IETF52 SIP WG Early Media Issues draftsensipearlymedia01 txt

IETF-52 SIP WG Early Media Issues draft-sen-sip-earlymedia-01. txt sanjoy@nortelnetworks. com jayshree@nortelnetworks. com chogg@nortelnetworks. com audet@nortelnetworks. com

Changes from Version 00 • Added early media requirements section • Identified additional issues assuming the use of draft manyfolksresource for allocating/identifying resource reservation needs for early media • Restructured PSTN and PBX scenarios to remove text duplications Dec 13, 2001 draft-sen-sip-earlymedia-01. txt 1

Early media requirements • Distinction of early media session from final negotiated session • Ability of provisional responses associated with early media to indicate whether or not local alerting by the SIP UA should be used or early media should be played instead. • Early media mechanism must be able to deal with forked call scenarios Dec 13, 2001 draft-sen-sip-earlymedia-01. txt 2

Issues • Separate early media offer/answer implies double resource reservation • Interaction with gateway is complicated - no way to decide if 180 requires local ringing • Offer-answer model provides 2 -way SDP negotiation only – manyfolks -resource uses PRACK for 3 -way negotiation Caller-A Caller-B INVITE (fm-offer) 183 (fm-answer) PRACK 200 OK (PRACK) Resource Reservation – final media COMET 200 OK (COMET) 183 (em-offer) PRACK (em-answer) 200 OK (PRACK) Resource Reservation –early media COMET 200 OK (COMET) 180 Ringing PRACK 200 OK (PRACK) Early Media 200 OK ACK Dec 13, 2001 draft-sen-sip-earlymedia-01. txt 3

Proposals Issues Proposals Separate early media offer/answer INVITE contains offer 1 st 183 contains answer Subsequent 183 (from same destination) contains new offer Indication of local Explicit indication required for in-band ringing media in 183/180 2 -way vs 3 -way Either: • Change manyfolks-resource to 2 -way negotiation OR • Change ‘offer/answer’ to ‘offer/answer/agreed’ Dec 13, 2001 draft-sen-sip-earlymedia-01. txt 4