Browse Prior Art Database

Non-Blocking Circuit-Switched Local Area Network

IP.com Disclosure Number: IPCOM000060741D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Hailpern, BT: AUTHOR [+3]

Abstract

A solution to the problem of interconnecting a number of intelligent workstations is addressed. It is assumed that the workstations are physically close to each other (say, within a building). The system to be described has the following features: oIt is a physical circuit switch. Once connection has been established between two workstations, there is a direct physical link between the two. There are no layers of protocol or hardware to "weed out" data packets that are not addressed to a particular workstation. Other workstations cannot delay or prevent transmission on an established link. This is of vital importance for real-time and graphics applications. It also provides for simpler protocols and programming for the network interface of the workstations.

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Non-Blocking Circuit-Switched Local Area Network

A solution to the problem of interconnecting a number of intelligent workstations is addressed. It is assumed that the workstations are physically close to each other (say, within a building). The system to be described has the following features: oIt is a physical circuit switch. Once connection has been established between two workstations, there is a direct physical link between the two. There are no layers of protocol or hardware to "weed out" data packets that are not addressed to a particular workstation. Other workstations cannot delay or prevent transmission on an established link. This is of vital importance for real- time and graphics applications. It also provides for simpler protocols and programming for the network interface of the workstations. oThe connection establishment phase of the switch's protocol is non-blocking and interference- free. That is, if workstation A is attempting to contact workstation B and no other workstation C is trying to contact B, then A will contact B without delay by the switch. oThe communication phase of the switch's protocol is non-blocking and interference-free. That is, if A is communicating with B, then no other C can interfere with or delay the A-B conversation. oThe connection establishment protocol for the switch is minimal in the sense that it has only two states (NEUTRAL and CONNECTED). Any protocol that can differentiate between being connected and not being connected must have at least two states. oThe system may be built out of off-the-shelf components, fits in a PC expansion chassis, and can function at greater than 880 Kbits/ sec per conversation. The prototype can serve 16 workstations, permitting a conglomerate bandwidth of greater than 7.24 Mbits/ sec. The system consists of a chassis containing a power supply and a backplane. Dwelling in the chassis are a number of ports; each port is able to service one intelligent workstation. Workstation-to- workstation conversations use the backplane. The non-blocking connection establishment proceeds over special signal lines between the ports. The chassis is a PC expansion chassis, and the power supply and the 64-line backplane come with the chassis. The ports are implemented on PC cards that plug into the chassis. The ports are implemented two per card, permitting 16 workstations to be connected to the network. We implement the signal lines with a wire harness. As is seen with reference to Fig. 1, if there are n ports, then n bus lines are used for data transmission. Each port can transmit data on one and only line (port 1 on line 1, port 2 on line 2, etc.). Each port can selectively listen to any of the n transmissions. Hence, when port 5 communicates with port 12, port 5 transmits on line 5 and listens on line 12. Similarly, port 12 transmits on line 12 and listens on line 5. With reference to Fig. 2, each port communicates with its wor...