[SR-Users] [OT] Fwd: [dispatch] proposed SIXPAC charter

Iñaki Baz Castillo ibc at aliax.net
Fri Oct 22 11:54:09 CEST 2010


2010/10/22 Daniel-Constantin Mierla <miconda at gmail.com>:
>> 1)
>> - Alice has two active resources (alice-1and alice-2).
>> - alice-1 uploads a new vCard.
>> How is alice-2 notified about that change if there is no possibility
>> of subscription to the vcard?
>
> Why it needs to be notified immediately? I haven't said that there is no
> subscription, but for some cases are just kind of "stateless subscription".
>
> Phone sends subscribe for a resource and gets the document in the reply if
> allowed or a negative reply if not allowed. Timestamps can be used to mark
> it has not be changed (like in http).
>>
>> 2)
>> IMHO avatar should be part of the vCard (as vCard already includes
>> photo and so):
>> - Alice is subscribed to Bob's presence (just presence).
>> - Alice retrieves the vCard (including avatar) of Bob. But there is no
>> subscription as you said.
>> - Bob uploads a new version of his vCard with a new photo.
>> How is Alice being notified about the change to display the new avatar?
>
> Avatar and photo in vcard can be different, but anyhow, not the scope here.
>
> In the light of useless traffic that can cost and not only that, would it
> bring benefits that the avatar is updated in realtime by your application
> even it is in standby and you don't want to communicate with that user? Or
> the application is asking for updates when is some activity related to that
> user? If there is no activity for a long time, it can do a periodic refresh,
> anyhow many SIP mechanisms require periodic actions.
>
>> 3)
>> Where is the limit to say "this info requires subscription but this one
>> not"?
>
> All require subscriptions, but in many cases is no state associated with,
> just one time pull of status/document. I haven't thought thoroughly, but I
> hope the servers don't need to know subscription states, only authorization
> rules, which are just stored documents and should be generic, not a language
> related to presence, but authorization for any kind of resources.


Hi Daniel, any "subscription" mechanism means PULL: the subscriber is
informed *by the server* about changes, so the server notifies the
user. In case of SIP this is achieved with a NOTIFY.
But you are speaking about PUSH: the interested user sends a periodic
request to the server to get possible new changes. IMHO this cannot be
called "subscription" neither "stateless subscription".

So, when you say "Phone sends subscribe for a resource and gets the
document in the reply" I would prefer "Phone sends a like-GET request
for a resource and gets the document in the reply". There is no way in
SIP to retrieve data without using subscription (which means the data
is sent in the NOTIFY, never in the 200 to the SUBSCRIBE). But here we
can introduce a new SIP method, As I told before, STORE method could
be use for uploading content or retrieving it (depending on a header,
URI parameter or whatever stil to define).

Do we agree here? :)


-- 
Iñaki Baz Castillo
<ibc at aliax.net>



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