BGP & MTU

Jared Mauch jared at puck.nether.net
Sat Jul 23 19:46:55 UTC 2016


> On Jul 22, 2016, at 1:37 PM, Grzegorz Janoszka <Grzegorz at Janoszka.pl> wrote:
> 
> On 2016-07-22 15:57, William Herrin wrote:
>> On a link containing only routers, you can safely increase the MTU to
>> any mutually agreed value with these caveats:
> 
> What I noticed a few years ago was that BGP convergence time was faster with higher MTU.
> Full BGP table load took twice less time on MTU 9192 than on 1500.
> Of course BGP has to be allowed to use higher MTU.
> 
> Anyone else observed something similar?

This has been well known for years:

http://morse.colorado.edu/~epperson/courses/routing-protocols/handouts/bgp_scalability_IETF.ppt

You have to adjust the MTU, Input queues and such.  The default TCP stack is very conservative.

- Jared


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