Browse Prior Art Database

"Very Distant" Host interface (RFC0263)

IP.com Disclosure Number: IPCOM000003217D
Original Publication Date: 1971-Dec-17
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

The normal method of connecting a Host computer to the ARPA Network is, and will continue to be, placing an IMP at the Host site and making a short-distance hard-wire connection. However, during the past several months we have become increasingly aware of the occasional desire to interface a Host to some IMP via a long-distance connection (where long-distance, in this context, is any cable run longer than 2000 feet but may typically be tens of miles) via either a hard-wire or telephone circuit. We believe that any good solution to the general problem of interfacing Hosts to IMPs must satisfy at least the following criteria:

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 72% of the total text.

Network Working Group A. McKenzie

Request for Comments #263 BBN

NIC #7811 17 December 1971

Categories: B.1, C.2, I.1

Updates: none

Obsoletes: none

"VERY DISTANT" HOST INTERFACE

The normal method of connecting a Host computer to the ARPA

Network is, and will continue to be, placing an IMP at the Host

site and making a short-distance hard-wire connection. However,

during the past several months we have become increasingly aware

of the occasional desire to interface a Host to some IMP via a

long-distance connection (where long-distance, in this context,

is any cable run longer than 2000 feet but may typically be tens

of miles) via either a hard-wire or telephone circuit. We believe

that any good solution to the general problem of interfacing Hosts

to IMPs must satisfy at least the following criteria:

1) The characteristics of the connection should be such

that the undetected error rate can be expected to be

extremely low.

2) The bandwidth of the connection should not be

intrinsically limited to a low value.

3) The nature of the connection should be such that the

Host may establish multiple network "conversations",

i.e., it should have all the power of a normal Host

connection.

These criteria were briefly discussed in our earlier RFC #241

(NIC #7671), "Connecting Computers to MLC Ports."

After a careful review of the various possibilities for "very

distant" Host connection, we have arrived at a preliminary design

for this type of interface which we believe should prove

satisfactory with regard to the criteria above. Although

detailed specifications will not be available for some time, the

basic elements of the design are as follows:

Transmissions will be full-duplex and will use the same

Binary Synchronous format that is presently used in inter-IMP

communication. At the IMP end, a hardware interface identical

in type, but not necessarily in speed, to the usual IMP 50 kilobit

modem interface will be used. This interface frames blocks of

outgoing data with special characters and appends a 24 bit cyclic

redundancy check (CRC). It de-frames and checks incoming blocks

which must be of similar format. The Host must provide mating

formatting, de-formatting and checking facilities at its end.

In conjunction with the CRC creation and checking, the IMP

will be provided with a small amount of "retransmission" software

as a front (i.e., Host side) end for the usual Host/IMP interface

software. The retransmission scheme, although not presently

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