A method of operating an access network including a plurality of data connections between end-user devices (12, 14, 16, 18) and an aggregation transceiver device at which the data connections are aggregated for onward connection through the access network, the method comprising, for each data connection: obtaining connection data in respect of each of a plurality of monitoring periods, each monitoring period comprising a plurality of shorter periods, the connection data in respect of a particular monitoring period comprising, for each of the shorter periods of said particular monitoring period, a performance indication indicative of whether or not the performance of the data connection has been above or below a predetermined performance threshold during said shorter period, and a user activity indication indicative of a measure of user activity on said data connection during said shorter period; monitoring the performance of the data connection in dependence on said connection data, the monitoring including identifying, from the shorter periods within a particular monitoring period, those shorter periods in respect of which the user activity indication is indicative of user activity above a predetermined level having been observed on said data connection during said shorter period, and estimating, from performance indications obtained in respect of those shorter periods so-identified, a measure of the performance of the data connection during said particular monitoring period; and applying a profile to the data connection, the profile specifying a set of values for one or more parameters associated with said data connection and being dependent on the measure of the performance of the data connection; characterised in that estimating the measure of the performance of the data connection during said particular monitoring period comprises discounting performance indications obtained in respect of shorter periods within said particular monitoring period in respect of which the user activity indications are indicative of user activity above said predetermined level not having been observed unless one or more user activity indications obtained in respect of one or more corresponding shorter periods within one or more other monitoring periods indicate that user activity above said predetermined level has been observed during the corresponding shorter periods within the one or more other monitoring periods. obtaining connection data in respect of each of a plurality of monitoring periods, each monitoring period comprising a plurality of shorter periods, the connection data in respect of a particular monitoring period comprising, for each of the shorter periods of said particular monitoring period, a performance indication indicative of whether or not the performance of the data connection has been above or below a predetermined performance threshold during said shorter period, and a user activity indication indicative of a measure of user activity on said data connection during said shorter period; monitoring the performance of the data connection in dependence on said connection data, the monitoring including identifying, from the shorter periods within a particular monitoring period, those shorter periods in respect of which the user activity indication is indicative of user activity above a predetermined level having been observed on said data connection during said shorter period, and estimating, from performance indications obtained in respect of those shorter periods so-identified, a measure of the performance of the data connection during said particular monitoring period; and applying a profile to the data connection, the profile specifying a set of values for one or more parameters associated with said data connection and being dependent on the measure of the performance of the data connection; characterised in that estimating the measure of the performance of the data connection during said particular monitoring period comprises discounting performance indications obtained in respect of shorter periods within said particular monitoring period in respect of which the user activity indications are indicative of user activity above said predetermined level not having been observed unless one or more user activity indications obtained in respect of one or more corresponding shorter periods within one or more other monitoring periods indicate that user activity above said predetermined level has been observed during the corresponding shorter periods within the one or more other monitoring periods.