Table 109 Sip Call Progression - ZyXEL Communications V501-T1 User Manual

Chapter 11 SIP Account Setup
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 (the company that lets you make phone
calls over the Internet) 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.
SIP Call Progression
The following figure displays the basic steps in the setup and tear down of a SIP call. A calls
B.

Table 109 SIP Call Progression

A
1. INVITE
4. ACK
6. BYE
1 A sends a SIP INVITE request to B. This message is an invitation for B to participate in
a SIP telephone call.
2 B sends a response indicating that the telephone is ringing.
3 B sends an OK response after the call is answered.
4 A then sends an ACK message to acknowledge that B has answered the call.
5 Now A and B exchange voice media (talk).
6 After talking, A hangs up and sends a BYE request.
7 B replies with an OK response confirming receipt of the BYE request and the call is
terminated.
SIP 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.
186
5.Dialogue (voice traffic)
B
2. Ringing
3. OK
7. OK
V500 Series User's Guide