T.38 is an ITU standard for sending FAX across IP networks in a real-time mode. T.38 faxing has been hyped a lot, while others pondered if T.38 was dead
. Regardless of which camp you stand in, we can all agree that T.38 hasn't exactly taken off, including on the Asterisk IP-PBX. Faxing support in general on the Asterisk platform has been sorely lacking and one of Asterisk's weaknesses. Though there are some workarounds such as Hylafax
. IAXmodem is used to interface Asterisk with HylaFax.
However, as of Asterisk 1.4, Asterisk allows the passthrough
of T.38 UDPTL data. Asterisk does not actually decode the T.38 protocol, it simply passes the T.38 data to a T.38 PSTN gateway. For termination you'd need something like the Gridborg HMP Server
. I should also mention that AudioCodes has helped write articles for TMC
as well as held webinars on TMC
discussing T.38 networking faxing used in conjunction with SIP, which are worth exploring. AudioCodes also makes voice TDM hardware which runs on the Asterisk platform.
The other issue with T.38 is that T.38 capabilities vary greatly between VoIP providers. Some do not support it at all, while others support it fully, up to and including V.34 FAX (high speed 33,600bps faxing). Similarly, some IP-FAX hardware supports some capabilities of T.38, but not all. Most don't support the higher speed V.34 spec.
One interesting solution that was launched last week at ITEXPO
was a new V.34 T.38 Fax-over-IP endpoint and gateway from Dialogic. They claim to be the industry’s first Fax Over IP Endpoint and Gateway solution supporting V.34 T.38. In theory you could use the T.38 passthrough function in Asterisk v1.4+ to send the V.34 T.38 fax traffic to the Dialogic fax gateway. Still, I'd like to see an integrated solution on Asterisk for sending/receiving faxes. One less server to manage plus less electricity utilization. We want to be green
In any event, here's the Dialogic release in case you missed it:
Dialogic Corporation ("Dialogic"), a global provider of world-class products and technologies for media and signal processing, today announced that it has released the industry’s first Fax Over IP Endpoint and Gateway solution supporting V.34 T.38.
The award winning Dialogic® Brooktrout® SR140 Fax Software and Dialogic® 3000 & 4000 Media Gateway Series (DMG3000 & DMG4000) enables enterprises to deploy fax server solutions confidently into existing Voice over IP (VoIP) installations, while leveraging their existing IP infrastructure. The addition of V.34 T.38 allows these products to transmit fax data at 33.6 kbps, surpassing the rest of the industry which currently transmits fax traffic over T.38 at a maximum of 14.4 kbps.
“The addition of rapid V.34 speeds to our highly reliable Brooktrout SR140 T.38 Fax over IP based fax server solutions is a significant break through in our industry, said Tom Linhard, President at FaxCore, Inc. A FoIP endpoint to gateway solution supporting V.34 T.38 will allow FaxCore and Dialogic’s mutual customers to send and receive faxes much faster. This will save them money by lowering both network bandwidth and telecom expenses.”
Dialogic Corporation is the market segment leader in fax and fax-over-IP platforms, offering one of the fullest featured and broadest fax solution portfolios on the market today. The Brooktrout SR140 and DMG3000 & DMG4000 platforms support real-time FoIP, providing companies with the ability to integrate fax servers into their VoIP network. In addition to capturing the benefits of IP-based communications, these products have excellent performance, reliability and scalability, attributes that enterprises have come to expect from the Dialogic Brooktrout Circuit Switch based fax product line.
“Dialogic’s fax technology is the engine of the modern fax server that delivers document management, business process automation and compliance with industry mandates, such as Sarbanes Oxley and HIPAA," stated Jim Machi, Senior Vice President of Marketing for Dialogic. By implementing V.34 T.38 fax on their IP network, enterprise customers will not only benefit from the savings achieved by automating fax document processing and ensuring the integrity of internal control procedures and transactions for regulatory compliance, but can also expect to have lower operating costs than if they were using comparable FoIP solutions currently on the market.”