> On Jul 22, 2016, at 1:37 PM, Grzegorz Janoszka <grzeg...@janoszka.pl> wrote:
> 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?

I have read about others experiencing this, and did some testing a few months 
back -- my experience was that for low latency links, there was a measurable 
but not huge difference. For high latency links, with Juniper anyway, there was 
a very negligible difference, because the TCP Window size is hard-coded at 
something small (16384?), so that ends up being the limit more than the tcp 
slow-start issues that MTU helps with.

With that said, we run MTU at >9000 on all of our transit links, and all of our 
internal links, with no problems. Make sure to do testing to send pings with 
do-not-fragment at the maximum size configured, and without do-not-fragment 
just slightly larger than the maximum size configured, to make sure that there 
are no mismatches on configuration due to vendor differences.

Best Regards,
-Phil Rosenthal

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