FoIP is short for Fax over Internet Protocol and refers to the process of sending and receiving faxes via a Voice over Internet Protocol (VoIP) network.
FoIP FAQ
What Is FoIP?
How Can We Use Our Legacy Fax Machines Over Our VoIP Network?
You can use Smart ATA, a specialized analog telephone adapter, to connect your fax machines to your VoIP network. You won’t have to keep your POTS lines for faxing any more with Smart ATA, because it’s powered by Commetrex’ Smart FoIP® technology.
How Can We Eliminate Our POTS Lines And Move To An All-IP Network?
You can use Smart ATA, a specialized analog telephone adapter, to connect your fax machines to your VoIP network. You won’t have to keep your POTS lines for faxing any more with Smart ATA, because it’s powered by Commetrex’ Smart FoIP® technology.
What Is T.38?
T.38 is a protocol that describes how to send a fax over an IP network. T.38 is needed because fax data cannot be sent over an IP network in the same way as voice communication. In essence, with T.38 an analog fax is converted to its digital form, sent to the other T.38 fax device, and then converted back to an analog fax signal. T.38’s job is to make the IP network “disappear” as far as the endpoint fax terminals are concerned.
What Is PCM Clock Sync?
PCM Clock Sync is a common problem that often causes non-T.38 Fax over IP to fail. The problem results from jitter buffer under-run and over-run caused by the PCM clocks at opposite ends of the link (the endpoint terminals) not being equal (and they’re never equal). The more out of sync they are, the quicker the session fails. Long-enough G.711 pass-through faxes and even long T.38 sessions can fail if the jitter buffers are not effectively handled. Commetrex’ Smart FoIP® solves the problem of PCM clock sync.
What Is A Late T.38 Re-Invite?
Most FoIP calls over carrier networks begin as a voice call using G.711 pass-through. That means that the two endpoint fax terminals can actually “hear“ each other over the RTP connection at the very beginning of the call, even if the gateways and servers end up switching to T.38. If the switch to T.38 takes more than six to eight seconds, and if often does, those two fax terminals can get so far into their T.30 protocol that they cannot be interrupted with a switch to T.38 without destroying the fax session. Historically, every gateway in the industry just blindly accepted any T.38 re-Invite, even if the two terminals were well into their conversation, which caused the fax to fail. With Commetrex’ Smart FoIP®, however, this problem is resolved.
