Method and apparatus for scheduling access to a CSMA communication medium

• US 5,175,537 A
• Filed: 11/23/1990
• Issued: 12/29/1992
• Est. Priority Date: 03/29/1990
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: Micron Technology, Inc.
• Inventors: Jaffe, David H., Johnson, Hoke S. III, Eidler, Chris W.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Weissman, Peter S.
• Application Number:
  US07/617,218
• Time in Patent Office: 767 Days
• Field of Search: 340/825.5, 379/111, 379/113, 379/131, 379/133, 379/137, 370/85.2, 370/61, 455/54, 455/58, 455/54.2, 455/58.2, 364/239.1, 364/240.9, 364/949.91
• US Class Current: 370/447
• CPC Class Codes: C07C 251/48 with the carbon atom of at least one of the oxyimino groups bound to a carbon atom of a six-membered aromatic ring
• CPC Class Codes: C07C 255/64 with the nitrogen atoms further bound to oxygen atoms
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/13 in a LAN segment, e.g. ring or bus
• CPC Class Codes: H04L 47/29 using a combination of thresholds

Abstract

A scheduling mechanism is provided for controlling when the arbitration circuit of a node sharing a CSMA communication medium is to start CSMA arbitration for access to the communication medium once the node has a message ready for transmission, the scheduling mechanism delaying the arbitration circuit from seeking access if total transmission activity on the communication medium exceeds a total use threshold value and transmission activity of the node exceeds a local use threshold value, and otherwise permitting the arbitration circuit to seek access to the communication medium by arbitration in accordance with a priority value assigned to the node.

Claims

1. In a network including a plurality of nodes, a system implemented within a first network node for limiting the rate at which the first network node transmits sequential transmissions to a second node in the network which also receives transmissions from other network nodes, the system comprising:

means for determining a dynamic estimate of the data handling capability of the second node from past transmissions between the first and second nodes, independently of any source of information directly indicative of the total data handling load on the second node caused by transmissions from the first and other network nodes;

means for defining a minimum delay period for sequential transmissions to the second node as a function of the determined estimate of the data handling capability of the second node; and

means for delaying a scheduled transmission to the second node if the minimum delay period has not elapsed since a prior transmission from the first node to the second node.

2. The system of claim 1, wherein the means for determining an estimate of the data handling capability of the second node comprises means for detecting over an interval the number of negative acknowledgment responses received from the second node in response to attempted transmissions from the first node to the second node.

3. The system of claim 1, further comprising means for interleaving transmissions to different nodes in the network during the delay of a transmission to the second node by the delaying means.