Later this month, a consortium of telecommunications companies founded by Internet telephony pioneer VocalTec Communications Ltd., based here, will release guidelines for implementing Voice-over-IP (VoIP) standards.

The document, the first in a series, is intended to improve compatibility among hardware and software products designed to transmit voice signals across IP networks. VARs, which have shied away from the promising but still immature VoIP market, have been holding out for interoperability assurances.

"Voice-over-IP is a big part of how communications will get delivered in the future," says Ben Grant, director of engineering technology at CyberSight, an Internet VAR in Portland, Ore. "But until it is standardized, we are waiting. We wish Voice-over-IP were stable now; we could do so much with it." For CyberSight and other VARs, the consortium, which is called Interoperability Now, or iNOW, may be just the ticket.

Two weeks ago, its original members, VocalTec, Lucent Technologies Inc., Murray Hill, N.J., and VoIP carrier ITXC Corp., Princeton, N.J., were joined by another half-dozen vendors, each promising to implement iNOW methods in their next product releases. These vendors included communications heavyweights Ascend Communications Inc., Alameda, Calif.; Cisco Systems Inc., San Jose; Siemens AG, Munich, Germany; as well as Clarent Corp., Redwood City, Calif.; Dialogic Corp., Parsippany, N.J.; and Natural MicroSystems Corp., Framingham, Mass.

The primary goal of the iNOW profile is to produce practical how-to instructions that other vendors can follow to ensure compatibility between VoIP gateways manufactured by different vendors, according to Lior Haramaty, vice president of technical marketing for VocalTec. The document is also intended to fill in the gaps in the H.323 standard, which is the standard for IP-based multimedia adopted by VoIP vendors.

One of the biggest failings of the H.323 standard, adds Haramaty, is a lack of guidelines for handling interdomain billing, which allows competing VoIP carriers to offer service on the same backbones and telephone networks. No method is outlined in H.323 for tracking multiple vendor calls terminating on a single network or tracking a single vendor''s calls terminating on multiple networks. The iNOW document will specify two such methods employed by VocalTec, Lucent and ITXC.

Haramaty stresses that the group''s goal is to jump-start the VoIP market by providing solutions to real-world problems.

"VocalTec''s mission is not just to define the standard, but to bring interoperability to the real world," says Haramaty.