Method for multi-priority, multicast flow control in a packet switch

• US 6,212,582 B1
• Filed: 12/29/1997
• Issued: 04/03/2001
• Est. Priority Date: 04/19/1996
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Chong, Song, Nagarajan, Ramesh, Wang, Yung-Terng
• Primary Examiner(s): Chan, Eddie
• Assistant Examiner(s): PATEL, GAUTAM
• Application Number:
  US08/999,311
• Time in Patent Office: 1,191 Days
• Field of Search: 709/234, 709/207, 709/231, 709/232, 709/233, 709/235, 370/414, 370/444, 710/56, 710/57
• US Class Current: 710/57
• CPC Class Codes: H04L 12/5602 Bandwidth control in ATM Networks, e.g. leaky bucket
• CPC Class Codes: H04L 2012/5635 Backpressure, e.g. for ABR
• CPC Class Codes: H04L 2012/5651 Priority, marking, classes
• CPC Class Codes: H04L 2012/5682 Threshold; Watermark
• CPC Class Codes: H04L 49/102 using shared medium, e.g. bus or ring
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports

Abstract

A method for controlling data packet traffic flow over a bus interconnecting two or more nodes in a data communication system, each node having a unique address associated therewith and having a respective buffer memory for temporarily holding incoming data communicated thereto, each node further being capable of multicast sending of data packets over the bus to one or more nodes having respective addresses logically associated a unique address, the method comprising: checking current available buffer memory occupancy upon receipt of a data packet, the node being capable of outputting for transmission on the bus a first flow control indicator message when the data temporarily stored in the buffer memory is above a first buffer occupancy threshold associated with data of a first priority type, and a second flow control indicator message when the data temporarily stored in the buffer memory is above a second buffer occupancy threshold, the second buffer occupancy threshold being greater than the first occupancy threshold; implementing logical flow control to prevent transmission of data packet traffic of the first priority from one or more sending nodes to two or more receive nodes logically associated with the outputting node at the priority in response to receipt of the first flow control indicator message; and, implementing physical logical flow control to prevent transmission of data packet at any data traffic priority in response to receipt of the second flow control indicator message.

Claims

1. In a data communications system having a switch fabric and one or more port cards, each port card having associated therewith at least one logical address and a physical address, and having, or coupled to, a buffer, the buffer adapted for coupling to, or being integrated into, the switch fabric, the buffer having a buffer occupancy defined as the number of memory locations in the buffer is used for storing incoming data as compared to the total number of memory locations in the buffer, a method of controlling multipriority data flow through the buffer, the multipriority data comprising a plurality of data types including a first data type having a first priority and a second data type having a second priority lower than the first priority, the first data type including one or more first-priority bit streams, and the second data type including one or more second-priority bit streams, the method comprising the steps of:

(a) monitoring the occupancy of the buffer on the port card;

(b) if the occupancy exceeds a second threshold greater than a first threshold, then disabling transmission of all second-priority bit streams destined for at least one corresponding logical address of the port card until the buffer occupancy drops below the first threshold;

(c) if the buffer occupancy drops below the first threshold, enabling transmission of all second-priority bit streams destined for the logical address of the port card previously under flow control;

(d) if the buffer occupancy exceeds a fourth threshold greater than a third threshold, then disabling transmission of all first-priority bit streams destined for at least one corresponding logical address of the port card until the buffer occupancy drops below the third threshold;

(e) if the buffer occupancy drops below the third threshold, enabling transmission of all first-priority bit streams destined to the logical address of the port card previously under flow control;

(f) determining whether the destination logical address of a received bit stream received by the port card is a multicast address;

(g) maintaining a list at the port card of all flow controlled bit streams whose destination logical address is a multicast address;

(h) disabling the transmission of all bit streams destined to the physical address of a port card having a buffer occupancy greater than a fifth threshold;

(i) if the buffer occupancy drops below the third threshold, enabling transmission of all first-priority bit streams destined to the physical address of the port card; and

(j) the buffer occupancy drops below the first threshold, enabling transmission of all second-priority bit streams destined to the physical address of the port card.

2. A flow control method as set forth in claim 1 further comprises the step of:

examining a sequence of packet arrivals corresponding to each of the bit stream and controlling the bit stream or bit streams in the order of the packet arrivals.

3. A flow control method as set forth in claim 1 wherein transmission of a multicast bit stream is disabled if one or more port cards receiving said multicast bit stream transmits a flow control signal to disable transmission of said multicast bit stream.

4. A flow control method as set forth in claim 1 wherein said enabling transmission steps further comprise the steps of:

determining whether any of said received bit streams previously under flow control were unicast or multicast transmissions;

for all unicast transmissions, transmitting a RESUME packet to itself, said RESUME packet including a flow control signal to deactivate control of all bit streams having a first priority and destined to the physical address of the port card; and

for all multicast transmissions, transmitting a RESUME packet to the logical multicast address, said RESUME packet including a flow control signal to deactivate control of all bit streams having the first priority and destined to said logical multicast address.

5. A flow control method as set forth in claim 1 wherein enabling transmission of a multicast bit stream requires a flow control signal indicating that each receiving port card of said multicast bit stream has sufficient buffer space to receive said multicast bit stream.

6. A flow control method as set forth in claim 4, further comprising the steps of:

monitoring data flow at a sending port card for a flow control signal;

if the flow control signal indicates disabling all bit streams to a second physical address and a second priority, then mapping all destination logical addresses for bit streams at said sending port card queued for transmission to said second physical address and disabling transmission of all bit streams having logical addresses mapped to said second physical address at said sending port card;

if the flow control signal indicates disabling transmission of a bit stream destined to a third logical address and having a third priority then disabling transmission of all bit streams having said third logical address and the third priority;

if the flow control signal indicates enabling transmission of a bit stream destined to a fourth physical address and having a fourth priority, then enabling transmission of all bit streams having logical addresses mapped to said fourth physical address and having the fourth priority; and

if the flow control signal indicates enabling transmission for bit streams destined to a fifth logical address and having a fifth priority, then enabling transmission of all bit streams destined to said fifth logical address and having the fifth priority.