SIP Events Framework Issues SIPPING WG IETF #63, August 4, 2005 Aki Niemi Nokia Research Center aki.niemi@nokia.com
Problem #1: Inability to Persist State ● Not possible to carry ● Solution: suppress over state in refresh superfluous NOTIFY ● Notifier always sends – NOTIFY carries SIP- ETag the latest state – SUBSCRIBE carries – Even when subscriber SIP-If-None-Match has it already ● Open issue: what to ● Contrast: conditional suppress? HTTP GET – Entire NOTIFY or – If-None-Match: “etag” body only
Problem #2: Intolerance to Network Connectivity Hiccups ● If NOTIFY times out, ● Solution: define the notifier SHOULD behavior for failing terminate subscription soft – Not clear when not to – When? terminate it (fail soft) – How? and how ● E.g., back-off scheme – Assumes subscriber and suppress state refreshes when net is back – Subscription-State: zombie;reason=timeout – Bad user experience in long-lasting subs
Summary ● Draft-niemi-sipping-subnot-issues-00 ● Aims to generate discussion and offer potential solutions ● Long term these could end up being part of a possible RFC 3265 bis
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