[88190] in North American Network Operators' Group
Re: Split flows across Domains
daemon@ATHENA.MIT.EDU (Robert E.Seastrom)
Tue Jan 24 13:21:26 2006
To: Joe Abley <jabley@isc.org>
Cc: "Christopher L. Morrow" <christopher.morrow@verizonbusiness.com>,
Glen Kent <glen.kent@gmail.com>, NANOG list <nanog@merit.edu>,
rs@seastrom.com
From: Robert E.Seastrom <rs@seastrom.com>
Date: Tue, 24 Jan 2006 13:20:13 -0500
In-Reply-To: <932BEF01-D702-49A7-A726-80C444D8ECF3@isc.org> (Joe Abley's
message of "Tue, 24 Jan 2006 13:14:57 -0500")
Errors-To: owner-nanog@merit.edu
Joe Abley <jabley@isc.org> writes:
> On 24-Jan-2006, at 13:09, Robert E.Seastrom wrote:
>
>> Joe Abley <jabley@isc.org> writes:
>>
>>> If you can get two candidate routes for the same destination into the
>>> FIB, then you'll get per-flow load balancing as long as CEF is
>>> running, no?
>>
>> Yes and no. CEF is {src, dst} hash IIRC, and "per-flow" usually means
>> {src, srcport, dst, dstport, [proto, tos]} hash in my experience.
>
> Even if the hash is only calculated over source and destination IP
> addresses, the end effect is still that packets associated with a
> single flow still follow the same route where there is more than one
> candidate route available.
And conversely, that different flows that ought to be load-balanced
aren't. But we're splitting semantic hairs here... ;-)
---rob
