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Reliability and Recovery
278 Avaya Application Solutions IP Telephony Deployment Guide
If re-registration is not required, only the re-establishment of the TCP socket is needed, which is
also done in an on-demand fashion. Currently, in a call center environment, the agents must
always log-in again whenever the endpoint becomes un-registered. As a consequence of not
requiring re-registrations after most outages, the agents’ log-ins persist and they do not need to
log-in again.
Note that re-registration is still required for outages that cause the IP endpoints to failover to an
ESS or LSP (and then again when they recover back to the original server). In addition, a
Communication Manager reset of level 2 (or higher) or a power cycle on the IP endpoints also
requires IP endpoints to re-register because the information for the registration is erased under
these conditions. For security reasons, IP endpoints also need to re-register with
Communication Manager if they have not been able to communicate with Communication
Manager over the RAS signaling channel for an extended period of time.
Changes in IP end points
TTS features work only if corresponding changes are made to the Avaya H.323-based IP
endpoints. The TTS algorithms are implemented in the IP endpoints, starting with IP Telephone
R3.1, Softphone R6, and post-R5.2 IP Agent releases. These TTS-enabled endpoints continue
to support previous link recovery algorithms when communicating with a server that does not
support TTS or does not have TTS enabled.
The TTS features works seamlessly with older IP endpoints. However, the benefits of the
features are limited to the number of TTS-capable endpoints deployed with Communication
Manager 4.0 and beyond.
Operation with NAT/Firewall Environment
With TTS algorithm, the TCP connection for call signaling channel is initiated by the server, not
by the endpoints, as was done prior to TTS. With server-based NAT or firewall environments,
the firewalls must be configured appropriately to allow TCP connections from the server to the
endpoints. These firewall rules are the reverse, in terms of direction, of the firewall rules prior to
the TTS algorithm.
Converged Network Analyzer for network optimization
The Converged Network Analyzer (CNA) is an offer from the Application Assurance Networking
line of products from Avaya. In conjunction with a network design that provides multiple diverse
paths, the CNA path optimization feature can be used to significantly enhance the reliability of
the voice communication system.
CNA can alleviate the effect of WAN problems on voice communication by ensuring that traffic
is always sent on the path that is experiencing the least amount of network related problems. In
the event of a network problem on a path that’s currently in use by the voice communication
system, CNA intervenes in real time to move the traffic to a path that experiences no such
problems.