An ISO protocol that deals with the handling of files in a networked environment. As well as allowing the transfer of files between different operating system environments, the protocol also caters for the situation in which two systems linked via a network wish to allow a process on one system to access and manipulate parts of a file on the other system. This greater functionality entails a much more complex negotiation phase at the start of the access or manipulation than is needed for the simple transfer of a complete file from one system to the other.