Erik Nordmark wrote: > >> > Perhaps I didn't see it, but which (if either) MTU corresponds >> > to what may be publically seen? Or does it matter (if IP >> > fragmenting hides the distinction)? > > IP fragmentation hides the distinction. > > It is the unicast MTU that is reported using the various interfaces that > report MTU (dladm, ifconfig, routing sockets).
If you're sending multicast, I'd think you'd want to avoid the complications involved with either fragmentation or (yikes!) MTU discovery. If the application writer doesn't just force the issue off onto the user (by requiring tuning) or always using 576 or 1280 minima, how can his IP multicast-using application discover the correct MTU? I didn't think it was too uncommon to rely on SIOCGIFMTU to determine how large a multicast packet one could send to directly-attached peers. E.g.: http://fxr.googlebit.com/source/usr.sbin/route6d/route6d.c?v=NETBSD-CURRENT#L788 -- James Carlson 42.703N 71.076W <carls...@workingcode.com> _______________________________________________ opensolaris-arc mailing list opensolaris-arc@opensolaris.org
