Network convergence in response to a topology change
In response to a network topology change, packets are initially flooded on ports of a network device. In addition, a bit array is cleared in response to the topology change. Each bit in the bit array is associated with a particular forwarding entry on the network device. In connection with the clearing of the bit array, the flooding of packets on ports of the network device is made conditional, reducing failover time of the network.
1. A computer-implemented method in a network device, the method comprising:
maintaining an age-bit array in a memory of the network device, the age-bit array comprising an age-bit for each of a plurality of forwarding entries of the network device, each of the age-bits in the age-bit array indicating whether a corresponding one of the plurality of forwarding entries is valid;
initially flooding packets on ports of the network device in response to a topology change in a network;
clearing the age-bit array responsive to the topology change rendering the plurality of forwarding entries of the network device as invalid; and
conditionally flooding packets on the ports of the network device responsive to the clearing of the age-bit array, wherein the conditional flooding comprises one of the following operations for each port among the ports of the network device:
a) confirming that flooding should continue on the port based on the age-bit associated with the forwarding entry for the port being cleared indicating the forwarding entry is invalid; and
b) terminating flooding on the port based on the age-bit associated with the forwarding entry for the port indicating the forwarding entry has been re-learned and is valid.
2. The computer-implemented method of claim 1 , wherein the network is a virtual local area network.
3. The computer-implemented method of claim 1 , further comprising:
setting the state of an age-bit in the age-bit array for a forwarding entry to indicate valid when the forwarding entry is learned on the network device.
4. The computer-implemented method of claim 3 , further comprising:
refreshing the state of the age-bit for the forwarding entry in the age-bit array when a packet processed by the network device generates a hit for the forwarding entry.
5. The computer-implemented method of claim 1 , wherein the initial flooding and the conditional flooding are limited to ports of the network device affected by the topology change.
6. The method of claim 1 , wherein initially flooding the packets on the ports of the network device comprises force-flooding the ports by sending copies of a packet out on all outgoing device ports associated with the network device with the exception of a port on which the packet was received.
7. The method of claim 6 , wherein the force-flooding is triggered by adding a forwarding reference to affected ports of the network device.
8. A non-transitory computer-readable storage medium containing instructions that, when executed by a processor in a network device, the instructions cause the network device to perform operations comprising:
maintaining an age-bit array in a memory of the network device, the age-bit array comprising an age-bit for each of a plurality of forwarding entries of the network device, each of the age-bits in the age-bit array indicating whether a corresponding one of the plurality of forwarding entries is valid;
initially flooding packets on ports of the network device in response to a topology change in a network;
clearing the age-bit array responsive to the topology change rendering the plurality of forwarding entries of the network device as invalid; and
conditionally flooding packets on the ports of the network device responsive to the clearing of the age-bit array, wherein the conditional flooding comprises one of the following operations for each port among the ports of the network device:
a) confirming that flooding should continue on the port based on the age-bit associated with the forwarding entry for the port being cleared indicating the forwarding entry is invalid; and
b) terminating flooding on the port based on the age-bit associated with the forwarding entry for the port indicating the forwarding entry has been re-learned and is valid.
9. The non-transitory computer-readable storage medium of claim 8 , wherein the network is a virtual local area network.
10. The non-transitory computer-readable storage medium of claim 8 , wherein the instructions cause the network device to perform further operations comprising:
setting the state of an age-bit in the age-bit array for a forwarding entry to indicate valid when the forwarding entry is learned on the network device.
11. The non-transitory computer-readable storage medium of claim 10 , wherein the instructions cause the network device to perform further operations comprising: refreshing the state of the age-bit for the forwarding entry in the age-bit array when a packet processed by the network device generates a hit for the forwarding entry.
12. The non-transitory computer-readable storage medium of claim 8 , wherein the initial flooding and the conditional flooding are limited to ports of the network device affected by the topology change.
13. The non-transitory computer-readable storage medium of claim 8 :
wherein initially flooding the packets on the ports of the network device comprises force-flooding the ports by sending copies of a packet out on all outgoing device ports associated with the network device with the exception of a port on which the packet was received; and
wherein the force-flooding is triggered by adding a forwarding reference to affected ports of the network device.
14. A network device, comprising:
a memory to store an age-bit array comprising an age-bit for each of a plurality of forwarding entries of the network device, each of the age-bits in the age-bit array to indicate whether a corresponding one of the plurality of forwarding entries is valid;
a processor to initially flood packets on ports of the network device in response to a topology change in a network;
the processor further to clear the age-bit array responsive to the topology change to render the plurality of forwarding entries of the network device as invalid; and
the processor to further conditionally flood packets on the ports of the network device responsive to the clear of the age-bit array, wherein the conditional flood comprises one of the following operations for each port among the ports of the network device:
a) an operation to confirm that flooding should continue on the port based on the age-bit associated with the forwarding entry for the port being cleared indicating the forwarding entry is invalid; and
b) an operation to terminate flooding on the port based on the age-bit associated with the forwarding entry for the port indicating the forwarding entry has been re-learned and is valid.
15. The network device of claim 14 , wherein the network is a virtual local area network.
16. The network device of claim 14 , further comprising:
the processor further to set the state of an age-bit in the age-bit array for a forwarding entry to indicate valid when the forwarding entry is learned on the network device.
17. The network device of claim 16 , further comprising:
the processor further to refresh the state of the age-bit for the forwarding entry in the age-bit array when a packet processed by the network device generates a hit for the forwarding entry.
18. The network device of claim 14 , further comprising:
the processor to limit the initial flooding and the conditional flooding to ports of the network device affected by the topology change.
19. The network device of claim 14 :
wherein the processor to initially flood the packets on the ports of the network device comprises the processor to force-flood the ports by sending copies of a packet out on all outgoing device ports associated with the network device with the exception of a port on which the packet was received.