Subject: Re: [rtcweb] How do we implement SIP event subscription in RTCweb?

From: "Hannes Tschofenig" <[email-masked]>
Date: Tue, 14 Jun 2011 16:33:31 +0200

Hi Igor,

 I do not quite understand where you are heading with your question.

 Your question can be interpreted in two ways, namely:

 a) How do I implement SIP event subscription alike concepts in a browser?
 (without using SIP itself but with browser technologies)

 b) I want to provide interworking with an existing SIP implementation that uses the SIP event package: how do I do it?

 In any case, you need to provide more details about what you want to accomplish in order for someone to provide you a good answer.

 For example, you may want to provide some information about
 * what data would you like to subscribe to,
 * where is the data,
 * who is supposed to receive it? 

 Ciao
 Hannes

 PS: Your remark that maintaining connectivity alive for asynchronous communication is correct but what do you want to do if that's your desired functionality?
 This aspect is independent of SIP, XMPP and the Web.

----- Ursprüngliche Nachricht -----
Von: Igor Faynberg
Gesendet: 11.06.11 01:01 Uhr
An: [email-masked]
Betreff: [rtcweb] How do we implement SIP event subscription in RTCweb?

 A question. When SIP is implemented in an application within the present RTCweb architecture, how exactly could we use WebSockets for SUBSCRIBE/NOTIFY? It appears to me that the only way to achieve that is to open a persistent connection. Am I right? If so, is it not a problem, given the potential duration of such connections and potential tie-up of network resources? If not, how else could that be done? With many thanks, Igor _______________________________________________ rtcweb mailing list [email-masked] https://www.ietf.org/mailman/listinfo/rtcweb

---

From: Igor Faynberg <[email-masked]>
Date: Tue, 14 Jun 2011 12:52:24 -0400

Hannes,

Thanks for following up! I actually think that my question has already 
been answered, but to reply to  your query, I think that of  the two 
options you mentioned, the closest one to my question  is

...
b) I want to provide interworking with an existing SIP implementation 
that uses the SIP event package: how do I do it?
...

More precisely, the problem statement was: I need to have SIP on my 
Internet appliance. Now that I have only the browser to rely on, how do 
I implement it?

  I assume that I have 1) JavaScript to program in and 2) the WebSockets 
interface.  All is well until asynchronous processing comes in.  To 
implement SUBSCRIBE/NOTIFY, I would need to be able to receive the 
NOTIFY messages (i.e., catch interrupts) whenever they come.   I thought 
that the only way to achieve that was to keep an open TCP connection... 
forever.  (I was under the impression that this was not considered a 
good practice--both in terms of resending "keep alive" and holding 
resources (such as NAT).

The responses that I got so far confirmed that my assumption about 
keeping a TCP connection open  was right, but that the practice of 
keeping a TCP connection open has no longer been considered wasteful and 
is, in fact, implemented.  There was also a message about the necessity 
of being tied to the page, but this appears to me as something that can 
be meaningfully worked around.

I guess more clarifications and implementation reports will come my 
way.  I do think it is critical that SIP be implementable in the 
browser-only environment.  I understand the reasons for the decision NOT 
to have SIP (or, for that matter ICE) as part of the browser, but that 
implied that SIP can be implemented in the application.

Igor

On 6/14/2011 10:33 AM, Hannes Tschofenig wrote:
> b) I want to provide interworking with an existing SIP implementation 
> that uses the SIP event package: how do I do it?
>
> In any case, you need to provide more details about what you want to 
> accomplish in order for someone to provide you a good answer.
>
> PS: Your remark that maintaining connectivity alive for asynchronous 
> communication is correct but what do you want to do if that's your 
> desired functionality?
>> A question.
>> When SIP is implemented in an application within the present RTCweb
>> architecture, how exactly could we use WebSockets for SUBSCRIBE/NOTIFY?
>>
>> It appears to me that the only way to achieve that is to open a
>> persistent connection.  Am I right?
>>
>> If so, is it not a problem, given the potential duration of such
>> connections and potential tie-up of network resources?
>>
>> If not, how else could that be done?
>>
>> With many thanks,
>>
>> Igor
>> _______________________________________________
>> rtcweb mailing list
>> [email-masked]
>> https://www.ietf.org/mailman/listinfo/rtcweb
>