1. Ron Shacham Henning Schulzrinne Srisakul Thakolsri Wolfgang Kellerer
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)

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

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

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

5. Session mobility options
Transfer and retrieve an active session
Retrieval not only of a session previously transferred
Transfer all media to a single device or split over multiple devices
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)

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

7. SIPPING - IETF 62 - Minneapolis (March 2005)
Session Handoff Mode
Retrieval of session not controlled by MN
Use “Nested REFER” for MN to retrieve
Handoff to multiple devices
Can’t currently bind multiple sessions at CN into one
Devices discover each other and form “Multi-device systems” where B2B UA receives REFER and controls other devices
SIPPING - IETF 62 - Minneapolis (March 2005)

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

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

10. SIPPING - IETF 62 - Minneapolis (March 2005)
Open issues
Can we avoid the B2BUA for SH mode?
Integration of text sessions (MSRP)
SIPPING - IETF 62 - Minneapolis (March 2005)

11. SIPPING - IETF 62 - Minneapolis (March 2005)
Service Discovery
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)