Subject: [mpls] Proposed response to liaison 406

From: Stewart Bryant <[email-masked]>
Date: Wed, 06 Feb 2008 15:53:40 +0000

We were sent this liaison rather late in the day (9th Jan)
an need to get a response back in time for the SG15 meeting
next week. In the meantime there have been a whole bunch 
of higher priority T-MPLS activities that have need priority
hence late response.

I drew the attention of the liaison to Yaakov Stein to review
the TDM material and Luca Martini to review the ATM material
and their commments are included verbatim.

The concerns about the semi-detailed redefinition of existing
texts and corresponding issues of difficulty of presentation
and normative reference conflict are mine. Please indicate
if I should tone this down.

I need to send this out friday evening my time.

Regards

Stewart

Thank you for your liaison of 9th January 2008 entitled 
"Addition of ATM and PDH clients to T-MPLS <https://datatracker.ietf.org/documents/LIAISON/file510.pdf>"

https://datatracker.ietf.org/liaison/406/

This rather short description of the packet processing is more 
difficult to read than the descriptions found in either
the relevant RFCs or the corresponding Y series recommendations
as such we found it difficult to review. Rather than defining
the operations in semi-detail we would prefer that you simply
indicate the primary references and modes that you propose to
support and refer the reader there for the description. This 
prevents any issue of conflicting definitions. In any case 
there needs to be a clear indication that this is a subset
of existing IETF PWE3 and SG13  recommendations 
and that their packet processing definitions are authoritative.

We are concerned that you only propose to use the structure
agnostic TDM mode. This mode has limitations which are 
addressed by  the structure aware modes jointly developed 
in the IETF PWE3 Working Group and ITU-T SG13.

Please can we suggest that you add text explaining that the 
structure-agnostic mode is not always the idea method of TDM
emulation and preferably include text describing the use of
the structure aware modes as described in Y.1413, RFC 5086 
and RFC 5087.

In the case of ATM, please can you be more specific about
the exact type of PW that you intend to support. The 
confusion arises as a result of the text at the end of 
section 7.1.4 of the document which says:

" For the case of Mode 1

   * Cell de-multiplexing according to the VPI value, including
     unmatched VPI cell discard
   * Remove the VPI field"

Since MODE 1 is defined as the N-to-One cell mode of [IETF RFC 4717] ,
this this text appears to be in error, and we believe that you should 
call up
Mode 2.

There are some other items that are unclear in this section. The paper
discusses  N-1 mode but then discusses  multiple VP. Is the mode that you
wish to use what we call cell relay mode PW type 0x0003 ?

Reagrds etc

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From: Stewart Bryant <[email-masked]>
Date: Sat, 09 Feb 2008 10:38:34 +0000

To:
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CC:
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For Action by ITU-T SG15 Question 12

IETF PWE3 WG Response to Addition of ATM and PDH clients to T-MPLS

Thank you for your liaison of 9th January 2008 entitled
"Addition of ATM and PDH clients to T-MPLS"

<https://datatracker.ietf.org/documents/LIAISON/file510.pdf>

We found this short description of the packet processing more

" For the case of Mode 1

Since MODE 1 is defined as the N-to-One cell mode of
[IETF RFC 4717], this this text appears to be in error, and
we believe that you should call up Mode 2.

There are some other items that are unclear in this section.
The paper discusses  N-1 mode but then discusses  multiple VP.
Is the mode  that you wish to use what we call cell relay
mode PW type 0x0003 ?

Regards

Stewart Bryant
Danny McPherson
IETF PWE3 WG Co-chairs