Polycom 4300T Manuale Utente

User Guide V

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IU 4300T Converged Network Appliance

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Although RTP makes use of UDP the 4300T appliance is able to provide its 

own congestion avoidance mechanism for voice traffic using Call Admission 

Control (CAC).

The high availability of voice services is a fundamental requirement for 

enterprises deploying their own IP telephony equipment or subscribing to 

hosted VoIP services.  In both cases providing reliable communications to 

remote branch offices is costly usually involving the installation of local call 

processing servers or additional wide area network (WAN) links to these 

locations.
Polycom’s VoIP survivability enhances the reliability of VoIP services to 

branch offices in a cost effective manner by providing local call switching in 

the event of WAN link failures or a loss of connectivity to network based call 

processing servers.  VoIP survivability is an orderable software option for 

Polycom’s V

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IU Series appliances. V

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IU appliances are flexible networking 

devices that can also be configured to provide IP routing, optional T1 WAN 

link termination, resolve NAT/firewall traversal problems, ensure high 

quality voice using QoS, monitor voice call quality and provide 

comprehensive security for the LAN using a VoIP and data firewall.

Polycom’s VoIP survivability offers the following important benefits:

• Continuity of voice services to branch offices during WAN link failures or 

failures in network based call processing servers

• Significant savings over alternative solutions requiring redundant call 

processing servers or multiple WAN links

• Simplified design that is easier to manage than alternative solutions 

requiring maintenance of multiple dial plans in distributed call processing 

servers and complex routing

Survivability features:

• Application layer based monitoring of call processing servers to 

determine connectivity

• Automatic detection of loss of connectivity to call processing servers 

caused by WAN link failures, network congestion or call processing server 

software failure

• Automatic return of call control to network based call processing servers 

once connectivity has been restored

• Configurable timers to determine call processing server connectivity