[SIPForum-techwg] Interoperability Draft v3 - comments on sections 14 and 15

[Horvath Ernst]

Chris,

- In section 14.1 it may not be the PBX and SAS that generate or process SDP, it may be terminals or gateways. Why not use language similar to other subsections 14.x?

- In 14.2 the spec mandates G.711 µlaw. This is o.k. if there is no intention to apply the spec outside America. If the intention is an international specification then the text should read "G.711 A-law or µ-law". Additionally a statement should be added to say that the side that uses µ-law encoding MUST provide A-law conversion if needed.

- Also in 14.2, forbidding VAD may be a bit too restrictive. It also contradicts statements in 14.5 - I prefer the latter formulation.

- I suggest to remove 15.1 because I think it is outside the scope of this specification. If anything at all is needed here, more general statements (e.g. that provision of tones is a matter of local policy/implementation) should be used. Note that tones are usually country-specific and may be subject to national regulation.

- I also consider 15.2 outside the scope of this specification. If the PBX has a notion of Q.931 cause values it would be more helpful to convey those values to the PBX; if it does not have such a notion then it does not care which PSTN event caused a SIP response code. And the mirror table (mapping SIP response codes to cause values) is missing - shouldn't that be there, too? 
If people feel such mappings are essential, why is the corresponding RFC not sufficient?

Thanks,
Ernst Horvath
Siemens AG