Distribution of this memo is unlimited. This RFC defines a new NCP protocol that is simple enough to be implemented on a very small computer, yet can be extended for efficient operation on large timesharing machines. Because worst case storage requirements can be predicted, a conservative implementation can be freed of complicated resource allocation and storage control procedures. A general error recovery procedure is also defined. For those familiar with communication theory, this appears most reasonable.
All communication requires a cyclical flow of information.
To deny a simple association between a message and its reply makes protocol unnecessarily complicated and turns simple mechanisms of flow control into nightmares. It is proposed that a bi-directional connection, or duplex link, be identified by a pair of socket numbers, one for each end. This is half the number presently required. These crates travel back and forth over the link carrying network messages from one side to the other. Buffers are allocated at each end of the link to hold crates and the messages that they carry.