"Basic Level of Interoperability for Session Initiation Protocol (SIP) Services (BLISS) Problem Statement", Jonathan Rosenberg, 9-Mar-09. ( bytes)

The Session Initiation Protocol (SIP) has been designed as a general purpose protocol for establishing and managing multimedia sessions. It provides many core functions and extensions in support of features such as transferring of calls, parking calls, and so on. However, interoperability of more advanced features between different vendors has been poor. This document describes the reason behind these interoperability problems, and presents a framework for addressing them.

"Call Completion for Session Initiation Protocol (SIP)", Dale Worley, Martin Huelsemann, Roland Jesske, Denis Alexeitsev, 13-Jul-09. ( bytes)

The call completion features allow the calling user of a failed call to be notified when the called user becomes available to receive a call. For the realization of a basic solution without queueing call- completion requests this document references the usage of the the dialog event package [RFC4235] as described as 'automatic redial' in [RFC5359]. For the realization of a more comprehensive solution with queueing call-completion requests this document introduces an architecture for implementing these features in the Session Initiation Protocol: "Call completion" implementations associated with the caller's and callee's endpoints cooperate to place the caller's request for call completion into a queue at the callee's endpoint, and, when a caller's request is ready to be serviced, re-attempt the original, failed call. The deployment of a certain SIP call-completion solution is also dependent on the needed level of interoperability with existing call- completion solutions in other networks.

"Shared Appearances of a Session Initiation Protocol (SIP) Address of Record (AOR)", Alan Johnston, Mohsen Soroushnejad, Venkatesh Venkataramanan, 13-Jul-09. ( bytes)

This document describes the requirements and implementation of a group telephony feature commonly known as Bridged Line Appearance (BLA) or Multiple Line Appearance (MLA), or Shared Call/Line Appearance (SCA). When implemented using the Session Initiation Protocol (SIP), it is referred to as shared appearances of an Address of Record (AOR) since SIP does not have the concept of lines. This feature is commonly offered in IP Centrex services and IP-PBX offerings and is likely to be implemented on SIP IP telephones and SIP feature servers used in a business environment. This document discusses use cases, lists requirements and defines SIP extensions to implement this feature.

"Implementing Call Park and Retrieve using the Session Initiation Protocol (SIP)", Michael Procter, 28-Jun-09. ( bytes)

Call Park and Call Retrieve are useful telephony services that are familiar to many users. Existing implementations using the Session Initiation Protocol (SIP) show that a variety of approaches can be Taken, with varying degrees of interoperability. This draft discusses a number of feature variations, and how they may be implemented using existing techniques. An additional URI parameter is also described, which enables further common use-cases to be implemented.

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