Implicit Subscriptions Jonathan Rosenberg Cisco Systems A Trend
Implicit Subscriptions Jonathan Rosenberg Cisco Systems
A Trend • IETF and SIP WG are (for the better) recognizing that industry usage doesn’t match specifications in several areas – NAT (behave) – SBCs (voipeer, sipping SBC work) • But, there are others – Unsolicited NOTIFY
Why is it common? • Perceived high cost of subscription maintenance at client – Refreshes, dialog for entire registration interval • Perceived high cost of subscription maintenance at server – One for EVERY user that is logged in • Perceived high cost of messaging compared to frequency of events – Not like presence • Assumption of endpoint interest – “Self” cases – unlike presence • There is a real engineering issue here
Other Problems • Avalanche restart: Metropolitan power outage and reboot • Endpoint messaging – SUBSCRIBE config-pkg – REGISTER – SUBSCRIBE for • • • MWI Reg-event Presence-list Winfo Dialog-event (BLA) – 13 SIP transactions! • Time to recover and potential scope of load directly proportional to this
Requirements • Reduce messaging volume – Ideally: 1 transaction (REGISTER) • Allow event servers to have a finite number of dialogs • Preserve compatibility with RFC 3265 mechanisms
Proposed Solution • Couple a subscription with a registration – Subscription lifetime bound to registration lifetime – Create subscription as a side effect of registration – Tunnel dialog identifiers through REGISTER request and response
- Slides: 6