8 Call Merging Algorithms

Oracle Communications Operations Monitor has the ability to find the call legs of the same call. This is an essential feature for troubleshooting and for providing deep device visibility and accurate statistics. While in the case of some SIP devices (like Proxies and B2BUAs that keep the Call-ID header) finding the matching call legs is easy, many other devices change most of the fields from the incoming leg for purposes like topology hiding, decoupling, and interoperability. This makes the call merging problem hard and impossible to solve in all cases with a single algorithm.

Operations Monitor gives the network operator the power to adjust the call merging algorithm by providing a comprehensive list of tests and a flexible way to combine them in call merging algorithms. This section describes the available tests and how to write the algorithms. The resulting scripts can be entered in the Platform Devices section for SBC/B2BUA devices by choosing the Use custom algorithm option.

The call merge algorithms always return a single Boolean value: true if the call legs are part of the same call, and false otherwise. They provide ordered tests, tests with parameters, and nested decisions trees. To keep the real-time nature of Operations Monitor, the tests are implemented natively in the Operations Monitor core, and the algorithms are compiled to an internal representation which can be executed with maximum performance.

This chapter also contains links to KM notes that describe how to enable various types of call merging and call correlation. For more information, see "Merging and Correlating Calls".

Note:

When call correlation is based on the correlation algorithm of a device, an incoming leg can be correlated with multiple outgoing legs. An outgoing leg, however, can be correlated to only one incoming leg.

For global call correlation based on the SIP Call ID, the restriction for outgoing legs does not apply. Call ID based correlation can be enabled with the Merge globally by Call ID setting in System Settings under System Management on the Settings page. For more information on this setting, see "Merge globally by Call-ID".