Hi Richard,
No of m-lines (Media lines) MUST same in offer and answer. So Bob
MUST not send D,E media information in 200-0K of INVITE
Refer section 6 of RFC 3264
"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"
If Bob want to send offer in 200 OK, he can send altogether different offer
With out violating following condition.
"if the previous SDP had N "m=" lines, the new SDP MUST have at least N "m="
lines"
Please refer section 8 of RFC 3264 for more details.
Regards
Ranjith
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Richard Wu
Sent: Monday, April 14, 2008 3:37 PM
To: sip-implementors@lists.cs.columbia.edu
Cc: Fu Siu Ming Claudio
Subject: [Sip-implementors] RE-INVITE question 14.2
Hi All,
In RFC 3264 chapter 14.2
"A UAS providing an offer in a 2xx (because the INVITE did not contain
an offer) SHOULD construct the offer as if the UAS were making a brand
new call, subject ....".
Consider the following scenario:
alice-----> INVITE with SDP media A, B, C ---> bob /* all are sendrecv */
alice<----- 200OK with SDP media A, B, C, D, E ---- bob /* all are
sendrecv */
alice------ ACK ----> bob
Then alice hold bob
alice-----> INVITE with SDP media A, B, C ---> bob /* all are sendonly */
alice<----- 200OK with SDP media A, B, C, D, E ---- bob /* all are
recvonly */
alice------ ACK ----> bob
Afterwards,
alice send a RE-INVITE with no SDP
alice-----> INVITE with no SDP---> bob
What should bob rely? Suppose bob support five medias A, B, C, D, and E.
Thanks in advance.
ichardR
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