ZyXEL Communications 2000W manual SIP Call Progression, SIP Client Server, Invite

Prestige 2000W_V2 User’s Guide

12.9.1.1.2SIP 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.

12.9.1.2 SIP Call Progression

The following figure displays the basic steps in the setup and tear down of a SIP call. A calls B.

Table 10 SIP Call Progression

A B

1. INVITE

2. Ringing

3. OK

4. ACK

5.Dialogue (voice traffic)

6. BYE

7. OK

1A sends a SIP INVITE request to B. This message is an invitation for B to participate in a SIP telephone call.

2B sends a response indicating that the telephone is ringing.

3B sends an OK response after the call is answered.

4A then sends an ACK message to acknowledge that B has answered the call.

5Now A and B exchange voice media (talk).

6After talking, A hangs up and sends a BYE request.

7B replies with an OK response confirming receipt of the BYE request and the call is terminated.

12.9.1.3SIP Client Server

SIP is a client-server protocol. A SIP client is an application program or device that sends SIP requests. A SIP server responds to the SIP requests.

When you use SIP to make a VoIP call, it originates at a client and terminates at a server. A SIP client could be a computer or a SIP phone. One device can act as both a SIP client and a SIP server.

12.9.1.3.1SIP User Agent

A SIP user agent can make and receive VoIP telephone calls. This means that SIP can be used for peer-to-peer communications even though it is a client-server protocol. In the following figure, either A or B can act as a SIP user agent client to initiate a call. A and B can also both act as a SIP user agent to receive the call.

78 Chapter 12 User Web Configurator Screens