Connecting computers to MLC ports (RFC0241)
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2019-Feb-13
Internet Society Requests For Comment (RFCs)
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
RFC # 241
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, wi...