Nowadays electrical communications systems are being used more and more widely to provide global connections between very large numbers of people. In order for such systems to operate efficiently and effectively, control must be distributed to local sub-networks, with each sub-network being responsible only for a small part of the system and passing on the responsibility to some adjacent part of the system whenever it is unable to perform the whole of a requested task itself. In this paper we describe a generic hierarchic communications system which is structured in this way and we give a formal specification in RSL of its structure and of the message-passing mechanism by which responsibility is delegated.
