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Re: [RRG] The use of UDP in LISP



On 11 dec 2007, at 22:19, Marshall Eubanks wrote:

I think that this will require a modification to (ugh!) RFC 2460 - which says

   o  Unlike IPv4, when UDP packets are originated by an IPv6 node,
      the UDP checksum is not optional.

Dino Farinacci has suggested this text :

o When a IPv6 router is using a UDP header as part of a tunnel encapsulation,
it MAY compute a UDP checksum.

At the least AMT and LISP would require this, and I suspect that there will be others.

This doesn't make me very happy. Within the limited scope of LISP it could work, but in the more general case it's a trainwreck waiting to happen because you can't know in advance if a receiver is going to accept the missing checksums. Please see my previous message on the subject, I think its pragmatic in both accommodating the desired IPv4 behavior and retaining compatibility with the IPv6 specs.

By the way: host NICs routinely handle IPv4 IP and TCP/UDP checksumming. I suggest router vendors start adding the same logic to their hardware, and in a somewhat more general way so that IPv6 can also be supported, with additional headers between the IP and TCP/UDP headers when present. This will avoid similar issues in the future.

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