METHOD AND APPARATUS TO MINIMIZE CONGESTION IN A PACKET SWITCHED NETWORK

• US 20030133406A1
• Filed: 11/10/1998
• Published: 07/17/2003
• Est. Priority Date: 11/10/1998
• Status: Active Grant

• Current Assignee: Arista Networks, Inc.
• Original Assignee: Extreme Networks, Inc.
• Inventors: FAWAZ, AYMAN, WALRAND, JEAN
• Granted Patent: US 6,970,424 B2
• Time in Patent Office: Days
• US Class Current: 370/229
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2425 for supporting services specification, e.g. SLA
• CPC Class Codes: H04L 47/2441 relying on flow classification, e.g. using integrated services [IntServ]
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames

Abstract

A packet-switched communication network in accordance with the invention provides a guaranteed minimum bandwidth between pairs of Packet Switches by defining Service Level Agreements (SLAs). An SLA is defined by at least a source identifier, a destination identifier, and a minimum data rate although other information can also be used. Upon arrival at certain networked nodes, packets are classified according to an SLA by reading the source and destination addresses in the packet. Once classified, the packets are placed in a queue and scheduled for transmission. A scheduler ensures that packets are transmitted at the minimum defined data rate for the SLA. The scheduler may use a statistical multiplexing method, such as deficit round robin, or deficit golden ratio, which is part of the present invention. The deficit golden ratio method assures a minimum rate to packets for a particular SLA, but minimizes jitter and delay. Further, the present invention implements congestion control that does not require nodes to be entirely turned off in congested conditions.

Claims

1. A method of controlling congestion on a network having a plurality of switching points, comprising the steps of:

sending, by a first switching point, a message to a second switching point, indicating that traffic between a source packet switch and a destination packet switch is congested;

reducing, by said second switching point, the data rate at which packets destined for said destination packet switch are output from said second switching point.

2. The method of claim 1, wherein each switching point manages a plurality of service level agreements (SLA) such that data packets corresponding to each service level agreement (SLA) are transmitted from each switching point at at least a minimum data rate corresponding to said respective SLA, and further including:

transmitting by said second switching point data packets for an SLA at a data rate greater than said minimum data rate resulting in congestion at said first switching point;

wherein said step of reducing includes, reducing said data rate for said SLA but not adjusting the data rate for other SLAs managed by said second switching point.

3. The method of claim 2, wherein said step of reducing said data rate includes reducing said data rate to said minimum data rate.

4. The method of claim 2, wherein said step of reducing said data rate includes reducing said data rate to zero.