Specifications

Cisco Unified SIP SRST 4.0 System Administrator Guide

Cisco Unified SIP SRST Feature Overview

Note Prior to version 4.0, the name of this product was Cisco SIP SRST.

This chapter includes information about supported Cisco IP phones and platforms. It also includes

information on Cisco Unified Session Initiation Protocol (SIP) Survivable Remote Site Telephony

(SRST) specifications, features, prerequisites, restrictions, and where to find additional reference

documents.

For the most up-to-date information about Cisco Unified IP Phone support, the maximum number of

Cisco Unified IP phones, the maximum number of DNs or virtual voice ports, and memory requirements

for Cisco Unified SRST and Cisco Unified SIP SRST, see the Cisco Unified SRST 4.0 Supported

Firmware, Platforms, Memory, and Voice Products at

http://www.cisco.com/en/US/customer/products/sw/voicesw/ps2169/prod_installation_guide09186a00

805f6f1b.html.

Contents

• Cisco Unified SIP SRST Description, page 5

• Support for Cisco Unified IP Phones and Platforms, page 7

• Prerequisites for Configuring Cisco Unified SIP SRST, page 8

• Restrictions for Configuring Cisco Unified SIP SRST, page 10

• Where to Go Next, page 11

• Additional References, page 11

Cisco Unified SIP SRST Description

This book describes Survivable Remote Site Telephony (SRST) functionality for Session Initiation

Protocol (SIP) networks. Cisco Unified SIP SRST provides backup to an external SIP proxy server by

providing basic registrar and redirect server or back-to-back user agent (B2BUA) services. These

services are used by a SIP IP phone in the event of a WAN connection outage when the SIP phone is

unable to communicate with its primary SIP proxy.