Network switch supporting rate-based and credit-based flow control mechanisms on a link-by-link basis

• US 6,452,903 B1
• Filed: 05/31/2000
• Issued: 09/17/2002
• Est. Priority Date: 05/31/2000
• Status: Expired due to Fees

• Current Assignee: Fujitsu Network Communications Incorporated (Fujitsu Limited)
• Original Assignee: Fujitsu Network Communications Incorporated (Fujitsu Limited)
• Inventors: Manning, Thomas A., Peck, David N.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): LY, ANH VU H
• Application Number:
  US09/583,608
• Time in Patent Office: 839 Days
• Field of Search: 370/229, 370/230, 370/230.1, 370/231, 370/232, 370/233, 370/235, 370/236.1, 370/236.2, 370/241.1, 370/395.1, 370/396, 370/395.5, 370/395.51, 370/395.6, 370/400, 370/465, 370/466, 370/469
• US Class Current: 370/235
• CPC Class Codes: H04L 12/56 Packet switching systems
• CPC Class Codes: H04L 2012/5635 Backpressure, e.g. for ABR
• CPC Class Codes: H04L 2012/5681 Buffer or queue management
• CPC Class Codes: H04L 49/3081 ATM peripheral units, e.g. policing, insertion or extraction
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

Network interface logic includes first logic executing a credit-based flow-control protocol (e.g., Quantum Flow Control or QFC) and second logic executing a rate-based flow control protocol (e.g. Explicit Rate or ER). The second logic transfers data cells between a network link and the first logic and inserts and extracts forward (FRM) and backward (BRM) flow-control/resource management (RM) cells. The second logic further (i) obtains cell buffer utilization information from the first logic, (ii) supplies transmission credits to the first logic based on rate information in BRM cells, (iii) induces the first logic to emit “dummy” RM cells when an RM cell is to be transmitted, and (iv) converts the dummy cells to either FRM or DRM cells for forwarding on the link. Rate information in the transmitted RM cells is calculated from the buffer utilization information and rate information in extracted BRM cells.

Claims

1. Network interface logic for use with a network link of either a first type or a second type, the first type of network link using a credit-based flow-control protocol, and the second type of network link using a rate-based flow-control protocol, the network interface logic comprising:

first cell processing logic operative to receive cells from the network link and to emit cells for transmission on the network link according to the credit-based flow-control protocol; and

second cell processing logic disposed between the network link and the first cell processing logic, the second cell processing logic being operative when the network link is of the first type to transfer flow-control cells between the network link and the first cell processing logic, and the second cell processing logic being operative when the network link is of the second type to (i) receive flow-control cells from the network and extend transmission credits to the first cell processing logic based on rate information contained in the received flow-control cells, and (ii) receive cell buffer status information from the first cell processing logic and generate and emit flow-control cells for transmission on the network link, the emitted flow-control cells. containing rate information calculated from the received cell buffer status information.

2. Network interface logic according to claim 1, wherein the first cell processing logic is further operative to generate and emit flow-control cells for transmission on the network link in response to flow-control messages supplied thereto, the emitted flow-control cells being formatted according to the credit-based flow-control protocol, and wherein the second cell processing logic is further operative when the network link is of the second type to (i) induce the first cell processing logic to generate and emit flow-control cells when flow-control cells are to be transmitted on the network link in accordance with the rate-based flow control protocol, and (ii) convert each flow-control cell emitted by the first cell processing logic to a flow-control cell formatted according to the rate-based flow-control protocol.

3. Network interface logic according to claim 1, wherein the flow-control cells received and emitted by the second cell processing logic are backward flow-control cells, and wherein the second cell processing logic is further operative when the network link is of the second type to (i) receive forward flow-control cells from the network link, the forward flow-control cells containing information about the rate at which cells are allowed to be transmitted on the network link by a remote transmitter at the other end of the network link, (ii) utilize the rate information from the received forward flow-control cells in calculating the rate information included in the backward flow-control cells generated and emitted by the second cell processing logic, (iii) calculate forward rate information based on the rate information in the received backward flow-control cells, and (iv) generate and emit forward flow-control cells containing the forward rate information for transmission on the network link.

4. Network interface logic according to claim 1, wherein the first cell processing logic separate receive and transmit logic, and wherein the second cell processing logic is further operative when the network link is of the first type to receive cell buffer status information from the receive logic and to forward the cell buffer status information to the transmit logic for use in controlling the transmission of cells on the network link in accordance with the credit-based flow-control protocol.

5. Network interface logic for use with a network link of either a first type or a second type, the first type of network link using a credit-based flow-control protocol, and the second type of network link using a rate-based flow-control protocol, the network interface logic comprising:

first cell processing logic operative to receive cells from the network link and to emit cells for transmission on the network link according to the credit-based flow-control protocol, the first cell processing logic including (i) a cell buffer memory in which received data cells are temporarily stored, and (ii) flow-control logic operative to control the emission of cells based on transmission credit information supplied thereto and to emit flow-control resource management (RM) cells for transmission on the network link in response to buffer state messages supplied thereto; and

second cell processing logic disposed between the network link and the first cell processing logic, the second cell processing logic being operative when the network link is of the first type to transfer data cells and RM cells between the network link and the first cell processing logic, and the second cell processing logic being operative when the network link is of the second type to;

(i) transfer data cells between the network link and the first cell processing logic;

(ii) extract RM cells received from the network link and refrain from forwarding the extracted RM cells to the first cell processing logic, the extracted RM cells including forward RM (FRM) cells and backward RM (BRM) cells, the FRM cells containing information about the rate at which cells are allowed to be transmitted on the network link by a remote transmitter, the BRM cells containing information about the rate at which cells should be transmitted on the network link to a remote receiver;

(iii) exchange buffer state messages with the first cell processing logic to (1) obtain information about the utilization of the cell buffer memory by received cells, (2) supply transmission credit information to the first cell processing logic, the transmission credit information being calculated from predetermined rate parameters and the rate information in the extracted BRM cells, and (3) induce the first cell processing logic to generate and emit RM cells when BPM and FPM cells are to be transmitted on the network link in accordance with the rate-based flow control protocol; and

(iv) convert each PM cell emitted by the first cell processing logic to either an FRM cell or a BRM cell and forward the FRM or BRM cell to the network link, each BRM cell containing feedback rate information calculated from the rate information in a corresponding extracted FRM cell and from the buffer utilization information received from the first cell processing logic, and each FRM cell containing forward rate information calculated from the predetermined rate parameters and the rate information in the extracted BRM cells.