The MPLS WG Archive

[Jeremy Lawrence <jlawrenc@cisco.com>]

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