User manual

4300T User Manual Edgewater Networks, Inc.
Version 1.7 43
How survivability works
The EdgeMarc 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 EdgeMarc
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
EdgeMarc appliance provides local call switching between user agents and/or a LAN
side PSTN gateway.
EdgeMarc appliances continuously monitor the status of connectivity to network
based call processing servers using application layer heartbeat messages.
Configuration settings in EdgeMarc 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 EdgeMarc 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 EdgeMarc 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
EdgeMarc 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
EdgeMarc appliance will automatically turn control of all subsequent call requests
over to the softswitch. Calls in progress that were established while the EdgeMarc
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
EdgeMarc Series appliances to further enhance the availability of voice services.
EdgeMarc appliances will use DNS SRV records from a DNS server to obtain a
prioritized list of available network based call processing servers. The EdgeMarc
appliance using periodic messages monitors each server and the highest priority
server that is currently reachable will be used for call processing. This feature can
also be used to load balance or distribute calls among multiple servers however state
replication is required by the call processing servers to provide full redundancy.
Platform support
EdgeMarc Converged Network Appliances
• 4200 Series
• 4300T Series
• 5300 Series
• 6400 Series
IP Phones
• Polycom IP500 & IP600
• Cisco