On Wed Aug 22 14:31:13 EDT 2012, sstall...@gmail.com wrote: > On Wed, Aug 22, 2012 at 10:18 AM, Gorka Guardiola <pau...@gmail.com> > wrote: > > I had this problem several years ago with an adsl router (9fans > > archive may know about this). There was a bug in my adsl router > > (which seems to be common, I have seen it since more than once) that > > dropped ethernet frames of size greater than 1480 (someone counted a > > header twice probably). Linux adapts the mss to 1480 if there are > > problems so it works in this case. > > > Not so much a bug as ATM overhead.
atm overhead is 5 bytes per 48 bytes transmitted. the original problem is a limit of 1496 bytes, not 1460, which is more constent with mpls than l2tp (1460) or pppoe (1492). but all that's guesswork. the "bug" here, if there is one, is that there's neither an icmp message nor fragmentation nor mss rewriting at the local gateway, which should (since it's eithernet) not silently drop mtu-sized frames that it's responsible for gatewaying. - erik
