Le 4 août 09 à 16:55, Mohacsi Janos a écrit :
On Tue, 4 Aug 2009, Rémi Després wrote:
Le 4 ao?t 09 ? 13:35, Iljitsch van Beijnum a écrit :
On 3 aug 2009, at 17:46, Rémi Després wrote:
if in charge of of an SIIT (which I am not either), I would
ensure that rather than discarding IPv4 zero-checksum datagrams
it forwards them with its zero checksum.
That's pointless, because the IPv6 spec, against which
implementations have been heavily tested, reject such packets.
You seem to have missed that the proposal includes a relaxation of
the constraint that zero-checksum UDP datagrams MAY be accepted by
hosts ion the future, just to avoid unnecessary black holes in
case of v4 to v6 translations.
But the translations cannot expect acceptance of zero checksum. So
I think it would be better to use other options...
YES, translators cannot expect that all hosts accept them.
But they can expect that at least some host will take advantage of it
once upgraded to accept them.
The point is what else do you prefer:
- Always dropping?
- Always computing payload checksums? (Not realistic in practice for
multi-segment datagrams)
Is progress from what is implemented today a taboo?
(I hope not.)
Not taboo, but changing implementation is very painful.
It depends on the modification.
Here it is just that hosts delete the current test that the received
IPv6 UDP checksums are zero in order to drop them. A trivial patch.
The following sentence of RFC 2460 was clearly not written with the
v4 to v6 translation in mind, and could advantageously be deprecated:
"IPv6 receivers must discard UDP packets containing a zero checksum,
and should log the error."
Have a look at e.g. RH0 deprecation.
See previous comment.
You cannot expect that every single IPv6 implementation is follows
RFC 5095... Especially in the embedded devices...
There is no need to expect all hosts to accept IPv6 zero-checksums
for others to benefit from it.
Regards,
RD
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