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MSRP Hop-by-Hop Mechanism. draft-levin-simple-msrp-review-00. SIMPLE WG Interim Meeting May 24th, 2004, Bedford MA. 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
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MSRP Hop-by-Hop Mechanism draft-levin-simple-msrp-review-00 SIMPLE WG Interim Meeting May 24th, 2004, Bedford MA MSRP 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 MSRP 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 MSRP Hop-by-hop Mechanism
MUX and Conferencing Scenario MCU RELAY Send 200 OK TCP connection Send MSRP Hop-by-hop Mechanism
Eliminating Hop-by-hopResponses 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 MSRP Hop-by-hop Mechanism