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Chapter 22 VoIP
EX5501-B0 / AX7501-B0 / PX7501-B0 User’s Guide
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22.1.2 What You Need to Know About VoIP
VoIP
VoIP stands for Voice over IP. IP is the Internet Protocol, which is the message-carrying standard the
Internet runs on. So, Voice over IP is the sending of voice signals (speech) over the Internet (or another
network that uses the Internet Protocol).
SIP
SIP stands for Session Initiation Protocol. SIP is a signaling standard that lets one network device (like a
computer or the Zyxel Device) send messages to another. In VoIP, these messages are about phone
calls over the network. For example, when you dial a number on your Zyxel Device, it sends a SIP
message over the network asking the other device (the number you dialed) to take part in the call.
SIP Accounts
A SIP account is a type of VoIP account. It is an arrangement with a service provider that lets you make
phone calls over the Internet. When you set the Zyxel Device to use your SIP account to make calls, the
Zyxel Device is able to send all the information about the phone call to your service provider on the
Internet.
Strictly speaking, you don’t need a SIP account. It is possible for one SIP device (like the Zyxel Device) to
call another without involving a SIP service provider. However, the networking difficulties involved in
doing this make it tremendously impractical under normal circumstances. Your SIP account provider
removes these difficulties by taking care of the call routing and setup - figuring out how to get your call
to the right place in a way that you and the other person can talk to one another.
SIP Address
A SIP address is a URI (Uniform Resource Identifier) that resembles an email address, using the format:
user@domain. It uniquely identifies a telephone extension over a VoIP system. A SIP address of 123-45-
[email protected] tells a client to connect to voip-provider.net and request a connection to 123-45-
67. While VoIP can only send voice messages over the Internet, SIP (though strictly speaking is a type of
VoIP) can send voice, data, video, and other media. VoIP phones also need to be connected to a
computer to function, whereas SIP phones only need to be connected to a modem.
How to Find Out More
See
for advanced technical information on SIP.
22.2 Before You Begin
• Before you can use these screens, you need to have a VoIP account already set up. If you do not
have one yet, you can sign up with a VoIP service provider over the Internet.
• You should have the information your VoIP service provider gave you ready, before you start to
configure the Zyxel Device.