RFC3840 for FoIP Routing?

In our testing, we’ve found that FoIP with T.38 over the open Internet – no carriers involved – is even more reliable than PSTN fax for just about any call. The big difference? No carrier routing and no TDM-IP conversion. It’s T.38 end-to-end.

So, how do we approach that ideal with carriers responsible for the routing? You might know that the FoIP Task Groups of the SIP and i3 Forums have been performing extensive testing of FoIP in international calls. And it hasn’t been pretty. In most cases, it was the carrier’s first exposure to FoIP qualification, leading to significant problems with equipment and network interoperability and configuration. These problems have been addressed one-by-one. But the remaining problems caused by least-cost routing-as-usual for FoIP calls are significant enough to slow the industry’s move to an all-IP global network. FoIP-aware routing, which would be IP everywhere but to and from the TDM-connected fax terminals, is usually required for success.

A SIP call switches from voice to FoIP (which usually means T.38) when the called fax endpoint answers. Of course, by that time the call has already been routed, since routing decisions begin when the on-ramp proxy or SIP server receives the first SIP Invite. At that point, the provider’s routing algorithm should, if possible, route the call over qualified FoIP routes.

Ten months ago the two task groups proposed that the SIP servers routing a fax call would set the user= parameter to user=fax in the header of the SIP Invite (see RFC 3261, section 25.1). But then just last month we found a better answer: RFC 3840, “Indicating User-Agent Capabilities in SIP”, which is specific to the task. According to RFC 3840, setting the header fields to indicate the capabilities of a terminal (user agent) can be used to “express a preference for routing.”

The SIP and i3 Forum FoIP task groups are now moving ahead to standardize “SIP.FAX=”. It is interesting to note that RFC3840 defines 18 different feature tags in its section10, with none of them being fax, so we are setting out to make that 19 tag definitions.

Want to learn more? Contact us at or 1-770-449-7775, and press 1.

The SIP Forum Presents SIPNOC on June 25-27

Should you be there?

The telecom-industry media focus on the cloud and mobile is understandable since readers can easily identify with both. But if you dig down just a little, the movement of SIP from the enterprise to the carrier is a very big deal. And three organizations are making it possible: The IETF gave us the SIP recommendations going back to the late 90s. Then, several equipment vendors that were developing SIP-based products formed the SIP Forum to promote SIP interoperability. And, in 2008, several telecom operators formed the i3 Forum to help the industry make the historic transition from TDM to an all-IP global network. According to Philippe Millet, Chairman of the i3 Forum, “We are laying the foundations and looking at the very basic elements of our businesses. This is important now because we are reaching an IP tipping point.”

Until very recently, what was missing was the integration of these different perspectives. So, one year ago last month the SIP Forum took an important step to leverage the then-ongoing cooperation of the SIP and i3 Forums by producing the first annual “SIP Network Operators Conference,” or SIPNOC. The second SIPNOC will be held June 25-27 at the Hyatt Dulles, which is close to Dulles Airport just outside Washington, DC.

SIPNOC is a conference for service providers and carriers to “focus on how to make SIP work in the network and to address the key operational issues facing SIP in today’s telecom world.” There are no exhibits; rather the conference brings together the technical leadership responsible for this epochal change, including keynote speaker Henning Shulzrinne, one of the inventors of SIP and currently the CTO of the US Federal Communications Commission.

There will be sessions on network security, interop testing, IPV6, VoIP deployment lessons, network resiliency, bridging ISUP and SIP, SIP trunking, IP interconnect, and the SIP-i3 Forum FoIP testing. The latter session features Commetrex’ CEO, Mike Coffee, who is the Co-Chair of the SIP Forum FoIP Task Group. Mike will also be a panelist on FoIP interoperability along with experts from Sonus and Voxbone.

If you’d like to learn more about SIPNOC, go to or give Mike Coffee a call at 1-770-407-6021.

Check Out Our New Website!

We were really getting tired of looking at our old website. You too? We redid the whole thing and recently launched the new site at In order to celebrate the occasion – and give ourselves yet another opportunity to talk about Smart ATA – we’re holding a drawing and the lucky winner will receive a FREE Smart ATA. All you have to do is correctly answer the three questions in our quiz, and you’ll be entered into the drawing. All entries are due by 6/30/12. Good luck!

Have You Met Angie?

It’s obvious she’s pretty sharp technically based on her explanation of the benefits of Smart ATA to John, her customer. You can see her in action by going to the NetGen Communications homepage.

We decided to employ the really cool Xtranormal videos to help us explain the somewhat amazing feature set of Smart ATA. In the latest video, Angie explains the ATA function, but John doesn’t have time to hear her explanation of Smart ATA’s gateway function. Guess we’ll have to wait until Angie calls on John again to be so enlightened.

If you have any questions about our video series, contact Marilyn Troup for more information by email or at 770-407-6032.

Smart ATA Application Story

A large auto dealership with multiple locations has a high volume of multi-page fax traffic, both between locations and between remote offices and the central office where an enterprise FoIP fax server is located. Their MPLS network did a fine job of delivering faxes to their V.17-capable ATAs, but with faxes at 14,400bps, many of the faxes took 15-20 minutes to transfer.

Then, they heard that Smart ATA was the first and only ATA to support T.38 V3 at speeds up to 33,600 bps. And it turns out that their fax server is also T.38 V3-capable. Wouldn’t it be great if Smart ATA and their fax server were compatible?

Well, they are. They report that Smart ATA has cut their fax times roughly in half … a big convenience and a big cost savings. At $70 per port you can’t go wrong with Smart ATA.

To learn more about Smart ATA, visit theNetGen Communications site or call 770-449-7704.