Systems and methods for blocking transmission of a frame in a network device

• US 9,882,823 B2
• Filed: 06/08/2015
• Issued: 01/30/2018
• Est. Priority Date: 03/08/2012
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Pannell, Donald
• Primary Examiner(s): Daniel, Jr., Willie J
• Application Number:
  US14/733,370
• Publication Number:
  US 20150365338A1
• Time in Patent Office: 967 Days
• Field of Search: None
• CPC Class Codes: H04J 3/0635 Clock or time synchronisation in a network timer in protocols H04L69/28
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node
• CPC Class Codes: H04L 45/745 Address table lookup; Address filtering
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/22 Traffic shaping
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 47/56 implementing delay-aware scheduling
• CPC Class Codes: H04L 47/6215 Individual queue per QOS, rate or priority
• CPC Class Codes: H04L 49/253 using establishment or release of connections between ports

Abstract

A network device including a queue, a timing module, an adjustment module, a register module and a blocking shaper. The queue is configured to store a frame. The timing module is configured to generate a local clock signal. The adjustment module is configured to determine (i) based on a first edge of a global clock signal, an expected time of a second edge of the global clock signal, and (ii) a window centered on the expected time of the second edge of the global clock signal. The register module is configured to capture a time of a first edge of the local clock signal. The adjustment module is configured to, based on the captured time of the first edge of the local clock signal and the time of the first edge of the global clock signal, generate an adjustment signal to center a second edge of the local clock signal in the window. The blocking shaper is configured to, subsequent to adjusting the second edge of the local clock signal, block transmission of the frame from the network device based on timing of the local clock signal.

Claims

1. A network device comprising:

a first queue configured to store a frame;

a first timing module configured to generate a local clock signal;

an adjustment module configured to determine (i) based on a first edge of a first cycle of a global clock signal, an expected time of a second edge of a second cycle of the global clock signal, and (ii) a window centered on the expected time of the second edge of the global clock signal, wherein each of the first edge and the second edge is a rising edge or a falling edge of the global clock signal;

a register module configured to capture a time of a first edge of a first cycle of the local clock signal,

wherein the adjustment module is configured to, based on the captured time of the first edge of the local clock signal and the time of the first edge of the global clock signal, generate an adjustment signal to center a second edge of a second cycle of the local clock signal in the window, and wherein each of the first edge of the local clock signal and the second edge of the local clock signal is a rising edge or a falling edge of the local clock signal; and

a blocking shaper configured to, subsequent to adjusting the second edge of the local clock signal, block transmission of the frame from the network device based on timing of the local clock signal.

2. The network device of claim 1, further comprising:

a plurality of ports, wherein each of the plurality of ports comprises (i) a plurality of queues, (ii) an egress module, and (iii) a respective one of a plurality of queue state tables, wherein each of the plurality of queue state tables comprises a plurality of entries, wherein each of the entries comprises a state of a respective one of the plurality of queues for the corresponding port, wherein the plurality of ports comprise a first port, wherein the first port comprises the first queue, and

wherein each of the egress modules is configured to cycle through the plurality of entries in a corresponding one of the plurality of queue state tables; and

a memory configured to store a port table, wherein the port table comprises a plurality of delays respectively for the plurality of ports,

wherein each of the egress modules is configured to, based on the respective delay, start cycling through the plurality of queues for the corresponding port.

3. The network device of claim 2, wherein:

the egress module of the first port is configured to, based on the corresponding delay in the port table, delay from an edge of the local clock signal cycling of the plurality of entries in the corresponding one of the plurality of queue state tables; and

each of the egress modules of the plurality of ports other than the first port is configured to, based on the corresponding delays in the port table, delay from an operation performed by a consecutively prior one of the plurality of ports cycling of the plurality of entries in the corresponding one of the plurality of queue state tables.

4. The network device of claim 3, wherein the first timing module or the adjustment module is configured to adjust timing of the local clock signal to adjust cycle start times of the plurality of ports through the plurality of tables.

5. The network device of claim 4, wherein the first timing module or the adjustment module is configured to adjust timing of the local clock signal without adjusting the delays of the port table.

6. The network device of claim 4, wherein the first timing module or the adjustment module is configured to adjust timing of the local clock signal without adjusting durations or delays of the plurality of queue state tables of the plurality of ports.

7. The network device of claim 1, wherein the adjustment module is configured to:

if the captured time of the first edge of the local clock signal is not within a predetermined range of the time of the first edge of the global clock signal, refrain from adjusting timing of the local clock signal; and

if the captured time of the first edge of the local clock signal is within the predetermined range of the time of the first edge of the global clock signal, adjust the timing of the local clock signal such that the second edge of the local clock signal is centered in the window.

8. The network device of claim 1, wherein the timing module is configured to generate the local clock signal based on the global clock signal.

9. The network device of claim 1, further comprising a second timing module configured to generate a trigger signal based on the global clock signal,

wherein the register module is configured to, based on the trigger signal, capture the time of the first edge of the local clock signal.

10. The network device of claim 1, wherein the register module is configured to, based on the global clock signal, capture the time of the first edge of the local clock signal.

11. The network device of claim 1, further comprising a memory configured to store a table, wherein:

the table includes a plurality of delay times;

the plurality of delay times are for respective ports of the network device; and

operational timing of the ports is based on (i) the plurality of delay times, and (ii) the local clock signal.

12. The network device of claim 11, wherein the plurality of delay times refer to respective amounts of delay from an edge of the global clock signal or the local clock signal.

13. The network device of claim 1, further comprising:

a memory configured to store a table, wherein the table includes a plurality of entries, wherein each of the plurality of entries includes (i) a state for a respective one of a plurality of queues, and (ii) a duration time to remain in the corresponding state; and

an egress module configured to cycle through the plurality of entries of the table,

wherein the blocking shaper is configured to, based on a current one of the plurality of entries, block the frame from being transmitted from the network device.

14. The network device of claim 1, further comprising:

a memory configured to store a table, wherein the table includes a plurality of entries, wherein each of the plurality of entries includes (i) a state for a respective one of a plurality of queues, and (ii) a delay time to wait prior to permitting transmission from a corresponding queue; and

an egress module configured to cycle through the plurality of entries of the table,

wherein the blocking shaper is configured to, based on a current one of the plurality of entries, block the frame from being transmitted from the network device.

15. The network device of claim 1, wherein the adjustment module is configured to adjust timing of the second edge of the local clock signal to be centered in the window to account for drift between the local clock signal and the global clock signal.

16. The network device of claim 1, wherein:

a phase difference between the local clock signal and the global clock signal varies; and

subsequent to synchronization of the local clock signal to the global clock signal and prior to the adjustment module generating the adjustment signal, the local clock signal drifts from the global clock signal.

17. The network device of claim 16, wherein the local clock signal drifts from the global clock signal due to at least one of (i) a difference in operation between a local clock circuit of the local clock signal and a global clock circuit of the global clock signal, (ii) a duration of operation of the local clock circuit and the global clock circuit, and (iii) a temperature of the local clock circuit and a temperature of the global clock circuit.

18. A network device comprising:

a first queue configured to store a frame;

a timing module configured to generate a local clock signal;

a plurality of ports, wherein each of the plurality of ports comprises (i) a plurality of queues, (ii) an egress module, and (iii) a respective one of a plurality of queue state tables, wherein each of the plurality of queue state tables comprises a plurality of entries, wherein each of the entries comprises a state of a respective one of the plurality of queues for the corresponding port, wherein the plurality of ports comprise a first port, wherein the first port comprises the first queue, and

wherein each of the egress modules is configured to cycle through the plurality of entries in a corresponding one of the plurality of queue state tables; and

a memory configured to store a port table, wherein the port table comprises a plurality of delays respectively for the plurality of ports,

wherein

each of the egress modules is configured to, based on the respective delay, start cycling through the plurality of queues for the corresponding port,

the egress module of the first port is configured to, based on the corresponding delay in the port table, delay from an edge of the local clock signal cycling through the plurality of entries in the corresponding one of the plurality of queue state tables; and

each of the egress modules of the plurality of ports other than the first port is configured to, based on the corresponding delays in the port table, delay from an operation performed by a consecutively prior one of the plurality of ports cycling through the plurality of entries in the corresponding one of the plurality of queue state tables.

19. A method of operating a network device, wherein the network device comprises a first queue, the method comprising:

storing a frame in the first queue;

generating a local clock signal;

determining (i) based on a first edge of a first cycle of a global clock signal, an expected time of a second edge of a second cycle of the global clock signal, and (ii) a window centered on the expected time of the second edge of the global clock signal, wherein each of the first edge and the second edge is a rising edge or a falling edge of the global clock signal;

capturing a time of a first edge of a first cycle of the local clock signal;

based on the captured time of the first edge of the local clock signal and the time of the first edge of the global clock signal, generating an adjustment signal to center a second edge of a second cycle of the local clock signal in the window, wherein each of the first edge of the local clock signal and the second edge of the local clock signal is a rising edge or a falling edge of the local clock signal; and

subsequent to adjusting the second edge of the local clock signal, blocking transmission of the frame from the network device based on timing of the local clock signal.

20. The method of claim 19, wherein the network device comprises a plurality of ports, wherein each of the plurality of ports comprises (i) a plurality of queues, (ii) an egress module, and (iii) a respective one of a plurality of queue state tables, wherein each of the plurality of queue state tables comprises a plurality of entries, wherein each of the entries comprises a state of a respective one of the plurality of queues for the corresponding port, wherein the plurality of ports comprise a first port, wherein the first port comprises the first queue, the method further comprising:

via each of the egress modules, cycling through the plurality of entries in a corresponding one of the plurality of queue state tables;

storing a port table, wherein the port table comprises a plurality of delays respectively for the plurality of ports; and

via each of the egress modules and based on the respective delay, start cycling through the plurality of queues for the corresponding port.

21. The method of claim 20, further comprising:

via the egress module of the first port and based on the corresponding delay in the port table, delaying from an edge of the local clock signal cycling of the plurality of entries in the corresponding one of the plurality of queue state tables; and

via each of the egress modules of the plurality of ports other than the first port and based on the corresponding delays in the port table, delaying from an operation performed by a consecutively prior one of the plurality of ports cycling of the plurality of entries in the corresponding one of the plurality of queue state tables.

22. The method of claim 21, further comprising adjusting timing of the local clock signal to adjust cycle start times of the plurality of ports through the plurality of tables.

23. The method of claim 22, further comprising adjusting timing of the local clock signal without adjusting the delays of the port table.

24. The method of claim 22, further comprising adjusting timing of the local clock signal without adjusting durations or delays of the plurality of queue state tables of the plurality of ports.

25. The method of claim 19, further comprising:

if the captured time of the first edge of the local clock signal is not within a predetermined range of the time of the first edge of the global clock signal, refraining from adjusting timing of the local clock signal; and

if the captured time of the first edge of the local clock signal is within the predetermined range of the time of the first edge of the global clock signal, adjusting the timing of the local clock signal such that the second edge of the local clock signal is centered in the window.

26. The method of claim 19, further comprising generating the local clock signal based on the global clock signal.

27. The method of claim 19, further comprising generating a trigger signal based on the global clock signal,

wherein the time of the first edge of the local clock signal is captured based on the trigger signal.

28. The method of claim 19, wherein the time of the first edge of the local clock signal is captured based on the global clock signal.

29. The method of claim 19, further comprising:

storing a table, wherein the table includes a plurality of delay times, and wherein the plurality of delay times are for respective ports of the network device; and

controlling operational timing of the ports based on (i) the plurality of delay times, and (ii) the local clock signal.

30. The method of claim 29, wherein the plurality of delay times refer to respective amounts of delay from an edge of the global clock signal or the local clock signal.

31. The method of claim 19, further comprising:

storing a table, wherein the table includes a plurality of entries, wherein each of the plurality of entries includes (i) a state for a respective one of a plurality of queues, and (ii) a duration time to remain in the corresponding state;

via an egress module of the network device, cycling through the plurality of entries of the table; and

based on a current one of the plurality of entries, blocking the frame from being transmitted from the network device.

32. The method of claim 19, further comprising:

storing a table, wherein the table includes a plurality of entries, wherein each of the plurality of entries includes (i) a state for a respective one of a plurality of queues, and (ii) a delay time to wait prior to permitting transmission from a corresponding queue;

via an egress module of the network device, cycling through the plurality of entries of the table; and

based on a current one of the plurality of entries, blocking the frame from being transmitted from the network device.