Siemens MOVIEMATE 50 - Manual (Page 10)

Open Communications Principles and Best Practices 19/03/2012, page 10
Call Completion (CCBS/CCNR)
Call completion is a telephony feature which takes action on a failure to complete a call. It
allows for notifying the calling user when the called user is available again.
The OpenStage callback feature covers two conditions for call completion:
CCBS (Call Completion Busy Subscriber) : The called party is busy.
CCNR (Call Completion No Reply) : The called party does not respond.
Call Completion features can be implemented on a PBX, a dedicated server (e.g. a voicemail
Server) or directly on the client device (e.g. messaging applications).
There are several commercial companies which provide call completion features, as well as
IETF documents specifying call completion features for open standards, such as SIP.
The RFC 5359 gives a best practice example for call completion. However, the SEN OSCAR
group has evaluated this RFC with the result that it is not useful for a B2BUA architecture.
The IETF BLISS working group currently provides a draft paper (http://www.ietf.org/id/draft-
ietf-bliss-call-completion-06.txt) on how call completion can be implemented. However, no
RFC is available for this topic yet.
Although no standard has been released until now, OpenStage phones already support
server based call completion.
An implementation according to the IETF BLISS draft is planned, but currently not available.
The OpenStage call completion implementation is purely stimulus based and can be found
at:
http://wiki.siemens-enterprise.com/images/6/65/White_Paper_CC_10090.pdf
CTI for OpenStage - UACSTA
There are several use cases where remote control of a VoIP phone is required. Among these
are server based features like ‘Call Forwarding’ or ‘Do not Disturb’, or agent desktop
applications requiring a seamless desktop integration of the phone.
There is one ECMA standard in place which covers all those requirements: uaCSTA.
By means of the uaCSTA interface, the OpenStage SIP user agent can use call and device
control services at the SIP Server and vice versa. A complete set of CSTA services are defined
in ECMA-269 [6], which should be referenced for additional information.
The following subset of CSTA services and events are supported by OpenStage:
Services on the SIP Server:
Set Forwarding
Get Forwarding
Set Do Not Disturb
Get Do not Disturb
Events Generated by the SIP Server:
Forwarding Event