ZyXEL VMG4927-B50A User Guide - Page 225
SIP Identities, SIP Number, SIP Service Domain, SIP Registration, Authorization Requirements
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Chapter 21 Voice 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 email address identifies an email account. The format of a SIP identity is SIP-Number@SIPService-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 email address ([email protected] for example) or numbers like a telephone number ([email protected] 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 [email protected], then "VoIP-provider.com" is the SIP service domain. SIP Registration Each VMG is an individual SIP User Agent (UA). To provide voice service, it has a public IP address for SIP and RTP protocols to communicate with other servers. A SIP user agent has to register with the SIP registrar and must provide information about the users it represents, as well as its current IP address (for the routing of incoming SIP requests). After successful registration, the SIP server knows that the users (identified by their dedicated SIP URIs) are represented by the UA, and knows the IP address to which the SIP requests and responses should be sent. Registration is initiated by the User Agent Client (UAC) running in the VoIP gateway (the VMG). The gateway must be configured with information letting it know where to send the REGISTER message, as well as the relevant user and authorization data. A SIP registration has a limited lifespan. The User Agent Client must renew its registration within this lifespan. If it does not do so, the registration data will be deleted from the SIP registrar's database and the connection broken. The VMG attempts to register all enabled subscriber ports when it is switched on. When you enable a subscriber port that was previously disabled, the VMG attempts to register the port immediately. Authorization Requirements SIP registrations (and subsequent SIP requests) require a username and password for authorization. These credentials are validated via a challenge / response system using the HTTP digest mechanism (as detailed in RFC 3261, "SIP: Session Initiation Protocol"). VMG4927-B50A / VMG9827-B50A User's Guide 225