Q: What is FoIP?
Q: Can I send an IP fax in real time?
Q: What’s the difference between traditional fax and FoIP?
Q: Is Fax over IP as reliable as using telephone lines?
Q: What is T.30 Protocol?
Q: What is T.38 protocol?
Q: In what ways does T.38 outperform FAX over VoIP?
Q: What are jitter buffers?

Q: What is FoIP?

FoIP (Fax over Internet Protocol) is also called IP faxing and is a method of sending faxes over the Internet or your wide area network. FoIP changes the transmission method of faxing in much the same way that VoIP (Voice over Internet Protocol) changes the transmission method of a phone call. In both FoIP and VoIP, data makes most of the connection between sending and receiving devices on a packet-switched network, often avoiding the long-distance phone lines of the telephone network. This reduces the cost of transmission and can be a more efficient setup for a business that already has access to Internet bandwidth or a wide area network.  It is a common misconception that all of the fax transmission from end to end is conducted over IP. Unless you are sending messages within the organisation this will not generally be the case; you will need to switch out through your PSTN gateways to deliver to the destination fax machine.

Q: Can I send an IP fax in real time?

Yes. In real-time IP faxing, fax information is transferred from fax server to fax server as IP data packets using a high-level Internet Protocol, T38. This protocol allows for real-time connections that let the fax machines exchange information along each step of the way. Real-time IP fax messages work just like traditional phone-line fax messages.

Q: What’s the difference between traditional fax and FoIP?

In any fax session, timing is crucial and traditional telephone lines are really good in this regard because they provide constant timing for each phase of the fax session; making the connection, exchanging signals, sending and confirming receipt of page data, sending and confirming multipage alerts, and terminating the call. At each step along the way, the machines are exchanging information with each other to make sure everything is going according to plan. A real-time FoIP session includes all of these phases and confirmations; FoIP uses the same method of compressing and interpreting image data as traditional fax (G3) does, but it uses a different protocol for transmitting that data. The protocol that enables real-time faxing over the Internet is the T.38 protocol.

Q: Is Fax over IP as reliable as using telephone lines?

FoIP is reliable over an organisation’s wide area network where a guaranteed level of service exists, however, FoIP over the internet has some way to go before it's as reliable as traditional phone-line faxing, but it may still be a very attractive option for anybody who sends a lot of long-distance faxes. In most cases, the cost savings and network integration of FoIP far outweigh the downside of having to occasionally resend a fax that doesn't go through.

Q: What is T.30 Protocol?

A T.30 is the protocol that describes how two fax machines communicate with each other over the public switched telephone network (PSTN).

Q: What is T.38 protocol?

T.38 is the real-time FAX over IP protocol. This means it is designed to work like traditional faxing. T.38 is used to encapsulate the traditional T.30 fax protocol for working over IP; it also provides facilities to eliminate the effects of packet loss through data redundancy i.e. previously sent packets are resent.

Q: In what ways does T.38 outperform FAX over VoIP?

VoIP technologies are designed to handle voice and not data and employ digitising and compression techniques that can't be tolerated in data transmissions - Fax over VoIP without T.38 sort of works but the quality is poor and the reliability unacceptable. T.38 is designed specifically for the transmission of fax over IP to eliminate these short-comings by providing facilities to eliminate the effects of packet loss through data redundancy and jitter buffering.

Q: What are jitter buffers?

In Fax over IP (FoIP), a jitter buffer is a shared data area where packets can be collected, stored, and sent in evenly spaced intervals. Variations in packet arrival time, called jitter, can occur because of network congestion, timing drift, or route changes. The jitter buffer, which is located at the receiving end of the connection, intentionally delays the arriving packets so that the end user experiences a clear connection with very little or no image distortion.