Hello,
I would like to know if it is mandatory to have in the SDP of the SIP response
(183 or 200 OK) a corresponding media attributes ( "a=" lines) for the ones
offered in the INVITE messages. I have checked the related RFC's (2327 & 3264)
but I couldn't come up with a clear understanding of this, what I have quoted
form the RFC's are only mentioning the media description ("m="):
6 Generating the Answer
For each "m=" line in the offer, there MUST be a corresponding "m="
line in the answer. The answer MUST contain exactly the same number
of "m=" lines as the offer. This allows for streams to be matched up
based on their order. This implies that if the offer contained zero
"m=" lines, the answer MUST contain zero "m=" lines.
And
a=* (zero or more session attribute lines)
The scenario that I have is as follows: SS1 <---> SS2 <---> SS3, SS1 and SS2
and communicating using SIP while H.323 is used
between SS2 and SS3. SS1 send the first invite that contains some media
attributes like the bitrate, rtpmap, fmtp, sendrcv...
SS2 the reply normally and respectively by 100 trying, 183 & 200 OK that do not
contains any media attributes,
which is making SS1 to send a re-invite.
I appreciate if you could help in this, is is mandatory to reply to a lines
media attributes and where can I find this in the RFC's, and is it normal for
SS1
to send a re-invite when there is no media attributes response in the 200OK.
Why SS2 is omitting the media attributes sent in the initial offer. Could it be
protocol conversion issue?
Thank you in advance for your help.
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