Subject: MPLS and Congestion

From: Anil Rao <[email-masked]>
Date: Tue, 19 Sep 2000 09:46:28 -0700

It is possible that in an MPLS enabled network routers face
congestion ?  If such is the case, is there any standard/recommendation of
how a router may deal with this?  Is the recommendation that a router set up
an alternate path?

	How does this problem magnify if the router can provision an optical
transport path?  Will the router try to avoid the congestion by trying to
setup another optical transport path or a non-optical LSP using alternate
router to router paths?

Thanks, 

Anil.

____________________________________________________________________________
___
Anil R. Rao
ONI Systems,
166 Baypointe Pkwy,
San Jose, CA 95134.
(408)571-3124

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From: Curtis Villamizar <[email-masked]>
Date: Tue, 19 Sep 2000 15:18:32 -0400

In message <[email-masked]>, An
> setup another optical transport path or a non-optical LSP using alternate

An LSR can experience congestion.  If it is carrying IP traffic then
active queue management (RED) is one thing that the router can do to
make the network operate well.  TCP congestion avoidance works well
and that is one of the primary reasons why the Internet has grown the
way it has (when it got congested it continued to work well enough
until capacity came to the rescue).

Another way to avoid congestion is to use the amount of remaining
reservable bandwidth as a rough indication of the load (though if
configured LSP bandwidths are sufficiently inaccurate it may hve
little correlation to actual load) and bias link metrics to avoid
heavily loaded links.  This still allows overbooking and multiplexing
gains.  This is preferred for elastic services.

The sure fire way to avoid congestion is to meter and police at the
ingress and strictly enforce reservations but multiplexing gain
suffers.  In this case MPLS starts to look a lot like ATM with frames.

Curtis