The MPLS-OPS Archive

["Andrew G. Malis" <Andy.Malis@vivacenetworks.com>]

Roger and Rick,

Here's an alternate take.  In many cases, the ATM backbone no longer
has sufficient capacity for the services the SP would like to sell, but
the ATM switch vendor has capped development on their switches, or for
some other reason the service provider is unable to continue to grow
their ATM network.  In this case, I would recommend using
multiservice MPLS switches to build a new IP/MPLS backbone to
interconnect the ATM switches, and also to migrate pure IP connectivity
and Layer 3 VPNs away from the overloaded ATM switches.  The ATM
switches can continue to provide ATM services for pure ATM applications
(AAL1, AAL2, FRF.8.1, ATM VPNs, etc.) and the IP/MPLS network can be used
to interconnect the ATM switches and service the IP traffic, layer 3
VPNs, and non-ATM layer 2 VPNs.  PNNI/MPLS signaling and routing
interworking can be used to signal and route ATM SVCs through the MPLS
core if the ATM networks is using SVCs in addition to PVCs.

Cheers,
Andy

-------

At 3/15/2003 12:48 AM -0500, Roger Clark Williams wrote:

> 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
> > X-Authentication-Warning: host.secure4-hosting.net: mplsrc12 set sender
> > to mpls-ops-request@mplsrc.com using -f
> > From: RickGall1@aol.com
> > Date: Fri, 14 Mar 2003 15:51:49 EST
> > To: mpls-ops@mplsrc.com ('mpls-ops@mplsrc.com')
> > X-Mailer: 6.0 for Windows XP sub 10500
> > Subject: [MPLS-OPS]: A question on ATM and MPLS
> > Resent-From: mpls-ops@mplsrc.com
> > X-Mailing-List: <mpls-ops@mplsrc.com> archive/latest/5428
> > X-Loop: mpls-ops@mplsrc.com
> > Resent-Sender: mpls-ops-request@mplsrc.com
> >
> > 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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