Open-door policy

This was the first public Session Initiation Protocol event. Previous SIP interoperability forums have been closed-door sessions in which vendors have tested conformance of their products with SIP and ironed out various issues relative to interpretation of the SIP specification.

This public on-the-record event (co-sponsored by Miercom, a Network World Global Test Alliance partner, and Network World) was designed to test basic interoperability on a functional level. We sought to find if SIP-based products could place calls, achieve an adequate level of voice quality, and hang up.

Vendors that Miercom's research determined were implementing SIP within their voice-over-IP products were invited to participate. Ground rules for the event established that vendors would have three days of prestaging to iron out any kinks before going on the record with results.

Miercom agreed that issues identified and ironed out during the prestage would not be a part of the public record, although we would assess and discuss the nature and scope of these problems. Any vendor that could not successfully establish basic interoperability after the three-day preliminary period was free to leave before the public event took place. No one did. And so, everything that followed was on the record.

Participating vendors were asked to prove basic interoperability with two reference products - Pingtel's xpressa SIP phones, acting as SIP user agents, and the dynamicsoft Session Management Suite (SMS), a prominent SIP proxy _server. These products were chosen based on two criteria: our research showed that they were widely regarded as among the most mature SIP implementations of their type currently available; and interviews with other vendors and end users indicated that these products would be the most likely to interoperate with other vendors' equipment.

Testing was based on the IETF's SIP RFC 2543bis-03 (Version 3 of the SIP specification, which was an Internet draft at the time). (For complete details on this specification, see www.ietf.org). Three basic types of voice-over-IP equipment were represented: SIP user agents, SIP proxy servers and SIP-based public switched telephone network gateways.

Yocom is senior editor, Percy is technology analyst and Bilger is senior lab-test engineer at Miercom, an independent testing lab located in Princeton Junction, N.J. They can be reached at byocom@mier.com; kpercy@mier.com and ubilger@mier.com.

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