Over the years, a number of ways have been developed to support fax in an IP environment. T.30 fax pass-through over G.711 and T.38 fax relay are the most prevalent. T.30 fax pass-through over G.711 is commonly used to support legacy fax machines across an IP network, whilst T.38 fax relay has become the de-facto standard for IP endpoints.
The thing to remember here is that fax is basically data over voice, a way of sending a document between two endpoints using voice communication, and that in the traditional voice network there is no way of knowing it is a fax call until the call is answered and the fax machines train, or try to train, with each other. In a hybrid legacy voice / IP network it falls to the voice gateway to handle the detection of fax and to convert it to a standard that can be understood by the IP network.
If you’re looking for a gateway to handle fax, the Aculab ApplianX IP Gateway supports both T.30 fax pass-through over G.711 and T.38 fax relay, allowing cross boundary fax support between legacy and IP networks. Aculab’s experience of fax support with its Prosody X range of enabling technologies, gives the ApplianX IP Gateway a maturity that allows it to deal with many of the issues seen over the years with regards to error correction and fax machine types. This and a comprehensive routing engine, give the ApplianX the ability to offer an all-inclusive fax solution.
One day, fax, like the legacy voice networks that support it, will become obsolete, but until that happens, and don’t hold your breath, gateways like the ApplianX IP Gateway will be required as part of the ongoing migration.