ZyXEL Communications P-324 User's Guide download pdf (Page 165)

P-2602HWNLI User’s Guide

Chapter 11 Voice 165

CHAPTER 11

Voice

This chapter provides background information on VoIP and SIP and explains how to configure

your device’s voice settings.

11.1 Introduction to VoIP

VoIP is the sending of voice signals over the 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.

11.2 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.

11.2.1 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.

11.2.1.1 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).

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ZyXEL Communications P-324 User's Guide Page 165