Subject: [SIMPLE] Mechanism for sending service-state notifications to a handset

From: [email-masked]
Date: Mon, 28 Feb 2005 17:09:00 +0100

Hi,

In TDM-networks, the service offering includes "supplementary services", 
such as call forwarding (on busy, no reply, unconditional, ...), 
CLIP/CLIR, call barring, etc.  When call forwarding (CF) is activated, a 
user typically is notified of this situation when he lifts the hook, 
either by a stutter tone or by an announcement that informs him/her of the 
condition.

As one possible use of SIP telephony is to replace a TDM-network, this CF 
notification should also be implemented in a SIP network.  It will be 
impossible to implement this in the same way as in a TDM network, since in 
a TDM network, the switch is aware of the activation of the call 
forwarding service and the switch detects when a phone is off-hook, and 
thus can play the stutter dial-tone or the notification.  In a SIP 
network, the softswitch is aware of the activation of the call forwarding, 
but the off-hook condition is typically not detected by the softswitch, 
but by the handset.  But the handset may not be aware of the activation of 
the call forwarding condition.
Two solutions seem evident:
the handset notifies the softswitch of the off-hook condition, so the 
softswitch can play the notification or the stutter dial-tone
the softswitch notifies the handset of the status of services, so the 
handset can show indicators or play notifications or tones

The first solution could give rise to a lot of traffic (every off-hook 
condition is sent to the softswitch) and a number of complications may 
pop-up (e.g. if the notification/tone are played via an INVITE-dialog, 
special rules are valid, since a user can begin dialling another number, 
etc).
The notification of "Message Waiting Indication" can be considered as a 
precedent for the second solution, so it seems evident to suggest the 
elaboration of a SIP event package for service-state-change, combined with 
a (XML-)document structure for the description of services.

KR
Eric Slabbinck
Systems & Network Architecture
Alcatel FSD/EA - IL23
Tel.: +32 3 240 4986 (Alcanet 605 4986)

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From: Paul Kyzivat <[email-masked]>
Date: Mon, 28 Feb 2005 11:53:41 -0500

Eric,

I don't see the relevance of this question to SIMPLE. This should 
probably be discussed on the sip-implementors list. So if you want to 
discuss further, please take it there.

A brief comment - you seem to be assuming a softswitch environment. But 
the feature you describe isn't limited to such an environment. Nor does 
IETF characterize and standardize features like this specifically. If I 
try to characterize what you are talking about in more general terms, it 
is that you want certain aspects of configurable behavior to be reported 
in the user interface of a UA. And you want this to be the case even if 
the configured state resides somewhere in the network rather than in the 
UA itself.

I would be inclined to hook such behavior to the config package. Either 
deliver information about the state directly in the config package, or 
else use the config package to inform the UA that it should subscribe to 
some other event package to get that information. Then have the UA 
adjust its user interface to report that state. In the case you cite, it 
could alter the dial tone it plays. (In general sip UAs that play a dial 
tone generate it themselves rather than receiving it in realtime.)

	Paul

[email-masked] wrote:
> either by a stutter tone or by an announcement that informs him/her of 
> the condition.
> 
> As one possible use of SIP telephony is to replace a TDM-network, this 
> CF notification should also be implemented in a SIP network.  It will be 
> impossible to implement this in the same way as in a TDM network, since 
> in a TDM network, the switch is aware of the activation of the call 
> network, the softswitch is aware of the activation of the call 
> forwarding, but the off-hook condition is typically not detected by the 
> softswitch, but by the handset.  But the handset may not be aware of the 
> activation of the call forwarding condition.
>    1. the handset notifies the softswitch of the off-hook condition, so
>       the softswitch can play the notification or the stutter dial-tone
>    2. the softswitch notifies the handset of the status of services, so
>       the handset can show indicators or play notifications or tones
> 
> 
> elaboration of a SIP event package for service-state-change, combined 
> with a (XML-)document structure for the description of services.
> 
> KR
> Eric Slabbinck
> ------------------------------------------------------------------------
>