SIP Application Behaviors

SIP applications can behave only as proxies or user agent servers (UAS) in the current version of this API.

The simplest form of proxy behavior (forwarding the message to the next host or recipient) is performed simply by creating an application manifest and setting the value of the proxyByDefault Element element to true.

However, the classes defined in the Microsoft.Rtc.Sip namespace allow for significantly more advanced message processing and transaction management.

Some common scenarios where you must develop a proxy application instead of relying on a message filter script include:

• Secure proxy applications that specifically authenticate and validate users, or perform additional encryption of specific message data.

• Applications that may reference other external sources of information besides the registrar to determine proxy behaviors, such as a local database or active directory.

The basic classes for a proxy application are the ServerAgent type and the base Transaction type (which has two specific child types: ServerTransaction and ClientTransaction). The ServerAgent object is the interface between the application and the Microsoft Lync Server 2010 computer. The lifetimes of Transaction objects can be managed programmatically within the application for additional efficiency.

The following two types of proxy applications are supported by the namespace:

• SIP Forwarding Proxy Application

• SIP Forking Proxy Application