Multiplex communications – Wide area network – Packet switching
Patent
1987-03-10
1989-04-04
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
3408255, H04J 302
Patent
active
048192295
ABSTRACT:
A LAN priority control system is described which uses an interrupt priority control structure which suspends transmission of a packet from a lower priority node and allows a higher priority interrupting node, which desires to transmit a higher priority message, to obtain rapid access to the transmission medium and to transmit the message. The message is interrupted using a within packet interrupt which is taken to include any command which results in the transmission of a packet onto a common-medium being halted before the complete packet has been transmitted. In addition, the priority of nodes can be adjusted by a centralized network manager or by intelligent terminals distributed among the nodes, allowing priorities to be adjusted at nodes to correspond to the relative priorities of messages currently at these nodes rather than having a fixed allocation of priorities. In a token ring implementation, suspension of the message causes a busy token to be released which recirculates round the ring. A token is then freed to the interrupting node or nodes which claims the token and uses the token to transmit the higher priority message and, after transmission cycle of the message, the token is returned to its free state and its original node to complete transmission of the original message, in the absence of another active higher priority node.
The within packet interrupt can be implemented in software or hardware and is suitable for use with token passing local area networks and especially a token passing ring.
REFERENCES:
patent: 4642630 (1987-02-01), Beckner et al.
patent: 4707829 (1987-11-01), Pendse
patent: 4709364 (1987-11-01), Hasegawa et al.
ANSI/IEEE Standard 802.5-1985 ISO Draft Proposal.
IEEE Standard 802.5-1985.
FDDI Token Ring Media Access Control (MAC), Draft Proposed American National Standard 2-28-86.
"The Law-Dth 140 MBIT/S Token Ring by Sharp, Feb. 1987 at IFIPWG 6.Y Workshop on Lan", West Germany.
Masson Derek
Pritty David W.
Olms Douglas W.
Rudisill Stephen G.
University of Strathclyde
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