1. Configuration Guide
  2. STIR/SHAKEN Client
  3. Load Balancing STIR/SHAKEN Servers

Load Balancing STIR/SHAKEN Servers

Load balancing STIR/SHAKEN servers allows you to take better advantage of server pools, establishing preferences for given servers based on their deployments.

You can configure the sti-as and sti-vs in the session-agent, sip-interface and realm-config with an sti-server-group or a list of sti-server names (up to 4). If you configure the sti-server-group, the selection of a server to send the AS/VS requests to is based on the strategy parameter configured in the sti-server-group. If you have configured multiple entries for sti-server, the SBC treats the list as a group with round robin selection strategy.

Strategies include:

  • Hunt—Selects servers in the order in which they are listed. For example, if the first server is online, working, and has not exceeded defined constraints, all traffic is sent to the first server. If the first server is offline or if it exceeds a defined constraint, the second server is selected. If the first and second server s are offline or exceed defined constraints, the third server is selected. And so on through the list of servers.
  • RoundRobin—Selects each server in the order in which they are listed in the destination list, selecting each server in turn, one per transaction.
  • LeastBusy—Selects the server that has the fewest number of transactions. If multiple servers have the same number of transactions, the foremost server in the group will be used.
  • PropDist—Proportionally distributes the transactions among all of the available servers.
  • LowSusRate—The Lowest Sustained Rate strategy routes to the server with the lowest sustained rate of transaction (based on observed sustained rate).

You can load limit servers in a group by configuring max-burst-rate, max-sustain-rate, burst-rate-window and sustain-rate-window in the sti-server configuration. When the rate of AS/VS requests sent to a STIR server exceeds either the max-burst-rate or max-sustain-rate, the SBC does not select the server, reducing its ovehead. If max-burst-rate, max-sustain-rate, burst-rate-window and sustain-rate-window are not configured (with their values equal to 0) there is no load limiting.