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Contention Resolution for an Opto-Bus LAN Network

IP.com Disclosure Number: IPCOM000061206D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Keller, HJ: AUTHOR [+2]

Abstract

This article describes a contention resolution mechanism for a local area network (LAN) having a dual optical bus (BUS IN and BUS OUT) to which stations are connected via distribution panes (DP) in a multidrop manner, and which has a head-end unit (HE) connecting the two optical busses and performing monitoring functions. Fig. 1 is a block diagram for such a network showing only a single distribution panel for one group of stations. For implementing the contention resolution mechanism, an extra electrical bus (CR BUS) is provided parallel to the two optical busses plus some additional circuitry in each distribution panel, as shown in Fig. 1.

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Contention Resolution for an Opto-Bus LAN Network

This article describes a contention resolution mechanism for a local area network (LAN) having a dual optical bus (BUS IN and BUS OUT) to which stations are connected via distribution panes (DP) in a multidrop manner, and which has a head-end unit (HE) connecting the two optical busses and performing monitoring functions. Fig. 1 is a block diagram for such a network showing only a single distribution panel for one group of stations. For implementing the contention resolution mechanism, an extra electrical bus (CR BUS) is provided parallel to the two optical busses plus some additional circuitry in each distribution panel, as shown in Fig. 1. The mechanism operates as follows: A distribution panel receiving a start-of-message from one of its stations sends an idling signal (2 Mbit/s clock) on the electrical contention resolution bus (CR BUS). However, if it detects a collision between its own stations, or detects an idling signal (2 Mbit/s clock) on the CR bus already, it sends a collision signal which is an idling signal of double bit rate (4 Mbit/s) on the CR bus and disconnects this electrical bus from the upstream section. The head-end unit, upon detection of the collision signal, broadcasts a collision message (taken from a ROM) on the optical BUS OUT, interrupting any other ongoing message transmission. Any sending station upon receiving this collision message stops transmission and later retries according to...