1. Slide # 1 SIMPLE Interim May 2004MSRP Hop-by-hop Mechanism MSRP Hop-by-Hop Mechanism SIMPLE WG Interim Meeting May 24th, 2004, Bedford MA draft-levin-simple-msrp-review-00

2. Slide # 2 SIMPLE Interim May 2004MSRP Hop-by-hop Mechanism Two Distinct Mechanisms Application Layer: End-to-end –For application use Network Layer: Hop-by-hop –For improved feedback (to application layer) in case of network failure –Require configuration of the first relay (only) The very first deployment will use RELAYs –Don’t build interim solutions for one hop only End-to-end abstraction MUST be provided even over a single hop –Applications need to be exposed to the end-to-end view ONLY

3. Slide # 3 SIMPLE Interim May 2004MSRP Hop-by-hop Mechanism Hop-by-Hop Mechanism Added Value –Automatic negative feedback in case of TCP link failure without additional application logic: requires state information (at least per MSRP connection) in relays –Ability to specify (with high probability) messages that have been affected by the failure – requires per message state + 200 OK –Improved timing for “stalled” TCP connections – requires “per something” state + “200 OK” + timer Issues –Specific message information can be misleading –OVERHEAD for BIG deployments ( > 25%, easily 50%) –Lack of throttling manageability for MUXing and CONFERENCING

4. Slide # 4 SIMPLE Interim May 2004MSRP Hop-by-hop Mechanism MUX and Conferencing Scenario MCURELAY Send 200 OK Send TCP connection

5. Slide # 5 SIMPLE Interim May 2004MSRP Hop-by-hop Mechanism Eliminating Hop-by-hop Responses per Message Negative Feedback by Network Layer - alternatives –None: can be implemented end-to-end by application with timer –By network layer per MSRP session: state implementation in relays –By network layer per message: state + timer + 200 OK Bilateral agreement between service providers –Over a single TCP hop –For all connections, sessions, messages Application signaling –Per instant message in a session –End-to-end “bit” inspected by relays