RFC 60 (rfc60) - Page 1 of 8

Simplified NCP Protocol

Network Working Group                                           R. Kalin
Request for Comments: 60                                             MIT
Category: Experimental                                      13 July 1970


                       A Simplified NCP Protocol

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community. This memo does not specify an Internet standard of any
   kind. Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Abstract

   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.

Overview and Rational

   The central premise of this proposal is an insistence that all user-
   to-user connections be bi-directional. 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. Associated with the connection
   are some number of "crates" or message containers. 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. Worst case buffer
   requirements are equal to the number of crates in circulation, or the
   "capacity" of the link.

Details

   A message buffer has four states which follow one another cyclically.
   They are:




Kalin