Subject: MPLS Trafficdriven

From: "MP LS" <[email-masked]>
Date: Wed, 25 Apr 2001 14:29:26 +0200

Hello all,

I have a question. Is there any possibile way to create a fully dynamical 
Traffic driven MPLS network. So that when any packet arives at an LSR it 
will analyse the IP pakket ads a label in front of it with it combines to a 
FEC and then just sent it to the Destination LSR?  Just till now i only 
found that you have to ask for an LSP manualy and then the data can be 
transported over it.

I hope someone can make this clear for me.

Kind regards,

Niels Sitters
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From: Robert Raszuk <[email-masked]>
Date: Wed, 25 Apr 2001 07:39:38 -0700

For me what you are asking for is just plane prefix-LSPs supported for
long time by means of TDP (Cisco) or LDP by a lot of vendors. It WILL
NOT be traffic driven, but control driven - and that is huge advantage
of mpls. For some people MPLS only means TE-LSPs, but this is just one
big misunderstanding.

> found that you have to ask for an LSP manualy and then the data can be

That is for TE-LSPs only. Prefix-based LSPs are build based on the IGP
routing table.

R.

> MP LS wrote:

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From: Robert Raszuk <[email-masked]>
Date: Wed, 25 Apr 2001 07:39:38 -0700

R.

> I hope someone can make this clear for me.

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From: David Charlap <[email-masked]>
Date: Wed, 25 Apr 2001 13:53:43 -0400

MP LS wrote:
> 
> I have a question. Is there any possibile way to create a fully
> dynamical Traffic driven MPLS network. So that when any packet
> arives at an LSR it will analyse the IP pakket ads a label in front
> of it with it combines to a FEC and then just sent it to the
> Destination LSR?  Just till now i only found that you have to ask
> for an LSP manualy and then the data can be transported over it.

What you describe is certainly possible, and may even be used by some
vendors' products.

In addition to manually configured LSPs, routers may auto-generate LSPs
based on the routing table.  (This is one of the primary ways that LDP
operates.)

There's no reason why a router, upon receiving an unlabeled packet that
doesn't classify into any LSP, couldn't signal an LSP for that packet's
destination, in order to more rapidly forward subsequent packets.  IMO,
this would be far more useful in an enterprise network than a core
network, but it's still a reasonable way of operating.  This technique
is similar to the way LANE operates on ATM networks - arriving traffic
causes a VC for the traffic to be set up.  The VC is torn down if too
much time elapses without any traffic.

Running MPLS directly to the desktop, where an application (or an IP
stack) explictly requests LSPs for traffic is also a possibility,
although I am unfamiliar with any work that may be going on in this
area.  IMO, this would be most useful in an all-MPLS enterprise network,
where you could actually have a single LSP going all the way from host
application to host application.

-- David