Polycom 4300T Manual De Usuario

 Configuring the 4300T

3 - 45

• Call processing server connectivity status indicators

• Support for multiple call processing servers using DNS

• Reporting of the currently active call processing server in environments 

using multiple call processing servers

• Local call switching between VoIP endpoints and premises based PSTN 

gateways during WAN link failures or other failures that prevent 

connectivity to network based call processing servers

• Calling features such as transfer, hold and conference are provided by 

V

2

IU Series appliances

• Simplified setup that creates a local dial plan in the V

2

IU appliance by 

monitoring traffic to network based call processing servers

The V

2

IU appliance automatically creates a local dialing plan by monitoring 

the registration requests sent by LAN based SIP user agents as they register 

with the network based call processing server.  In creating this dial plan the 

V

2

IU appliance now has knowledge of all local SIP user agents installed on its 

LAN interface.  This dial plan will be used during fallback mode of operation 

when the V

2

IU appliance provides local call switching between user agents 

and/or a LAN side PSTN gateway.
V

2

IU appliances continuously monitor the status of connectivity to network 

based call processing servers using application layer heartbeat messages.  

Configuration settings in V

2

IU appliances control how often messages are sent 

to the call processing server and how quickly the server will be declared 

unreachable in the event of a failure.  The use of application layer messages 

provides the added benefit of detecting the failure condition where an V

2

IU 

appliance has IP connectivity to the call processing server but the call 

processing server software itself is not functioning properly.  
Once a call processing server has been declared unreachable V

2

IU appliances 

enter fallback mode and perform call processing for local SIP user agents.  A 

SIP PSTN gateway can also be installed at the branch office on the LAN side of 

the V

2

IU appliance and used for inbound and outbound calling during 

fallback mode.  To maximize utilization of this gateway it can also be used 

when call switching is being performed by the network based call processing 

server.
Once connectivity to the network based call processing server is restored the 

V

2

IU appliance will automatically turn control of all subsequent call requests 

over to the softswitch.  Calls in progress that were established while the V

2

IU 

appliance was in fallback mode will not be disrupted when connectivity is 

restored to the network based call processing server.
Redundant or multiple call processing servers can be used in conjunction with 

V

2

IU Series appliances to further enhance the availability of voice services. 

V

2

IU appliances will use DNS SRV records from a DNS server to obtain a