realize that this can be put in
a simpler way:
Where HC-03 says:
C: Checksum:
0: All 16 bits of Checksum are carried in-line. The Checksum
MUST
be included if there are no other end-to-end integrity checks
that are stronger than what is provided by the UDP checksum.
Such an integrity check MUST be end-to-end and cover the IPv6
pseudo-header, UDP header, and UDP payload.
1: All 16 bits of Checksum are elided. The Checksum is recovered
by recomputing it.
How does the compressor know that there are "other end-to-end
integrity checks
that are stronger than what is provided by the UDP checksum."?
It might on the sending end node.
It's hard to know that on a router, however; just looking at the
packet doesn't tell.
Oracles only help if both cases are supported at both the compressor
and the decompressor side, because the oracle can err.
Gruesse, Carsten
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