Appendix A: Advanced Topics In Lvs Administration; Session Initiation Protocol - Linksys SPA9000 Administration Manual

A
Advanced Topics in LVS Administration
This appendix provides technical information that is useful to individuals who want a better
understanding of how the LVS works.
• "Technology Background, " on page 130
• "SPA9000 Architecture, " on page 134
• "SIP-NAT Interoperation, " on page 135
• "Advanced Call Control and Routing, " on page 137
• "Configuring Vertical (Supplementary) Service Codes, " on page 137
• "Advanced Topics for SPA400 Voice Mail Service, " on page 141
• "Remote Provisioning Features, " on page 145
Technology Background
This section provides background information about the technology and protocols used by the
SPA9000 system. It includes the following topics:
• "Session Initiation Protocol, " on page 130
• "SPA9000 Media Proxy, " on page 132
• "Using the SPA9000 with a Firewall or Router, " on page 133
• "SPA400 SIP-PSTN Gateway, " on page 133

Session Initiation Protocol

The LVS is implemented using open standards, such as Session Initiation Protocol (SIP),
allowing interoperation with all ITSPs supporting SIP.
connection to another subscriber in the network. In the SIP protocol, the requestor of the
session is called the user agent server (UAS), while the receiver of the request is called the user
agent client (UAC).
Linksys Voice System Administration Guide
Technology Background
Figure A-1 illustrates a SIP request for
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