Inline.
ext Martin Hynar wrote:
Hello,
I read through the draft sip-subnot-etags-00 and I found several issues
that needs to be clarified.
1. typo in introduction
In sentence "Typically, a SUBSCRIBE request is issued whenever a
subscription is installed, periodically refreshed or terminated." shall
be probably "NOTIFY".
No, it really means SUBSCRIBE, but I think it's a little confusing. Perhaps:
Typically, a SUBSCRIBE request is issued by the subscriber
whenever it needs a subscription to be installed, periodically
refreshed or terminated.
2. some kind of misleading in text when talking about SIP PUBLISH
message as an example of entity tags usage. When talking about PUBLISH I
think, there is slightly different usage scenario. In response to
initial PUBLISH message, server generates entity tag. Client is mandated
to use this entity tag if she wants to change state of that particular
presence source. If this entity tag is not used, PUBLISH message
installs new presence source and not overwrites the former state. For
purposes of presence notifications, these publications are then
composed. This usage is a bit different that supposed for SUBSCRIBE
messages, The text evokes feeling of something different.
Yes, the details in PUBLISH are a bit different. Do you have better
wording in mind?
3. What is exactly meant with "Meta-information-check"? What is this
meta information.
Entity-tag for one. Added:
...meta-information related to a resource, e.g., its current
entity-tag value.
4. Besides RLS subscriptions there is one more problem, the
subscriptions to changes in documents. So extend the problem also on
notification about changes in multiple documents.
Don't understand what you mean by "multiple documents". What use-case do
you have in mind?
5. In my mind, there popped up an idea to move the SIP-Etag into the
response to SUBSCRIBE message. This way client can be informed about the
entity tag also without sending the NOTIFY message at all. Have you
considered this possibility?
Yes, this was considered, but rejected as there is currently no use for
it in the 2xx. The way the "Suppress-Notify-If-Match" condition works is
that a) the etag is the same and a 204 response is generated and b) the
etag has changed and a NOTIFY is generated, which includes the new etag
in SIP-ETag.
6. What about situation when e.g. presentity has no presence document
installed and some body subscribes her. The the notifier sends empty
document, wouldn't be there some special handling? E.g. no entity tag.
There is nothing specific to subnot-etags in this case.
The server basically has two choices. Either it generates an etag for
the empty document, and as a publication is received, changes that etag
to a new value; or the server treats the empty document as some sort of
floor value, gives it a constant etag value, in which case a subscriber
that fetched an empty document once, would never get an update in case
it happened to fetch again when there was no active publication.
Either option is completely an implementation detail.
Cheers,
Aki
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