Subject: [Megaco] ABNF individual audit: some copy & paste ERRORs?

From: "Contardi Angelo" <[email-masked]>
Date: Wed, 9 Nov 2005 18:22:39 +0100

In H.248.1 V2 probably there are some "copy N paste" errors,
highlight the fact that indAudxxx are sons of the whole ones :-)

1) The comment above indAudmediaParm:

      ; at-most-once per item
      ; and either streamParm or streamDescriptor but not both
      indAudmediaParm = (indAudstreamParm / indAudstreamDescriptor /
                         indAudterminationStateDescriptor)
   should be:

      ; at-most-once per item
      ; and either indAudstreamParm or indAudstreamDescriptor but not both

   Furthermore i have already follow the questions this comment arised (indAudmediaParm
   is not a list of items but just one item of just one kind, ASN.1 and ABNF aren't
   the same, etc) ... but i don't understand the "end of the story": ABNF syntax will be
   changed (and where in V2 or V3) to allow a "SEQUENCE of items" or not ?

2) This one is probably a "true" ERROR, not subject to various interpretations :-)

      indAudsignalsDescriptor = SignalsToken LBRKT [ indAudsignalParm ] RBRKT

   As the syntax say, indAudsignalsDescriptor may be EMPTY (just the token and the brakets).
   What does it means? In the whole signalsDescriptor, an EMPTY signal descriptor
   means to stop signals generation (MGC->MC), but here the indAudsignalsDescriptor is
   inside an auditDescriptor (MGC->MG). What signal should be "audited" in the case of
   indAudsignalsDescriptor empty?

AN IMPLEMENTATION QUESTION from MG point of view (ABNF syntax):

- Suppose the MGC would like to audit some (not ALL) parameters value of a stream.
  It will send to the MG a sequence of indAudmediaDescriptor (one for each parameter
  bacause a list is not allowed in ABNF) with inside just one indAudstreamDescriptor
  (if the stream is not the number ONE, that may be "implicit" if StreamID is omitted).
  So the MG should collect (merge) all these indAudstreamDescriptor-s with the
  same StreamID and answer to MCG with ONE mediaDescriptor with inside ONE
  appropriate streamDescriptor. Isn't it?

- More in general terms: a sequnce of indAudxxxDescriptor from MGC, referred to the same
  "object", cause ONE appropriate xxxDescriptor as reply, from MG. Is it correct?

Best Regards

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