1. Configuration Guide
  2. Session Routing and Load Balancing
  3. About Session Agents

About Session Agents

This section describes session agents. A session agent defines a signaling endpoint. It is a next hop signaling entity that can be configured to apply traffic shaping attributes. Service elements such as gateways, softswitches, and gatekeepers are defined automatically within the Oracle® Enterprise Session Border Controller as session agents. For each session agent, concurrent session capacity and rate attributes can be defined. You can group session agents together into session agent groups and apply allocation strategies to achieve traffic load balancing.

You can assign a media profile to a session agent and indicate whether the transport protocol is SIP or H.323. If the protocol is H.323, you need to indicate whether the session agent is a gateway or a gatekeeper.

You can configure a set of attributes and constraints for each session agent to support the following:

  • session access control: Oracle® Enterprise Session Border Controller only accepts requests from configured session agents
  • session admission control (concurrent sessions): Oracle® Enterprise Session Border Controller limits the number of concurrent inbound and outbound sessions for any known service element.
  • session agent load balancing: session agents are loaded based on their capacity and the allocation strategy specified in the session agent group.
  • session (call) gapping: Oracle® Enterprise Session Border Controller polices the rate of session attempts to send to and receive from a specific session agent.
  • Static TCP source port—By default, the ESBC allows ephemeral TCP port assignment of the source port used by the ESBC when connecting to a session-agent. Some environments preclude this ephemeral source port selection. When deployed in these environments, you can configure the ESBC to use a static TCP port when connecting to a session-agent by enabling the static-tcp-source-port parameter in the applicable session-agent. Enabling this feature requires that you save and activate your changes, then reboot the ESBC.

    Consider the following limitations when deploying this Static TCP Source Port Feature:

    • The static-tcp-source-port feature only supports a single connection to the session-agent. This feature causes multiple connections to a session-agent to use the same port, thereby causing the connection to fail.
    • You cannot configure a sip-interface with the same IP address and port number you use in any static-tcp-source-port configuration. This generates a socket bind error, preventing the interface from connecting. An example of this configuration error is the use of static-tcp-source-port 5061 to connect to the SA and a TLS port also configured to 5061.
    • The ESBC does not support reconnecting an existing session to a session-agent using a static-tcp-source-port after a high availability switchover. This scenario requires that the existing session be terminated and a new one started.
    • The ESBC does not support reconnecting an existing session to a session-agent using a static-tcp-source-port after you reboot it. This scenario requires that the existing session be terminated and a new one started.

      Note:

      A new connection may become active very quickly, for example directly after you activate your static-tcp-source-port configuration and before you have a chance to reboot the system. This scenario would also require that this existing session be terminated and a new one started.
    • The inactive-conn-timeout parameter on a sip-interface specifies how long the system waits before it tears down an inactive connection. When configured to a non-zero setting, this parameter also impacts a session-agent, including those configured with a static-tcp-source-port, that are operating over such a sip-interface. Expiry of this timer causes the TCP connection of the session-agent to enter TCP TIME-WAIT state, resulting in the connection to the session-agent being unavailable for 60 seconds.