Memory architecture for high speed network devices

• US 8,077,610 B1
• Filed: 06/12/2006
• Issued: 12/13/2011
• Est. Priority Date: 02/22/2006
• Status: Active Grant

• Current Assignee: Marvell Israel MISL Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell Israel MISL Limited (Marvell Technology Group Limited)
• Inventors: Arad, Carmi, Nachum, Youval
• Primary Examiner(s): Ahmed, Salman
• Application Number:
  US11/453,349
• Time in Patent Office: 2,010 Days
• Field of Search: 370/229, 370/395, 370/412, 370/419, 370/428, 370/463, 370/413, 370/423, 370/424, 370/230.1, 370/235, 370/389, 370/392, 370/395.3, 370/4, 370/395.42, 370/230, 707/10, 707/E17.034, 711/1
• US Class Current: 370/230
• CPC Class Codes: H04L 45/60 Router architectures
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports

Abstract

An embodiment of the present invention reduces certain memory bandwidth requirements when sending a multicast message from a network device such as a router, bridge or switch. Separate output buffers are provided for different groups of egress ports, and incoming messages are written to some or all of the output buffers. A processing determination is made as to which egress ports will forward the message. Buffers associated with non-forwarding ports are released and the message is queued at the forwarding egress ports. When the message is forwarded, data is read from the output buffers associated with the forwarding egress ports.

Claims

1. A method of forwarding a data packet using different sets of buffers of a network device, the method comprising:

writing the data packet to a first set of buffers coupled with a first set of egress ports for the network device before determining whether to forward the data packet through the first set of egress ports based on accessing at least one forwarding database;

writing the data packet to a second set of buffers coupled with a second set of egress ports for the network device before determining whether to forward the data packet through the second set of egress ports based on accessing the at least one forwarding database;

determining whether to forward the data packet through the first set of egress ports or the second set of egress ports based on accessing the at least one forwarding database;

releasing the first set of buffers if it is determined that the data packet is to be forwarded through the second set of egress ports and not to be forwarded through the first set of egress ports; and

forwarding the data packet from the second set of buffers through a subset of the second set of egress ports if it is determined that the data packet is to be forwarded through the second set of egress ports.

2. The method of claim 1, further comprising:

queuing the data packet for forwarding through the subset of the second set of egress ports, wherein the releasing step occurs before the data packet is queued.

3. The method of claim 1, wherein releasing the first set of buffers comprises:

identifying the first set of buffers as available.

4. The method of claim 1, further comprising:

accessing a forwarding database to determine the subset of the second set of egress ports through which the data packet is to be forwarded.

5. The method of claim 4, wherein,

the determination that the data packet is not to be forwarded through the first set of egress ports comprises the accessing step.

6. The method of claim 1, wherein,

the second set of egress ports are not configured to receive data read from the first set of buffers;

and

the first set of egress ports are not configured to receive data read from the second set of buffers.

7. The method of claim 1, further comprising:

reading the data packet from the second set of buffers,

wherein the forwarding step comprises forwarding the data packet read from the second set of buffers.

8. The method of claim 1, wherein the data packet comprises payload encapsulated in a Media Access Control (MAC) frame.

9. The method of claim 1, wherein the network device comprises a selection from the group consisting of a router, a switch, a bridge, and any combination thereof.

10. A method of forwarding a data packet using different memory banks of a network device, the method comprising:

writing the data packet to a first set of buffers in a first memory bank before determining whether the data packet is to be forwarded through the first set of egress ports based on accessing at least one forwarding database, the first memory bank coupled with a first set of egress ports for the device;

writing the data packet to a second set of buffers in a second memory bank before determining whether the data packet is to be forwarded through the second set of egress ports based on accessing the at least one forwarding database, the second memory bank coupled with a second set of egress ports for the device;

determining whether the data packet is to be forwarded through the first set of egress ports or the second set of egress ports based on accessing the at least one forwarding database;

releasing the first set of buffers if it is determined that the data packet is to be forwarded through the second set of egress ports and not to be forwarded through the first set of egress ports;

queuing a descriptor of the data packet written to the second set of buffers after the first set of buffers is released, the descriptor identifying a port of the second set of egress ports through which the data packet is to be forwarded; and

forwarding the data packet identified by the descriptor from the second set of buffers through the port identified in the second set of egress ports if it is determined that the data packet is to be forwarded through the second set of egress ports.

11. The method of claim 10, wherein the queuing step comprises:

queuing the descriptor in a transmit queue identifying the sequence that data packets are to be transmitted through the port.

12. The method of claim 10, further comprising:

receiving additional packets through a plurality of ingress ports; and

writing each additional packet received both to buffers in the first memory bank and to buffers in the second memory bank.

13. The method of claim 10, wherein the first memory bank and the second memory bank each comprise a plurality of memory modules.

14. The method of claim 10, wherein the first memory bank and the second memory bank comprise a selection from the group consisting of static Random Access Memory (RAM), dynamic RAM, flash memory, other media capable of storing data, and any combination thereof.

15. An apparatus for forwarding a data packet using different sets of buffers, the apparatus comprising:

a plurality of egress ports;

a first set of buffers coupled with a first subset of the plurality of egress ports;

a second set of buffers coupled with a second subset of the plurality of egress ports;

a receive unit configured to receive a data packet through an ingress port;

a memory access unit configured to;

write the data packet to the first set of buffers before a determination whether the data packet is to be forwarded through the first subset of the plurality of egress ports, the determination being based on accessing at least one forwarding database,

write the data packet to the second set of buffers before a determination whether the data packet is to be forwarded through a second subset of the plurality of egress ports, the determination being based on accessing the at least one forwarding database

determine whether to forward the data packet through the first subset of the plurality of egress ports or the second subset of the plurality of egress ports based on accessing the at least one forwarding database, and

release the data packet from the first set of buffers if it is determined that the data packet is to be forwarded through the second subset of the plurality of egress ports and not to be forwarded through the first subset of the plurality of egress ports;

a forwarding database configured to identify one or more ports through which a received packet is to be forwarded;

a forwarding database engine configured to access the forwarding database to determine whether the data packet is to be forwarded through the first set of egress ports; and

a transmit unit configured to forward the data packet from the second set of buffers through at least one port of the second subset of egress ports if it is determined that the data packet is to be forwarded through at least one port of the second subset of egress ports.

16. The apparatus of claim 15, further comprising:

a transmit queue unit coupled with the second set of buffers and with the at least one port of the second subset of egress ports, and configured to schedule the data packet for forwarding through the at least one port,

wherein the memory access unit is further configured to release the data packet from the first set of buffers before the data packet is scheduled in the transmit queue unit.

17. The apparatus of claim 15, wherein the memory access unit is configured to release the first set of buffers by identifying the first set of buffers as available.

18. The apparatus of claim 15,

wherein the forwarding database engine is configured to access the forwarding database to determine the at least one port of the second set of egress ports to which the data packet is to be forwarded.

19. The apparatus of claim 18, wherein the determination that the data packet is not to be forwarded through the first set of egress ports comprises the forwarding database engine determination of the at least one port of the second set of egress ports to which the data packet is to be forwarded.

20. The apparatus of claim 15, wherein,

the second set of egress ports are not configured to receive data read from the first set of buffers;

and

the first set of egress ports are not configured to receive data read from the second set of buffers.

21. The apparatus of claim 15, wherein,

the memory access unit is further configured to read the data packet from the second set of buffers;

and

the transmit unit forwards the data packet read from the second set of buffers.

22. The apparatus of claim 15, wherein the data packet comprises a payload encapsulated in a Media Access Control (MAC) frame.

23. The apparatus of claim 15, wherein the apparatus comprises a selection from the group consisting of a router, a switch, a bridge, and any combination thereof.

24. An apparatus for forwarding a data packet using different memory banks, the apparatus comprising:

a plurality of egress ports;

a first memory bank coupled with a first subset of the plurality of egress ports;

a second memory bank coupled with a second subset of the plurality of egress ports;

a receive unit configured to receive a data packet via an ingress port;

a memory access unit configured to;

write the data packet to a first set of buffers in the first memory bank before a determination is made from accessing at least one forwarding database whether the data packet is to be forwarded through the first subset of the plurality of egress ports,

write the data packet to a second set of buffers in the second memory bank before a determination is made from accessing the at least one forwarding database whether the data packet is to be forwarded through the second subset of the plurality of egress ports, and

release the first set of buffers in response to the determination made from accessing the at least one forwarding database that the data packet is to be forwarded through the second subset of the plurality of egress ports and not to be forwarded through the first set subset of the plurality of egress ports;

a transmit queue unit configured to queue a descriptor of the data packet written to the second set of buffers after the first set of buffers are released, the descriptor identifying a port of the second subset through which the data packet is to be forwarded if it is determined that the data packet is to be forwarded through the second subset of egress ports; and

a transmit unit configured to forward the data packet identified by the descriptor from the second set of buffers through the port of the second subset of egress ports if it is determined that the data packet is to be forwarded through the second subset of egress ports.

25. The apparatus of claim 24, wherein the transmit queue unit identifies the sequence that data packets are to be transmitted through the port.

26. The apparatus of claim 24, further comprising:

at least one additional ingress port, wherein,

the receive unit is further configured to receive an additional packet through the at least one additional ingress port; and

the memory access unit is further configured to write the additional packet received to both buffers in the first memory bank and buffers in the second memory bank.

27. The apparatus of claim 24, wherein,

the first memory bank and the second memory bank each comprise a plurality of memory modules.

28. The apparatus of claim 24, wherein the first memory bank and the second memory bank comprises a selection from the group consisting of static Random Access Memory (RAM), dynamic RAM, flash memory, other media capable of storing data, and any combination thereof.