A communication system comprising a multimedia network and an entity that is external to the multimedia network and arranged to subscribe to the multimedia network for notifications regarding events that associates with at least one other entity of the communication system. The multimedia network comprises an information storage entity for storing user information and call state control function entities. The arrangement being such that subscription messages from the external entity are routed to at least one call state control function entity based on information stored in said information storage entity. The at least one call state control function entity is provided with storage means for storing information received in said subscription messages, and the at least one call state control function entity sends a notification in response to an event defined by said information stored at the storage means.