SIP application composition
Reference materials for the WAS implementation of JSR 116 standards.
Application composition specification
The JSR 116 standard states in Section 2.4 that multiple applications may be invoked for the same SIP request.
This standard requires that implementations must obey a cascaded services model, stating: "Triggering of service applications on the same host, shall be performed in the same sequence as if triggering had occurred on different hosts." This means that responses will flow upstream, that they will hit applications in the reverse order of their corresponding requests.
JSR 116 does not specify how to implement this when developing SIP applications, thus there are many ways to comply with this standard.
Application composition in the WAS environment
Composition of the application depends on the deployed application order, and on the order of mapping rules within the deployment descriptor of each application.
For an initial incoming request, the SIP container tries each potential rule in order. Upon finding the nth match, the container then invokes the corresponding servlet.
If the servlet needs to proxy the request, the container re-scans the rules searching for additional matches. Upon finding the (n+1)th match, the container invokes the corresponding servlet.
Matching the request excludes any servlet in the same application as the previously invoked servlet. As stated in the standards, no servlet will be invoked twice for the same SIP request.
Related tasks
Browse all SIP topics
Developing SIP applications
Related Reference
Compliance with industry SIP standards
Reference topic