Subject: [Sipping] SIP and Call Waiting.

From: Ramesh Ramamurthy <[email-masked]>
Date: Tue, 16 Mar 2004 13:53:16 -0700

Hi all,
   how do we do call waiting indication using SIP? The SIP Server needs 
to controll this feature and we cannot let the Endpoint manage this 
service for us.

Thanks in advance
Ramesh

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From: Rahul Arvind Jadhav <[email-masked]>
Date: Wed, 17 Mar 2004 10:05:17 +0530

But SIP endpoint is the one who also receives the call (Invite) request.
Moreover if SIP server controls this feature then it has to maintain no 
of simultaneous calls permission on per user. Now if that limit exceeds 
only than SIP server can invoke Call waiting funtionality for the 
caller. Now the reason why SIP server will have to maintain simultaneous 
calls permission on per user basis is that ,,, a single user can receive 
multiple calls .... simultaneously.... But thats true that SIP server 
can still implement call waiting functionality .... but call waiting is 
a feature which endpoints can manage in a more customized/personalized 
way than SIP server.....

-- 
Rahul Arvind Jadhav
Tech Lead, NetYantra India Pvt. Ltd, India
www.netyantra.com

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From: 황진경 <[email-masked]>
Date: Wed, 17 Mar 2004 13:50:12 +0900

That is what I contributed this meeting (though failed to get consensus)

    http://www.ietf.org/internet-drafts/draft-hwang-sipping-infomidcall-00.txt    

Since SIP application server know and can manage Subscriber's call status,
the call waiting service can be provided by network-based scheme with B2BUA control.

Thank you

Jinkyung Hwang
KT

----- Original Message ----- 
From: "Rahul Arvind Jadhav" <[email-masked]>
To: <[email-masked]>
Cc: <[email-masked]>
Sent: Wednesday, March 17, 2004 1:35 PM
Subject: Re: [Sipping] SIP and Call Waiting.

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From: Dean Willis <[email-masked]>
Date: Wed, 17 Mar 2004 15:19:05 -0600

> the call waiting service can be provided by network-based scheme with B2BUA control.

But what if the subscriber's UA has some other active session that does 
not transit the B2BUA in question? SIP, in general, has no requirement 
that a UA use one and only one "master node" for all services. In fact, 
SIP UAs can be reasonably deployed without any proxy support whatsover.

In the general SIP architecture, the only network element with perfect 
knowledge of the state of a given UA is the UA itself.

Unless extreme limitations to configuration and network design are 
applied (and such limitations are not likely to be specified here, 
although they seem to be part of some mobile push to talk models that 
couple network UAs to handset UAs), the service-providing B2BUA has only 
partial knowledge of UA state.

This means that, in general, only a UA can determine whether requests to 
that UA should be dealt with by presenting a "call waiting" alert to the 
user of that UA.

--
Dean