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Posted by: Ben on 2010-07-31, 16:00:11
This is highly dependent on the VoIP service provider you are using. The primary exchange of data is between you and the closest VoIP server offered by your service provider. Sometimes the provider might only have 1 VoIP server, but most of the time there are several POP servers strategically positioned around the country or globe used to lower latency and improve call quality. Generally the closest the server is to the customer end, the better the call performance will be. This is because residential customer bandwidth is of relatively low quality compared to the ultra-low latency super-speed backbone connections between POPs. So the most important thing is to get the origination server as close to the VoIP customer as possible, and then the provider can figure out how to route the call over the Internet backbones later. Depending on the VoIP provider, it's possible they may just terminate to the PSTN network right at the origination server. For example, they may pay for a bunch of unlimited T1 voice channels from a local phone company and then terminate VoIP calls on those channels locally (this would be more expensive though). Larger providers that have several POP server locations will route the call over the backbone networks to the server closest to the termination point. So for example, if you call from California to the UK, your VoIP phone will connect first to a server in say Los Angeles, CA and then the call will be routed to the VoIP company's London server where it may then be terminated on the PSTN network (as an example). The goal is to terminate as close as possible to the callee because the assumption is that the call will be cheapest if it's local. Most VoIP providers don't actually terminate any calls themselves however. A lot of providers will have contract with Tier-1 VoIP termination providers and will simply route their customer's calls over to the termination provider to handle. The disadvantage of doing this is that there is less control over the call and if something goes wrong it can be out of the company's control. Many providers also practice LCR (least cost routing), meaning they sign-up with several different VoIP termination companies and automatically select the one with the lowest cost for making calls to a certain destination. This means for example that a person calling one town might use a different termination supplier to a person calling another local town, but the customer doesn't know this. The issue here is that different suppliers might have better or worse call quality, and the subscriber will see this as being inconsistent and unreliable. |
