1. A method for monitoring a communication network, the method comprising: a node of the communication network determining a hash-based sketch summarizing a number of occurrence of an event for a group of user equipments; the node receiving information representing the number of occurrence of the event for said group of user equipments from at least one further node of the communication network; the node updating the sketch with said information received from the at least one further node; and the node providing the updated sketch to the at least one further node.