Re: avoiding tunnel fragmentation

acollins@hotate
Thu, 29 Oct 1998 15:20:19 -0800 (PST)

> Of course i suppose any solution that involves path MTU discovery might
> sometimes (for un/misconfigured hosts) incur an extra (host)<->(detour
> edge router) exchange as the detour router says "nope, ain't gonna take a
> 1500 byte packet" & the host resends.

We can actually do MTU discovery one better here. Figure we know the
MTU for each tunnel in the system (move that information around with
the rest of the measurement data, and we won't even notice the
overhead), so the first hop knows the path MTU when it computes the
route, and can drop too-large packets immediately, so that the MTU
discovery cost is just the local RTT rather than half the wide-area
RTT.

Andy

-- 
//-------------------------------------------------------------------------
//  Andy Collins -- KC6YEY                     acollins@cs.washington.edu
//                              Graduate Student, University of Washington
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