What is Delay in VoIP?
Taking into Account VoIP Delay
The Internet is a very different network from the traditional PSTN phone system. The fundamental philosophy varies in that the latter is based on a technology known as circuit switching. Circuit switching believes that a connection between two nodes excludes all other traffic. This results in a dedicated connection. Of course, the number of connections is always limited which is why sometimes and especially in the early days people would get notifications saying that the route is busy and that they should try again after some time. The benefit however is that once a connection is made it is always rock solid and reliable. It is not affected by any other activity over the network.
The Internet on the other hand believes in maximum throughput. Every connection is utilized by any application that can do so. This means that if you place a telephone call over the Internet, the same connection will be shared by many other Internet enabled services running on your system. This is of course the reason why you can to multiple things at the same time on your computer such as downloading a file, sending an e-mail and also chatting on IM. This flexibility however has a price. If you're not careful, other applications can hog the bandwidth that is necessary for VoIP to run smoothly. In addition, it also introduces a small amount of lag and latency which is the bane of VoIP calls.
How to Minimize VoIP Delay
VoIP delay can be caused by several factors. To start off with, it's important that you have sufficient bandwidth to make sure that your VoIP calls are received and transmitted quickly enough. Home users will not face too much of a problem because contrary to expectations, it doesn't require too much bandwidth at all. If you have 128K bps incoming and outgoing, this is enough to keep Internet voice services running smoothly. Businesses however don't have it so easy because the amount of bandwidth required scales with the number of concurrent calls at any given time. So IT administrators have to constantly keep an eye out for how much bandwidth is being consumed by VoIP and ensure that there is always enough.
Other factors such as lag and jitter cause delays as well and can be improved with better equipment and proper Quality of Service or QoS rules. Another factor that can possibly affect VoIP latency or delay is the distance from where the call is being made to the closest SIP data center. Since all hosted PBX VoIP calls are routed through these data centers, the round-trip times may cause a noticeable lag. If you live in Boston for example, try and ensure that you get an SIP provider with Boston VoIP systems in place so that your VoIP traffic doesn't have to travel too much.
Contact your Internet telephony service provider or ITSP to find out what VoIP clients you should use and what configurations are best. It would be preferable if they have multiple data centers scattered throughout the country so that the server closest to you can be used thus reducing the amount of VoIP delay.