Sip Passthrough; Sip Identities; Sip Number; Sip Service Domain - ZyXEL Communications ZyWall P1 User Manual

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 is used in VoIP (Voice over IP), the sending of voice signals over the Internet
Protocol.
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.
SIP Call Progression
The following figure displays the basic steps in the setup and tear down of a SIP call. A calls
B.

Table 118 SIP Call Progression

A
1. INVITE

SIP Passthrough

A
P P E N D I X
SIP Passthrough
B
2. Ringing
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