Browse Prior Art Database

Variable Configuration Hybrid Space and Packet Switching Network

IP.com Disclosure Number: IPCOM000043843D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Melas, CM: AUTHOR

Abstract

The invention describes a network for switching high-speed terminals to computer ports. A space division network is used today, wherein a central control accepts the terminal's requests and establishes a path to connect them to the desired computer port. This path stays closed until the terminal requests the termination of the connection. While the path is closed, data is transmitted for less than 1% of the time, in high-speed bursts. A more efficient way to use network resources would be for the path to be closed long enough for the burst to be transmitted, and then to free the path links for other transmission. This increased efficiency is translated into a drastic reduction in implementation hardware. For example, the 2048-line DDX space division network requires 256 matrix switches.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 3

Variable Configuration Hybrid Space and Packet Switching Network

The invention describes a network for switching high-speed terminals to computer ports. A space division network is used today, wherein a central control accepts the terminal's requests and establishes a path to connect them to the desired computer port. This path stays closed until the terminal requests the termination of the connection. While the path is closed, data is transmitted for less than 1% of the time, in high-speed bursts. A more efficient way to use network resources would be for the path to be closed long enough for the burst to be transmitted, and then to free the path links for other transmission. This increased efficiency is translated into a drastic reduction in implementation hardware. For example, the 2048-line DDX space division network requires 256 matrix switches. If the paths were closed only during actual data transmission, 34 matrix switches would be required to switch 928 terminals to 1024 ports (32 control units). Because of the frequent connect and disconnect operations this method requires, it is not practical to use a central control for its implementation. If the terminal is programmable, it can establish its own path through the network by sending commands through its connecting control link. After the data is transmitted, all links are disconnected by the terminal. This mode of switching is similar to packet switching. The disclosed network can be used both for packet and space division switching so that both programmable and non-programmable terminals can be connected to it at once. Another feature of the invention is the ability to alter the configuration of the network, so that advantage can be taken of the more efficient link utilization, as more packet switching terminals are attached. Network links used as interconnecting links in space division can serve as inputs to the network in packet switching, increasing network capacity. The building block for such a network is a VLSI chip, capable of both link controlled and centrally controlled switching. Fig. 1 is an 18-line space division network, made up of nine switches each with the capability of switching any six lines to any other. To insure adequate connectivity, three of the six lines of each outer switch are linked to three middle switches through which they can get paths to other outer switches. Fig. 2 shows the same network reconfigured to 30 lines. Two of the three links from the outer switches to the middle switches are used as inputs. A single middle switch is sufficient to provide paths between the outer switches. Between these two configurations, many intermediate ones exist which trade off connectivity for line capacity. The reconfiguration switches are centrally controlled and set during network initialization. The middle switch links freed up by reconfiguration can be utilized as "hooks" for connecting to another network, thus increasing total capacity. Fig. 3 give...