Subject: Question: ATM OAM PM/Security cells in ATM AAL5 over MPLS

From: Megan Bao <[email-masked]>
Date: Wed, 03 Sep 2003 20:07:22 -0700

Hi,

In earlier version of Martini draft: draft-martini-atm-encap-mpls-01.txt(06/2003-12/2002) section 
6.3, it is recommended that in AAL5 over MPLS oam transparent mode, the ATM OAM Performance 
Management(PM) and Security cells are to be disgarded on ingress PE. However in later version of the 
draft: Draft-ietf-pwe3-atm-encap-00.txt, this recommendation is taken away, instead, there is a 
warning to not use AAL5 mode for performance management and security.

Could somebody tell me the background to suggest OAM PM/security cells disgard and why it's being 
obsoleted?

Thanks,
Megan Bao

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From: Mustapha Aissaoui <[email-masked]>
Date: Fri, 05 Sep 2003 09:10:08 -0400

Hello Megan,
I believe that we felt this was an unnecessary restriction given there are deployed ATM networks which
do not carry OAM security and performance management cells. AIS/RDI, loopback, and continuity
verification cells are not sensitive to re-ordering with respect to user cells and can therefore operate
properly in the AAL5 SDU mode.

Note that the AAL5 PDU mode has a built-in fragmentation that allows the proper handling of the OAM
security and PM cells.

Finally, there is a new revision of the ATM draft, draft-ietf-pwe3-atm-encap-02.txt, with improved OAM
and applicabilty sections.

Regards,
Mustapha.
------------
Megan Bao wrote:

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