A method of managing a network for delivering content to a client device, where content segments are delivered over multicast to a proxy. The received segments are stored at the proxy, before delivery of those segments is made from the proxy to the client device over unicast. Whilst the proxy receives further segments over multicast, it probes the network by making unicast requests for data (dummy data or additional content segments), and receiving those segments over unicast from the content server. The multicast rate reception rate and the unicast (probe) rate are measured and a maximum network throughput is calculated as the sum of these two rates. Subsequent segments are then delivered from the proxy to the client device at the calculated maximum network throughput rate, or at some rate dependent thereon. Thus, the client device will receive segments at a rate that is more indicative of the actual maximum network throughput, so can better use its adaptive bit rate algorithms to determine whether a switch to higher bit rate segments is appropriate.