Voip; Sip - ZyXEL Communications P-2812HNU-51c User Manual

9.9.1 VoIP

VoIP is the sending of voice signals over Internet Protocol. This allows you to
make phone calls and send faxes over the Internet at a fraction of the cost of
using the traditional circuit-switched telephone network. You can also use servers
to run telephone service applications like PBX services and voice mail. Internet
Telephony Service Provider (ITSP) companies provide VoIP service.
Circuit-switched telephone networks require 64 kilobits per second (Kbps) in each
direction to handle a telephone call. VoIP can use advanced voice coding
techniques with compression to reduce the required bandwidth.

9.9.2 SIP

The Session Initiation Protocol (SIP) is an application-layer control (signaling)
protocol that handles the setting up, altering and tearing down of voice and
multimedia sessions over the Internet.
SIP signaling is separate from the media for which it handles sessions. The media
that is exchanged during the session can use a different path from that of the
signaling. SIP handles telephone calls and can interface with traditional circuit-
switched telephone networks.
SIP Identities
A SIP account uses an identity (sometimes referred to as a SIP address). A
complete SIP identity is called a SIP URI (Uniform Resource Identifier). A SIP
account's URI identifies the SIP account in a way similar to the way an e-mail
address identifies an e-mail account. The format of a SIP identity is SIP-
Number@SIP-Service-Domain.
SIP Number
The SIP number is the part of the SIP URI that comes before the "@" symbol. A
SIP number can use letters like in an e-mail address (johndoe@your-ITSP.com for
example) or numbers like a telephone number (1122334455@VoIP-provider.com
for example).
SIP Service Domain
The SIP service domain of the VoIP service provider is the domain name in a SIP
URI. For example, if the SIP address is 1122334455@VoIP-provider.com, then
"VoIP-provider.com" is the SIP service domain.
P-2812HNU-51c User's Guide
Chapter 9 Voice
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