Session Initiation Protocol SIP Session Mobility draftshachamsippingsessionmobility00 Ron

Session Initiation Protocol (SIP) Session Mobility draft-shacham-sipping-session-mobility-00 Ron Shacham Henning Schulzrinne Srisakul Thakolsri Wolfgang Kellerer SIPPING - IETF 62 - Minneapolis (March 2005) 1

Motivation l Session mobility = move active sessions from one (mobile) terminal to one or more (stationary) terminals l l l Move active sessions back to controlling device l l i. e. , not just call transfer Service examples l l audio on hardware phone, video on PC move conference to conference room facilities requires no new SIP protocol mechanisms Real system also requires discovery mechanism l we use SLP SIPPING - IETF 62 - Minneapolis (March 2005) 2

Local Devices Transcoder Internet SLP DA SLP SA SLP UA SIP SM SIP UA Correspondent Node (CN) SIP SM SIP UA SLP UA SIPPING - IETF 62 - Minneapolis (March 2005) Mobile Node (MN) SLP SIP RTP 3

Requirements l Interoperability l l Backward Compatibility l l Support local devices with basic functionality Flexibility l l Only require CN to support RFCs and mature IDs Discover and reconcile device capability differences Seamlessness l Limit disruption of media SIPPING - IETF 62 - Minneapolis (March 2005) 4

Session mobility options l Transfer and retrieve an active session l l Retrieval not only of a session previously transferred Transfer all media to a single device or split over multiple devices l l l Privacy: keep audio on handset, watch video on large screen Take advantage of benefits of different devices Includes division of full-duplex media into half-duplex streams SIPPING - IETF 62 - Minneapolis (March 2005) 5

Session mobility modes l l MN may retain control of or relinquish session signaling Mobile node control mode l l 3 pcc (call control flow I) Session handoff mode l REFER, “Replaces” header, Referred-By mechanism for security SIPPING - IETF 62 - Minneapolis (March 2005) 6

Session Handoff Mode l Retrieval of session not controlled by MN l l Use “Nested REFER” for MN to retrieve Handoff to multiple devices l l Can’t currently bind multiple sessions at CN into one Devices discover each other and form “Multi-device systems” where B 2 B UA receives REFER and controls other devices SIPPING - IETF 62 - Minneapolis (March 2005) 7

Handoff to a Multi-Device System 5 RTP MDSM 3 INVITE, Replaces/ 200 OK/ ACK CN 2 INVITE / 200 4 ACK (CN SDP) 5 RTP 6 BYE/ 200 OK 2 INVITE / 200 1 REFER ORIGINAL SESSION 7 SESSIONS TERMINATED 4 ACK (CN SDP) 2 INVITE / 200 MN 4 ACK (CN SDP) 5 RTP SIPPING 5 -RTP IETF 62 - Minneapolis (March 2005) 8

Device Capability Differences l Local device does not support any codec supported by CN l l Transfer carried out through transcoder using 3 pcc Local device has higher bandwidth and may receive media at a higher framerate l Local device includes such information in response, as is done for H. 263+ SIPPING - IETF 62 - Minneapolis (March 2005) 9

Open issues l l Can we avoid the B 2 BUA for SH mode? Integration of text sessions (MSRP) SIPPING - IETF 62 - Minneapolis (March 2005) 10

Service Discovery l l Architecture is not dependent on a single protocol Low-power wireless protocols find close devices without knowing location Query-based protocols (eg. , SLP) allow larger areas and other locations to be queried Integration of both types of protocols could prove useful SIPPING - IETF 62 - Minneapolis (March 2005) 11