Managing Distributed Feature Interactions in Enterprise SIP Application Servers

Several trends in SIP application server deployments in large scale telephony environments exacerbate the classic problem of feature interaction : use of distributed feature servers, mixing of legacy and green-field feature servers, and the co-existence of multiple third-party feature implementations provisioned in the same environment. Next-generation SIP application servers will include an application router (AR) to provide more application control over feature sequencing. As we discuss here, the AR can be augmented to incorporate feature interaction detection and resolution logic. We describe a novel design for run-time feature interaction detection and resolution in an environment of distributed feature servers using a SIP application server with application routing function, such as that defined in JSR 289. The approach is based on the algorithm of the Kolberg-Magill (K-M) method for feature interaction detection. Here we extend the notation of the algorithm to cover advanced call control services, enable the algorithm to work in topologies involving B2BUAs (Back-to-Back User Agents) and SBCs (session border controllers), and test the approach with a substantial feature set of 32 features found in large enterprise solutions.