Dynamic communication link scaling

Abstract

Traffic between a first device and a second device across a plurality of communication lanes of a communication link is stalled. A first device side of the communication lane is powered-down on at least one of the plurality of communication lanes to deactivate the at least one communication lane. A power-down request is sent from the first device to the second device to power-down a second device-side of the at least one communication lane. Traffic between the first device and the second device is restarted over the active communication lanes.

What is claimed is: 
     
       1. A method comprising:
 sending traffic between a first device and a second device over a plurality of active communication lanes of a communication link; 
 stalling at the first device, the traffic between the first device and the second device across the plurality of active communication lanes of the communication link; 
 altering a number of the active communication lanes of the communication link; 
 sending a power-down request from the first device to the second device to power-down a second device side of the at least one communication lane; 
 receiving from the second device a power-down acknowledgement indicating that traffic has been stalled at the second device; 
 restarting traffic on active communication lanes between the first device and the second device over the communication link; 
 sending a power-down complete message to the second device indicating that traffic has been restarted over the communication link; 
 sending traffic over the altered number of active communication lanes. 
 
     
     
       2. The method of  claim 1 , wherein altering the number of active communication lanes comprises:
 powering-down a first device side of at least one of the plurality of communication lanes to deactivate the at least one of the plurality of communication lanes. 
 
     
     
       3. The method of  claim 2 , wherein the first device comprises a first linecard, the second device comprises a second linecard, and the communication link comprises a fabric link between the first linecard and the second linecard. 
     
     
       4. The method of  claim 2 , further comprising:
 sending to the second device a power-down mark indicating that the first device side of the at least one communication lane has been powered-down; and 
 receiving from the second device a power-down mark indicating that the second device side of the at least one communication lane has been powered-down. 
 
     
     
       5. The method of  claim 2 , wherein powering-down the first device side of at least one of the plurality of communication lanes to deactivate the at least one of the plurality of communication lanes comprises powering down the at least one of the plurality of communication lanes after traffic has restarted over the communication link. 
     
     
       6. The method of  claim 2 , wherein placing the deactivated at least one of the plurality of communication lanes in a low-power mode comprises alternating the state of the first device side of the deactivated at least one of the plurality of communication lanes from a quiet state to an alert state. 
     
     
       7. The method of  claim 4 , wherein sending the power-down mark comprises sending a plurality of power-down marks to the second device; and
 receiving the power-down mark comprises receiving a plurality of power-down marks from the second device. 
 
     
     
       8. The method of  claim 4 , wherein powering-down the first device side of the at least one communication lane comprises disabling a scrambler at the first device; and
 receiving the power-down mark comprises receiving an indication that a descrambler has been disabled at the second device. 
 
     
     
       9. The method of  claim 1 , wherein stalling traffic comprises stalling traffic over each of the plurality of communication lanes. 
     
     
       10. The method of  claim 1 , wherein sending the power-down request comprises sending the power-down request prior to powering-down the first device side of at least one of the plurality of communication lanes. 
     
     
       11. The method of  claim 1 , wherein before stalling at the first device, the traffic between the first device and the second device across the plurality of active communication lanes of the communication link or after sending traffic over the altered number of active lanes, further comprising:
 sending a power-up request to the second device; 
 powering-up a first device side of at least one inactive communication lane of the communication link to activate the at least one communication lane; 
 stalling traffic with the second device in response to sending the power-up request; 
 sending a realignment request to the second device; 
 sending a power-up complete message to the second device; and 
 restarting traffic with the second device in response to sending the power-up complete message. 
 
     
     
       12. The method of  claim 11 , wherein powering-up the at least one first device side of the deactivated communication lane comprises synchronizing the first device side with a second device side of the deactivated communication lane. 
     
     
       13. The method of  claim 11 , further comprising:
 receiving a realignment acknowledgment from the second device. 
 
     
     
       14. The method of  claim 1 , further comprises:
 receiving from the first device the power-down request at the second device, 
 stalling, at the second device, traffic between the first device and the second device across the plurality of communication lanes of the communication link, 
 powering-down the second device side of at least one of the plurality of communication lanes to deactivate the at least one of the plurality of communication lanes. 
 
     
     
       15. The method of  claim 14 , further comprising:
 sending the power-down acknowledgement from the second device to the first device indicating that traffic has been stalled at the second device; 
 receiving a power-down mark from the first device indicating that a first device side of the at least one communication lane has been powered-down; 
 sending a power-down mark to the first device indicating that the second device side of the at least one communication lane has been powered-down. 
 
     
     
       16. The method of  claim 15 , wherein stalling traffic is performed in response to receiving the power-down request; powering-down the second device side of the at least one communication lane is performed in response to receiving the power-down mark; and
 sending the power-down mark is in response to powering-down the second device. 
 
     
     
       17. The method of  claim 15 , wherein receiving the power-down mark comprises receiving a plurality of power-down marks from the first device; and
 sending the power-down mark comprises sending a plurality of power-down marks to the first device. 
 
     
     
       18. The method of  claim 1 , wherein before stalling at the first device, the traffic between the first device and the second device across the plurality of active communication lanes of the communication link or after sending traffic over the altered number of active lanes, further comprising:
 receiving a power-up request from the first device; 
 powering-up a second device side of at least one deactivated communication lane of the communication link; 
 stalling traffic with the first device in response to the powering-up of the second device side of the at least one deactivated communication lane; 
 receiving a realignment request from the first device; 
 receiving a power-up complete message from the first device. 
 
     
     
       19. The method of  claim 18 , further comprising:
 sending a realignment acknowledgment to the first device. 
 
     
     
       20. An apparatus comprising:
 a network interface unit configured to enable communications over a network on behalf of a first device; and 
 a processor coupled to the network interface unit and configured to:
 send and receive traffic from a second device over a plurality of active communication lanes of a communication link; 
 stall at the first device, the traffic between the first device and the second device across the plurality of active communication lanes of the communication link; 
 alter a number of the active communication lanes of the communication link; 
 send, via the network interface, a power-down request from the first device to the second device to power-down a second device side of the at least one communication lane; 
 receive from the second device a power-down acknowledgement indicating that traffic has been stalled at the second device; 
 restart traffic on active communication lanes between the first device and the second device over the communication link; 
 send a power-down complete message to the second device indicating that traffic has been restarted over the communication link; 
 send traffic over the altered number of active communication lanes. 
 
 
     
     
       21. The apparatus of  claim 20 , wherein the processor is further configured to:
 power-down a first device side of at least one of the plurality of communication lanes to deactivate the at least one of the plurality of communication lanes. 
 
     
     
       22. The apparatus of  claim 21 , wherein the processor is further configured to:
 send to the second device, through the network interface unit, a power-down mark indicating that the first device side of the at least one communication lane has been powered-down; and 
 receive from the second device a power-down mark indicating that the second device side of the at least one communication lane has been powered-down. 
 
     
     
       23. The apparatus of  claim 21 , wherein the processor is further configured to:
 send a plurality of power-down marks to the second device; and 
 receive a plurality of power-down marks from the second device. 
 
     
     
       24. A tangible, non-transitory computer readable medium comprising instructions that when executed by a processor cause the processor to:
 send and receive traffic between a first device and a second device over a plurality of active communication lanes of a communication link; 
 stall at the first device, the traffic between the first device and the second device across the plurality of active communication lanes of the communication link; 
 alter a number of the active communication lanes of the communication link; 
 send a power-down request from the first device to the second device to power-down a second device side of the at least one communication lane; 
 receive from the second device a power-down acknowledgement indicating that traffic has been stalled at the second device; 
 restart traffic on active communication lanes between the first device and the second device over the communication link; 
 send a power-down complete message to the second device indicating that traffic has been restarted over the communication link; 
 send traffic over the altered number of active communication lanes. 
 
     
     
       25. The computer readable medium of  claim 24 , wherein the instructions further cause the processor to:
 power-down a first device side of at least one of the plurality of communication lanes to deactivate the at least one of the plurality of communication lanes. 
 
     
     
       26. The computer readable medium of  claim 25 , wherein the instructions further cause the processor to:
 send to the second device a power-down mark indicating that the first device side of the at least one communication lane has been powered-down; and 
 receive from the second device, a power-down mark indicating that the second device side of the at least one communication lane has been powered-down. 
 
     
     
       27. The computer readable medium of  claim 25 , wherein the instructions further cause the processor to:
 send a plurality of power-down marks to the second device; and 
 receive a plurality of power-down marks from the second device.