Cisco Systems is making a big push to advance T.38, an International Telecommunication Union (ITU) (define) standard that governs real-time fax relay over IP networks.

The San Jose, Calif.-based computer-networking equipment maker Tuesday said it has finished interoperability testing with Commetrex, Roswell, Georgia-based company that is focused on open-communications fax technology.

Faxing over the Internet has been somewhat of a pariah of late. Fed up with a glut of unwarranted or "junk" faxes, a group of California consumers recently filed federal and state class action lawsuits totaling an unprecedented $2.2 trillion against fax broadcaster fax.com, Inc.

But the T.38 standard serves valuable functions. Without it, a gateway will sense that a modem (fax or data) call is being initiated, and switch from, possibly, a low-bit-rate vocoder to G.711 (64,000 bps, full-duplex).

Commetrex says as long as the packets can be reassembled at the far end and streamed out to the receiving modem isochronously, the session will be successful. But that's a big if. The use of a T.38-compliant relay lets a gateway withstand several seconds of packet delay, lost packets, and packets in error without creating errors in the received image. For the same reasons, the TIA and the ITU are working on V.MoIP, a standard for real-time data-modem relay, which Commetrex said should be "determined" later this year.

The testing was handled completely over the public Internet on a Cisco AS5350 Universal Gateway in Commetrex' T.38 Interoperability Lab. The results of the 16-point test are posted on the lab's Web site (http://www.commetrex.com/T38LabForum.html).

"With Cisco's market position, it is no coincidence that the first gateway an early customer of our TerminatingT38 product tested with, was a Cisco gateway. But we looked forward to Interop testing directly with Cisco in order to perform the in-depth testing only possible when the testing is between the two manufacturers," said Commetrex' T.38 Interoperability Lab lead engineer Mike Wells.

In January 2002, Commetrex announced the opening of its T.38 Interoperability Lab, which offers no-fee interop testing to any vendor with a fielded T.38-capable gateway. Since then, 12 companies have signed up for testing, five are currently in the process, and four are complete.

As part of the test Commetrex' TerminatingT38 is used to send faxes through the participant's gateway. Trace and debugging logs are frequently run with continual analysis by a senior engineer until all faxes sent are clean and differences in T.38 implementation completely understood. Testing engineers analyze sessions and timing, noting any interoperability problems or other potential problems that might be in violation of basic ITU T.38 standards.