RE: [PWE3] PWE Service interworking

["Hamid Ould-Brahim" <hbrahim@nortelnetworks.com>]

Shahram,

>
> Regarding Service interworking I believe the simplest and
> most logical model is to do service interworking with MPLS
> on both IWFs. Assuming (PL= Payload), the following figure shows an
> example of what I think is a proper AT-MPLS-FR service interworking:
>
>
> CE--------PE-------P--------PE---------CE
>      PL        PL      PL        PL
>     AAL5       X       X        Q.922
>     ATM       MPLS    MPLS       FR
>
> Both PEs do service interworking. One does ATM-MPLS service
> interworking and the other one does FR-MPLS service interworking.
>

Okay, but in this example MPLS is just a transport not a service

(I don't think ATM-MPLS service interworking is the

right term).

I would have assumed service interworking implies interworking
between an attachment circuit of type X (that attaches
to the client device) and another attachment circuit
of type Y and there is a pw or tunnel between X and Y (like
in your example).

 

In fact if I reuse the scheme described in the PW architecture

document (the "protocol layering model" - sorry Eric for the

use of the term layer ;-)), for that scenario (as in

Shahram figure), a service interworking is as well a

pseudo-wire (PW) that:

 

a) connects two heterogeneous attachment/service types where

b) the encapsulation is null and

c) the PSN convergence which can be null

 

(we still have the PW demultiplexing and PSN)

 

In that case there is a service interworking scenario even if there

is no service interworking function implemented on the PE that takes

frames received on attachment circuit X and send them as type Y

on that PE on either the PSN or CE sides.

Hamid.