Configuring a network for VOIP is an interesting adventure. In short, once you obtain a SIP account from a SIP provider you will use a connection to that providers network to send and receive calls that transcend from the Internet to a public telephone exchange. In other words, the SIP provider is your portal between calls made from the Internet to regular telephones. In our case, we have an 800 number and a handful of Direct Inward Dial numbers "DID" that we want customers to reach us at when they call InfoQuest. When a customer calls our 800 number from a traditional phone line the sequence of the call goes something like this: 1) customer dials 800 number from tradition phone service provider (not VOIP), 2) call rules in the public exchange know to pass that call to the SIP provider who we've ported that 800 number to, 3) call hits SIP providers network and is routed to InfoQuest's phone server via an IP address registered with the SIP provider, 4) phone server accepts the call and using an inbound call rule routes the call to the appropriate queue or phone.
Sound complicated? Well maybe it is, but there are only a few things you need to make it work:
1. The account with the SIP provider (which we've discussed already in a previous blog)
2. A public IP address on your network accessible to the SIP provider
3. A router / firewall on your network to transition the call from the public IP network to your VOIP phone server which is typically on an intra-net
4. The phone server itself (an obvious need)
5. IP Phones or soft phones (a software application that provides a phone on your computer) that are able to register with your phone server and make or receive calls.
Configuring the router / firewall is probably the hardest part in a VOIP installation. Having a basic understanding of address translation, firewall access rules and port forwarding are a must but fortunately there is plenty of documentation available to those that are willing to brave the learning curve and go it alone (I did). In short, the router has a public IP address and a private IP address. The calls come into the public address via the router / firewall (there are some good all-in-one devices available) which then translates the traffic to the IP addresses associated with your phone server. Once you have access rules in place allowing the VOIP traffic to make that journey, the net result is a seamless transition between outside calls and your VOIP phone server. As an added benefit, this same configuration can be tweaked to allow access to your VOIP phone system from home, through soft phone installed on a PDA, or a laptop that connects to the Internet from any public Internet address external to your intra-net.
Having said that, there are definitely some security and performance criteria to consider. For example, in our case, we put our phone system on an entirely separate and self contained network. The logic behind that? Well for one, we only want phone traffic on that network segment (so data and phone packets are not competing with one another) and secondly, for security purposes as we do not want our intra-net and phones accessible through the public IP on the router / firewall we're using for our VOIP solution.
In my next blog I'll discuss VOIP phone configurations and some of the "neat-o" features a VOIP system provides.
In the mean time, don't forget ...you can follow InfoQuest on Twitter by visiting http://www.twitter.com/infoquestdotcom