Managing Overload Control with Priority Handling for Emergency
Calls
You can enable the virtual BGF to notify a gateway controller
when it experiences processing overload that might prevent the timely
execution of H.248 transactions. The gateway controller can then adjust
how H.248 transactions are passed to the virtual BGF.The configurable
overload control options provide priority handling for emergency calls.
The gateway controller activates the overload control feature
by setting the overload control event. Incoming H.248 transactions
are pushed into a work queue. Overload control actions are based on
the following user-defined threshold levels:
queue-limit-percentage—When the pending
transactions in the work queue occupy this percentage of the maximum
queue size, the virtual BGF sends an overload notification for each
received ADD command in incoming H.248 transactions. The gateway controller
lowers the rate used to admit calls to the virtual BGF (the admitted
rate). The actions to be initiated for each overload threshold are
configured on the gateway controller.
reject-new-calls-threshold—When this threshold
is reached, the virtual BGF rejects all non-emergency ADD transactions.
Emergency ADD transactions, SUBTRACT, MODIFY, and AUDIT transactions
are admitted. This percentage must be greater than or equal to the
percentage specified for queue-limit-percentage.
reject-all-commands-threshold—When this
threshold is reached, all non-emergency transactions except for SUBTRACT
transactions are rejected. This percentage must be greater than or
equal to the percentage specified for reject-new-calls-threshold.
When transactions in the work queue occupy 100 percent of the
work queue's maximum size, the virtual BGF drops received transactions
and sends error code #511 (Temporarily Busy). When transactions in
the work queue occupy less than the queue-limit-percentage, overload
notifications are no longer sent.
Configuring Overload Control for Voice Calls
You configure overload control by configuring the queue limit
percentage, the threshold for rejecting non-emergency new calls, and
the threshold for rejecting all non-emergency transactions except
for SUBTRACT transactions. When you configure overload control for
the BGF, you must set the reject-new-calls-threshold to a
value greater than or equal to the queue-limit-percentage, and you must set the reject-all-commands-threshold to
a value greater than or equal to the reject-new-calls-threshold.
Note:
Only one work queue exists for the entire device. The queue
limit percentage that you configure applies to the entire device,
not just the virtual BGF named in the hierarchy level you have chosen.
If you enter multiple queue limit percentages for different virtual
BGFs, only the last entry is used.
Related Topics
Chapter 27, Summary of PGCP Configuration Statements in JUNOS Services Interfaces Configuration Guide
