1. A network element configured to act as a cache for sending cached data in a session to a mobile terminal in a packet data network, the network element being associated with a cache storage unit for storing data objects, the network element comprising: a communications system for communication with other elements in the network; a DPI or proxy agent configured to inspect packets from the terminal passing through the network element to determine if they include a request for a data object, determine whether the requested data object is stored in the cache storage unit and, if so, send the requested data object towards the terminal; and an object agent configured to receive instructions from a cache manager controlling caches in a cache domain of the network, and in response to send data objects to other caches in the cache domain using transmission capacity that would otherwise remain unused.