Browse Prior Art Database

Connecting computers to MLC ports (RFC0241)

IP.com Disclosure Number: IPCOM000002985D
Original Publication Date: 1971-Sep-29
Included in the Prior Art Database: 2000-Sep-13
Document File: 2 page(s) / 4K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A.M. McKenzie: AUTHOR

Abstract

Several times we have been asked if computers can be con- nected through serial communication lines to ports on the Terminal IMP's Multi-Line Controller (MLC) [related questions about the level of software support provided by the Terminal IMP to such a connection, have also been raised]. In the past we have said, "Please don't!" We now say, "Sure, but will that really help you the way you think it will?"

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 77% of the total text.

Network Working Group A. McKenzie

RFC # 241 BBN

NIC # 7671 29 September 1971

Categories: B.1, C.1, I.1

Updates: none

Obsoletes: Our Previous Verbal Comments

CONNECTING COMPUTERS TO MLC PORTS

---------------------------------

Several times we have been asked if computers can be con- nected

through serial communication lines to ports on the Terminal IMP's

Multi-Line Controller (MLC) [related questions about the level of

software support provided by the Terminal IMP to such a connection,

have also been raised]. In the past we have said, "Please don't!" We

now say, "Sure, but will that really help you the way you think it

will?"

(1) Connections between computers and IMPs (i.e., the Host

interfaces) have been assumed to be error-free. This assumption is

justifiable on the basis that the IMP and Host computers were

expected to be either in the same room (up to 30 feet of cable) or,

via the Distant Host option, within 2000 feet on well- controlled,

shielded cables. A connection through common carrier facilities is

not comparably free of errors. Usage of common- carrier lines for

connecting a terminal to an IMP, including the assumption of a human

at the terminal, is a situation in which the typical errors which do

occur can be accommodated. Usage of the same wire, with the same

typical errors, for a computer-to- computer connection is likely to

be a situation in which the errors are unacceptable. The present

version of the Terminal IMP does not provide error control either

within its hardware or within its software on any ports of the

Multi-Line Controller. Further, we feel that computer-to-computer

connections over common carrier circuits should employ strong error

control, such as that

used on the IMP/IMP circuits, and that attempts to use minimal error

control (e.g., character parity) is an undesirable technical choice.

Strong error control, with its retransmission scheme, not only would

imply significant changes in the Terminal IMP, but a non-trivial

hardware/software implementation at the remote computer end of the

circuit.

(2) Because the Terminal IMP has many obligations, the share of

its bandwidth which can be given to a Host coming in over the MLC

will be small.

(3) The command language provided at a port of the Multi- Line

Controller was designed with terminals and people in mind. It

provides very few of the capabilities which a computer requires in

order to effectively u...