I have been referencing people to an article I wrote recently when they have come to me looking for basic information on fax over IP principles and solutions. So, I thought I would share that article here as well for anyone new to fax over IP or for those looking for a broad overview of current FoIP technologies.

http://www.cisco.com/public/news_training/itsnews/tech/chalktalk/200808.html

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Fax communications (whether IP is involved or not) are dependent on some fundamental protocols. These protocols are defined by the ITU-T Recommendations of T.30, T.4, and T.6. If you really want to understand how Group 3 (G3) fax machines communicate, then everything is detailed in these specifications.

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I am often asked about the fax server solutions that interoperate with Cisco voice products. Customers are interested in knowing what fax server brands and vendors are compatible with their Cisco Unified Communications networks. The answer that I give to customers is quite simple - any fax server solution that adheres to the fax relay standard of T.38 and a standard call control protocol such as H.323 or SIP should interoperate within a Cisco Unified Communications environment. However, at the same time, I let them know that Cisco also has partnered with two fax server vendors if they are interested in Cisco branded IP fax servers solutions.

For centralized, enterprise fax server deployments, Cisco offers the Cisco Fax Server product. This product uses a Dialogic fax engine and the Captaris RightFax application. More information on the Cisco Fax Server can be found here -

http://www.cisco.com/en/US/products/ps6178/index.html

The other fax server solution that Cisco offers is the AXP-XMediusFAX solution. Residing on the ISR AXP module running a LINUX OS, the AXP-XMediusFAX solution is targeted for branch deployments where a minimal server footprint and ease of management and integration is needed. More information on the AXP-XMediusFAX solution can be found here -

http://www.cisco.com/en/US/prod/collateral/routers/ps9701/data_sheet_c02_459083.html


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As touched on in some of my previous blog postings, T.38 fax relay is the de facto standard for fax communications today. This was not always the case however. When I first started working with FoIP regularly about 8 years ago, the numerous Cisco customers that I worked with almost always implemented Cisco fax relay (Cisco's pre-standard fax relay implementation) or passthrough for transporting their fax communications over IP. Only rarely did I see T.38 being implemented at all. A lot of this probably had to do with Cisco fax relay being the default fax transport option on Cisco products, and fax passthrough's reputation for simplicity and reliability. However, starting about 4-5 years ago this trend started changing drastically. It was not long before it seemed most customers were deploying T.38 and the usage of Cisco fax relay and passthrough was declining sharply.

So, why did this transition away from Cisco fax relay and passthrough to T38 fax relay occur? Well, I see three main reasons why T.38 has pretty much taken over as the FoIP transport method today:

1) T.38 is standards-based. Cisco fax relay is proprietary and only implemented on Cisco voice products. While the ITU-T V.152 specification offers a standards-based form of fax passthrough, it has yet to be implemented by Cisco and the other FoIP companies that I work with. Therefore, fax passthrough is implemented differently by vendors and even Cisco itself has two different fax passthrough implementations. However, T.38 has been widely adopted by numerous vendors. So, for Cisco customers who may want to integrate fax communications with third party products, such as voice gateways and fax servers, T.38 fax relay is a necessity.

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On the last day of Cisco Networkers Australia, I gave a presentation titled "Understanding, Implementing, and Troubleshooting Fax Communications." Of all the sections in my presentation, the one that drew the most questions afterwards and appeared to have the most interest to the attendees was the section on fax servers. Not surprisingly, this interest in fax servers in Australia parallels the same interest that I see in the US and Europe.

Fax server solutions allow an organization to centralize their fax communications and provide users the ability to access their faxes through a variety of methods, including email, web browsers, and MFPs (Multi-Function Peripherals) that combine faxing with copying and printing. In addition to numerous other benefits, fax servers also allow faxing to be automated with business workflow processes and helps companies in complying with federal regulations such as Sarbanes-Oxley and HIPAA.

While fax servers with traditional telephony fax boards have always been a compelling solution for many businesses where faxing is critical, it is only within the last few years that I see customers in large numbers deploying IP-based fax servers. Additionally, customers that may not have had an interest in traditional fax servers with PSTN connections are often interested in IP-based fax servers. I believe that this is part of the trend where most organizations that have dedicated VoIP solutions using an IP-based PBX product like Cisco Unified Communications Manager, are looking for a similar solution for their fax communications. IP-based fax servers provide this solution and neatly integrate an organization's fax communications into their Unified Communications environment.

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This week I am presenting at the Cisco Networkers conference in Brisbane, Australia and yes, I am fully aware of how special this country is and I am taking the time to enjoy the amazing food, wonderful scenery, and friendly people. While presenting part of an 8 hour techtorial on Unified Communications, I asked the audience about fax communications in their IP environments as I discussed the fax over IP slides in the presentation. My basic question was -

How many of you deal with fax communications in your Unified Communications environments?

I would say about 80-90% of the 100 or so attendees raised their hands. I am expecting that I would see similar numbers in most other parts of the world as well. This is one thing that I love about participating in technical conferences outside of the US. Presenting at international conferences such as this, provides me with the opportunity to deal directly with large numbers of Unified Communications customers and partners in places that I do not usually have much exposure to. While I would not read too much into my anecdotal hand-raising survey, I believe this reinforces the fact that globally fax communications are an important part of a comprehensive Unified Communications solution.

More to come from Networkers Australia in a few days!

-David

With Cisco voice products (and most others), ALL fax calls start off as a regular VoIP call. This is a simple but critical concept to remember when dealing with faxing using Cisco gear. So, even though you may want to transport the fax call using T.38 fax relay, the fax call will use a voice codec in the beginning. If at any point after this voice call is connected, fax tones are detected, then a fax switchover must occur. This switchover transitions the call from voice mode to the configured fax transport mode (i.e. T.38 fax relay, passthrough, etc.).

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Those that are new to the transport of fax communications over IP (FoIP) are confronted with two different transport methods, passthrough and relay. Conceptually, passthrough is the same as a voice over IP (VoIP) call except that a low compression codec such as G.711 must be used. The reason that a codec such as G.711 must be used is because high compression codecs are optimized for human speech. Consequently, high compression codecs distort the fax tones and will cause FoIP calls to fail.

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Hi Everyone,

Welcome to the blog, Just the Fax with David Hanes!

I am looking forward to blogging on fax technologies and fax over IP (FoIP) solutions. First, let me provide you with a little background about myself.

My first step into the world of computer networking happened right out of college when I joined Sprint as a Systems Engineer working with the X.25 and Frame Relay protocols. From there, I joined Cisco in 1997 as a Technical Assistance Center (TAC) engineer, where I served on a number of different teams specializing initially in WAN technologies and then later in VoIP.

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