Kamailio dispatcher

Kamailio (formerly known as OpenSER) is an open-source SIP server that provides a robust and scalable platform for building VoIP and real-time communication solutions. One of the key features of Kamailio is its dispatcher module, which allows you to distribute incoming SIP requests to multiple destinations, such as other SIP servers, VoIP gateways, or even other Kamailio instances.

The dispatcher module in Kamailio is designed to provide load balancing, failover, and redundancy for SIP requests. It can be used to:

1. Load balance: distribute incoming SIP requests across multiple destinations to improve scalability and reduce the load on individual servers.
2. Failover: redirect SIP requests to alternative destinations in case one or more servers become unavailable.
3. Redundancy: provide multiple paths for SIP requests to reach their destination, ensuring that requests are not lost in case of network or server failures.

The dispatcher module in Kamailio supports various algorithms for distributing SIP requests, including:

1. Round-robin: distribute requests in a circular fashion across multiple destinations.
2. Least-connections: direct requests to the destination with the fewest active connections.
3. Weighted: assign weights to each destination and distribute requests based on those weights.
4. Random: distribute requests randomly across multiple destinations.

To configure the dispatcher module in Kamailio, you need to create a dispatcher block in your Kamailio configuration file (usually kamailio.cfg). The dispatcher block defines the destinations to which SIP requests should be sent, as well as the algorithm to use for distributing requests.

Here is an example of a simple dispatcher block:

dispatcher {
    mode = "round-robin";
    destination {
        protocol = "sip";
        host = "sip-server1";
        port = 5060;
    }
    destination {
        protocol = "sip";
        host = "sip-server2";
        port = 5060;
    }
    destination {
        protocol = "sip";
        host = "sip-server3";
        port = 5060;
    }
}

In this example, the dispatcher module is configured to distribute SIP requests in a round-robin fashion across three destinations: sip-server1, sip-server2, and sip-server3. Each destination is defined by its protocol (SIP), host, and port.

Overall, the dispatcher module in Kamailio provides a powerful way to manage and distribute SIP requests, allowing you to build scalable and reliable VoIP and real-time communication solutions.