[SIPForum-discussion] How should B2BUA maintain the SDP.

[Pavel Gavronsky]

Hello, everyone,
 
Setup:
 
B2BUA - tandem SIP softswitch (tandem between softswitch_1 and softswitch_2)
ORIGINATOR: Subscriber connected to softswitch_1 
TERMINATOR1: Subscriber connected to softswitch_1
TERMINATOR2: Subscriber connected to softswitch_2
TERMINATOR3: Subscriber connected to softswitch_1
 
Scenario (only important messages shown):
Call comes from the ORIGINATOR and is routed to TERMINATOR1:
 
INVITE (to:TERM1, SDP=ORIG) -> B2BUA -> INVITE (to: TERM1, SDP=ORIG)
100 trying <- B2BUA <- 100 Trying
180 Ringing (SDP=TERM1) <- B2BUA <- 180 Ringing (SDP=TERM1)
_____________B2BUA -> Cancel (According to its internal logic B2BUA releases
the TERM1 leg in order to make new call to TERM2)
_____________B2BUA -> INVITE (to:TERM2, SDP=ORIG) (According to its internal
logic B2BUA makes new call to TERM2)
_____________B2BUA <- 100 Trying
180 Ringing (SDP=TERM1) <- B2BUA <- 180 Ringing (no SDP) ( ??? Is it
correctly to provide the old SDP=TERM1 toward the ORIG in that case ???)
_____________B2BUA -> Cancel (According to its internal logic B2BUA releases
the TERM2 leg in order to make new call to TERM3)
_____________B2BUA -> INVITE (to:TERM3, SDP=ORIG) (According to its internal
logic B2BUA makes new call to TERM3)
_____________B2BUA <- 100 Trying
180 Ringing (SDP=TERM3) <- B2BUA <- 180 Ringing (SDP=TERM3) (Here the B2BUA
correctly passes the SDP=TERM3)
 
 
Question:
If the 180/183 from the TERM leg does not include the SDP, should the B2BUA
use the "remembered" old SDP value for the 180/183 toward ORIG leg? 
 
________________________________________ 
Thank you in advance,
Pavel Gavronsky
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20120213/888300ef/attachment-0002.html>