RINA - scott whaps at the nanog hornets nest :-)

Mikael Abrahamsson swmike at swm.pp.se
Sun Nov 7 01:44:45 CDT 2010

On Sat, 6 Nov 2010, George Bonser wrote:

> And by that I mean using 1500 MTU is what degrades the performance, not 
> the ethernet physical transport.  Using MTU 9000 would give you better 
> performance than SONET.  That is why Internet2 pushes so hard for people 
> to use the largest possible MTU and the suggested MINIMUM is 9000.

I tried to get IEEE to go for higher MTU on 100GE. When taking into 
account what the responses were, this is never going to change.

Also, if we're going to go for bigger MTUs, going from 1500 to 9000 is 
basically worthless, if we really want to do something, we should go for 
64k or even bigger.

About 1500 MTU degrading performance, that's a TCP implementation issue, 
not really a network issue. Interrupt performance in end systems for 
high-speed transfers isn't really a general problem, and not until you 
reach speeds of several gigabit/s. Routers handle PPS just fine, this was 
"solved" long ago after we stopped using regular CPUs in them.

Increasing MTU on the Internet is not something driven by the end-users, 
so it's not going to happen in the near future. They are just fine with 
1500 MTU. Higher MTU is a nice to have, not something that is seriously 
hindering performance on the Internet as it is today or in the next few 
tens of years.

Mikael Abrahamsson    email: swmike at swm.pp.se

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