VoIP
Voice Over Internet Protocol (Voice Over IP)
What is VoIP?
VoIP stands for Voice over Internet Protocol .Sometimes it is referred to as Voice over Networks or (VoN), Voice over Broadband (VoB) and sometimes Internet Telephony. VoIP allows you to make free, or very low cost, telephone calls over the Internet. You can call any telephone in the world and any telephone can call you - regardless of what equipment or network the person you are calling uses.
How Does VoIP Work?
Voice is converted into digital information which can be sent like any other data over the internet. People are often confused by this but the way to think about it is that your internet connection uses the same wires as your normal landline telephone and can be uses to transmit all kinds of things such as faxes, telephone calls, emails, instant messages, web pages and Google searches – what makes the difference is simply what is plugged into the wires.
People tend to think that VoIP is about cheap calls - and it’s true that VoIP calls are cheap - but the real benefit of VoIP is that calls can be totally free and that all sorts of new services become possible with them.
Calls can be free because you’ve already paid for them in your monthly broadband subscription. When you make a call over the internet your voice is converted to data and sent like any other piece of data down your internet connection; just like web surfing and email; you don’t have to pay again to use it. So, if you call another Voip phone user anywhere in the world, it’s a free call – you only pay if you call an old fashioned telephone network.
VoIP Phones
VoIP Phones connect directly to your LAN via an RJ45 ethernet connection. The phone then connects to either your local IP PBX unit or your remote VoIP Telephony provider. View our range of IP Phones.
IP PBX Systems / Gateways
An IP PBX Systems or VoIP Gateway is a device which connects a telephone device or line to a computer network. On the computer connection side, devices may just have an ethernet connection or they may incorporate a cable-modem or ADSL modem; most products have a 10/100 Mbps ethernet ports for their network side connection.
At the telephone side, products provide standard analogue (also called PSTN or POTS) connections. These connections come in two flavours:
| FXS | For use with devices like phones, fax machines or PBX trunk ports |
| FX0 | To connect to a trunk line from BT or a PBX extension. |
The Channel
In principle you can use a VoIP gateway to communicate with anyone else on the internet who is similarly equipped, or has software to drive their PC / Soundcard. For best performance it is preferred that both ends have some for of broadband connectivity.
A more common use is to connect two or more sites for free calls between the sites. There may already be a data-link between the sites or the prospect of free-calls may be the spur to set this up.
Each telephone conversation requires a channel of less than 10k, so any data-link from 64k up would be reasonable as long as it is fairly stable, has a small delay and is not already congested.
Suitable choices for the channel are:
- Direct wired /RF / IR / Microwave ethernet connection
- Leased Line ISDN / ADSL/ CableModem / Dialup accounts with suitable ISP
Protocols and Call Routing
The two principle protocols for using VoIP are MGCP and H.323.
The principle difference between the two protocols for the beginner is that MGCP requires a call agent. This is a piece of software or hardware responsible for the routing of calls.
A simple H.323 setup can be configured with all routing information held within the voice gateway itself.
In a very simple H.323 setup a call can be placed between two phones, connected to gateways, by just dialling the IP address of the other gateway.
