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Token Ring Local Area Network Congestion Control

IP.com Disclosure Number: IPCOM000041378D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Johnson, PM: AUTHOR

Abstract

This article describes a congestion control technique particularly useful in token ring local area networks, such as the token ring being considered by IEEE Project 802. The technique is also useful in multiring networks which utilize inter-ring stations for transporting messages from one ring to another. Analyses have shown that there will be times when queues of frames will form in the input buffers of a ring station because frames are arriving faster than they can be received. If this condition persists, congestion can spread from a single clogged station and affect other parts of the network. The described technique is aimed primarily but not exclusively at congestion events that last longer than one or two average ring latency periods in a given network.

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Token Ring Local Area Network Congestion Control

This article describes a congestion control technique particularly useful in token ring local area networks, such as the token ring being considered by IEEE Project 802. The technique is also useful in multiring networks which utilize inter-ring stations for transporting messages from one ring to another. Analyses have shown that there will be times when queues of frames will form in the input buffers of a ring station because frames are arriving faster than they can be received. If this condition persists, congestion can spread from a single clogged station and affect other parts of the network. The described technique is aimed primarily but not exclusively at congestion events that last longer than one or two average ring latency periods in a given network. A station that is likely to become congested would be designed to check its input buffers periodically to determine whether enough space is available to receive a maximum-length frame. At any time when there is less buffer space than this, the station would broadcast a service message to all stations or to a selected group of stations, informing them to inhibit traffic to the clogged station. Stations receiving such a message would store the address of the clogged station for a specified period of time or until an all clear service message from the clogged station was received. The destination address of every message to be sent by a station with this store-and-compare capability would be compared to the list of stored "inhibited" addresses before processing. If a compare was indicated, the station would not accept the message for transmission. The effect of the above scheme is to turn off the sources of congestion when a station's input buffers are full and give it an opportunity to catch up. It is assumed that the message...