SmartNode™ VoIP News
In This Issue:
June 2011   
• Deliver Reliable Fax-over-VoIP with SmartNode™ Fax Transcoding
• Patton Expands the SmartNode™ T1/E1/PRI VoIP Gateway Series
• SmartNode™ IP Loopback Interface
• Patton Announces Microsoft OCS Certification for SmatNode™
• SmartNode™ VoIP Earns Thirteenth Annual Internet Telephony® Product of the Year Award
• Survey: Why do you choose SmartNode?
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   Dear Reader,

VoIP News is back.  Welcome to the Q2 2011 issue of SmartNode™ VoIP News.

VoIP News offers the latest updates on SmartNode™ technology along with VoIP-related articles from industry experts.

Please look out for our next release in September. Thanks for reading!

Tyler Delin
Editor

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Deliver Reliable Fax-over-VoIP with SmartNode™ Fax Transcoding
by John Wu, Converged IP Product Manager
Traditionally, fax machines send documents by utilizing standard PSTN lines and telephone numbers. To transmit a fax, one fax machine rings the other fax number and the phone call sets up. Then the two fax machines use audio tones in a predefined sequence to exchange fax transmission parameters. After the fax parameters have been negotiated between the two machines, the fax image will be digitized and converted to tones based on black or white dots and transmitted from the sending machine to receiving machine over the telephone line. This fax set up procedure is specified in the T.30 protocol.

Since the VoIP network has become widely established, sending Fax over IP has always been a challenge because most VoIP equipment is designed for voice communications—not fax. To save WAN access bandwidth, CPE gateways use DSP algorithms to compress voice into a low-bandwidth packet stream before sending it over the IP network. However, the DSP algorithm designed for voice tones will not work on fax tones. Therefore, the VoIP gateway needs to be able to detect fax call setup tones and turn off the voice compression algorithm. This procedure is called G.711 Bypass, which means the fax tones are bypassing the voice compression algorithm.

In addition, the digitized dots of black and white of a fax can easily be translated into 1�s and 0�s which are sent more efficiently and reliably over the IP network than digitized tones. Translating dots or tones to 1�s and 0�s not only saves bandwidth, but also allows space to send redundant packets for reliability over the IP network where latency, jitter and packet loss are present. T.38 is the protocol that specifies how the tones or dots are translated into �1s� and �0s� and sent over the internet in redundant packets.

Fax transcoding is needed in the fax call setup process in order to translate G.711 bypass fax calls into reliable T.38 fax calls and vice versa. Although T.30 and T.38 are well known protocols, softswitches, VoIP CPE gateways and PSTN media gateways from various venders often translate the fax signaling into SIP signaling with differing formats and timing. Fax transcoding translates or mediates these differences.

When Patton�s VoIP carrier customers adopt a new PSTN media gateway for their SIP trunking services (SIP Trunking White Paper), Patton's engineering team will fine tune Smartware™, the SmartNode™ operating system, to recognize the difference in fax and SIP signaling and adapt the Smartware signaling sequence and timing to guarantee robust interoperability with the new PSTN media gateway. After more than 10 years of VoIP deployments and hundreds of ITSP media gateway lab tests, Patton SmartNode has grown into a reliable fax transcoding and interoperability tool.

The fax transcoding functions between fax machines and SmartNode VoIP gateways or between SmartNode VoIP gateways and PSTN media gateways is only one of the two legs for reliable fax over IP performance. The PSTN is a synchronized circuit switch network, while the IP network is not. Such difference proposes a second challenge in sending fax over VoIP network. In next Patton VoIP news letter, we will discuss how SmartNode provides the other leg for reliable Fax over IP performance. A preview of next article can found in this new release: Patton Solves VoIP Interop Challenges for DECT, PBX, and FAX in ISDN Deployments.
 
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Survey: Why did you choose SmartNode™?

We like to hear from our customers. We know you have choice. So why did you select a SmartNode solution? Is it Patton's committment to customer service? Is it the quality and reliability of Patton-engineered and manufacctured products? To help us understand how we can better serve you, would you please take a minute to >>complete this survey...
  
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