Managing Distributed Feature Interactions in Enterprise SIP Application Servers

Abstract

Several trends in SIP application server deployments exacerbate the classic problem of feature interaction in large enterprise telephony environments: 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 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 and SBCs, and test the approach with a substantial feature set of 32 features.

Feature interactions between internet services and telecommunication services

“…For instance, the difference of Call Forwarding on Busy and Call Forwarding Unconditional cannot be captured as the K-M syntax has no concept of this. However, as has been shown in an extensive case study [17] these abstractions do not impact on feature interaction detection between call control services.…”

“…In the next section we describe how the rules from [17] can be mapped to the notation presented in section 4.…”

“…If both widgets are CWs, we use existing detection rules, such as [15][16] [17] to detect feature interactions. In the next section we describe how the rules from [17] can be mapped to the notation presented in section 4.…”