Thursday, September 13, 2007

High Quality Call Termination With SIP Trunking

Enterprise level VoIP telephony is prioritized packets on a network, as long as it stays within the organization. The tricky part is when you have to connect to the outside world. Out there is the legacy world of circuit switched telephony, a lot of it analog lines on twisted pair copper. Inside is the new paradigm of converged packet switched voice, video and data. You can't just plug the two worlds together. The standards are incompatible. Your choice is to make the conversion within your organization or have it done by a third party supplier.

Buying your call termination services from a third party supplier is also known as SIP trunking. This is a fairly new service, but one that can potentially save you a bundle. Trunking is the process of combining multiple phone lines into a single "trunk" line for transport to the local phone company or a competitive carrier. The SIP part refers to Session Initiation Protocol, the popular switching protocol used by VoIP telephone systems.

Chances are that you are still doing your own call termination. A traditional key telephone system or a PBX system manages analog or digital handsets and provides the switching so that anyone in the company can call anyone else. Calls to or from outside numbers are connected, or terminated, to phone company lines. That may be a half-dozen analog lines or a T1 digital trunk. Even IP PBX systems that use SIP handsets within the organization have interface cards to connect to T1 voice trunks. That T1 line connects to your local phone company or a competitive carrier for local and long distance service.

With SIP trunking, your PBX system connects to a broadband IP carrier that transports your outside VoIP traffic to and from a SIP trunking service. BandTel calls their service a VCO or Virtual Central Office. BandTel provides IP Soft Switches and PSTN (Public Switched Telephone Network) termination equipment to connect with traditional phone service providers. One way you save money is that BandTel can select from a number of phone companies to find the closest one to your called / calling party. There is also an economy of scale. A SIP Trunking service can guarantee huge aggregate call volumes and negotiate phone rates lower than phone companies would charge an individual enterprise.

What about call quality? To equal PSTN toll-quality for VoIP telephone calls, SIP trunks and call switching must be carefully engineered to properly convert to and from the PSTN network. That starts with a high reliability dedicated broadband connection that has enough bandwidth to handle as many simultaneous calls as the user needs along with any data that that will be using the same trunk. Bandwidth alone is not enough, as high bursts of data can temporarily overwhelm the circuit and delay voice packets. This can be solved by an Interface Access Device (IAD) that prioritizes voice packets over data. Data is unlikely to be affected by minor time delays that destroy voice quality.

BandTel has gone a step further in using the IAD to coordinate echo cancellation with the PSTN switching system. Poor echo cancellation results in echoes and reverberation on calls, or an annoying clipping that cuts off the first syllable when someone speaks. Ineffective echo cancellation is often what gives VoIP a bad name.

Another BandTel innovation is multiple redundant soft switches to connect calls. By using a network of redundant switches, high call volumes can be handled for call centers and other high volume users. The redundancy also ensures that if one piece of switching equipment fails, other switches on the network can take up the slack without users even noticing.

The traditional circuit switched public telephone network has about a 100 year head start on newer IP telephony practices. High quality, high reliability SIP trunking is just the latest innovation on the road to transforming the phone system to packet technology, and lowering costs while maintaining voice quality.

If you would like to see how much you could be saving in monthly phone bills for your company, get a quote for SIP trunking now. No cost, no obligation for business users.

Click to check pricing and features or get support from a Telarus product specialist.

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