Subject: [Megaco] v2 mismatch ABNF & ASN.1 IndAudmediaParm?

From: Micael Karlberg <[email-masked]>
Date: Mon, 16 Jun 2003 15:54:20 +0200

Hi,

In draft-ietf-megaco-h248v2-04.txt there appear to be a mismatch
between the ABNF and the ASN.1 regarding indAudmediaDescriptor.
My question is: Should the definition of ABNF indAudmediaDescriptor
really be:

      indAudmediaDescriptor   = MediaToken LBRKT indAudmediaParm
                                *(COMMA indAudmediaParm) RBRKT 

The comment for indAudmediaParm and the ASN.1 IndAudMediaDescriptor 
indicates that it should be a list. Or am I missing something?

Also, see definition of mediaDescriptor!

ABNF:
----
      indAudmediaDescriptor   = MediaToken LBRKT indAudmediaParm RBRKT 
       
      ; at-most-once per item 
      ; and either streamParm or streamDescriptor but not both 
      indAudmediaParm = (indAudstreamParm / indAudstreamDescriptor /  
                         indAudterminationStateDescriptor) 

ASN.1:
-----
      IndAudMediaDescriptor ::= SEQUENCE 
      { 
          
         termStateDescr    IndAudTerminationStateDescriptor OPTIONAL, 
         streams  CHOICE 
               { 
                  oneStream      IndAudStreamParms, 
                  multiStream    SEQUENCE OF IndAudStreamDescriptor 
               } OPTIONAL, 
         ... 
      } 

Regards,
	/BMK

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---

From: Christian Groves <[email-masked]>
Date: Tue, 17 Jun 2003 10:58:51 +1000

Hello Micael,

I don't understand what the problem is nor the comments in the ASN.1 you are
referring to? If you are referring to the ::= SEQUENCE this is actually an ASN.1
construct that says that a sequence of information elements may be encoded, in
this case "termStateDescr" & a choice of streams. This same information is
represented by the ABNF.

Regards, Christian

---

From: Christian Groves <[email-masked]>
Date: Tue, 17 Jun 2003 10:58:51 +1000

Hello Micael,

Regards, Christian

---

From: Micael Karlberg <[email-masked]>
Date: Tue, 17 Jun 2003 19:25:34 +0200

Hello Christian,

Christian Groves writes:
 > referring to? 

The comment ("at-most-once per item...") is in the ABNF.

 > If you are referring to the ::= SEQUENCE this is actually an ASN.1
 > this case "termStateDescr" & a choice of streams. 

This is how see it also.

 > This same information is represented by the ABNF.

This I _cannot_ find!

The comment in the ABNF seems to indicate that it should be as in 
the ASN.1 but the ABNF definition of the indAudmediaDescriptor 
allow for only one value of indAudmediaParm.

Therefor my _question_ if the definition should'nt really be:

Also, the defintion of the mediaDescriptor strikes me as _very_
similar to my "proposal":

      mediaDescriptor = MediaToken LBRKT mediaParm 
                        *(COMMA mediaParm) RBRKT 
       
      ; at-most one terminationStateDescriptor 
      ; and either streamParm(s) or streamDescriptor(s) but not both 
      mediaParm = (streamParm / streamDescriptor /  
                    terminationStateDescriptor) 

Regards,
	/BMK

-- 
Micael Karlberg          Ericsson AB, Älvsjö Sweden
Tel:  +46 8 727 5668     EAB/UHK/KD - OTP Product Development
ECN:  851 5668           Mail: [email-masked]
Fax:  +46 8 727 5775

---

From: Micael Karlberg <[email-masked]>
Date: Tue, 17 Jun 2003 19:25:34 +0200

Hello Christian,

This is how see it also.

This I _cannot_ find!

       

Regards,
	/BMK