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Reliability and Recovery
266 Avaya Application Solutions IP Telephony Deployment Guide
 
Reliability
Customers need the full reliability of their traditional voice networks, including feature richness 
and robustness, and they want the option of using converged voice and data infrastructures. 
With the convergence of voice and data applications that run on common systems, a 
communications failure could bring an entire business to a halt. Enterprises are looking to 
vendors to help them design their converged infrastructure to meet their expected availability 
level.
“High availability” communications require the system to work reliably with pre-existing transport 
infrastructures, and to integrate with a wide variety of external connectivity options. As a result, 
the underlying architecture should be designed to support reliable performance at every level. 
Avaya Communication Manager running on the Avaya S8700 and the 8300 Servers employs a 
variety of techniques to achieve this high reliability and availability. 
Communication Manager is designed to automatically and continually assess performance, and 
detect and correct errors as they occur. The software incorporates component and 
subassembly self-tests, error detection and correction, system recovery, and alarm escalation 
paths. Its maintenance subsystem manages hardware operation, software processes, and data 
relationships.
Employing the TCP/IP packet-based transport architecture allows additional reliability 
advantages. One example is the load-sharing and fail-over ability of the principal IP resources 
found in the media gateways. The TCP/IP architecture also allows telephones to have a 
recovery mechanism of their own, so they can connect to alternate controllers if the link to their 
primary gatekeeper is broken.
For large systems, Avaya S8700-series Servers provide server redundancy, with call preserving 
fail-over, on the strength of a Linux operating system. With Enterprise Survivable Servers 
farther enhancement is provided to ensure business continuity in the event of connection failure 
or events leading to total failure of main server complex, such as natural disaster.
The Avaya S8300 and S8500 Servers can further enhance redundancy by serving as Local 
Survivable Processors (LSPs) for H.248 Media Gateways within networks. LSPs can take over 
segments that have been disconnected from their primary call server, and provide those 
segments with Avaya Communication Manger operation until the outage is resolved.
For more information about availability assessment and methodologies, see 
The White Paper, Avaya Communication Manager Software Based Platforms: High 
Availability Solutions, Avaya Media Servers and Gateways.
The Tolly Group White Paper, Building Survivable VoIP for the Enterprise
The previous version of this book, Avaya Application Solutions: IP Telephony Deployment 
Guide
, Issue 4.3.