On Tue, 25 Jun 2013 16:36:51 +0000 Christian Huitema <huit...@microsoft.com> wrote:
> > I also believe that FreeBSD has done the best it can, and reasonably so. It > > is debatable whether a ICMP6 PTB message should apply to all currently open > > TCP sessions to the same destination, as I wonder about multi-path TCP and > > path diversity here. > > There are certainly different ways to implement that, without inserting a > fragmentation header. For example, if the lower layer knows that the packet > is too big, it could send the local equivalent of "ICMP too big" back to the > TCP layer. This certainly seems like a bug, no matter how you slice it: * If the implementation wanted to allow for different MTUs on a per-flow basis (reasonable given the prevalence of NATs), it should go ahead and send a full-sized packet for the second flow, and find out what the MTU is. * If the implementation wanted to efficiently use the first Packet Too Big it got to fix all possible flows, TCP should re-segment the data in the second flow, rather than allowing fragmentation. I can't think of a case in which it would be better for TCP to fragment rather than re-segment (since it's a lot more efficient to recover from a dropped segment than a dropped fragment), but I'm sure I will as soon as I hit send. Kevin k...@patheticgeek.net -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
