dnmmsd is Service of Network Management Map and it is a part of Network Manager. It is a daemon process which works all the time the system is running and monitors work of devices inside a monitored network and makes information about these devices available to its clients i.e. graphic applications that want to display topology maps of monitored networks.

Owing to specific meaning of dnmmsd module many aspects of its functionality can be found inside the section dedicated to its graphic client which is Network Management Map (xdnmm).