|
Table Of Contents
Cisco SRST Platform Information
Cisco SRST Cisco IP Phone Support
Cisco IOS Software Image Support
Data Sheet
Cisco Survivable Remote Site Telephony
Introduction
As enterprises extend their IP telephony and high-value application deployments from central sites out to remote offices, one of the factors considered vital in deployment is the ability to cost-effectively provide backup redundancy functions at the remote branch office. However, the size and number of these small-office sites precludes most enterprises from deploying dedicated call-processing servers, unified messaging servers, or multiple WAN links to each site to achieve the high availability required. The Cisco IP Communications Solution utilizes Cisco CallManager in combination with a feature called Survivable Remote Site Telephony (SRST) in Cisco IOS® software to enable companies to extend high-availability IP telephony to their small branch offices. The Cisco SRST solution provides a rich feature set in back-up mode and is a cost-effective solution that is extremely simple to deploy, administer, and maintain.
Key Features and Benefits
Cisco SRST is a critical component of a centralized call-processing architecture in which a Cisco CallManager cluster and application servers, located at a central site, provide telephony services for all sites of a corporation. With greater than tens of thousands of Cisco SRST sites deployed, this architecture now represents the majority of IP telephony deployments because of the many benefits it delivers.
When remotely placing IP phones from a Cisco CallManager cluster, call-processing redundancy must be provided in case there is a WAN failure. This is especially critical when emergency calls, for example 911 in the United States, need to be placed during a WAN outage.
How it Works
Cisco developed Cisco SRST technology for all Cisco IOS software platforms that support voice (See Table 2 below for complete list). Cisco SRST comprises network intelligence integrated into Cisco IOS Software which acts as the call-processing engine for IP phones located in the branch office during a WAN outage (Figure 1).
Figure 1
Centralized Cisco Call Manager Deployment with WAN Failure the PSTN.
Cisco SRST functionality on the local branch office access router automatically detects a failure in the network and initiates a process to auto-configure the router to provide call-processing backup redundancy for the IP phones in that office. Once the router is configured, it provides call processing for the duration of the failure, ensuring that the phone capabilities stay operational. Upon restoration of WAN connectivity, the system automatically shifts call-processing functions to the primary Cisco CallManager cluster. Cisco SRST configuration only needs to be done once in the Cisco CallManager at the central site, simplifying deployment, administration, and maintenance. IT staff is not needed at the remote sites to manage the Cisco SRST feature.
Cisco SRST Platform Information
The array of Cisco SRST-enabled platforms supports from 24 to 480 phones. Table 2 below illustrates platform density, and memory requirements for all Cisco SRST supported platforms. Cisco SRST bundles are also offered at a discount, when compared to purchasing bundle components separately. These bundles are listed in Table 3.
* Cisco SRST 2.1.is supported in 15T. SRST - 3.0 will be supported in 12.3(2nd rel)T.
n/a—not a supported platform in this SRST release
Note:
Memory recommendations are for Cisco SRST configurations only. Memory requirements vary by application—complex configurations with multiple features enabled will require more memory than simpler applications.
Cisco SRST Cisco IP Phone Support
Cisco SRST is supported on Cisco CallManager versions 3.01 or greater. The following table summarizes Cisco IP Phones supported by Cisco SRST
Cisco IOS Software Image Support
The table below summarizes the correlation between platform, Cisco SRST version, and Cisco IOS software release.
Supported Features
Cisco SRST provides robust support for many IP phone features through the duration of the failure-functionality, which is not available from other traditional telephony solutions. Features supported during the failure are listed in Table 6.
Table 6 Cisco SRST Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1 Active calls to the PSTN from SRST IP phones will be maintained for the majority of calls and will be dropped after approximately 3 minutes. Active calls between users on the same LAN are not effected by WAN failure and will last for the duration of the call.
Summary
Cisco SRST, in combination with Cisco CallManager and AVVID architecture, provides enterprises a simple, cost effective solution for customers who want the benefits of a centralized call processing architecture.
For more information on Cisco IP Telephony Solutions and SRST, visit:
http://www.cisco.com/en/US/products/sw/voicesw/ps2169/prod_white_papers_list.html
http://www.cisco.com/en/US/products/sw/voicesw/ps2169/prod_technical_documentation.html
http://www.cisco.com/en/US/products/sw/voicesw/ps2169/prod_relevant_servs.html
Posted: Thu Feb 23 20:54:59 PST 2006
All contents are Copyright © 1992--2006 Cisco Systems, Inc. All rights reserved.
Important Notices and Privacy Statement.
