The MPLS-OPS Archive

[Roger Clark Williams <rogerw@nordlink.com>]

RIck, here is one take on it:

MPLS, since it runs over IP, can run happily on a network that is running
IP over ATM. The ATM is effectively invisible to the MPLS as it would be
to IP. The ATM switches and the ATM pipes between switches are simply
open pipes to IP, and therefore to MPLS. This would be called "frame
mode over ATM" (thanks to Pepelnjak and Guichard).

In this case, the label switch/routers "see" each other through
the pipe, labels are exchanged directly between MPLS routers but across
the ATM links, routing goes on just as it would with IP. The ATM is
simply providing a path that is invisible to IP. I think the better image
is a pipe because as a kid I would look through a long pipe under the
road and see - the other side! Nothing between me and there.

Network design is still an issue, and that depends on your particular
needs, how your traffic needs to flow, link capacities and the 
like.

Roger Williams

> Resent-Date: Fri, 14 Mar 2003
> 16:16:58 -0500
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> From: RickGall1@aol.com
> Date: Fri, 14 Mar 2003 15:51:49 EST
> To: mpls-ops@mplsrc.com ('mpls-ops@mplsrc.com')
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> Subject: [MPLS-OPS]: A question on ATM and MPLS
> Resent-From: mpls-ops@mplsrc.com
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>
> I was sent a question (below) that I think that
> you that are more ATM aware might be able to help with if you will...
>
> Thank you 
> Rick Gallaher 
>
> I have had numerous discussions with co-workers on how to implement MPLS
> over an existing ATM network.  My initial thought is that it would
> be beneficial to have an MPLS aware ATM function in the LER.  This
> would allow the control of the ATM plane at the ingress side of the
> network.  However there are case in which the vendor is not
> producing MPLS awareness into their ATM support.  If that's the case
> then I need to treat the PVC as just that, however I am a little fuzzy on
> how that would work and how the label gets carried to the LSR.  Any
> suggestions. Thanks. 

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