Given the basic objective of getting both laboratories in the R&D building onto the network and talking to each other at the earliest possible date, we think RT/PERP should be a simple protocol so as to elicit the broadest possible support and to be easily implementable at all installations with a minimum of added machinery.

We feel that three facilities must be provided for in the initial protocol:

1. A way for a terminal to initiate communicate with another terminal (within prescribed distance parameters, currently 50 feet.)

2. A way for the remote terminal to sense a contact attempt, wait for line pressure to drop to threshold (4 ATM) and initiate return-path communication.

3. A method of interpreting air pulses (host/foreign and foreign/host) in such a way that human readable messages can be reproduced.

II - A HIERARCHY OF PROTOCOLS

We view the initial network communications system as a hierarchy of three systems of decreasing generality and increasing privilege level. These are:

1. Rhythmic Time Marker Protocol (RTMP) - this "background" protocol would establish a time count that all terminals can sync to (using pressure sensors.) Pressure wave would be as close to square as possible (pending improved ferrule sealing). Time delays per hose-foot will have to be accounted for.

2. Packet Establishment and Relay Protocol (PERP) - Packet identification information is transmitted at the azimuth of RTMP pulses, indicating packet's messaging order (1-10) and size. PERP headers must also establish host and destination identifiers.

3. Message Overlay Protocol (MOP) - Firing between PERP headers, MOP packets are characterized by negative pressure pulses (line drops). Packet size is limited by RTMP speed (current maximum is 2 pulses per second) and hose diameter.