--On 25 November 2004 13:16 +0000 Michael.Dillon@radianz.com wrote:
In today's network, is there anyone left who uses 1500 byte MTUs in their core?
I expect there are quite a few networks who will give you workable end-to-end MTU's >1500 bytes, either because of the above or because of peering links. Given how pMTUd works, this speculation should be relatively easy to test (take end point on >1500 byte MTU, run traceroute with appropriate MTU to various points and see where fragmentation required comes back). Of course I'd have tried this myself before posting, except, urm, I can't find a single machine I have root on that I can get more than a hop or two from without running into 1500 byte (or less) MTU. I am guessing also that a recent netflow sample from a commercial core (not Internet2), even with jumbo frames enabled, will show <0.01% of packets will not fit in 1500 byte MTU. Anyone have data? Alex