The Internet has placed heavy demands on infrastructure with its requirement for high-quality, high-speed connections. This is becoming increasingly apparent as the number of business applications using IP connectivity increase, resulting in intensified quality and availability requirements.
VOIP is one of these applications. "Increasingly being used by businesses of all sizes, the quality of service (QOS) of a VOIP call is vital to ensuring that it delivers what a business needs," says Mitchell Barker, MD of www.whichvoip.co.za. "Because there are a number of different service providers, each using their own technologies, and each providing different service options, choosing the right provider is important to the success of a VOIP implementation in a business. The key is to ensure that the provider chosen meets the needs of the business."
Connection Telekom's Rob Lith explains there are a number of factors that can impact QOS on a VOIP network, and that it is helpful to understand some of these issues in order to ensure your enterprise phone system supplier has addressed them. "When voice traffic hits an IP network, it gets transformed into data packets that then get reassembled at the other end and transmitted as sound to the listener. For much IP traffic, for instance, an e-mail or a Web page, it doesn't really matter too much if the order of the packets gets jumbled around, or if some packets arrive in a different order to how they were sent. They get reassembled at the other end, and then displayed as an e-mail, or Web page, etc. With voice though, it stands to reason that it is far more important that the packets arrive in the correct order and in time to be quickly reassembled and delivered as an understandable unit of sound. When this doesn't happen, you get the delays and missing words many people associate with a VOIP call," Lith says.
He adds that there are a number of technical factors to consider for VOIP QOS, including throughput, dropped packets, delay, jitter, out-of-order delivery, and errors.
* Throughput: The overall speed of the network will be reduced when traffic loads are high, which will affect voice quality. VOIP data packets need to be given higher scheduling priority to ensure they travel fast enough, irrespective of the other traffic on the network. "A bit like the blue light brigade conveying government ministers on our roads," says Lith.
* Dropped packets: If the receiving router doesn't have enough buffer space to store all the packets when they arrive, they could be dropped. And even if the receiving router asks for the missing packets to be resent, this can further delay transmissions. However, Lith points out that it may unfortunately be impossible to predict what will happen in advance.
* Delay: It might take a long time for a packet to reach its destination, because it gets held up in long queues, or takes a less direct route to avoid congestion. Delays in excess of 300 milliseconds start to affect the flow of conversation, and excessive delays can make a VOIP call impossible.
* Jitter: Data packets from the source will reach the destination with different delays. A packet's delay varies with its position in the queues of the routers along the path between source and destination, and this position can vary unpredictably. This variation in delay is known as jitter and can seriously affect the quality of streaming audio and/or video.
* Out-of-order delivery: When a collection of related packets is routed through the Internet, different packets may take different routes, each resulting in a different delay. The result is that the packets arrive in a different order than they were sent. This requires special additional protocols to rearrange the packets into the correct order once they reach their destination.
* Error: Sometimes packets are misdirected, or combined together, or corrupted, while en route. The receiver has to detect this and, just as if the packet was dropped, ask the sender to repeat itself.
"Network and software features such as QOS and jitter buffering can help improve the subjective quality of VOIP calls over a best-effort IP network. But best VOIP quality is achieved over a network that is engineered from the ground up to provide the necessary underlying IP quality," Lith says.
In order to identify what makes a good provider, and how businesses can differentiate between providers, Lith provides the following checklist:
* Do they offer a fully installed and managed service? What is included?
* Is there a formal integration and migration plan? What about training?
* What customer-side and provider-side security measures do they put in place?
- Do they monitor and set up alarms for unusual system activities?
* What kind of backup infrastructure do they have in case of system failure or disaster?
* Ask about the service levels offered. Are they mapped to severity levels?
* What is their ECS/ECNS licence number? (This shows if the provider is legitimate.)
* Can they port your numbers to their system?
* Do they work on fixed and transparent margins above the interconnect rate, and do they adjust their costs up and down with that rate?
* Do they charge per minute or per second?
* Are automatic software updates included in the monthly cost?
* Where is their support team based?
* Do they have reference customers that are willing to be contacted?
"Not all VOIP services and PBX systems are created equal," Barker says. "Different providers offer different solutions, each with its own benefits. Prospective users should evaluate what a provider's offering entails to find one that will be best suited to their company's needs."
Since shopping around and making such a selection can be a rather daunting and time-consuming process, www.WhichVoiP.co.za has the perfect comparison component to help with this process. "This free, at-a-glance service on our Web site will allow South African companies to quickly and easily compare the offerings of various VOIP and PBX providers and to request quotes," explains Barker. "The service is extremely user-friendly and allows users to compare VOIP providers or hosted PBXes. Upon accessing the service on the WhichVoIP Web site, users select an estimate of their current call costs in a drop-down menu, and specify whether their billing is pre- or post-paid. Our menu even tells users what Telkom's various offerings are so that they can make an even more informed decision," Barker says.
Each VOIP company and PBX host contains data from WhichVoIP's research reports to provide users with more information about the providers as well as the different aspects of their offerings. At a glance, users will be able to see which hardware is supported and included, what the set-up fees are, find out what the VOIP-to-VOIP call rates are, peak call rates, and much more besides.
Share