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What is the T.38 Fax Protocol and How is It Used?

 In Blog, FoIP, Productivity, Technology, Unified Communications, Voice

We’ve written extensively about the reasons why fax remains relevant in today’s society from a functional standpoint (widespread systemic adoption within certain industries, privacy regulations, and security), but it can be hard to wrap one’s head around how Fax over IP (FoIP) technology is different from simply uploading and downloading image files from e-mail attachments, file sharing applications, etc.

The key difference is that fax images are still transmitted as electrical impulses via the phone line rather than files. That makes the core of the technology, even in the age of FoIP, closer to telephony than computer networking.

Just like Voice over IP (VoIP) technology bypasses large portions of the phone network, FoIP uses IP networks to transmit fax impulses long distances in real time. While full IP transmission is possible, the FoIP data packets are often converted (via a “gateway”) to and/or from traditional phone signals at the beginning or end of their journey to travel some portion via the phones (typically as a local call). Many FoIP solutions use T.38 as their protocol for crossing the IP-based portion of the journey.


1. How is T.38 FoIP Different than VoIP?

In terms of their goals and technology, FOIP and VoIP are quite similar, and at least one voice protocol (RTP/G.711) can be used for fax transmission.

However, some VoIP protocols are balanced for different strengths that can make them less than ideal for FoIP. These protocols are designed to preserve the real-time flow of audio conversation in situations with inconsistent bandwidth, even if they have to drop bits of voice data (typically evidenced by momentary drops in quality like jitter, delay, etc) here and there to do it.

Given that a fax is being transmitted with the goal of having a complete whole clearly resolved on the other side, this style of omitting compression can cause problems for FoIP.

T.38 was instead designed with the opposite goal: to preserve the completeness and accuracy of image data, even if it has to use additional bandwidth and time in order to transmit it. In order to do this, there are redundant sections and accuracy checks built into the data streaming in order to make sure everything arrives safely on the other end.

It’s worth noting that FoIP messages transition to conventional fax protocols (like T.3) if they’re filtered through a gateway and spend time on the conventional phone system. That means that the packet-integrity protections in T.38 only apply while the fax is travelling on the IP network.


2. Do fax machines use T.38?

No, most do not. T.38 is generally reserved for fax servers, devices that package faxes in data packets for transmission across IP networks. Traditional fax machines (still in widespread use, despite their drawbacks) and non-FoIP-connected Multifunction Printers (MFPs) rely on traditional phone lines and the fax protocols associated with them (T.3, etc).


3. How does FoIP save money?

Traditional faxing has several substantial costs associated with it that FoIP can avoid entirely. Organizations sending & receiving via FoIP can eliminate their fax-dedicated phone lines entirely, dramatically reducing service costs. In addition, because FoIP can be handled by computers rather than fax machines, faxes don’t need to be a physical object. That eliminates the cost of ink, paper, shredding and storage. Finally, fax machines are notoriously unreliable – maintenance and repairs can eat up a lot of IT staff’s time and budget.

FoIP systems also centralize an organization’s fax processing through a single server that is easier for IT departments to manage, with the various integrated devices and programs sending the faxes (e-mail clients, fax applications, Multifunction Printers, etc) serving merely as points of origin.


Bring your organization’s document transfer systems into the modern era

Just because fax is a technology with a history stretching back to the mid-19th century (predating the telephone) doesn’t mean that it has to be clunky today. XMedius offers a cutting-edge FoIP solution that provides all the benefits that have kept fax technology in use (and more!), without the hassles and costs that make traditional fax machines infamous.

Reach out to us to learn more about how this technology is saving organizations money, streamlining workflows, and preserving security.






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