Newsletter

1. FoIP: Can We Please Agree on What it Means?
2. Cognitronics, Convedia, IP Unity, Snowshore: How do their Media Servers Communicate with App Servers?
3. Commetrex Ships T.38 for Brooktrout Boards
4. What do Atelo, BroadSoft, and SnowShore Have in Common?
5. Echo Canceller Specs Revealed

FoIP: Can We Agree on What it Means?
    Well, for starters, it's "fax over IP". But what's that? Apparently, not everyone understands what that actually means. It is generally accepted that VoIP (voice over IP) is the use of an IP network to transport a voice conversation in real time between two parties. So, it seems logical to apply the same reasoning to FoIP. But beware, this is not always the case. There are some service providers out there that apply the term to e-mailing a file containing a fax image, rather than reserving it to describe the use of IP as a real-time transport for G3 fax terminal transactions.
    G3 (Group 3) fax refers to the ITU recommendations that specify or define the fax terminals we use every day, and how they communicate. The keystone ITU recommendation is T.30, which specifies the protocol two G3 terminals use to exchange a fax document. Each fax endpoint must execute T.30 for a G3 fax transaction to occur. You know the way it works: while the paper is being fed in here, it's coming out there. If an IP network is used to transport the data and that network is standards-based, then the ITU T.38 recommendation governs how the two IP-network edge devices translate between the G3 world, which was intended for the PSTN, and the IP world, as shown below (GW=gateway): [G3 Fax Term.]==[PSTN-IP GW]==[IP Network]==[IP-PSTN GW]==[G3 Fax Term.]*
    But there are some service providers that will take a fax-image file from your computer via e-mail, and send it to the destination PSTN-connected terminal using a traditional multi-line fax board, or e-mail it to another PC...and they call it FoIP.
    But, this is not FoIP. It's using the Internet, instead, to send an image file. So, don't be fooled.
    *Note: The underlying network elements have been combined by Commetrex to allow IP-connected endpoints, such as media servers, to directly terminate faxes. If it's IP connected and it terminates T.38 faxes, it's Commetrex technology.
    Want to discuss your IP-network development? Contact Mike Coffee at 770-449-7775 x310 or sales@commetrex.com. Visit http://www.commetrex.com/products/
algorithms/faxrelay/PowerRelay/
PowerRelayProductBulletin.html and http://www.commetrex.com/products/
algorithms/fax/T30/
PortableT30ProductBulletin.html for more on T.38 and T.30.

Cognitronics, Convedia, IP Unity, and Snowshore: How do their Media Servers Communicate with App Servers?
    In the decomposed IP network, media servers are controlled by application servers. Application servers? Media servers? These are elements of the IP value-adding service network like media gateways, gateway controllers, and signaling gateways. And the really interesting thing about the emerging IP-based telephony network is that these network elements are made by different companies and they interoperate. (Well, many do.) Visit the web sites of the companies that develop these different products and you will see a partner page listing companies that market compatible network elements. This is pretty amazing when you compare this ecosystem with the closed paradigm of the legacy network.
    There are ITU recommendations, such as H.248 (MEGACO), that specify protocols between media gateways and media-gateway controllers. The W3C's VoiceXML allows an application server to describe an IVR dialog to a media server. And, there are plenty of IETF RFCs that specify things like RTP and RTCP. Recently, Commetrex worked with Snowshore Networks to add fax extensions to SnowShore's Media Server Control Mark-Up Language (MSCML). MSCML specifies an application server-media server control protocol. Typical applications include unified messaging (voice, fax, and e-mail), voice announcements, IVR, conferencing, and traditional fax-server functions. Commetrex has implemented MSCML for fax and delivers it as application-level example code with BladeWare(tm) when it includes Multi-Modal Terminating Fax (MMTF) or TerminatingT38(tm).
    Recently, Convedia has developed Media Sessions Markup Language (MSML) and Media Objects Markup Language (MOML). MSML and MOML have been designed to work closely together: MOML addresses controlling and manipulating media-processing operations (e.g., announcement, IVR, play and record, ASR/TTS, fax, video), while MSML addresses the relationships of media streams (e.g., conferencing). Together, MSML and MOML create a general-purpose media server control architecture. MSML can also be used to invoke other IVR languages, such as VoiceXML.
    Commetrex will begin work with Convedia to add fax extensions to MSML and MOML in early October.
    If you're developing a media server, either enterprise or carrier class, and want to explore the full range of options, call Commetrex, the leading technology supplier to the media-server OEM at (770) 449-7775 x310. For more on Multi-Modal Terminating Fax and TerminatingT38, visit http://www.commweb.com/shared/
article/showArticle.jhtml?articleId=9400206 and http://www.commetrex.com/products/
algorithms/TT38PB.html

Commetrex Ships T.38 for Brooktrout Boards
    A customer of ours recently came to us with a problem. They had licensed our software, OpenEndpoint(tm), to develop an IP endpoint and were developing the gateway to the legacy network using Brooktrout boards for the VoIP gateways. The problem was that Brooktrout doesn't have T.38 fax relay, yet T.38 was needed to get the fax calls from the IP endpoint to the legacy network.
    Not a problem!
    We delivered a host-signal-processing version of PowerRelay(tm) for T.38. The IP connection was via the gateway's NIC, from there to our T.38 protocol engine, and from there, to our host-based fax modems. The G.711 output of the modems was then fed to the Brooktrout board as if it were a voice message. Naturally, fax calls from the PSTN work the same way in reverse.
    So, we effectively added T.38 to Brooktrout fax boards. We would be pleased to do the same for you. If you're interested, contact Mike Coffee at 770-449-7775 x310 or at sales@commetrex.com. To learn more about OpenEndpoint and BladeWare, visit http://www.commetrex.com/products/
algorithms/OpenEndpoint.html and http://www.commetrex.com/products/
algorithms/fax_relay/PowerRelay/
PowerRelayProductBulletin.html.

What do Atelo, BroadSoft, and SnowShore Have in Common?
    Host signal processing (HSP) is coming, and it's causing the price of telephony servers to plummet. It's not just low-density systems that use Commetrex' MSP-H8 PCM interface. The big hit is coming to IP media servers in both the enterprise and carrier networks. Atelo is targeting the enterprise and service provider, and SnowShore and BroadSoft the service provider. Intel has an integrated platform for the enterprise system developer. And, if you've been reading your Commetrex Outlook, you have heard about BladeWare(tm), our open HSP platform for the equipment OEM.
    So, what's going on? Really sorry to have to say this, but it's the often heralded paradigm shift. And you heard it here first. This would have happened even if blade servers hadn't arrived on the telephony scene. But they have. Blade servers make scaling an HSP system even simpler than adding a DSP-resource board to a system. It would even happen without IP, but IP means there's no need for telephony-specific network interfaces. This lets you build the entire system with processor boards and near-commodity pricing.
    Do you have a strategy in place for dealing with HSP? Commetrex can help. Give Mike Coffee a call at 770-449-7775 x310 to discuss your application or e-mail him at sales@commetrex.com. Visit http://www.commetrex.com/
BladeWare_front.html

Echo Canceller Specs Revealed
    Echo cancellers have been with us for a long time, but the increasing use of IP as a transport for voice is causing the importance of ECAN to increase. Why? Because the processing delays in IP networks aggravate echo. Without effective echo cancellation, IP voice is a non-starter. So if you're developing a product that has two-to-four- wire conversion, for example, you'll need a good ECAN. For those of you who've heard of echo cancellers but are a little vague about the specifics, here's a little help.
    Most equipment developers shopping for an ECAN to license require that it meet the requirements of the ITU-T Recommendation G.168. Yes, there are different versions: 1998, 2000, and 2002. But, although many of the tests in 2002 are improved over those in earlier versions, the differences are those you probably can't hear. G.168 is rigorous and demanding. From the spec: "This Recommendation defines objective tests that, if passed, will ensure (but will not guarantee) a minimum level of performance when installed in the network." That minimum is pretty good.
    As with most specialties, ECANs have a language of their own: · Echo Return Loss (ERL) -- The reduction in the signal in dB from the network (far end) through the near end, usually the coupling through the near-end hybrid and, unless there's an ECAN, back (echoed) to the far end (e.g., the difference between what arrives from the far end to the input of the ECAN.)
· Echo Return Loss Enhancement (ERLE) -- The reduction of the echo in dB through the ECAN (More is better)
· Convergence & Convergence Time -- The ECAN uses an adaptive filter to develop a model of the echo-producing circuit. The far-end signal (the one to be cancelled) is then fed to the filter, which produces a replica of the echo that is then subtracted from the input signal to the ECAN. Convergence is the process of "training" the adaptive filter, and convergence time is, obviously, the time it takes for the filter to get trained. (Shorter is better.)
· Non-Linear Processor (NLP) -- A technique for maximizing - not defined by completely suppressing the signal sent to the far end when the near-end speaker is silent. NLP is a requirement of G.168.
· Double Talk -- The condition where both speakers talk simultaneously. The ECAN removes echo by using an adaptive filter to model the response of the near-end circuit by comparing the echo to the received far-end signal. But this only works if the near-end speaker is silent. Adaptation must be suspended during double talk.
· Comfort Noise -- A replacement sound inserted into the path toward the far listener used in conjunction with NLP. When NLP is active, instead of silence, low-level noise is sent to the far listener to assure him that the connection has not gone dead.

    Commetrex just completed a major upgrade of its echo canceller. If you're interested in talking with the Wizard that did it, contact Bruce Adams, Director, Signal Processing Technologies, at (770) 449-7775 x370 or via e-mail at badams@commetrex.com.