RE: [PWE3] draft-ietf-pwe3-tdmoip-04.txt - comments

["Yaakov Stein" <yaakov_s at rad.com>]

Joe,  


> Based on the text it forces any implementation that uses MPLS as the
PSN must setup a separate Pseudowire for each TDMoIP Pseudowire to
communicate OAM information. 

No, you don't set up a separate PW. You simply set up a VCCV channel
inside the PW already being used.

> Can someone please explain why this has been allowed? For MPLS
implementations why isn't the requirement to either disable the optional
deep packet inspection feature for LSPs that carry Pseudowire traffic
using inband OAM or allow the optional deep packet inspection feature
provided that OAM is done out-of-band.

In the original TDMoIP draft we specified setting up a separate PW for
OAM purposes.
When many TDM PWs are being sent in a single PSN tunnel, 
and assuming fate sharing of all TDM PWs in the PSN tunnel, 
this seems to be the most frugal way.

On the other hand, when using only a single TDM PW there is 100%
increase in the number
of PWs (and setups, etc).

In the newer drafts we have given up on the special OAM PW method
(it remains for the IP PSN) and use VCCV. Tom is quite right that it no
longer
is necessary to say very much, but the text was added a while ago.

If you have many fate-sharing TDM PWs and desire a single OAM channel
for packet loss or PDV measurement, then you can use a single VCCV
channel
in any one of the PWs, or even open a single 64kbps channel just for the
VCCV
capabilities.

Y(J)S

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