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

From: venkatesan mahalingam <[email-masked]>
Date: Mon, 26 Jul 2010 17:43:35 +0530

*Maarten,*
*As per RFC-5659, Section **8.1**.  Multiplexing*

   The purpose of the PW Demultiplexer Layer at the S-PE is to
   demultiplex PWs from ingress PSN tunnels and to multiplex them into
   egress PSN tunnels.  Although each PW may contain multiple native
   service circuits, e.g., multiple ATM virtual circuits (VCs), the
   S-PEs do not have visibility of, and hence do not change, this level
   of multiplexing because they contain no Native Service Processor
   (NSP).
<VM> IMO, client signals will not be decapsulated in the S-PE.
S-PE does only the asociation of one segment PW with the another PW segment.
In which case, the client signals of one PW segment need to be decapsulated
and encapsulated in the next segment PW in S-PE?
**
*Thanks,*
*Venkat.*

   - *From*: Maarten Vissers <maarten.vissers at
huawei.com<[email-masked]>>

   - *To*: mpls-tp at ietf.org <[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

-- 
Best Regards,
Venkatesan Mahalingam.

---

From: Maarten Vissers <[email-masked]>
Date: Mon, 26 Jul 2010 16:40:40 +0200

Venkat,

The text you quote does not state explicit that the client signal is not
decapsulated and then again encapsulated; it only refers that it would not
do client demultiplexing and remultiplexing. Missing (but perhaps in another
paragraph/section) is text that states that PW labels are swapped and no
other operation on the packets with client information is performed.

Regards,
Maarten

________________________________

From: venkatesan mahalingam [mailto:[email-masked]] 
Sent: maandag 26 juli 2010 14:14
To: [email-masked]; [email-masked]
Subject: Re: [mpls-tp] Is MS-PW a Transport Service layer Transport Path?

Maarten,
As per RFC-5659, Section 8.1.  Multiplexing

 
Thanks,
Venkat.

*	From: Maarten Vissers <maarten.vissers at huawei.com
<mailto:[email-masked]> > 
*	To: mpls-tp at ietf.org <mailto:[email-masked]>  
*	Date: Mon, 26 Jul 2010 10:55:45 +0200 

________________________________

Regards,
Maarten

-- 
Best Regards,
Venkatesan Mahalingam.