RE: [PWE3] PWE3 new WG items?

[benjamin.niven-jenkins at bt.com]

Folks,

> QOS stuff of course... :-)
> 
> We submitted PWE3 Control protocol extension to 
> exchange capabilities as a way to add more stuff
> and to negotiate. I think QOS for PW is important.

An observation/fact: A PW acts as a client to a server layer (be it MPLS, IP or whatever) and as a result the QoS that can be provided by a PW cannot be better than the QoS provided by the server layer used by the PW.

My comments:
1) Assuming that the QoS in the available server layers (e.g EXP bits/DiffServ for the MPLS/IP server layers) is adequate (and it could be argued that it isn't) then given that a PW is basically a MPLS LSP with sequence number support, why does PW QoS need its own specification?  Why can't a PW use the same QoS mechanisms as MPLS LSPs?

For example, why would a service provider deploying PWs over a MPLS core want to use two different but interacting QoS mechanisms (one for PWs, one for MPLS LSPs) and add significant additional fault conditions/complexity/opex to their network when they could use the same QoS mechanism for both PWs and MPLS?

2) Assuming that QoS in the available server layers is not adequate then seeing as PW QoS is dependant on the server layer QoS, shouldn't the problem of specifying adequate QoS in the available server layers be addressed first?  Once there is adequate QoS in the available server layers then comment (1) above applies.

So either:
QoS for MPLS is adequate and ergo the problem of QoS for PWs has already been addressed.

Or, QoS for MPLS is inadequate and ergo QoS for MPLS should be addressed first and then the problem of QoS for PWs has already been addressed.

Ben

The above is my personal view and does not necessarily reflect the opinion of my employer.

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