sipcore Y. Gao Internet-Draft ZTE Intended status: Standards Track August 25, 2009 Expires: February 26, 2010 Suspending and Resuming for Modification draft-gaoyang-sipcore-suspending-and-resuming-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, and it may not be published except as an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 26, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Gao Expires February 26, 2010 [Page 1] Internet-Draft Suspending and Resuming for Modification August 2009 Abstract RFC3312 & 4032 has defined semantics of suspending and resuming for session establishment. But suspending and resuming for session modification needs clarification, especially for modification with part of the streams with precondition. This text just aims for giving out some use case for further analysis. And if we need do some standard track for this issue, IMO, the "Re-INVITE Handling" draft can be more proper and systematic. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Drawbacks of suspending and resuming for whole session . . . . 4 2.1. To delay using of new parameters for stream without precondition may arose media clip problem . . . . . . . . . 4 2.2. Behavior of streams without precondition would be depend on the existence of other streams . . . . . . . . . 4 2.3. Various streams are not controlled by the same entity, so that coordination of when they take effect could be problematic . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Normative references . . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Gao Expires February 26, 2010 [Page 2] Internet-Draft Suspending and Resuming for Modification August 2009 1. Introduction RFC3312 & 4032 did not talk about session modification with precondition for detail. And, there are two alternatives for this issue here: o suspending and resuming for whole session; o suspending and resuming for streams with precondition separately; Considering a use case, A and B has a audio only session. Then A send a Re-INVITE for adding vedio stream( with precondition) and changing codec or address for audio stream( without preconditon). If suspending is effective for whole session, then streams without precondition should use old parameters while in suspending state. If suspending is effective for streams with precondition, the then streams without preconditio can use new parameters after first O/A during the Re-INVITE. I will use some use cases to reveal the drawbacks of "suspending and resuming for whole session". Gao Expires February 26, 2010 [Page 3] Internet-Draft Suspending and Resuming for Modification August 2009 2. Drawbacks of suspending and resuming for whole session 2.1. To delay using of new parameters for stream without precondition may arose media clip problem Considering a use case, A and B has a audio only session. Then A send a Re-INVITE(F1) for adding vedio stream(with precondition) and changing codec or address for audio stream(without preconditon). If suspending is effective for whole session, then streams without precondition should use old parameters while in suspending state. But sometimes, A has no way to use old parameters anymore, for example session mobility. Then, it aroses media clip problem. Media clip problem A B | session established | |<===================>| | | | F1 re-INVITE (SDP) | |-------------------->| | F2 1xx-rel (SDP) | |<--------------------| | F3 UPDATE | |-------------------->| | F4 2xx UPT | |<--------------------| | | | F5 180 ringing | |<--------------------| | | | F6 2xx INV | |<--------------------| | F7 ACK | |-------------------->| | | Figure 1 2.2. Behavior of streams without precondition would be depend on the existence of other streams Considering a use case, A and B has a audio only session. Then A send a Re-INVITE(F1) for adding vedio stream and changing codec or address for audio stream(without precondition). If suspending is effective for whole session, then the behavior of audio stream would be depend on the condition of vedio stream. The user will be Gao Expires February 26, 2010 [Page 4] Internet-Draft Suspending and Resuming for Modification August 2009 confused. As: If vedio stream is without preconditon too, B will send F2 with answer at once. And B can use new parameters of audio stream just after F2. Vedio stream without preconditon A B | session established | |<===================>| | | | F1 re-INVITE (SDP) | |-------------------->| | F2 2xx INV (SDP) | |<--------------------| | F3 ACK | |-------------------->| | | Figure 2 If vedio stream is with preconditon, B can use new parameters of audio stream after the time point of precondition met. Vedio stream with preconditon A B | session established | |<===================>| | | | F1 re-INVITE (SDP) | |-------------------->| | F2 1xx-rel (SDP) | |<--------------------| | F3 UPDATE | |-------------------->| | F4 2xx UPT | |<--------------------| | F5 2xx INV | |<--------------------| | F6 ACK | |-------------------->| | | Figure 3 Gao Expires February 26, 2010 [Page 5] Internet-Draft Suspending and Resuming for Modification August 2009 2.3. Various streams are not controlled by the same entity, so that coordination of when they take effect could be problematic Considering a use case, A and B has a audio only session. Then A send a Re-INVITE(F1) for adding vedio stream and changing codec or address for audio stream(without precondition). And B is controller of Media Servers. So, it will dispatch the offer(or part streams of the offer) to media servers. As in Figure, the controller will send audio stream to media server1 using Re-INVITE, and send vedio stream to media server2 using INVITE. If suspending is effective for whole session, then the new parameters of audio stream should not be used. And it is complex or difficult for controller to do so. Coordination problem A B(Controller) Media Server1 Media Server2 | session established | | | |<=========================================>| | | | | | | F1 re-INVITE (SDP) | | | |-------------------->| F2 re-INVITE (SDP) | | | |-------------------->| | | | F3 INVITE (SDP) | | | |------------------------------------------>| | | F4 2xx INV | | | |<--------------------| | | | F5 1xx-rel (SDP) | | | |<------------------------------------------| | F6 1xx-rel(SDP) | | | |<--------------------| | | | | | | Figure 4 Gao Expires February 26, 2010 [Page 6] Internet-Draft Suspending and Resuming for Modification August 2009 3. Acknowledgment Thanks Paul Kyzivat's suggestion. Gao Expires February 26, 2010 [Page 7] Internet-Draft Suspending and Resuming for Modification August 2009 4. Normative references Gao Expires February 26, 2010 [Page 8] Internet-Draft Suspending and Resuming for Modification August 2009 Author's Address Gao yang ZTE CHINA Email: gao.yang2@zte.com.cn Gao Expires February 26, 2010 [Page 9]