[140357] in North American Network Operators' Group
Re: L3 ECMP over links with different RTT
daemon@ATHENA.MIT.EDU (Iljitsch van Beijnum)
Tue May 10 10:40:24 2011
From: Iljitsch van Beijnum <iljitsch@muada.com>
In-Reply-To: <4DD46B838E59A647A9FE326E7552F8361A98E43C4F@WPGMSXMBX02.ca.canwest.com>
Date: Tue, 10 May 2011 16:37:08 +0200
To: "Dikkema, Michael (Business Technology)" <MDikkema@postmedia.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 10 mei 2011, at 16:28, Dikkema, Michael (Business Technology) wrote:
> Is it foolish to build a L3 ECMP connection between 2 iBGP routers =
with one of the links having a 50% longer RTT?
No problem at all as long as you don't do per-packet load balancing but =
something that makes sure a single flow only goes over a single link. =
There are many ways to skin that particular cat, best practice is based =
on the 5-tuple (source and dest addresses and ports and the protocol =
number) which will give you the best chance of having a similar load on =
both links as long as you have at least some 1000 flows at any given =
time. With less granular load balancing there's a much bigger risk that =
one link will be full and the other more or less idle unless you have =
very, very many flows. You may want to use VLANs so you can load balance =
some stuff as per the above and manually balance some other stuff to go =
over the faster link.=
