Layer 2 and 3 latching loopbacks on a pluggable transceiver

1. A method for using a pluggable transceiver in a network element of an Ethernet network for looping back frames, the transceiver having an upstream datapath, a downstream datapath and a logic array having a first latching loopback logic block (LLBLB) and a second LLBLB connected in series through both the upstream and downstream datapaths, the method comprising:

(a) receiving, in the first LLBLB, a frame from the downstream datapath;

(b) comparing, in the first LLBLB, the frame from (a) to first loopback conditions yielding a match or a mismatch;

(c) in response to (b) yielding a mismatch, sending, in the first LLBLB, the frame from (b) to the second LLBLB;

(d) in response to (b) yielding a match, looping back, in the first LLBLB, the frame from (b) on the upstream datapath if there is available bandwidth on the upstream datapath;

(e) receiving, in the first LLBLB, a frame from the second LLBLB;

(f) transmitting, in the first LLBLB, the frame from (e) on the upstream datapath;

(g) receiving, in the second LLBLB, a frame from the upstream datapath;

(h) comparing, in the second LLBLB, the frame from (g) to second loopback conditions yielding a match or a mismatch;

(i) in response to (h) yielding a mismatch, sending, in the second LLBLB, the frame from (h) to the first LLBLB; and

(j) in response to (h) yielding a match, looping back, in the second LLBLB, the frames from (h) on the downstream datapath if there is available bandwidth on the downstream datapath;

(k) receiving a frame, in the second LLBLB, from the first LLBLB;

(l) transmitting, in the second LLBLB, the frame from (k) on the downstream datapath.

2. The method of claim 1 wherein:

(a) further comprises receiving the frame from the downstream datapath unit by unit; and

(b) further comprises comparing the successively received units of the frame received from (a) to successive units of the first loopback conditions.

3. The method of claim 2 wherein comparing the successively received units of the frame received from (a) to successive units of the first loopback conditions comprises:

masking for comparison bits of the next unit of the frame and bits of a next unit of a provisioned frame header (PFH);

yielding a mismatch when the bits masked for comparison do not match;

repeating the comparing on subsequent units while the bits masked for comparison match and there are more units of the frame and the PFH;

yielding a match when there are no more units of the frame or no more units of the PFH and no mismatch was yielded.

4. The method of claim 2 wherein (a) further comprises copying each unit to both a forwarding FIFO and a loopback FIFO; and

wherein (b) further comprises deleting the units from the forwarding FIFO when comparing yields a match and deleting the units from the loopback FIFO when comparing yields no matches.

5. The method of claim 1 wherein (d) further comprises swapping the address fields of the frame for looping back.

6. The method of claim 5 wherein (d) further comprises recalculating the CRC checksum after swapping the address fields.

7. The method of claim 1 wherein (d) further comprises deleting the frame from (b) if there is insufficient bandwidth on the upstream datapath.

8. The method of claim 7 wherein (d) further comprises transmitting a loopback frame drop message on the upstream or downstream datapath in response to deleting the frame from (b).

9. The method of claim 1 further comprising prioritizing (f) over (d) and (l) over (j) to maintain data throughput requirements of the pluggable transceiver on the upstream and downstream datapaths respectively.

10. The pluggable transceiver of claim 1 wherein the output logic comprises a scheduler for deleting the frame from the downstream datapath if there is insufficient bandwidth on the upstream datapath.

11. The pluggable transceiver of claim 10 wherein the logic array further comprises transceiver management logic for instructing the transmitting a loopback frame drop message on the upstream or downstream datapath in response to the scheduler deleting the frame for looping back.

12. The pluggable transceiver of claim 10 wherein the scheduler comprises prioritization logic for prioritizing transmitting the frame from the second LLBLB on the upstream datapath over looping back the frame from the downstream datapath on the upstream datapath to maintain an upstream data throughput requirement of the pluggable transceiver.

13. A pluggable transceiver for use in a network element of an Ethernet network for looping back frames, the transceiver comprising:

a downstream datapath for relaying frames downstream through the transceiver;

an upstream datapath for relaying frames upstream through the transceiver;

a logic array connected through the upstream and downstream datapaths and comprising a first latching loopback logic block (LLBLB) and a second LLBLB connected in series through both the upstream and downstream datapaths;

the first LLBLB having filter logic for receiving a frame from the downstream datapath; and comparing the frame from the downstream datapath to first loopback conditions yielding a match or a mismatch;

the first LLBLB having a forwarding FIFO for sending the frame from the downstream datapath to the second LLBLB in response to the first LLBLB's filter logic yielding a mismatch;

the first LLBLB having a loopback FIFO for looping back the frame from the downstream datapath on the upstream datapath if there is available bandwidth on the upstream datapath, in response to the first LLBLB's filter logic yielding a match;

the first LLBLB having output logic for receiving a frame from the second LLBLB and transmitting the frame from the second LLBLB on the upstream datapath;

the second LLBLB having a filter logic for receiving a frame from the upstream datapath and comparing the frame from the upstream datapath to second loopback conditions yielding a match or a mismatch;

the second LLBLB having a forwarding FIFO for sending the frame from the upstream datapath to the first LLBLB in response to the second LLBLB's filter logic yielding a mismatch;

the second LLBLB having a loopback FIFO for looping back the frames from the upstream datapath on the downstream datapath if there is available bandwidth on the downstream datapath, in response to the second LLBLB's filter logic yielding a match; and

the second LLBLB having an output logic for receiving a frame from the first LLBLB and transmitting the frame from the first LLBLB on the downstream datapath.

14. The pluggable transceiver of claim 13 wherein the first LLBLB's filter logic comprises:

further logic for receiving the frame from the downstream datapath unit by unit; and

bit matchers logic for comparing the successively received units of the frame received from the downstream datapath to successive units of the first loopback conditions.

15. The pluggable transceiver of claim 14 wherein the bit matchers logic further comprises:

a provisioned frame header (PFH) having units for comparing to units of the frame from the downstream datapath;

a bit comparison mask for masking for comparison bits of a next unit of the frame and bits of a next unit of the PFH;

wherein the bit matchers logic yields a mismatch when the bits of the next unit of the frame and the next unit of the PFH masked by the bit comparison mask do not match;

wherein the bit matchers logic repeats the comparing on subsequent units while the next units for the frame and the PFH match under the bit comparison mask and there are more units of the frame and the PFH; and

wherein the bit matchers logic yields a match when there are no more units of the frame or no more units of the PFH and no mismatch was yielded under the bit comparison mask.

16. The pluggable transceiver of claim 13 wherein the loopback FIFO of the first LLBLB comprises further logic for swapping address fields of a frame for looping back.

17. The pluggable transceiver of claim 16 wherein the output logic comprises further logic for recalculating the CRC checksum.