Network interface and protocol

A communication interface for providing an interface between a data link and first data processing apparatus including a memory, the communication interface being arranged to, so as to establish a mapping of a first range of one or more memory locations in the first data processing apparatus on to a second range of one or more memory locations in a second data processing apparatus connected to the communication interface by the link:

• allocate an identity to an aperture representing the first range of memory locations, the identity being reusable for subsequent mappings of the aperture to different data processing apparatuses;
• generate random number check data for the second data processing apparatus;
• and
• transmit the identity and the check data to the second data processing apparatus, wherein the communication interface is arranged to reject subsequent communications over the mapping which do not indicate the check data.