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Cloud Fax, Not VoIP, for Fax Over IP Networks

Cloud Fax, Not VoIP, for Fax Over IP Networks

Voice over Internet Protocol (VoIP) is a collection of technologies enabling the transmission of digital audio. The first commercial products enabling voice communications over the Internet networks appeared in 1995. VoIP usage spread rapidly, spurred by personal computer software like Skype that enabled international voice communication at substantially lower cost in comparison to rates charged by established telephone companies.

Modern networking infrastructures, based on advanced transmission designs like optic fiber and cellular wireless and driven by programmable digital devices, offer vast improvements over the copper wire infrastructures that have existed since the commercialization of electricity itself. The telecommunications carriers that provide the global communications infrastructure are moving steadily towards replacement of those legacy wire networks with the newer transmission technologies, to capture advantages of efficiency, ease of maintenance, scalability, and versatility.

The shifting paradigm of telephone communications motivated a transformational wave of change in business operations across all vertical markets. Most significantly, more and more businesses are replacing their conventional telephone systems, interior telephone wiring and connections, and eliminating the related monthly service charges by adopting VoIP services. The phones you see in business offices are digital IP phones, not the analog devices of the past. Phone jacks are no more. Phones and computers plug into the same connections to the LAN and the Internet beyond.

In light of the robust marketplace of readily available Internet based business solutions, businesses that rely on Fax in their operations are increasingly looking for a way to plug their Fax machines into those new office jacks and send Faxes over the Internet.

The Challenges of Fax Migration

Cloud based and internet based technologies are the only players in town these days as POTS lines are being phased out and legacy infrastructure is going to the cloud. While this shift is happening rapidly companies are faced with the struggle of migrating legacy analog applications to the more modern digital counterparts.

This migration is particularly challenging when it comes to moving Fax to the Internet. As many IT departments have discovered by now, getting the Fax machines off the phone network and onto the Internet is more than just connecting the Fax machines into the network jacks.

VoIP and Fax, Not Made for Each Other

The challenges begin with the fact that Fax machines must be supported by communication carriers, who provide the technical infrastructure and take care of the obvious things like administration of phone numbers and customer accounts. The intuitive solution chosen by business is VoIP providers, and so the question is often posed to them: Can we connect our Fax machines to our new VoIP adapters alongside our phones? Can we then Fax over our VoIP service?

The VoIP carriers know that the answer to that is a very tentative and qualified yes, accompanied by conditions and disclaimers.

That's because they know that analog Fax and analog phone operation are significantly different. They know that the idea of transmitting voice between two phones over the Internet is a different problem than transmitting images between two Fax machines over the Internet. They know that from the beginning, VoIP design did not consider Fax design, so that today, the intuitive idea of Fax over VoIP networks is really a less-than-optimal, error-prone fit, analogous to using a plastic dinner knife to drive a screw.

Specific Issues

Fax machines were originally designed to operate in point-to-point mode, transmitting images in analog signal format over dedicated switched circuits. That is the way phones used to operate.

The Fax machine contains all the features needed to do its job. That includes:

The Fax machine is an active device designed to work over a relatively passive analog connection, where the only significant network function was setting up and tearing down the switched circuit.

By contrast, VoIP uses software protocols to

Analog phones are relatively passive devices, and VoIP networks are relatively active digital networks that do all the work of establishing and managing voice transmission.

The result of combining Fax and VoIP is a degree of conflict in functionality that ultimately affects the behavior of the Fax machine and the quality of the Fax itself.

There are two main sources of conflict.

First, VoIP networks may use one of several IP protocols to perform session management and voice content transmission. These are:

SIP (Session Initiation Protocol) - is a standards-based protocol that is used and supported by the vast majority of VoIP phone systems and services.
SCCP (Cisco Skinny Client Control Protocol) - is a proprietary protocol used by Cisco's Call Manager and IP phones.
MGCP - (Media Gateway Control Protocol) standards-based protocol also known as H.248. It is no longer widely used and or supported.
H.323 – Similar to MGCP, H.323 is an older VoIP protocol that is no longer widely used and or supported.

SIP, the primary protocol in current use, is an application layer IP protocol that runs on top of UDP (or optionally TCP). This means that digital packets containing voice data may arrive at their destination in bursts, out of sequence, and some may even be dropped. Furthermore, timely packet transmission is subject to network bandwidth network traffic conditions.

Those behaviors can cause odd, sporadic problems for telephone calls, including choppy audio, call timeout, and poor voice quality.

The situation is worse for Fax over SIP. Fax machines are designed to transmit continuously through the end of the document being sent. There is no error recovery in case of irregular lapses in the signal; Fax machines may wait for a few moments and then simply time out, ending the transmission in mid-document or mid-page and forcing the document to be resent from the beginning.

The next major conflict is due to the various codecs used in VoIP. The SIP protocol may use any of several codecs, each designed to achieve increased transmission throughput by compressing the digital payloads more. The most common codec used in VoIP is G.729, which results in bandwidth consumption of 8Kbps. Modern Fax machines actually digitize their output before modulating it back to analog, and they do so use G.711, which compresses 64Kbps bandwidth into V.34 analog waveforms for transmission. When a Fax machine is connected to a VoIP adapter, the double sampling of the Fax output by the adapter can potentially create problems in Fax quality at the receiving end.

This discussion raises another point. For proper functioning, the various capabilities of VoIP networks make it essential that VoIP phones and adapters be configured to match the technical VoIP parameters of the service provider's network. This point is even more urgent when attempting to send Fax over VoIP networks.

To avoid these issues, many VoIP providers will offer the T.38 protocol to accommodate Fax on their networks. T.38 is a standard protocol designed specifically to handle digitized Fax data packets and importantly, it runs on top of TCP, so that packets are sequenced and resent if dropped. That is not a perfect cure for Fax though, because too many resends can cause Fax timeouts. And T.38 must still use SIP for call setup.

Finally, not all VoIP networks implement the same protocols and functions. Some, for example, do not feature T.38 at all. VoIP networks are often built with interfaces to the legacy PSTN, to enable connections to analog phones. These differences are often accommodated using specialized gateway devices that translate protocols and perform the necessary encoding and decoding. As explained, Fax transmissions are sensitive to time delays. They may time out as transmissions cascade through gateway devices.

The Solution is Cloud Fax

Because of the approximate-at-best fit between VoIP networks and Fax technology, Fax transmission over digital networks requires a fresh perspective. The modern solution is Cloud Fax.

Cloud Fax changes the nature of remote document replication by treating the document as a file system object rather than the content of an interactive communication session. The most significant thing about this approach is that the Fax documents may be transmitted using multimedia messaging techniques, which are much less sensitive to the networking details discussed earlier, and importantly, are totally independent of VoIP networks. Like all cloud technologies, Cloud Fax is Internet-based and requires no premises resident equipment, no significant installation costs, no ongoing maintenance costs, centrally administered (and often automatic) upgrades, and easy scalability. Cloud Fax works by use of the established Internet protocols of HTTPS, TLS, and SMTP to enable documents from the hard drive or the database to be transmitted as attachments to email messages.

WestFax Cloud Fax extends this functionality to provide a complete suite of Cloud Fax services. A comprehensive online portal enables users to organize Fax documents into familiar folders, with controls for privacy and sharing as needed. The portal is accessible from desktops and from mobile phones, so that Faxes may be sent, received, and viewed at the user's convenience. Available software extensions enable select Multifunction Printers to send and receive hardcopy Fax documents directly to and from the cloud.

WestFax also offers advanced document processing functions to support office document workflows, including Optical Character Recognition and WestFax Comprehend, an AI-driven process that extracts semantic content from inbound Fax documents and readies it for updating any database. WestFax Fax-to-FHIR is designed to extract medical information content from incoming Fax documents and prepare it for an update to an EHR systems that adheres to the FHIR standard.

These features of WestFax Cloud Fax are supported by the WestFax digital network. Physical security of WestFax data centers, and virtual security of all transmissions on the WestFax network, are provided in strict compliance with the regulatory requirements of HIPAA. All WestFax products are available for use in healthcare environments and others that have rigorous security requirements.


In the 1990s the evolution of digital networking, in particular the rise of the public Internet, gave rise to commercial voice communication services using the Internet as an alternative to established telco services, which operated over a far-flung analog network of copper wires that extended to each residence and office. The development of digital voice communication, or Voice Over Internet Protocol (VoIP), sparked a paradigm shift in business operations and inspired hundreds of new business applications based on the Internet.

Among them was the application of Fax over IP. Intuitively for many consumers and businesses, the new VoIP services would support Fax machines, just like the conventional analog phone services did. However, the technologies of Fax and VoIP evolved at different points in time and without consideration for each other. Fax over VoIP was never a perfect fit and attempts to merge the two are problematic to this day.

Cloud Fax takes a different approach by providing advanced Fax functionality hosted on the Internet. Using Internet protocols specifically designed for multimedia messaging, WestFax Cloud Fax offers advanced Fax services that eliminate the conflicts between VoIP and Fax to provide high-quality, robust, secure, and HIPAA-compliant Fax processing. WestFax extends its Fax services with advanced document processing and workflow management, including services for Optical Character Recognition, WestFax Comprehend for semantic content extraction, and WestFax Fax-to-FHIR for integration with Electronic Health Records systems.