Subject: [mpls-tp] Is MS-PW a Transport Service layer Transport Path?

From: Maarten Vissers <[email-masked]>
Date: Mon, 26 Jul 2010 10:55:45 +0200

Based on a discussion I was involved in last week I have a question if a
MS-PW is a Transport Service layer Transport Path?

Up to last week I assumed that the answer to this question was 'yes'. My
assumption was based on the expectation that a MS-PW in MPLS-TP would
perform a simple label swap in a S-PE node. Now I am not sure that my
understanding is correct... It could be that a MS-PW in a MPLS-TP node
decapsulates its client signal on its S-PE ingress line card, transport this
client signal over the backplane to the egress line card and then
encapsulate the client signal again in a next PW...

If this latter is the case, then a MS-PW is not a Transport Service layer
Transport Path, but instead a set of SS-PWs interconnected via the client
layer (e.g. Ethernet, TDM). A MS-PW would in this case have to be replaced
by a SS-PE transported in a multi-segment service-LSP. The multi-segment
service-LSP would in this case be monitored (e.g. CC/CV, packet loss,
loopback).

Regards,
Maarten