If one wanted to have large MTU that is supported by ATM. As Steven points out, you are limited by the endpoints (well, actually the smallest MTU anywhere in the path). What large MTU might help with at an exchange point is allowing an entire BGP UPDATE to fit in single packet where lots of routes are exchanged. OTOH, initial table transfer is nothing to worry about at these speeds and if you're flapping so many routes that the fragmentation of BGP UPDATE becomes an issue then aren't there other, bigger, problems? ----- Original Message ----- From: "Steven M. Bellovin" <smb@research.att.com> To: "Mikael Abrahamsson" <swmike@swm.pp.se> Cc: <nanog@merit.edu> Sent: Wednesday, June 14, 2000 9:17 PM Subject: Re: exchange point media (was: Re: MAE-EAST Moving? ...)

In message <Pine.LNX.4.10.10006142245540.750-100000@uplift.swm.pp.se>, Mikael A brahamsson writes:

...

Gigabit ethernet sounds nice but the MTU of 1500 is really restricting that technology. I have heard rumours that 10gig ethernet will have at least 4000+ byte MTU, probably 9000+ which might make it viable to use for a shared medium exchange point as the hardware probably will be fairly cheap and/as it will be widely available supported by many vendors.

How will that type of MTU help an exchange point? Aren't you really limited by what size packets the customers are originating and/or can pass through the net to that point?

--Steve Bellovin