[Sip] Review of draft-ietf-sip-subnot-etags-01
"Asveren, Tolga" <tasveren@sonusnet.com> Tue, 02 October 2007 14:53 UTC
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From: "Asveren, Tolga" <tasveren@sonusnet.com>
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Subject: [Sip] Review of draft-ietf-sip-subnot-etags-01
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Draft: draft-ietf-sip-subnot-etags-01 Reviewer: Tolga Asveren [tasveren@sonusnet.com] Review Date: 2 October 2007 Review Deadline: Status: post-WGLC Summary: This draft is on the right track for publication and requires a few additions/clarifications before publication Detailed Comments: * 1.2 Terminology , definition of representation The definition of "representation" does not provide a definition. There are just some statements about "representation". I am not sure whether such a definition is necessary either. I would suggest deleting "representation" from this section. * 3. Overview of Operations, remembering entity-tags for all versions Why is it necessary for the notifier to remember all versions of an entity? To check entity-tags in SUBSCRIBEs to determine whether an update has happened, it just needs to know the entity-tag for the last version. To generate unique entity-tags, it can just use a counter with some extra information to deal with restart situations, e.g. some information extracted from current time. * 5.2 Generating SUBSCRIBE requests, presence of multiple conditional headers I assume simultaneous presence of both "Suppress-Body-If-Match" and "Suppress-Notify-If-Match" is allowed. This could be useful for polling/resuming a previous subscription scenarios, where the subscriber isn't sure about the capabilities of the notifier. Mentioning about this possibility could be useful IMHO: "It should be noted that subscribers MAY include both Suppress-Body-If-Match and Suppress-Notify-If-Match conditional header fields together in a SUBSCRIBE request. This type of usage could be utilized for the cases where the subscriber is not sure about the suppressing capabilities of the notifier." I guess, we would also need to define what a notifier should do upon receipt of both headers: "If a notifier receives both Suppress-Notify-If-Match and Suppress-Body-If-Match headers, it SHOULD suppress the notification if the condition evaluates to true if it has this capability. Otherwise it SHOULD suppress the body of the notification if it has this capability. If the notifier can't do either of these, it simply SHOULD ignore these headers." * 5.4 Polling or Fetching Resource State, meta-information query What is a real life use case for meta-information query? What value would learning current entity-tag value provide from subscriber perspective? * 6.1 Generating Entity-tags "For example, one possible method is to implement the entity-tag as a simple counter, incrementing it by one for each generated notification per resource" I have a few questions regarding this sentence: i- Multiple notifications to different subscribers could be generated for the same state. I don't think all these should cause a new e-tag value. AFAICS, the rule for a new entity-tag is as follows: "If a notification is generated for the current state and if the state changes, a new entity-tag MUST be assigned". ii- What about notifier restarts? It may be helpful to indicate about some differentiator between cycles, e.g. some information based on current time. I guess the crucial point is to make sure that the same entity-tag is not reused for two different versions because that may suppress necessary state notifications. It is still tolerable if the notifier -for whatever reason- uses two different entity-tags for the same version at two distinct times. Maybe a sentence could be added about this : "Subscribers MUST not assume that a notifier will always use the same entity-tag for a specific version. Especially after notifier restarts, this MAY not be the case." * Forking RFC3265 4.4.9 has the following: " If such behavior is not allowed, the first potential dialog-establishing message will create a dialog. All subsequent NOTIFY messages which correspond to the SUBSCRIBE message (i.e., match "To", "From", "From" header "tag" parameter, "Call-ID", "CSeq", "Event", and "Event" header "id" parameter) but which do not match the dialog would be rejected with a 481 response. Note that the 200-class response to the SUBSCRIBE can arrive after a matching NOTIFY has been received; such responses might not correlate to the same dialog established by the NOTIFY. Except as required to complete the SUBSCRIBE transaction, such non-matching 200-class responses are ignored. " It could make sense to amend this behavior. Consider the case, where the SUBSCRIBE forks and the first 200/NOTIFY arrives from a notifier which does not support suppressing and after a short while subscriber receives the NOTIFY from another notifier with an entity-tag. It could be preferable for the subscriber to terminate the first dialog and continue the second one. * Implicit Subscriptions, REFER I think this mechanism is applicable for implicit subscriptions as well. It could be an idea to mention this somewhere (maybe in 2.3. Requirements) To say a sentence or two about REFER initiated subscriptions could be useful as well. I guess it doesn't make much sense to use suppressing capability in this case: "Although technically it is possible to use notification/body suppressing capability for REFER initiated subscriptions, this is not seen as desirable considering the REFER use case." Nits: * 3. Overview of Operation, middle of the second paragraph ", and attaches includes it in a SIP-ETag" Just use either "attaches" or "includes" _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use sip-implementors@cs.columbia.edu for questions on current sip Use sipping@ietf.org for new developments on the application of sip
- [Sip] Review of draft-ietf-sip-subnot-etags-01 Asveren, Tolga
- [Sip] Review of draft-ietf-sip-subnot-etags-01 Avshalom Houri
- Re: [Sip] Review of draft-ietf-sip-subnot-etags-01 Aki Niemi
- Re: [Sip] Review of draft-ietf-sip-subnot-etags-01 Aki Niemi