How we tested SBCs

How we performed the Clear Choice Tests of session border controllers.

The session border controller (SBC) test bed consisted of simulated enterprise and carrier sites, connected by a T-1 IP WAN link. The network infrastructure at both sites consisted of Extreme Networks Summit48 L2 and L3 switch/routers.

Each SBC tested was configured and inserted, one at a time, into the test bed. The same carrier-side SBC, a leading carrier-class SBC from Sansay, the VSX, Release 6.7.2, was used in all cases.

A T-1 of simulated Session Initiation Protocol (SIP) traffic was generated and delivered from the carrier side by Touchstone Industries' WinSIP (Version 2.4.7) traffic generator. Another T-1 of simulated SIP traffic was generated from a Spirent Abacus 5000 (Version 3.2) SIP traffic generator from inside the enterprise.

These enterprise calls were terminated at their respective matching endpoints at the carrier site across the WAN link. For consistency, all SIP calls and traffic from the enterprise had to traverse the Sansay VSX carrier SBC. This also provided a rudimentary view of SBC interoperability.

Tests were performed to assess each SBC's ability to handle standard-SIP calls, and G.711- and G-729-encoded Real-time Transport Protocol (RTP) VoIP streams. The SBCs were set to pass the traffic as sent. Voice quality was measured using automated International Telecommunication Union-standardized PESQ, PESQ-LQ and R-factor algorithms.

Also measured were jitter, call-setup time and one-way latency. In addition, if supported, the SBC's ability to transcode the traffic to the simulated carrier was also tested.

Our intent with this testing was to verify features and gauge the effects of SBC processing on VoIP traffic flows. The load we applied was a modest T-1's worth, a few dozen concurrent calls in both directions. These products could reasonably be expected to handle hundreds, perhaps even thousands, of concurrent calls. Users shopping for an SBC will need to assure that call volumes at and beyond anticipated loads are supported on a sustained basis.

- Edwin Mier, Anthony Mosco, Robert Tarpley and Robert Smithers, Network World Lab Alliance


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