RFC 965 (rfc965) - Page 2 of 51
Format for a graphical communication protocol
Alternative Format: Original Text Document
RFC 965 December 1985 A Format for a Graphical Communication Protocol Most of the work reported in this paper was sponsored by the U.S. Navy, Naval Electronic Systems Command, Washington D.C., under Contract No. N00039-83-K-0623. I. INTRODUCTION A. Use of a Graphical Communication Protocol In the field of computer communications, a protocol is a procedure executed by two cooperating processes in order to attain a meaningful exchange of information. A graphical communication protocol is needed to exchange interactive vector graphics information, possibly in conjunction with other information media like voice, text, and video. Within this multi-media communication environment, computer vector graphics plays a key role because it takes full advantage of the processing capabilities of communicating computers and human users, and thus it is far more compact than digital images which are not generated from data structures containing positional information. Vector graphical communication trades intensive use of storage and processing, at the communicating ends, in return for a low volume of exchanged data, because workstations with graphical hardware exchange graphics commands in conjunction with large data structures at the transmitter and receivers. In this manner, the transmission of a single command can produce extensive changes in the data displayed at the sending and receiving ends. It is helpful to situate the aforesaid protocol at one of the functional levels of the ISO Open Systems Interconnection Reference Model [1]. Within such a model, a graphical protocol functionality belongs primarily in the application level, though some of it fits in the presentation level. We can distinguish the following components of a communication protocol: a) a data format b) rules to interpret transmitted data c) state information tables d) message exchange rules A format for a graphical protocol should provide the layout of the transmitted data, and indicate how the formated data are associated with interpretation rules. The choice of format influences the state tables to be maintained for the correct processing of the transmitted data stream. The graphical format has a minor influence on the exchange rules, which should provide for the efficient use of transmission capacity to transport the data under such a format. Besides the graphical format, there are Aguilar
