H.323 standard has already defined how the lower network layer QOS (e.g., RSVP [guaranteed, controlled, best effort], ATM QOS [CBR, rt-VBR, nrt-VBR, ABR, UBR]).

Now, if we define H.323 application layer QOS only without defining the mapping, this will not provide backward compatibility to the existing H.323 standard.

This is the concern.

So, the "scope" should include the "mapping" of the H.323 QOS to the lower network layer QOS.

I don't think we can define such a mapping. There are many ways to use ATM. The one we used in Annex C is based on CBR AAL5. AAL1 or AAL2 could be candidates. VBR is also something to consider. We alse did single channel adaptation. We could multiplex. There is no reason why we need to specify the ATM transport and associated QoS mechanism.

On the diffserv side, I am also not convinced that there is much to say since network operators are free to use diffserv in any way they see fit.