On 2009-07-30 13:09, Christian Huitema wrote: >> On 2009-07-29 19:43, Benny Amorsen wrote: >>> Brian E Carpenter <[email protected]> writes: >>> >>>> Er, do your routers do that when they throw away packets due to >>>> congestion? >>> If a router throws away a packet due to congestion, there's a good >>> chance that a retransmission will go through. In this case you can >>> retransmit as many no-UDP-checksum packets you want, none of them will >>> get through. The host really ought to be told that it is wasting its >>> time. >> There's no retransmission in UDP. >> >> Presumably there is no harm in sending back some kind of ICMP error, >> most likely Parameter Problem, at a throttled rate. But we shouldn't >> mandate >> it IMHO, and you certainly can't rely on a host stopping a UDP stream >> as a result. > > What happened to being conservative with what we send and permissive with > what we receive? > > It seems that the direct application should be: > > 1) Be conservative: hosts should not send UDP packets with null checksums. > 2) Permissive: gateways who receive UDP packets with null checksum should > compute a checksum based on the received bytes, and then forward the packet. > > I understand there may be resource limits on gateways, and that the UDP > checksum compute requirement might throw the packet back to some kind of slow > path, with potential packet loss due to congestion. But that's way better > than a black hole.
The problem is *fragmented* IPv4 UDP packets with zero checksum; the translator would have to reassemble them. Brian -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
