[asterisk-users] Is this SDP payload Asterisk created valid?

[Gareth Blades]

On 27/09/13 14:28, Gareth Blades wrote:
> On 27/09/13 14:15, Gareth Blades wrote:
>>
>> Can anyone with a bit more knowledge about the SDP standard tell me 
>> if what asterisk is doing is correct?
>> Or if it must be a bug with our customers equipment? 
>
> Reading RFC2327 it cais the c= line 'must' be present in all updates 
> while 'm=' media lines are optional.
> I am therefore inclined to believe that Asterisk is working correctly 
> and there is a bug in the customers SIP equipment.
> But thats just my personal interpretation from briefly reading the 
> standard.
>
>
Well looking at RFC4566 section 5 :-

    Some lines in each description are REQUIRED and some are OPTIONAL,
    but all MUST appear in exactly the order given here (the fixed order
    greatly enhances error detection and allows for a simple parser).
    OPTIONAL items are marked with a "*".



       Session description
          v=  (protocol version)
          o=  (originator and session identifier)
          s=  (session name)
          i=* (session information)
          u=* (URI of description)
          e=* (email address)
          p=* (phone number)
          c=* (connection information -- not required if included in
               all media)
          b=* (zero or more bandwidth information lines)
          One or more time descriptions ("t=" and "r=" lines; see below)
          z=* (time zone adjustments)
          k=* (encryption key)
          a=* (zero or more session attribute lines)
          Zero or more media descriptions

       Time description
          t=  (time the session is active)
          r=* (zero or more repeat times)

       Media description, if present
          m=  (media name and transport address)
          i=* (media title)
          c=* (connection information -- optional if included at
               session level)
          b=* (zero or more bandwidth information lines)
          k=* (encryption key)
          a=* (zero or more media attribute lines)


So if I am reading that correctly the m= line is required only if we 
include a media description entry. It basically sais its required if we 
decide to include it (yes I know that doesnt make sense). What I presume 
this means is that if a media description is included such as there 
being a 'a=' line then the 'm=' line then becomes required.
So it still sounds like Asterisk is behaving correctly.