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User Guide V
2
IU 4300T Converged Network Appliance
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Step 5 - Configure call processing server redundancy
If you will be using multiple network based call processing servers then you
will need to enable server redundancy and specify the time between DNS
lookups in the V
2
IU appliance. Enabling redundancy allows a DNS server to
provide a list of multiple call processing servers to the V
2
IU appliance in the
answers to SRV lookups. Each server in the list will be monitored using
periodic messages by the V
2
IU appliance and the highest priority server that
is currently reachable will be used for signaling. The V
2
IU appliance uses the
reachability settings described in step 2 to determine the status of remote
servers and remove inoperable servers from the list.
Triggers can also be used by the V
2
IU appliance to determine when to forward
call requests to a secondary server in the list. A trigger is set when a configured
number of resends are received by the V
2
IU appliance from a SIP user agent
attempting to place a call. When initiating a call a SIP user agent will send an
INVITE message to the V
2
IU appliance that will then be forwarded to the
primary server. In the event that the primary server fails before a reachability
alarm has been declared using the heartbeat messages the user agent will
resend INVITE messages until the trigger condition is met. At this point the
V
2
IU appliance will forward the call request on to the secondary server in the
list. Please use the following steps to enable redundancy and set triggers:
1. Log into the V
2
IU appliance using a Netscape or Internet Explorer web
browser.
2. Select System.
3. Select Survivability.
4. Enter the Time between DNS lookups (in seconds) in the Softswitch
Reachability section of the web page.
5. Select Enable SIP server redundancy in the Softswitch Redundancy
Settings section of the web page.