RFC 241 (rfc241) - Page 1 of 2

Connecting computers to MLC ports

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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


        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

        (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

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