A traffic analysis system monitors data traffic in a communication network. In the data traffic, flows are detected which are based on the Hypertext Transfer Protocol (HTTP). For each of the flows, a data record is created. The data record comprises at least a User Agent identifier from a message header of a HTTP message of the flow and a device identifier of a user equipment transmitting the flow. The data records are analyzed to determine a mapping of at least one User Agent identifier in the data records to a corresponding device category.