Re: [RAM] Tunnelling & GigE jumbo frame size
RJ Atkinson <rja@extremenetworks.com> Wed, 12 September 2007 17:43 UTC
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From: RJ Atkinson <rja@extremenetworks.com>
Subject: Re: [RAM] Tunnelling & GigE jumbo frame size
Date: Wed, 12 Sep 2007 13:42:58 -0400
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On 12 Sep 2007, at 12:42, Iljitsch van Beijnum wrote: > On 12-sep-2007, at 16:24, RJ Atkinson wrote: >> Correction: >> Just as "4K" MTU really means 4470 bytes, Jumbo Ethernet >> sizes of "9K" really mean an IP MTU of 9180 bytes. This >> means the link MTU for Jumbo Ethernet is really: >> (9180 + sizeof(Ethernet header) + sizeof(VLAN tag)) > > I think most people take it to mean 9000 bytes. I strongly disagree -- speaking as someone who spends a lot of time talking with A LOT of different Ethernet end users around the world, including users with deployments on all continents. The origin for the requirement came from super-computing sites with ATM deployments, and they drove all the vendors in the same direction (and vendors that didn't comply with their definition lost potential business as a result; economics tends to win in such cases). > This is the only real jumboframe IP MTU size I've seen implemented > in hosts. You should look around more broadly then. I've seen the jumbo MTU that I outlined in multiple versions of UNIX and in other kinds of systems. Moreover, the jumbo MTU is primarily deployed by service providers and super-computer centers, and is not often used by ordinary end systems (e.g. one's home computer). I'm not current with MTU support in current Windows, but earlier versions of Windows did support more than 9000 bytes on Gigabit Ethernet. > However, routers and especially switches come with many different > maximum frame sizes. I've looked over some product literature and > compiled the following list: 1508, 1530, 1536, 1546, 1998, 2000, > 2018, 4464, 4470, 8092, 8192, 9000, 9176, 9180, 9216, 17976, 64000 > and 65280. As there is no standard, the maximum for a particular device will vary. Most networking devices make this parameter *configurable*, below some maximum value. Varying maxima was not the question on the table, however. The question on the table is *narrowly* "what is meant by 9K MTU ?". I stand by the contents of my original note. Ran _______________________________________________ RAM mailing list RAM@iab.org https://www1.ietf.org/mailman/listinfo/ram
- [RAM] Tunnelling & GigE jumbo frame size RJ Atkinson
- Re: [RAM] Tunnelling & GigE jumbo frame size Iljitsch van Beijnum
- Re: [RAM] Tunnelling & GigE jumbo frame size RJ Atkinson
- Re: [RAM] Tunnelling & GigE jumbo frame size Iljitsch van Beijnum
- Re: [RAM] Tunnelling & GigE jumbo frame size Dino Farinacci
- Re: [RAM] Tunnelling & GigE jumbo frame size RJ Atkinson
- Re: [RAM] Tunnelling & GigE jumbo frame size Iljitsch van Beijnum
- Re: [RAM] Tunnelling & GigE jumbo frame size Dino Farinacci
- Re: [RAM] Tunnelling & GigE jumbo frame size Gert Doering
- Re: [RAM] Tunnelling & GigE jumbo frame size RJ Atkinson
- Re: [RAM] Tunnelling & GigE jumbo frame size Gert Doering