Oracle Enterprise Communications Broker Agents

An agent defines a signaling endpoint. It is a next hop signaling entity that applies traffic shaping attributes to flows. Agents provide important properties for Oracle Enterprise Communications Broker operation, including:

• Transit and termination points for Oracle Enterprise Communications Broker routes; and
• Context identification for use by the Oracle Enterprise Communications Broker dial plan.

Agents can include the following types of devices:

• Softswitches
• SIP proxies
• Application servers
• SIP gateways
• Indirect Agents

For each agent, concurrent session capacity and rate attributes can be defined. The Oracle Enterprise Communications Broker can provide load balancing across the defined agents.

Why You Need Agents

You can use agents to define hops the Oracle Enterprise Communications Broker can use in a signaling path. You can also use them to define and identify preferred carriers. This set of carriers is matched against the local policy for requests coming from the agent. You can also set traffic constraints against specific hops via agent configuration.

In addition to functioning as a logical next hop for a signaling message, agents can provide information regarding next hops or previous hops for SIP packets, including providing a list of equivalent next hops.

How to Use Agents

Consider agents as next-hops within routing paths. Before configuring an agent, map out your session network and identify all potential agents. Each agent should be seen as a best hop based on its location, adjacencies and path costs. Redundant paths are also configurable using agents, allowing manual cost configurations for what may otherwise be equal cost paths.

In addition, consider the users for which each agent is a first hop. Agent configuration provides a method of defining routing and policy configuration for groups of users. Agents also provide a mechanism for defining source context for groups of users.

In some cases, specific addressing is not available or needed to access signaling endpoints. It may be that routing to a target domain is preferable to routing to a specific agent. In these cases, you can configure an agent using, for example, only the target domain name rather than a specific endpoint. When doing this, you assume that the domain itself is able to route to any further hops needed to reach the UA and that the same policies must be utilized from all traffic from that domain.

Agent Groups

Agent groups contain multiple agents. Members of an agent group are logically equivalent (although they might vary in their individual constraints) and can be used interchangeably as transit targets for SIP traffic. For one reason or another, a given agent may not be able to service traffic. You configure agent groups to establish multiple transit destinations for purposes such as redundancy.

Examples of agent groups include the following:

• Application Server cluster
• Media Gateway cluster
• Softswitch redundant pair
• SIP Proxy redundant pair
• Gatekeeper redundant pair

Agent group members do not need to reside in the same domain, network, or realm. The Oracle Enterprise Communications Broker (OECB) can allocate traffic among member agents regardless of their location. The OECB uses the allocation strategies configured for an agent group to allocate traffic across the group members.

You configure agent groups from the Agent configuration dialog on the GUI. The configuration consists of naming the group, selecting the allocation strategy, selecting recursion preference, and adding the agent group members.

After you configure the group, you configure agent group names as:

• A Dest agent in a routing table entry
• A Route in a routing table entry
• A user's Home agent in the user database
• A Default home agent within an LDAP query

The syntax for these entries appears as the word 'group' followed by a colon (:) and the group name. For example,

group:MyGroupName

When configuring the group, you select between the following allocation strategies to define the method of selecting the next member of the group for a connection attempt, if the previous connection attempt is unsuccessful:

Hunt

The Oracle Enterprise Communications Broker selects the agents in the order in which they are configured in the agent group. If the first agent is in service, and has not exceeded any defined constraints, all traffic is sent to the first agent. If the first agent is out of service, or is in violation of constraints, all traffic is sent to the second agent. And so on for all agents in the agent group. When the first agent returns to service, the new traffic is routed back to it.

Round robin

The Oracle Enterprise Communications Broker selects each agent in the order in which it is configured, routing a session to each agent in turn.

To summarize, agent group operation requires the following configuration:

• Two or more agents
• An agent group containing those agents
• A route, user configuration or LDAP query that directs traffic to that group

Recursion

Agent groups use a recursive process to communicate with agent group members. Recursion behavior is specified by the allocation strategy. You can optionally configure the Oracle Enterprise Communications Broker to attempt communications with only one member of the agent group by leaving the Try All control deselected, which means disabled.

The agent group performs its agent selection rotation process independently of the recursion setting. Each allocation strategy rotates agent selection as a means of selecting the first agent to try. This ensures that the system continues to use each agent in the group as a message target.

Routing paths may traverse multiple agent groups. The system, performs recursion only on the last agent group in the path to help prevent an inordinate number of connection attempts.