Thoughts on increasing MTUs on the internet

Thu Apr 12 15:34:43 UTC 2007

I think it's a great idea operationally, less work for the routers and 
more efficient use of bandwidth.   It would also be useful to devise some 
way to at least partially reassemble fragmented frames at links capable of 
large MTU's.  Since most PC's are on a subnet with a MTU of 1500 (or 1519) 
packets would still be limited to 1500B or fragmented before they reach 
the higher speed links.  The problem with bringing this to fruition in the 
internet is going to be cost and effort.  The ATT's and Verizons of the 
world are going to see this as a major upgrade without much benefit or 
profit.  The Cisco's and Junipers are going to say the same thing when 
they have to write this into their code plus interoperability with other 
vendors implementations of it.

Iljitsch van Beijnum <iljitsch at muada.com> 
Sent by: owner-nanog at merit.edu
04/12/2007 05:20 AM

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Subject
Thoughts on increasing MTUs on the internet

Dear NANOGers,

It irks me that today, the effective MTU of the internet is 1500 
bytes, while more and more equipment can handle bigger packets.

What do you guys think about a mechanism that allows hosts and 
routers on a subnet to automatically discover the MTU they can use 
towards other systems on the same subnet, so that:

1. It's no longer necessary to limit the subnet MTU to that of the 
least capable system

2. It's no longer necessary to manage 1500 byte+ MTUs manually

Any additional issues that such a mechanism would have to address?

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