Network Deployment (Distributed operating systems), v8.0 > Administer applications and their environment > Administer Session Initiation Protocol (SIP) applications > Administer SIP applications > Configure multihomed hosting
Multihomed hosting
SIP can support the ability to route outbound SIP requests through more than a single interface with the multihomed host feature of JSR 289.
In a multihomed host environment, the SIP container has the ability to select a particular outbound interface for routing messages. The SIP container can accept from the SIP proxy a list of outbound interfaces and expose it to any SIP application. This functionality is for applications that require tighter control over the outgoing request flow.
The following two methods can be used to select the outbound interface to use when sending requests, as defined in section 14.2 of the JSR 289 specification:
- setOutboundInterface(java.net.InetAddress address)
- setOutboundInterface(java.net.InetSocketAddress address)
A SIP application can obtain a list of available of SIP URIs it can send outbound requests on from the ServletContext attribute "javax.servlet.sip.outboundInterfaces," defined with the static string javax.servlet.sip.SipServlet.OUTBOUND_INTERFACES.
The application must set the interface on the Proxy, the ProxyBranch, or the SipSession objects before any outbound requests are sent. The interface is passed back in the attribute for outbound interfaces. The container then notifies the proxy which interface to send the outbound request on. Routing of non-request messages is controlled by other means, such as headers. For instance, a response message always flows through the same interface that the request arrived on.
Modify the outbound routing of a request can affect all of the following SIP headers that are inserted into the outgoing SIP request, and subsequent responses in the dialog:
- Via header
- Contact headers
- Record-Route and Route headers
- Path header
Three SIP proxy custom properties specify the default chain names that define the appropriate interface to use for outbound requests. See the information on configuring multihomed hosting.
SIP with multihomed host is only supported in a distributed environment and must be configured at the WebSphere SIP proxy. A stand-alone SIP container does not support this capability.
Related information
SIP Servlet Specification 1.1
Concept topic