Fibre channel credit extender and repeater

• US 7,822,055 B2
• Filed: 09/22/2008
• Issued: 10/26/2010
• Est. Priority Date: 12/10/1999
• Status: Expired due to Fees

• Current Assignee: Cavium International (Marvell Technology Group Limited)
• Original Assignee: Qlogic Switch Products Incorporated (Marvell Technology Group Limited)
• Inventors: Betker, Steven M., George, William R.
• Primary Examiner(s): Trost, IV; William
• Assistant Examiner(s): Nguyen; Toan D
• Application Number:
  US12/235,210
• Publication Number:
  US 20090046731A1
• Time in Patent Office: 764 Days
• Field of Search: 370/231, 370/232, 370/236, 370/404, 370/405, 370/406, 370/419, 398 30- 37, 398/51, 398/54, 398/57, 398/151
• US Class Current: 370/419
• CPC Class Codes: G06F 13/4045 where the bus bridge performs an extender function
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/39 Credit based

Abstract

The Fibre Channel Credit Extender (FCCE) (600) is a network device that is disposed between and connected to an end node (210) and an optical repeater (220). The FCCE (600) contains as many buffer credits as necessary, to solve bandwidth problems in a network. In a situation where maximum bandwidth is required in both directions of a link, the FCCE (600) breaks a single logical link into three physically separated “linklets.” The short-distance linklets attain maximum bandwidth by use of the existing buffer credits of the end nodes. The long-distance linklet attains maximum bandwidth by use of very high receive buffer credits in the FCCEs (600). In this way, only those links that need maximum bandwidth over distances not covered by end-node credit counts need be attached to an FCCE (600). The FCCE (600) contains the optical repeater to gain distance on that link, and contains high credit count receive buffers to gain bandwidth on the link. All other ports of the switch can have smaller and less expensive receive buffers.

Claims

1. A method for augmenting a transmission bandwidth of an existing Fibre Channel port that functions as a first node on a Fibre Channel link, the Fibre Channel link including a first linklet between the first node and a first repeater, a second linklet between the first repeater and a second repeater, and a third linklet between the second repeater and the second node, the second linklet being significantly longer than the first and third linklets, the method comprising:

receiving at a first inline link device a login request frame transmitted from the first node, wherein the first inline link device is between the first node and the first repeater in the fibre channel link;

programming a credit count for the first node contained in the login request frame into the first inline link device for use by an inbound transmitter of the first inline link device to transmit signals toward the first node;

replacing the credit count for the first node in the login request frame with a credit count for an inbound receive buffer of the first inline link device, wherein the inbound receive buffer of the first inline link device has a larger credit count than the credit count of the first node and is adapted to receive signals transmitted over the second linklet for the inbound transmitter of the first inline link device to transmit toward the first node; and

using an outbound transmitter of the first inline link, transmitting the login request frame with the credit count value of the inbound receive buffer of the first inline link device to the first repeater for transmission across the second linklet toward the second node.

2. The method of claim 1, further comprising:

receiving the login request frame at a second inline link device, wherein the second inline link device is between the second repeater and the second node;

programming the credit count for the inbound receive buffer of the first inline link device contained in the login request frame into the second inline link device for use by an outbound transmitter of the second inline link device to transmit signals toward the second repeater for transmission across the second linklet toward the first node;

replacing the credit count for the inbound receive buffer of the first inline link device in the login request frame with a credit count of an outbound receive buffer of the second inline link device, wherein the outbound receive buffer of the second inline link device is adapted to receive signals from the second node for the outbound transmitter of the second inline link device to transmit toward the second repeater for transmission across the second linklet toward the first node; and

using an inbound transmitter of the second inline link device, transmitting the login request frame with the credit count for the inbound receive buffer of the second inline link device toward the second node.

3. The method of claim 2, further comprising:

receiving the login request frame at a second node and programming the credit count for the outbound receive buffer of the second inline link device contained in the login request frame for use by a transmitter of the second node;

creating a login reply frame, wherein the reply frame includes a credit count of the second node; and

transmitting the reply frame with the credit count of the second node toward the second inline link device.

4. The method of claim 3, further comprising:

receiving the login reply frame at the second inline link device;

programming the credit count for the second node contained in the login reply frame into the second inline link device for use by the inbound transmitter of the second inline link device;

replacing the credit count for the second node in the login reply frame with a credit count for an inbound receive buffer of the second inline link device, wherein the inbound receive buffer for the second inline link device has a larger credit count than the credit count of the second node and is adapted to receive signals transmitted over the second linklet for the inbound transmitter of the second inline link device to transmit toward the second node, and

transmitting the login reply frame with the credit count for the inbound receive buffer from the second inline link device to the second repeater for transmission across the second linklet toward the first node.

5. The method of claim 4, further comprising:

receiving the login reply frame at the first inline link device;

programming the credit count for the inbound receive buffer of the second inline link device contained in the login reply frame into the first inline link device for use by the outbound transmitter of the first inline link device to transmit signals toward the first repeater for transmission across the second linklet toward the second node;

replacing the credit count for the inbound receive buffer for the second inline link device in the login reply frame with a credit count for an outbound receive buffer of the first inline link device, wherein the outbound receive buffer of the first inline link device is adapted to receive signals from the first node for the outbound transmitter of the first inline link device to transmit toward the first repeater for transmission across the second linklet toward the second node, and

using the inbound transmitter of the first inline link device, transmitting the login reply frame with the credit count for the outbound receive buffer of the first inline link device toward the first node.

6. The method of claim 5, further comprising:

receiving the login reply frame at the first end node; and

programming the credit count for the outbound receive buffer of the first inline link device contained in the login reply frame for use by a transmitter for the first node.

7. A system for transmitting signals over a fibre channel link, comprising:

a first node, a first repeater, a first inline link device between the first node and the first repeater, a second repeater, and a second node, wherein;

the fibre channel link includes a first linklet between the first node and the first repeater, a second linklet between the first repeater and the second repeater, and a third linklet between the second repeater and the second node;

the second linklet is significantly longer than the first and third linklets;

the first node includes a credit count;

the first inline link device includes an outbound receiver adapted to receive a signal from the first node, an outbound transmitter adapted to send a signal to the first repeater for transmission across the second linklet, an inbound receiver adapted to receive a signal transmitted across the second linklet, and an inbound transmitter adapted to transmit a signal to the first node, the inbound receiver having a credit count larger than the credit count of the first node;

the first node is adapted to form a login request frame with the a credit count for the first node, and transmit the login request frame; and

the first inline link device is adapted to receive the login request frame from the first node, program the credit count of the first node contained in the login request frame into a inbound transmitter of the first inline device, and replace the credit count for the first node in the login request frame with a credit count for an inbound receive buffer for the first inline device, and transmit the login request frame to the first repeater for transmission across the second linklet toward the second node.

8. The system of claim 7, further comprising:

a second inline link device between the second node and the second repeater, wherein;

the second node includes a credit count;

the second inline link device includes an outbound receiver adapted to receive a signal from the second node, an outbound transmitter adapted to send a signal to the second repeater for transmission across the second linklet, an inbound receiver adapted to receive a signal transmitted across the second linklet, and an inbound transmitter adapted to transmit a signal to the second node, the inbound receiver having a credit count larger than the credit count of the second node;

the second inline link device is adapted to receive the login request frame with the credit count for the inbound receive buffer for the first inline device, program the credit count for the inbound receive buffer for the first inline device into the outbound transmitter for the second inline link, replace the credit count for the inbound receive buffer for the first inline device in the login request frame with a credit count for the outbound receive buffer for the second inline link device, and transmit the login request frame with the credit count for the outbound receive buffer for the second inline link device to the second node.

9. The system of claim 8, wherein:

the second end node is adapted to receive the login request frame with the credit count for the inbound receive buffer of the second inline link device, program the credit count for the inbound receive buffer of the second inline link device into a transmitter of the second node, create a login reply frame with a credit count for the second node, and transmit the reply frame to the second inline link device.

10. The system of claim 9, wherein:

the second inline link device is adapted to receive the login reply frame, program the credit count for the second node into the second transmitter, replace the credit count for the second node in the login reply frame with the credit count for the inbound receive buffer of the second inline link device, and transmit the login reply frame to the second repeater for transmission across the second linklet toward the first node.

11. The system of claim 7, wherein:

the first inline link device is adapted to receive the login reply frame, program the credit count for the inbound receive buffer of the second inline link device into the outbound transmitter of the first inline link device, replace the credit count for the inbound receive buffer of the second inline link device in the login reply frame with a credit count for the outbound receive buffer of the first inline link, and transmit the login reply frame to the first node.

12. The system of claim 11, wherein:

the first node is adapted to receive the login reply frame, program the credit count for the outbound receive buffer of the first inline link into transmitter of the first node.

13. A system, comprising:

a fibre channel switch with a plurality of fabric ports;

a repeater connected to a selected one of the plurality of fabric ports through a fibre channel linklet, wherein the selected one of the plurality of fabric ports includes a number of credits; and

an inline link device connected in the fibre channel linklet between the repeater and the fibre channel switch, the inline link device including an outbound receiver associated with a first number of credits to receive data packets from the fibre channel switch, and an inbound receiver associated with a second number of credits, the second number of credits associated with the inbound receiver being larger than the first number of credits associated with the outbound receiver.

14. The system of claim 13, further comprising at least one fabric manager adapted to control initialization and credit distribution for the fibre channel switch and the inline link device.

15. The system of claim 13, wherein the repeater includes an optical repeater.

16. The system of claim 13, wherein the inline link device includes a controller adapted to:

read a buffer-to-buffer credit value from a login frame and write the buffer-to-buffer credit value to an inbound credit limit register,

replace the buffer-to-buffer credit value in the login frame with the second number of credits for the inbound receiver, and

write the login frame to a first frame buffer, wherein the first frame buffer performs a transformation from an uncoded to a coded signal.

17. The system of claim 16, wherein the inline link device further comprises:

an outbound buffer adapted to recognize that the login frame is a fabric login (FLOGI) or a processor login (PLOGI) and route the login frame to a second frame buffer adapted to perform a transformation from a coded to an uncoded signal, and adapted to send a full signal to the controller.

18. The system of claim 17, wherein the outbound receiver is adapted to receive a login frame and pass the login frame to the outbound buffer.

19. The system of claim 13, wherein the inline link device includes a controller adapted to:

read a buffer-to-buffer credit value from a login frame and write the buffer-to-buffer credit value to an outbound credit limit register,

replace the buffer-to-buffer credit value in the login frame with a value of an outbound buffer, and

write the login frame to a first frame buffer adapted to perform a transformation from an uncoded to a coded signal.

20. The system of claim 19, further comprising:

an inbound buffer adapted to recognize that the login frame is a fabric login (FLOGI) or a processor login (PLOGI) and route the login frame to a second frame buffer adapted to perform a transformation from a coded to an uncoded signal, and adapted to send a full signal to the controller.

21. The system of claim 20, wherein the inbound receiver is adapted to receive a login frame and pass the login frame to the inbound buffer.