>>>>> "rm" == Roy Marples <roy%marples.name@localhost> writes: >> net.inet.tcp.mss_ifmtu = 1 >> net.inet6.tcp6.mss_ifmtu = 1 rm> My understanding is that only works on the router and not the rm> ones connected by NAT. [...] if you weren't changing MTU on your ethernet segment that'd be true. but in your case, no: rm> Maybe I'll look into allowing NetBSD to use the MTU as rm> advertised by rtadvd as it currently ignores it. the above sysctl's are likely to do exactly this. MTU != mss MTU is for all protocols and controls what you are allowed to send. mss is for TCP only, and advises the other end about what you are prepared to receive. If you presume asymmetric routing, what you are prepared to receive doesn't necessarily have anything to do with what you are allowed to send. so NetBSD may well be obeying the mtu in rtadv's, but even if it were, this would cause no change in the mss (with the default '0' setting of those sysctl's) and would not solve your problem. The sysctl's say, ``go ahead and make the assumption that the receive path uses the same interface as the send path,'' so NetBSD will calculate an mss based on IP + TCP overhead and the MTU of the route for sending TO the peer. of course there could easily be two problems...
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