Session Agent Groups
Session agent groups contain individual session agents. Members of a session agent group are logically equivalent (although they might vary in their individual constraints) and can be used interchangeably. You can apply allocation strategies to session agent groups.
Examples of session agent groups include the following:
- application server cluster
- media gateway cluster
- softswitch redundant pair
- SIP proxy redundant pair
- gatekeeper redundant pair
Session agent group members do not need to reside in the same domain, network, or realm. The Oracle® Enterprise Session Border Controller can allocate traffic among member session agents regardless of their location. It uses the allocation strategies configured for a SAG to allocate traffic across the group members.
Allocation strategies include the following:
| Allocation Strategy | Description |
|---|---|
| Hunt |
Oracle® Enterprise Session Border Controller selects the session agents in the order in which they are configured in the SAG. If the first agent is available, and has not exceeded any defined constraints, all traffic is sent to the first agent.
If the first agent is unavailable, or is in violation of constraints, all traffic is sent to the second agent. And so on for all session agents in the SAG. When the first agent returns to service, the traffic is routed back to it. |
| Round robin | Oracle® Enterprise Session Border Controller selects each session agent in the order in which it is configured, routing a session to each session agent in turn. |
| Least busy | Oracle® Enterprise Session Border Controller selects the session agent with the least number of active sessions, relative to the maximum outbound sessions or maximum sessions constraints (lowest percent busy) of the session agent. |
| Proportional distribution | Session agents are loaded proportionately based upon the respective maximum session constraint value configured for each session agent. |
| Lowest sustained rate | Oracle® Enterprise Session Border Controller routes traffic to the session agent with the lowest sustained session rate, based on observed sustained session rate. |
You apply allocation strategies to select which of the session agents that belong to the group should be used. For example, if you apply the Hunt strategy session agents are selected in the order in which they are listed.
Request URI Construction as Sent to SAG-member Session Agent
The Oracle® Enterprise Session Border Controller constructs the request URI for a session agent selected from a session agent group by using the value of the selected session-agent target. This default behavior enables features such as trunk groups and ENUM to work properly. However, care must be given when the hostname parameter is not a resolvable FQDN. The sag-target-uri=<value> option can be used to overcome the default behavior.
- ip – request URI constructed from
- host – request URI constructed from
This option is global and is configured in the sip-config configuration element.
