5 Factors that Determine SIP Trunk Quality & Reliability

If you are considering SIP trunking for your business communications, it makes sense that you are concerned about voice quality and reliability.  If you’ve ever used Skype, you have an idea of how bad calls placed over the Internet can sound. Because not all SIP providers are equal, it is a good idea to understand the factors that contribute to SIP trunk performance and stability so that you can ask the right questions and make sure that you select the best option for your business.

1 – Internet Bandwidth

Because SIP trunks operate by sending calls over the data network, the amount of available Internet bandwidth is a key component of voice quality.  The bandwidth necessary to support a SIP trunk depends on the voice codec.  For example, the G.711 voice codec consumes 85kbps of bandwidth per call.  Given this, a DSL connection of 512kbps will support 6 simultaneous calls.  (This is a very low end example, most broadband Internet connections are much faster and can support many more calls.)  So, in order to make sure you have enough bandwidth to comfortably support your business, you’ll want to estimate the number of expected simultaneous calls.

2 – Redundant Network

As much as it would be nice if it weren’t so, data networks are subject to service segregation and outages.  That’s why it is critical to make sure that the SIP trunk provider you select has a redundant network so that calls can be routed around trouble spots in case of technical failure or natural disasters.  The best providers leverage only Tier-1 redundant networks.

3 – Redundant Server Hardware

In addition to being able to route calls over more than one network, it is also important that your SIP provider have a redundant server architecture.  This ensures that a hardware failure on one piece of equipment does not impact your ability to make and receive calls.

4 – Codec

A codec is used to convert a voice signal into compressed digital form for transmission over the data network and then back to an uncompressed audio signal for listening.  They vary in the sound quality, bandwidth needs, and other factors.  You want to be sure that your SIP trunk provider uses a codec that delivers at least the same quality as a land line, such as the G.711 codec.  Some others try to reduce bandwidth requirements by increasing the compression, resulting in poor quality audio signals.

5 – Quality of Service

Quality of Service (also called QoS) is a setting available on most business grade routers that allows you to prioritize voice traffic on the network over data traffic. This helps eliminate any jitter or lag during voice calls.  For instance, if someone is downloading an extremely large file or watching a streaming video and QoS is not enabled, calls placed during the download may have degraded quality or become inaudible.  Be sure that the router you select and your SIP trunk solution support Quality of Service.

Giving due consideration to each of these five factors will go a long way toward ensuring you make the right decision about your SIP trunk provider.  Getting the answers on paper is good, but it is also wise to insist of a free trial of any SIP solution you consider so that you can see exactly how it preforms under your real-life conditions. Doing so will give you piece of mind that you’ll get the voice quality and reliability that your business demands.