In-order traffic aggregation with reduced buffer usage
One embodiment provides a system that performs in-order traffic aggregation from a number of low-speed ports to a high-speed port. During operation, the system receives at a low-speed port a packet, stores it in a store-and-forward FIFO associated with the low-speed port, extracts a sequence number associated with the stored packet, and stores the extracted sequence number in a sequence-number FIFO associated with the low-speed port. The system further generates an expected sequence number, which maintains a linear order with respect to sequence numbers associated with previously forwarded packets, and determines whether a front end of the sequence-number FIFO matches the expected sequence number. If so, the system removes the front end of the sequence-number FIFO buffer, retrieves a packet associated with it, forwards the retrieved packet on the high-speed port, and updates the expected sequence number by adding 1 to the packet number of the retrieved packet.
1. A method comprising:
storing a plurality of received packets in a set of packet buffers;
converting a bit width of the received packets to a higher bit width;
identifying runt packets and flow-control packets from the received packets;
extracting packet sequence numbers and a sequence number valid bit from the received packets; and
in response to no sequence number matching an expected sequence number and a timeout event, removing a head entry having a smallest sequence-number value from a set of sequence number buffers.
2. The method of claim 1 , wherein the timeout event comprises at least one of the following events:
a waiting time exceeds a predetermined amount; and
a buffer exceeds a predetermined threshold.
3. The method of claim 1 , further comprising:
in response to a received packet containing an error, forwarding the received packet; and
keeping the expected sequence number unchanged.
4. The method of claim 3 , wherein the error includes at least one of:
an invalid sequence number;
a packet header checksum error;
a sequence number parity error; and
a sequence number smaller than the expected sequence number.
5. The method of claim 1 , further comprising:
in response to receiving a flow-control packet, forwarding the received flow-control packet; and
keeping the expected sequence number unchanged.
6. The method of claim 5 , wherein forwarding the received flow-control packet is performed in a round-robin fashion among a number of input ports.
7. The method of claim 1 , further comprising determining whether an end-of-frame (EOF) field associated with a particular packet is received, and wherein storing a sequence number of the particular packet occurs after the EOF field is received.
8. The method of claim 1 , further comprising storing the sequence numbers associated with the received packets in the set of sequence-number buffers.
9. The method of claim 1 , further comprising generating the expected sequence number based on a previously forwarded packet.
10. The method of claim 1 , further comprising determining whether a match exists between head entries of the set of sequence-number buffers and the expected sequence number.
11. The method of claim 1 , further comprising:
retrieving a packet corresponding to the removed head entry from a corresponding packet buffer; and
forwarding the retrieved packet.
12. A system comprising:
a set of packet buffers configurable to store a plurality of received packets,
a packet parser operable to:
convert a bit width of the received packets to a higher bit width;
identify runt packets and flow-control packets from the received packets; and
extract packet sequence numbers and a sequence number valid bit from the received packets; and
a sequence-number managing module operable to, in response to no sequence number matching an expected sequence number and a timeout event, remove a head entry having a smallest sequence-number value from a set of sequence-number buffers.
13. The system of claim 12 , wherein the timeout event comprises at least one of the following events:
a waiting time exceeding a predetermined amount; and
a buffer exceeding a predetermined threshold.
14. The system of claim 12 , further comprising a packet forwarding module, wherein, in response to a received packet containing an error, the packet forwarding module is operable to forward the received packet while the expected sequence number is kept unchanged.
15. The system of claim 14 , wherein the error includes at least one of:
an invalid sequence number;
a packet header checksum error;
a sequence number parity error; and
a sequence number smaller than the expected sequence number.
16. The system of claim 12 , further comprising a packet forwarding module, wherein, after a flow-control packet is received, the packet forwarding module is operable to forward the received flow-control packet while the expected sequence number is kept unchanged.
17. The system of claim 16 , wherein the packet forwarding module is operable to forward the received flow-control packet in a round-robin fashion among a number of input ports.
18. The system of claim 12 , further comprising a sequence-number buffer operable to store a packet-sequence number after an end-of-frame field is received.
19. The system of claim 12 , further comprising the set of sequence-number buffers operable to store the sequence numbers associated with the received packets.
20. The system of claim 12 , further comprising a sequence-number generation module operable to generate the expected sequence number based on a previously forwarded packet.
21. The system of claim 12 , further comprising a determination module operable to determine whether a match exists between head entries of the set of sequence-number buffers and the expected sequence number.
22. The system of claim 12 , further comprising a packet forwarding module operable to:
retrieve a packet corresponding to the removed head entry from a corresponding packet buffer; and
forward the retrieved packet.
23. A switching means, comprising:
a packet buffering means for storing a plurality of received packets in a set of packet buffers;
a packet-parsing mechanism for:
converting a bit width of the received packets to a higher bit width;
identifying runt packets and flow-control packets from the received packets; and
extracting packet sequence numbers and a sequence number valid bit from the received packets; and
a sequence-number managing means for removing a head entry having a smallest sequence-number entry from a set of sequence-number buffers in response to no sequence number matching an expected sequence number and a timeout event.
24. The means of claim 23 , further comprising a sequence-number generating means for generating the expected sequence number based on previously forwarded packets.