[55430] in North American Network Operators' Group
Re: Aggregate traffic management
daemon@ATHENA.MIT.EDU (Serge Maskalik)
Wed Jan 29 02:53:42 2003
Date: Wed, 29 Jan 2003 07:46:03 +0000
From: Serge Maskalik <serge@netvmg.com>
To: Stanislav Rost <stanrost@lcs.mit.edu>
Cc: nanog@merit.edu
In-Reply-To: <1043791140.1156.1963.camel@progressor.lcs.mit.edu>; from stanrost@lcs.mit.edu on Tue, Jan 28, 2003 at 04:59:00PM -0500
Errors-To: owner-nanog-outgoing@merit.edu
Stanislav,
It depends what control mechanism you are using:
o routes learned via an IGP - ECMP would work and if it's a single
destination host, per-packet loadbalancing between the outgoing
links is your only practical choice; rest of ECMP schemes work
by distributing flows or routes amongst links
o learned via BGP and the traffic consists of a variety of flows
that all use the same reachability information (BGP route); you
could de-aggregate the announcement locally if you have an idea
how the per-flow volume maps into the route; BGP Multipath feature
set exists in most router implementations, but the distribution
methods are statistically different
For the latter, several systems exist in the market place that try
to automate TE for BGP-learned routes, one of which is ours. These
system require a closed feedback loop for traffic volume per flow
and link mappings; this needs to occur close to real time to be
effective.
- Serge
Thus spake Stanislav Rost (stanrost@lcs.mit.edu):
>
> Dear NANOGers,
>
> I have a very hands-on question:
> Suppose I am a network operator for a decent-sized ISP, and I decide
> that I want to "divide" aggregate traffic flowing through a router
> toward some destination, in order to then send some of it through one
> route and the remainder through another route. Thus, I desire to
> enforce some traffic engineering decision.
>
> How would I be able to accomplish this "division"? What technologies
> (even if vendor-specific) would I use?
>
> I can think of some methods like prefix-matching classification and
> ECMP, but I am still not sure exactly how the latter works in practice
> (at the router level) and how one may set them up to achieve such
> load-sharing.
>
> Thank you for your expertise and lore,
>
> --
> Stanislav Rost <stanrost@lcs.mit.edu>
> Laboratory for Computer Science, MIT
