The MPLS WG Archive

[mukul@texas.cplane.com]

> 
> Thank you for the insight.
> So if I understand correctly, there are three possible MPLS over ATM
> schemes:

Yes..

> 1. ATM-LSR: Here the the LSR (maybe all of the links) has a IP address and
> participates in L3 routing protocols. MPLS controls signaling and assigns
> VPI/VCIs in a meaningful way to create VC to next hops.

 In the first case the ATM switch could also be running ATM protocols
 and participate in a ATM cloud (ships in Night mode). 

> 2. The ATM cloud has a mesh of PVC which MPLS uses as ptp links. This is
> frame based not cell based. This is an overlay model where MPLS works on top
> of CLIP or LANE? And the LSR still participate in L3 routing protocols? (as
> well as ATM routing protocols being run).


   The third model is not an overlay case, rather in this the 
  MPLS LSP is established with direct peering with the ATM.  
  
 Regards
 - Mukul

> 3. the VCID case. Again an overlay model where there exists CLIP or LANE
> except here MPLS coordinates with ATM signaling to create SVCs as needed. L3
> & ATM routing protocols are run.
> 
  
> Is this correct? If so case 1 would seem to be the preferable solution in
> order for MPLS to allow ATM to scale and to reduce configuration headaches.
> 
> -Paul
> -----Original Message-----
> From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf Of Jeremy
> Lawrence
> Sent: Wednesday, August 23, 2000 8:40 PM
> To: Paul Tasillo
> Cc: mpls@UU.NET
> Subject: Re: FW: basic MPLS ATM question
> 
> 
> At 17:54 08/23/2000 -0400, Paul Tasillo wrote:
> 
> 
> >Hi-
> >        In draft-ietf-mpls-ldp-applic-02.txt it says,
> >
> >  LDP, together with an IP routing plane and software to program ATM
> >   switch or Frame Relay switch cross-connect tables, can implement IP
> >   in a network of ATM and/or Frame Relay switches without requiring an
> >   overlay or the use of ATM-specific or Frame Relay-specific addressing
> >   or routing.
> >
> >In the absence of ATM/FR specific addressing or routing, what is being used
> >for addressing? If the answer is IP, then am I safe in assuming that this
> >requires each ATM switch to have an IP address?
> 
> Yes, in the same way that a router does, for the purposes of
> participating in an IP routing protocol. (From the perspective
> of an IP routing protocol, an ATM-LSR is indistinguishable from
> a router.) The links may also have IP addresses.
> 
> >I understand the ATM
> >switches will be participating in L3 routing protocols (BGP, OSPF, etc).
> >
> >Is there also an overlay MPLS model? Where MPLS make decisions on a frame
> >basis rather then cell and uses ATM/FR specifc addressing and routing?
> 
> Aside from VCID (covered in another email), MPLS-enabled routers
> can be connected by RFC 1483 (or whatever the latest RFC number is)
> PVCs. This is like ordinary IP over ATM, except that it is
> frame-based MPLS over ATM. The PVCs act like any other non-channelized
> point-to-point link between frame-based LSRs.
> 
> Regards,
> 
> Jeremy Lawrence
> 
> 
>