Re: [RAM] Tunnelling & GigE jumbo frame size

Iljitsch van Beijnum <> Wed, 12 September 2007 19:37 UTC

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From: Iljitsch van Beijnum <>
Subject: Re: [RAM] Tunnelling & GigE jumbo frame size
Date: Wed, 12 Sep 2007 21:35:39 +0200
To: RJ Atkinson <>
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On 12-sep-2007, at 20:34, RJ Atkinson wrote:

>> We need to move to a situation where the capability to use larger
>> packets is used where it exists and to the degree that it exists.

> I know of a LOT of metro SPs and ISPs and IXs that already support
> the 9180++ MTU that I outlined before

Yes, but the way IP currently works means that ALL equipment in an IP  
subnet must share the same MTU. This is not a problem in itself if  
you have a homogonous ISP network (but the fact that you need to  
enable the larger size by hand is even there) but that requirement  
makes it extremely hard to deploy larger packet sizes in many other  

>> But for the purposes of a jack up solution we just need a few  
>> dozen extra bytes to accommodate the new headers without  
>> triggering the breakage that ensues when 1500-byte packets can't  
>> be forwarded without fragmentation.

> If you believe the above, why have you been wasting everyone's time
> just now ?

Does anyone believe anything else??

I guess I should read the latest LISP draft as apparently there  
specific a jumboframe size is mentioned, and I have no idea for what  

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