Prioritization and preemption of data frames over a switching fabric

• US 7,464,180 B1
• Filed: 11/06/2002
• Issued: 12/09/2008
• Est. Priority Date: 10/16/2001
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Benning, Michael A., Jacobs, Mick R.
• Primary Examiner(s): Najjar; Saleh
• Assistant Examiner(s): Hamza; Faruk
• Application Number:
  US10/288,937
• Time in Patent Office: 2,225 Days
• Field of Search: 709/240, 709/200, 709/223, 709/238, 370/395.4, 370/395.42, 370/444, 370/419, 370/463, 370/455
• US Class Current: 709/240
• CPC Class Codes: H04L 47/2441 relying on flow classification, e.g. using integrated services [IntServ]
• CPC Class Codes: H04L 47/245 using preemption
• CPC Class Codes: H04L 49/101 using crossbar or matrix
• CPC Class Codes: H04L 49/15 Interconnection of switching modules
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/205 Quality of Service based
• CPC Class Codes: H04L 49/25 Routing or path finding in a switch fabric
• CPC Class Codes: H04L 49/254 Centralised controller, i.e. arbitration or scheduling
• CPC Class Codes: H04L 49/3018 Input queuing

Abstract

Network switching and/or routing devices can use multiple priority data streams and queues to support prioritized serial transmission of data from line cards (or the like) through a fabric switch to other line cards (or the like). Preemption logic is used to insert within a data stream commands indicating a switch from one priority level data to another. Delimiter commands and combination switch/delimiter commands can also be used. Multiple crossbars are implemented in the fabric switch to support the various data stream priority levels.

Claims

1. An apparatus comprising:

at least one input buffer operable to receive data, wherein the data includes data having a first priority level and data having a second priority level;

a first crossbar coupled to the at least one input buffer, the first crossbar operable to receive the data having the first priority level;

a second crossbar coupled to the at least one input buffer, the second crossbar operable to receive the data having the second priority level;

a first data path coupled between the at least one input buffer and the first crossbar;

a second data path coupled between the at least one input buffer and the second crossbar;

wherein the at least one input buffer is configured to simultaneously transmit data having the first priority level and data having the second priority level to the first and second crossbars, respectively, via the first and second data paths, respectively;

wherein the first and second crossbars switch the data having the first priority and the data having the second priority separately on respective corresponding ones of the first and second crossbars according to priority level; and

at least one output buffer coupled to the first crossbar and the second crossbar, the at least one output buffer operable to receive the data having the first priority level from the first crossbar and the data having the second priority level from the second crossbar.

2. The apparatus of claim 1 wherein the at least one input buffer further comprises:

a plurality of data queues, each of the plurality of data queues storing data having a particular priority.

3. The apparatus of claim 2 further comprising a memory, wherein the memory is logically organized into a first data queue and a second data queue.

4. The apparatus of claim 1 wherein the at least one input buffer includes a priority detection circuit, the priority detection circuit operable to distinguish between data having the first priority level and data having the second priority level.

5. The apparatus of claim 1 further comprising:

a plurality of line cards, each of the plurality of line cards being coupleable to at least one network device and configured to transmit/receive data to/from the at least one network device;

wherein each of the plurality of line cards is coupled to a respective one of the at least one input buffer; and

wherein each of the plurality of line cards is coupled to a respective one of the at least one output buffer.

6. The apparatus of claim 5 wherein at least one of the plurality of line cards includes a priority selection circuit, the priority selection circuit operable to generate priority level control codes and to selectively transmit data having the first priority level and data having the second priority level.

7. The apparatus of claim 1 wherein the data having the first priority level is preferentially transferred from the at least one input buffer before data having the second priority level is transferred.

8. The apparatus of claim 1 wherein the first priority level is greater than the second priority level.

9. The apparatus of claim 1 wherein the data includes data having at least one additional priority level, the apparatus further comprising:

at least one additional crossbar operable to receive the data having at least one additional priority level.

10. The apparatus of claim 1 wherein the at least one output buffer further comprises:

a plurality of data queues, each of the plurality of data queues storing data having a particular priority.

11. The apparatus of claim 10 further comprising a memory, wherein the memory is logically organized into a first data queue and a second data queue.

12. The apparatus of claim 1 wherein the at least one output buffer includes a priority selection circuit, the priority selection circuit operable to generate priority level control codes and to selectively transmit data having the first priority level and data having the second priority level.