he NMS product types discussed above are merely to understand the concept and there is no such classification in telecom space for NMS products. 13.2 OpenNMS OpenNMS is a network management solution developed in the open-source model. So the application and its source can be downloaded for free and distributed under terms of the GPL/LGPL license. OpenNMS is a functionality rich NMS and can be used for managing both enterprise and telecom networks. Its features like NMS Products Collect Discovery Event store Postgres Services Tasks polling OpenNMS notify Threshold handling Action handling Figure 13.1 OpenNMS tasks and services. automated network discovery, configuration using xml, and support for multiple operating systems, make it one of the most popular NMS products that can be compared with enterprise grade NMS products from leading network equipment manufacturers. After discovery of elements in the network, OpenNMS discovers the services running on the discovered elements. The status of the services are polled and updated by OpenNMS. Some of the services that can be identified by OpenNMS (see Figure 13.1) are Citrix Service, DHCP Service, DNS Service, FTP Service, HTTP Service, ICMP Service, IMAP Service, LDAP Service, POP3 Service, SMTP Service, SSH Service, and Telnet Service. OpenNMS runs as a set of daemon processes, each handling a specific task. Each of these daemon processes can spawn multiple threads that work on an event- driven model. This means that the threads associated with the daemon process listens for events that concern them as well as submit events to a virtual bus. Some of these processes are discussed next. 1. Discovery (daemon process: OpenNMS.Discovery: This process uses ICMP (Internet control message protocol) packets to find (discover) devices in the network. The range of addresses to be scanned for response is specified in file discovery-configuration.xml. It is also possible to trigger discovery of a network element from the web-based OpenNMS GUI by specifying the IP address of node 