[c-nsp] BGP convergence with jumbo frames

[Tantsura, Jeff]

You do :)
The difference in loading full BGP table between a router with standard
MSS of 536 or MSS of 4430 on POS with ip tcp path-mtu-discovery turning
on is more than 3 time.

Jeff

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Tony Li
Sent: Monday, August 02, 2004 9:01 AM
To: Pete Kruckenberg
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP convergence with jumbo frames


How are your huge processor buffers set up?

I would not expect a larger MTU/MSS to have much of an effect, if at
all.  BGP is typically not constrained by throughput.  In fact, what you
may be seeing is that with really large MTUs and without a bigger TCP
window, you're turning TCP into a stop and wait protocol.

Tony


On Aug 1, 2004, at 10:42 PM, Pete Kruckenberg wrote:

> Spent some time recently trying to tune BGP to get convergence down as

> far as possible. Noticed some peculiar behavior.
>
> I'm running 12.0.28S on GSR12404 PRP-2.
>
> Measuring from when the BGP session first opens, the time to transmit
> the full (~128K routes) table from one router to another, across a
> jumbo-frame (9000-bytes) GigE link, using 4-port ISE line cards (the
> routers are about 20 miles apart over dark fiber).
>
> I noticed that the xmit time decreases from ~ 35 seconds with a
> 536-byte MSS to ~ 22 seconds with a 2500-byte MSS.
>> From there, stays about the same, until I get to 4000, when
> it beings increasing dramatically until at 8636 bytes it takes over 2
> minutes.
>
> I had expected that larger frames would decrease the BGP converence
> time. Why would the convergence time increase (and so significantly)
> as the MSS increases?
>
> Is there some tuning tweak I'm missing here?
>
> Pete.
>
>
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>

_______________________________________________
cisco-nsp mailing list  cisco-nsp at puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/


Our name has changed.  Please update your address book to the following format: "recipient at capgemini.com".

This message contains information that may be privileged or confidential and is the property of the Capgemini Group. It is intended only for the person to whom it is addressed. If you are not the intended recipient,  you are not authorized to read, print, retain, copy, disseminate,  distribute, or use this message or any part thereof. If you receive this  message in error, please notify the sender immediately and delete all  copies of this message.