Method and system for managing time division multiplexing (TDM) timeslots in a network switch

• US 20030026287A1
• Filed: 07/31/2002
• Published: 02/06/2003
• Est. Priority Date: 07/31/2001
• Status: Active Grant

• Current Assignee: Brocade Communications Systems, Inc. (Broadcom, Inc.)
• Original Assignee: Brocade Communications Systems, Inc. (Broadcom, Inc.)
• Inventors: Mehta, Anil, Oberman, Stuart F., Mullendore, Rodney N., Schakel, Keith, Malik, Kamran
• Granted Patent: US 7,283,556 B2
• Time in Patent Office: Days
• US Class Current: 370/442
• CPC Class Codes: H04L 49/103 using a shared central buffer; using a shared memory
• CPC Class Codes: H04L 49/3018 Input queuing
• CPC Class Codes: H04L 49/3027 Output queuing
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/357 Fibre channel switches
• CPC Class Codes: H04Q 11/04 for time-division multiplexing H04Q11/0001 takes precedence
• CPC Class Codes: H04Q 2213/13292 Time division multiplexing, TDM
• CPC Class Codes: H04Q 2213/13296 Packet switching, X.25, frame relay
• CPC Class Codes: H04Q 2213/13332 Broadband, CATV, dynamic bandwidth allocation
• CPC Class Codes: H04Q 2213/13389 LAN, internet

Abstract

A system and method for managing the allocation of Time Division Multiplexing (TDM) timeslots in a network switch. The network switch may use a TDM cycle comprising multiple timeslots to manage shared resources and to schedule data ingress and egress through the ports of the current configuration, wherein each port is assigned one or more timeslots. The network switch may be reprogrammed to support one of multiple timeslot assignment schemes for one of multiple port configurations. The network switch may support configurations with varying numbers of ports, e.g. 8- and 16-port configurations. A network switch may also support configurations where two or more ports are combined to form one port, for example, a 2 Gbs Fibre Channel port. To meet the requirements of the various configurations, the timeslot assignment scheme may be reprogrammed to meet the scheduling requirements of each of the possible port configurations.

Claims

1. A method for managing the assignment of Time Division Multiplexing (TDM) timeslots of a TDM cycle in a network switch comprising a plurality of ports, the method comprising:

programming the network switch to support a first TDM timeslot assignment scheme for a first subset of the plurality of ports in a first port configuration;

reprogramming the network switch to support a second TDM timeslot assignment scheme for a second subset of the plurality of ports in a second port configuration;

wherein, in a current port configuration, a subset of the plurality of ports are configured to receive input data and to convey output data for the network switch;

wherein the network switch is configured to schedule the receiving of the input data and the conveying of the output data through the subset of the plurality of ports in the current port configuration using a currently programmed TDM timeslot assignment scheme associated with the current port configuration; and

wherein, in the current port configuration, the subset of the plurality of ports are each assigned one or more timeslots of the currently programmed TDM timeslot assignment scheme.

2. The method as recited in claim 1, wherein the network switch further comprises one or more programmable registers, the method further comprising:

storing the currently programmed TDM timeslot assignment scheme in the one or more programmable registers;

wherein the network switch is configured to access the currently programmed TDM timeslot assignment scheme from the one or more programmable registers when scheduling data through the subset of the plurality of ports in the current port configuration.

3. The method as recited in claim 1, wherein the first subset of the plurality of ports in the first port configuration comprises N ports, and wherein the second subset of the plurality of ports in the second port configuration comprises 2N ports, where N is a positive integer.

4. The method as recited in claim 3, where N is 8.

5. The method as recited in claim 3, wherein the TDM cycle comprises a first group of consecutive read timeslots and a second group of consecutive write timeslots.

6. The method as recited in claim 5, wherein the TDM cycle further comprises a first turnaround timeslot after the last read timeslot and a second turnaround timeslot after the last write timeslot, wherein the first turnaround timeslot is used for transitioning from read to write operations and the second turnaround timeslot is used for transitioning from write to read operations.

7. The method as recited in claim 5, wherein the first group comprises 2N read timeslots and the second group comprises 2N write timeslots.

8. The method as recited in claim 5, wherein each of the N ports in the first port configuration is assigned two read timeslots and two write timeslots in the TDM cycle.

9. The method as recited in claim 8, wherein the two read timeslots for each of the N ports are adjacent to each other, and wherein the two write timeslots for each of the N ports are adjacent to each other.

10. The method as recited in claim 5, wherein each of the 2N ports in the second port configuration is assigned one read timeslot and one write timeslot in the TDM cycle.

11. The method as recited in claim 10, wherein

the assigned read timeslots for a first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned read timeslots for a second group of N consecutive ports of the 2N ports in the second port configuration;

and

wherein the assigned write timeslots for the first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned write timeslots for the second group of N consecutive ports of the 2N ports in the second port configuration.

12. The method as recited in claim 5,

wherein each of the N ports in the first port configuration is assigned two read timeslots and two write timeslots in the TDM cycle, wherein the two read timeslots for each of the N ports are adjacent to each other, and wherein the two write timeslots for each of the N ports are adjacent to each other;

and

wherein each of the 2N ports in the second port configuration is assigned one read timeslot and one write timeslot in the TDM cycle, wherein the assigned read timeslots for a first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned read timeslots for a second group of N consecutive ports of the 2N ports in the second port configuration, and wherein the assigned write timeslots for the first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned write timeslots for the second group of N consecutive ports of the 2N ports in the second port configuration.

13. The method as recited in claim 1, wherein the first subset of the plurality of ports in the first port configuration includes one or more 2-Gigabit Fibre Channel ports formed by combining at least two ports of the plurality of ports in the network switch.

14. The method as recited in claim 13, wherein the network switch comprises M ports, and wherein the TDM cycle comprises 2 M timeslots for reading and writing packets, where M is an integer greater than 1.

15. The method as recited in claim 14, wherein each of the one or more 2-Gigabit Fibre Channel ports is assigned one timeslot in the TDM cycle for each of the ports combined to form the 2 Gigabit Fibre Channel port.

16. The method as recited in claim 14, wherein two adjacent ports are combined to form each 2 Gigabit Fibre Channel port, wherein one timeslot in the TDM cycle is assigned to each 2 Gigabit Fibre Channel port for each of the two adjacent ports combined to form the 2-Gigabit Fibre Channel port, and wherein the two assigned timeslots for each 2-Gigabit Fibre Channel port are at least M timeslots apart in the TDM cycle.

17. The method as recited in claim 1, wherein the first subset of the plurality of ports in the first port configuration includes 1-Gigabit Fibre Channel ports, and wherein the second subset of the plurality of ports in the second port configuration includes 2-Gigabit Fibre Channel ports.

18. The method as recited in claim 1, wherein the first subset of the plurality of ports in the first port configuration includes one or more of Gigabit Ethernet ports, 1-Gigabit Fibre Channel ports, and 2-Gigabit Fibre Channel Ports, and wherein the second subset of the plurality of ports in the second port configuration includes one or more of Gigabit Ethernet ports, 1-Gigabit Fibre Channel ports, and 2-Gigabit Fibre Channel Ports.

19. A network switch comprising:

a plurality of ports configured to receive input data and to convey output data for the network switch;

scheduler logic coupled to the plurality of ports, wherein the scheduler logic is configured to schedule the receiving of the input data and the conveying of the output data through the plurality of ports using a Time Division Multiplexing (TDM) cycle comprising a plurality of timeslots;

wherein the network switch is programmable to implement any of a plurality of TDM timeslot assignment schemes for the TDM cycle, wherein each of the plurality of TDM timeslot assignment schemes supports a different port configuration of the network switch, wherein each port configuration supports a subset of the plurality of ports, wherein each TDM timeslot assignment scheme assigns one or more timeslots to each port that is present in the subset of the plurality of ports that is supported by the particular port configuration; and

wherein the network switch is reprogrammable from a current TDM timeslot assignment scheme supporting a current port configuration of the network switch to a new TDM timeslot assignment scheme supporting a new port configuration of the network switch.

20. The network switch as recited in claim 19, further comprising one or more programmable registers, wherein the programmable registers are configured to store the current TDM timeslot assignment scheme programmed into the network switch, and wherein the scheduler logic is configured to access the current TDM timeslot assignment scheme from the one or more programmable registers during said scheduling data through the plurality of ports.

21. The network switch as recited in claim 20, further comprising a Time Division Multiplexed (TDM) random access memory configured to store received data for the network switch, wherein the scheduler logic is coupled between the memory and the ports.

22. The network switch as recited in claim 19, wherein the current port configuration supports N ports of the plurality of ports, and wherein the new port configuration supports 2N ports of the plurality of ports, where N is a positive integer.

23. The network switch as recited in claim 22, where N is 8.

24. The network switch as recited in claim 22, wherein the TDM cycle comprises a first group of consecutive read timeslots and a second group of consecutive write timeslots.

25. The network switch as recited in claim 24, wherein the TDM cycle further comprises a first turnaround timeslot after the last read timeslot and a second turnaround timeslot after the last write timeslot, wherein the first turnaround timeslot is used for transitioning from read to write operations and the second turnaround timeslot is used for transitioning from write to read operations.

26. The network switch as recited in claim 24, wherein the first group comprises 2N read timeslots and the second group comprises 2N write timeslots.

27. The network switch as recited in claim 24, wherein each of the N ports in the current port configuration is assigned two read timeslots and two write timeslots in the TDM cycle.

28. The network switch as recited in claim 27, wherein the two read timeslots for each of the N ports in the current port configuration are adjacent to each other, and wherein the two write timeslots for each of the N ports in the current port configuration are adjacent to each other.

29. The network switch as recited in claim 24, wherein each of the 2N ports in the new port configuration is assigned one read timeslot and one write timeslot in the TDM cycle.

30. The network switch as recited in claim 29,

wherein the assigned read timeslots for a first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned read timeslots for a second group of N consecutive ports of the 2N ports in the second port configuration;

and

wherein the assigned write timeslots for the first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned write timeslots for the second group of N consecutive ports of the 2N ports in the second port configuration.

31. The network switch as recited in claim 24,

wherein each of the N ports in the current port configuration is assigned two read timeslots and two write timeslots in the TDM cycle, wherein the two read timeslots for each of the N ports are adjacent to each other, and wherein the two write timeslots for each of the N ports are adjacent to each other;

and

wherein each of the 2N ports in the new port configuration is assigned one read timeslot and one write timeslot in the TDM cycle, wherein the assigned read timeslots for a first group of N consecutive ports of the 2N ports in the new port configuration are interleaved with the assigned read timeslots for a second group of N consecutive ports of the 2N ports in the new port configuration, and wherein the assigned write timeslots for the first group of N consecutive ports of the 2N ports in the new port configuration are interleaved with the assigned write timeslots for the second group of N consecutive ports of the 2N ports in the new port configuration.

32. The network switch as recited in claim 19, wherein said current port configuration includes one or more 2-Gigabit Fibre Channel ports formed by combining at least two ports of the plurality of ports in the network switch.

33. The network switch as recited in claim 32, wherein the network switch comprises M ports, and wherein the TDM cycle comprises 2M timeslots for reading and writing packets, where M is an integer greater than 1.

34. The network switch as recited in claim 33, wherein each of the one or more 2-Gigabit Fibre Channel ports is assigned one timeslot in the TDM cycle for each of the ports combined to form the 2-Gigabit Fibre Channel port.

35. The network switch as recited in claim 33, wherein two adjacent ports are combined to form each 2-Gigabit Fibre Channel port, wherein one timeslot in the TDM cycle is assigned to each 2-Gigabit Fibre Channel port for each of the two adjacent ports combined to form the 2-Gigabit Fibre Channel port, and wherein the two assigned timeslots for each 2-Gigabit Fibre Channel port are at least M timeslots apart in the TDM cycle.

36. The network switch as recited in claim 19, wherein the current port configuration includes 1-Gigabit Fibre Channel ports, and wherein the new port configuration includes 2-Gigabit Fibre Channel ports.

37. The network switch as recited in claim 19, wherein the current port configuration includes one or more of Gigabit Ethernet ports, 1-Gigabit Fibre Channel ports, and 2-Gigabit Fibre Channel Ports, and wherein the new port configuration includes one or more of Gigabit Ethernet ports, 1-Gigabit Fibre Channel ports, and 2-Gigabit Fibre Channel Ports.

38. A network switch comprising:

a plurality of ports configured to receive input data and to convey output data for the network switch; and

scheduler logic coupled to the ports, wherein the scheduler logic is configured to schedule the receiving of input data and the conveying of output data through the plurality of ports using a TDM cycle comprising a plurality of timeslots;

wherein the network switch is programmable to implement a first port configuration supporting N network switch ports and a second port configuration supporting 2N network switch ports, where N is a positive integer;

wherein the TDM cycle comprises a first group of consecutive read timeslots and a second group of consecutive write timeslots, wherein the first group comprises 2N read timeslots and the second group comprises 2N write timeslots;

wherein each of the N ports in the first port configuration is assigned two read timeslots and two write timeslots in the TDM cycle, wherein the two read timeslots for each of the N ports are adjacent to each other, and wherein the two write timeslots for each of the N ports are adjacent to each other;

wherein each of the 2N ports in the second port configuration is assigned one read timeslot and one write timeslot in the TDM cycle;

wherein the assigned read timeslots for a first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned read timeslots for a second group of N consecutive ports of the 2N ports in the second port configuration; and

wherein the assigned write timeslots for the first group of N consecutive ports of the 2N ports in the second port configuration are interleaved with the assigned write timeslots for the second group of N consecutive ports of the 2N ports in the second port configuration.

39. The network switch as recited in claim 38, where N is 8.

40. The network switch as recited in claim 38, wherein said first port configuration includes one or more of Gigabit Ethernet ports, 1-Gigabit Fibre Channel ports, and 2-Gigabit Fibre Channel Ports, and wherein said second port configuration includes one or more of Gigabit Ethernet ports, 1-Gigabit Fibre Channel ports, and 2-Gigabit Fibre Channel Ports.

41. A network switch comprising:

a plurality of ports configured to receive input data and to convey output data for the network switch; and

scheduler logic coupled to the ports, wherein the scheduler logic is configured to schedule the receiving of input data and the conveying of output data through the plurality of ports using a TDM cycle comprising a plurality of timeslots;

wherein the network switch comprises M ports, and wherein the TDM cycle comprises 2M timeslots for reading and writing packets, where M is an integer greater than 1;

wherein the network switch is programmable to implement a port configuration including one or more 2-Gigabit Fibre Channel ports, wherein each of the one or more 2-Gigabit Fibre Channel ports is formed by combining two of the M network switch ports;

wherein each 2-Gigabit Fibre Channel port is assigned two timeslot in the TDM cycle, with one timeslot for each of the two network switch ports combined to form the 2-Gigabit Fibre Channel port; and

wherein the two assigned timeslots for each 2-Gigabit Fibre Channel port are at least M timeslots apart in the TDM cycle.