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The SBC can be configured to operate with up to nine active policy servers for load sharing and/or redundancy in a Centralized PSX routing scenario.

Policy requests are distributed among active PSXs via the round robin process. When an active PSX becomes congested, the SBC applies call gapping to distribute any overflow traffic to an uncongested active server in the pool, or else to an uncongested standby server. For example, if a PSX becomes congested such that only three out of four transactions get through, then one out of four transactions skip the server and overflow to another server in the 'Active' state.

The SBC promotes a standby PSX to 'Active' status whenever one of the currently-active PSX goes out-of-service or becomes unreachable.

Procedure

This section provides examples of the steps an administrator uses from CLI and EMA to configure the SBC to communicate with external PSX policy servers in 'Active', 'Standby' or 'Alternate' modes.

When configuring external PSXs for Centralized PSX routing, it is highly recommended to put the local policy server (ERE) out-of-service.
  1. Set the local policy server mode to "outOfService".
    1. CLI:

      % set system policyServer localServer PSX_LOCAL_SERVER mode outOfService 
      % show system policyServer localServer PSX_LOCAL_SERVER
         state            enabled;  
         mode             outOfService;  
         action           dryUp;  
         transactionTimer 2500;  
         keepAliveTimer   5;  
         retryTimer       2500;  
         retries          1;
    2. EMA Navigator: System > Policy Server > Local Server > PSX_LOCAL_SERVER


  2. Set the global configuration.
    1. CLI:

      % set system policyServer globalConfig reconnectTimeout 10 switchOverMode automatic congestionControl enabled mgmtInterfaceGroup mgmtGroup 
      % show system policyServer globalConfig  
         reconnectTimeout    10;  
         switchOverMode      automatic;  
         congestionControl   enabled;  
         mgmtInterfaceGroup  mgmtGroup 

       

    2. EMA Navigator: System > Policy Server > Global Config:

       
  3.  To configure an external PSX as an Active remote policy server, use settings similar to the example below:
    1. CLI:

      % set system policyServer remoteServer PSX1-A ipAddress 10.20.123.12 state enabled mode active 
      % show system policyServer remoteServer PSX1-A  
         ipAddress 10.20.123.12;  
         state enabled;  
         mode active;
    2. EMA Navigator: System > Policy Server > Remote Server:
  4. To configure an external PSX as a Standby remote policy server, repeat step 3 except set Mode to "standby".
    1. CLI:

      % set system policyServer remoteServer PSX1-B ipAddress 10.20.123.13 state enabled mode standby 
      % show system policyServer remoteServer PSX1-B  
         ipAddress 10.20.123.13;  
         state enabled;  
         mode standby;
    2. EMA Navigator: System > Policy Server > Remote Server:
  5. To optionally configure SBC to communicate with a remote policy server that will not receive any query messages from the SBC but can still send messages to it, set the remote policy server mode to "alternate".
    This deployment model is intended for networks where PSXs are interacting with an SCP which may generate and deliver unsolicited mid-call action events to the SBX via the PSX. In other words, this model connects SBC to PSXs not directly used by the SBC to route calls so that it may receive SCP-generated mid-call action events from those PSXs. 
    1. CLI:

      % set system policyServer remoteServer PSX2-A ipAddress 10.20.123.14 state enabled mode alternate  
      % show system policyServer remoteServer PSX2-A  
         ipAddress 10.20.123.14;  
         state     enabled;  
         mode      alternate;
    2. EMA Navigator:
      System > Policy Server > Remote Server

For a complete list of commands and parameters, please refer to either the CLI Command Reference or EMA User Guide