- Slides: 9
SIP Events: Open Issues IETF 51 / SIP Working Group Adam Roach adam. [email protected] com
Do. S Attacks Problem: SUBSCRIBE in, RESPONSE plus NOTIFY out = amplifier. n No one seems to notice or care. No proposals have been made. Similar problems exist with e. g. 100 and 180 responses to INVITE. n Proposal: move from open issues section to security section. n
Forking n n No technical problems preclude the forking of SUBSCRIBE requests. Some have voiced philosophical objections, although I’ve received indications that some of the most vocal opponents are softening their stance. If we disallow it globally, no one can use it, even if it works well for some as-yet-undefined package. If we let packages allow/disallow it according to their needs, and no one ever allows it, no harm done. Proposal: Status Quo; describe technical solution in base draft, let individual drafts make a decision to allow or disallow it.
Notification of Expiration n “Expires” header in NOTIFY used to convey time remaining on subscription. This is not really a change from previous drafts; however, it has recently raised some objections. Proposal: New header “Subscription-Expires” for this purpose; it may contain a “reason” parameter (when set to 0), which aids in subscription migration.
Leg Correlation Original draft described SUB/NOT legs as being stand-alone and/or part of INVITE-initiated legs. n Early objections led to removal of distinction. n Recently, there have been calls to add INVITE-initiated legs back in. n Proposal: I don’t care. Let’s add it back. n
Package Name Syntax Previously, any token was okay; private packages were in the form of “org. monkeys. foo” n New sub-package syntax uses “. ” to separate packages, which causes ambiguity. n Proposal: Drop private name spaces altogether. n
Complete State vs. Sub-State n n n Current draft proposes (although it doesn’t require) conveying complete state in NOTIFY messages. To save message space, we can define a mechanism to convey complete state immediately following SUBSCRIBE, and only state deltas in subsequent NOTIFYs. CSeq gaps can be used to detect lost NOTIFYs, triggering re-subscriptions for full state.
Main Changes Since Last Draft New section detailing what information is to appear in event packages. n Added concept of sub-packages (including supporting syntax changes). n Added IANA Considerations Section. n
Main Changes to Next Draft Alignment with 2543 bis REGISTER handling: allow Expires to be increased and decreased by notifier. n Output from nits reviewer(s) (thanks, Bert!) n Further fleshing out of requirements on sub-packages. n