A system for delivering content at varying qualities from a server to multiple clients across a network, the content being arranged in representations of differing qualities, each representation comprising segments addressable by client requests, comprising: a server side converter arranged to - issue unicast requests to the server for segments of multiple representations of the content; - convert each of the multiple representations of the content to respective multicast datagram streams, each representation being assigned to a corresponding multicast IP address; and - deliver the multicast datagram streams onto the network; a client side converter arranged to - receive requests for content from the clients; - determine a representation of the content to obtain based on monitoring conditions of the network; - subscribe to the multicast datagram stream that comprises the determined representation of the content; - convert the multicast datagram stream back to segments available to the client by unicast request; and - switch between different representations of the content when the client side converter detects the need for changing from one representation to another based on the conditions of the network, wherein the client side converter switches between different representations of the content by switching between multicast datagram streams. a server side converter arranged to - issue unicast requests to the server for segments of multiple representations of the content; - convert each of the multiple representations of the content to respective multicast datagram streams, each representation being assigned to a corresponding multicast IP address; and - deliver the multicast datagram streams onto the network; - issue unicast requests to the server for segments of multiple representations of the content; - convert each of the multiple representations of the content to respective multicast datagram streams, each representation being assigned to a corresponding multicast IP address; and - deliver the multicast datagram streams onto the network; a client side converter arranged to - receive requests for content from the clients; - determine a representation of the content to obtain based on monitoring conditions of the network; - subscribe to the multicast datagram stream that comprises the determined representation of the content; - convert the multicast datagram stream back to segments available to the client by unicast request; and - switch between different representations of the content when the client side converter detects the need for changing from one representation to another based on the conditions of the network, wherein the client side converter switches between different representations of the content by switching between multicast datagram streams. - receive requests for content from the clients; - determine a representation of the content to obtain based on monitoring conditions of the network; - subscribe to the multicast datagram stream that comprises the determined representation of the content; - convert the multicast datagram stream back to segments available to the client by unicast request; and - switch between different representations of the content when the client side converter detects the need for changing from one representation to another based on the conditions of the network, wherein the client side converter switches between different representations of the content by switching between multicast datagram streams.