Re: Comparing an old flow snapshot with some packet size data
John Hawkinson <jhawk@bbnplanet.com> Wed, 21 August 1996 21:13 UTC
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Subject: Re: Comparing an old flow snapshot with some packet size data
To: "Kent W. England" <kwe@6sigmanets.com>
Date: Wed, 21 Aug 1996 16:50:14 -0400
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From: John Hawkinson <jhawk@bbnplanet.com>
Cc: asp@partan.com, big-internet@munnari.oz.au
In-Reply-To: <2.2.32.19960821182334.00740718@mail.cts.com> from "Kent W. England" at Aug 21, 96 11:23:34 am
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> Backbones must support at least 1500 bytes and should support up to 9180. > The only difference is how the routers use memory for buffering. If each > packet is allocated the router's MTU, then there is a lot of wasted buffer > memory between 500 bytes typical and 9180. If a router vendor has a problem > with that much memory wastage, then I'd say it was up to them to allocate, > say, 1500 bytes per packet, and handle an exception for anything beyond that > MTU. Kent, I think you're slightly confused. Part of this is what defines "the mtu a backbone can support". There are two ways (at least!) to look at that: 1. The minimum MTU of all the interfaces in the backbone. 2. Various buffering considerations on all of the equipment involved in the backbone. Without the former, the latter seems kind of irrelevent, since path MTU discovery will never let you go above that minimum (and rightly so). If you say that "backbones should support up to 9180" then you've just disallowed most folks' DS3 interfaces and FDDI, and are mandating that folks should all go and use ATM. I think you're well aware there are a strong contingent of people who will not throw out their DS3 and FDDI infrastructure for ATM :-) I think the brunt of asp's question was really "Is it acceptable for a backbone service provider to provide a min mtu of 1500 instead of a min mtu of of 4352". What this really translates into is: Is it OK for a backbone service provider to use fast ethernet as a interconnect medium instead of FDDI. Answers seem varied, some folks may have contractual obligations to provide that 4k MTU, but most don't. Is that 4k MTU worth the trade-offs? It's certainly the case that the 1.5k MTU isn't very-well exploited right now, and it's difficult to see the 4k MTU being exploited well in the short term, though it may be that end-users who check the "4k MTU requirement" checkbox are actually folks who have lots of hosts with 4k MTUs on their interfaces who exchange significant amounts of traffic with others who have similarly-configured hosts and who implement path MTU discovery and "all that good stuff". --jhawk
- Re: Comparing an old flow snapshot with some pack… Greg Minshall
- Re: Comparing an old flow snapshot with some pack… Dorian R. Kim
- Re: Comparing an old flow snapshot with some pack… John Hawkinson
- Re: Comparing an old flow snapshot with some pack… Michael A. Patton
- Re: Comparing an old flow snapshot with some pack… Greg Minshall
- Re: Comparing an old flow snapshot with some pack… Kent W. England
- Re: Comparing an old flow snapshot with some pack… Paul Ferguson
- Re: Comparing an old flow snapshot with some pack… Andrew Partan
- Re: Comparing an old flow snapshot with some pack… Greg Minshall
- Re: Comparing an old flow snapshot with some pack… Paul Ferguson
- Re: Comparing an old flow snapshot with some pack… Karl Denninger, MCSNet
- Re: Comparing an old flow snapshot with some pack… Evan Wetstone
- Re: Comparing an old flow snapshot with some pack… Kent W. England
- Re: Comparing an old flow snapshot with some pack… Kent W. England
- Re: Comparing an old flow snapshot with some pack… Jeremy Porter
- Re: Comparing an old flow snapshot with some pack… Dorian R. Kim
- Re: Comparing an old flow snapshot with some pack… Brian Carpenter CERN-CN
- Re: Comparing an old flow snapshot with some pack… Andrew Partan
- Re: Comparing an old flow snapshot with some pack… Andrew Partan
- Re: Comparing an old flow snapshot with some pack… Dorian R. Kim
- Re: Comparing an old flow snapshot with some pack… John Lekashman
- Re: Comparing an old flow snapshot with some pack… Robert Moskowitz
- Re: Comparing an old flow snapshot with some pack… Kent W. England
- Re: Comparing an old flow snapshot with some pack… Robert Moskowitz
- Re: Comparing an old flow snapshot with some pack… John Hawkinson
- Re: Comparing an old flow snapshot with some pack… Dorian R. Kim