[SR-Users] Meaning of empty body in NOTIFY

Daniel-Constantin Mierla miconda at gmail.com
Fri Jun 10 12:18:45 CEST 2011


Hello,

On 6/10/11 12:04 PM, Eugen Dedu wrote:
> Thank you very much for your answer.
>
> Do you confirm that for kamailio, when a user has not been online 
> since a long time ago, (1) it answers with an empty body notify (and 
> not with a body with Offline status), and more importantly (2) that 
> this means the user is offline?
>
> I ask this because this seems contradictory to what SIP standard says 
> (see below): it does not say that empty body means offline, but just 
> does not have "meaningful state".
>
> In fact, opal (SIP library among others) developers (in CC) consider 
> that empty body means no information (which is different than 
> offline!), while kamailio uses it for offline!
it is not for online, it is like the others understood -- an empty body 
does not change anything. Because of that I said that if the UA knew the 
user is offline, it stays offline. When a UA has a user with online 
state, if it is a notify with empty body, stays like that, nothing changes.

Cheers,
Daniel

>
> On 09/06/11 13:10, Daniel-Constantin Mierla wrote:
>> Hello,
>>
>> the notify is sent to inform about the state of the subscription, which
>> is active in this case. If it would the first subscription to that user
>> and force_active will not be set, then should be subscription state
>> pending, iirc.
>>
>> The empty body does not change anything to the phone information about
>> the watched presentity, which was known to be offline.
>>
>> Cheers,
>> Daniel
>>
>> On 6/8/11 10:06 PM, Eugen Dedu wrote:
>>> No idea?
>>>
>>> On 05/06/11 22:31, Eugen Dedu wrote:
>>>> Hi,
>>>>
>>>> ekiga.net registrar uses kamailio 1.5.3 (yes, a bit old...) and for
>>>> users who are not registered an empty NOTIFY body is returned when 
>>>> asked
>>>> by a SUBSCRIBE. What does this mean from SIP standard point of 
>>>> view, and
>>>> from kamailio point of view (are they identical?) I see in
>>>> RFC3265/3.1.6.2:
>>>> .... If the resource
>>>> has no meaningful state at the time that the SUBSCRIBE message is
>>>> processed, this NOTIFY message MAY contain an empty or neutral body
>>>> but is difficult for me to interpret what it means.
>>>>
>>>> Example: I ask the presence for a user xyz who registered and quit
>>>> application long time ago:
>>>>
>>>> SUBSCRIBE sip:xyz at ekiga.net SIP/2.0
>>>> CSeq: 1 SUBSCRIBE
>>>> Via: SIP/2.0/UDP
>>>> 82.238.108.175:5060;branch=z9hG4bKdabe824f-1a8e-e011-9efc-0024d693d8e8;rport 
>>>>
>>>>
>>>>
>>>> User-Agent: Ekiga/3.3.1
>>>> From:
>>>> <sip:eugen.dedu at ekiga.net>;tag=4888824f-1a8e-e011-9efc-0024d693d8e8
>>>> Call-ID: f602824f-1a8e-e011-9efc-0024d693d8e8 at snoopy
>>>> Supported: eventlist
>>>> To: <sip:xyz at ekiga.net>
>>>> Accept: application/pidf+xml
>>>> Accept: multipart/related
>>>> Accept: application/rlmi+xml
>>>> Contact: <sip:eugen.dedu at 82.238.108.175:5060>
>>>> Allow:
>>>> INVITE,ACK,OPTIONS,BYE,CANCEL,SUBSCRIBE,NOTIFY,REFER,MESSAGE,INFO,PING,PRACK 
>>>>
>>>>
>>>>
>>>> Expires: 300
>>>> Event: presence
>>>> Content-Length: 0
>>>> Max-Forwards: 70
>>>>
>>>> I receive the following answer:
>>>>
>>>> NOTIFY sip:eugen.dedu at 82.238.108.175:5060 SIP/2.0
>>>> CSeq: 1 NOTIFY
>>>> Via: SIP/2.0/UDP 86.64.162.35;branch=z9hG4bK2a99.b8a72c47.0
>>>> User-Agent: Kamailio (1.5.3-notls (i386/linux))
>>>> From: sip:xyz at ekiga.net;tag=f85b0bd16aaafa8479586ac9f88b3198-10a0
>>>> Call-ID: f602824f-1a8e-e011-9efc-0024d693d8e8 at snoopy
>>>> To: sip:eugen.dedu at ekiga.net;tag=4888824f-1a8e-e011-9efc-0024d693d8e8
>>>> Contact: <sip:86.64.162.35:5060>
>>>> Subscription-State: active;expires=370
>>>> Event: presence
>>>> Content-Length: 0
>>>> Max-Forwards: 70
>>>>
>>>> To resume: What does SIP standard say about this NOTIFY with empty 
>>>> body?
>>>> Does this mean that the user xyz is offline?
>>>>
>>>> Or does this mean that user's status has not changed? In fact, the
>>>> NOTIFY with empty body (as shown above) is the first one sent by
>>>> kamailio, so there is no "previous" state of that user, hence
>>>> "unchanged" status has no meaning.
>>>>
>>>> Thank you,

-- 
Daniel-Constantin Mierla -- http://www.asipto.com
http://linkedin.com/in/miconda -- http://twitter.com/miconda




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