LAN switch with rapid fault recovery

Abstract

One embodiment disclosed relates to a method of fault recovery by a switch in a local area network. A link failure is detected at a port of the switch. In response to the link failure detection, a medium access control (MAC) address table of the switch is cleared. Clearing the address table causes a discovery process to fill the table to begin immediately. In addition, a link on another port of the switch may be dropped to propagate the link failure.

1. A method of fault recovery by a switch in a local area network, the method comprising:
 a switch port detecting a link failure at a port of the switch the switch port; and 
 the switch clearing all medium access control (MAC) address entries from a MAC address table of the switch in response to the link failure detection and without receiving from outside the switch any signal that signifies that the MAC address table of the switch is to be cleared. 
 
     
     
       2. The method of  claim 1 , wherein clearing all MAC address entries from the MAC address table causes a discovery process to fill the table to begin immediately. 
     
     
       3. The method of  claim 1 , further comprising:
 momentarily dropping a link on another port of the switch, wherein momentarily dropping a link comprises stopping transmission of a link signal for a period of time. 
 
     
     
       4. The method of  claim 3 , wherein momentarily dropping the link on the other port causes propagation of the link failure to a next switch. 
     
     
       5. The method of  claim 3 , wherein the link is momentarily dropped for a length of time sufficient for a next switch to detect the link drop. 
     
     
       6. The method of  claim 5 , wherein the length of time is no more than fifty milliseconds. 
     
     
       7. The method of  claim 5 , wherein the length of time is under ten milliseconds. 
     
     
       8. The method of  claim 1 , wherein the MAC address table is cleared of all MAC address entries by overwriting each entry in the table with a template from a register. 
     
     
       9. The method of  claim 1 , wherein the MAC address table is cleared of all MAC address entries by momentarily turning off power within the switch. 
     
     
       10. A network apparatus comprising:
 a medium access control (MAC) address table; and 
 a plurality of ports wherein at least one port implements a link-loss-learn protocol wherein upon detecting a link failure at the at least one port, the MAC address table is cleared of all MAC address entries therein without receiving from outside the network apparatus any signal that signifies that the MAC address table of the network apparatus is to be cleared. 
 
     
     
       11. The network apparatus of  claim 10 , wherein upon clearing all MAC address entries from the MAC address table, a discovery process is begun by the network apparatus. 
     
     
       12. The network apparatus of  claim 11 , wherein the link-loss-learn protocol protocol in which the MAC address table is cleared upon link failure detection without receiving from outside the switch network apparatus any signal that signifies that the MAC address table of the switch network apparatus is to be cleared further comprises, upon detecting the link failure at the at least one port, momentarily dropping one or more links on one or more other ports of the network apparatus which implement the link-loss-learn protocol so as to propagate the link failure, wherein momentarily dropping a link the one or more links comprises stopping transmission of a link signal one or more link signals for a period of time. 
     
     
       13. The network apparatus of  claim 12 , wherein the network apparatus comprises a multi-port Ethernet switch. 
     
     
       14. A network comprising:
 a plurality of Ethernet switches in a redundant topology, 
 wherein at least one Ethernet switch implements a link-loss-learn protocol for rapid fault recovery, 
 wherein the link-loss-learn protocol comprises, upon detecting a link failure at a port of the at least one Ethernet switch, clearing a medium access control (MAC) address table of all MAC address entries therein, without receiving from outside the at least one Ethernet switch any signal that signifies that the MAC address table of the at least one Ethernet switch is to be cleared. 
 
     
     
       15. The network of  claim 14 , wherein upon clearing all MAC address entries from the MAC address table, a discovery process is begun by the switch. 
     
     
       16. The network of  claim 15 , wherein the link-loss-learn protocol further comprises, upon detecting the link failure at the port, momentarily dropping links on other ports of the at least one Ethernet switch that implements the link-loss-learn protocol in which the MAC address table is cleared upon link failure detection without receiving from outside the at least one Ethernet switch any signal that signifies that the MAC address table of the at least one Ethernet switch is to be cleared, and wherein momentarily dropping a link comprises stopping transmission of a link signal for a period of time. 
     
     
       17. A network apparatus comprising:
 a plurality of ports wherein at least one port implements a link-loss-learn protocol wherein upon detecting a link failure at the at least one port, a medium access control (MAC) address table is cleared of all MAC address entries therein, wherein the network apparatus is configured to clear the MAC address table regardless of whether or not the network apparatus receives an outside signal signifying that the MAC address table is to be cleared.    
     
     
       18. The network apparatus of claim 17, wherein upon clearing all MAC address entries from the MAC address table, a discovery process is begun by the network apparatus.  
     
     
       19. The network apparatus of claim 17, wherein the MAC address entries are cleared by overwriting each entry in the MAC address table with a template from a register.  
     
     
       20. The network apparatus of claim 17, wherein the MAC address entries are cleared by momentarily turning off power within the network apparatus.  
     
     
       21. The network apparatus of claim 17, wherein the network apparatus momentarily drops a link on a port on which the link failure was not detected is momentarily dropped to cause the link failure to propagate to another network apparatus.  
     
     
       22. A network apparatus comprising:
 a port configured to detect a link failure at the port, wherein, upon detecting the link failure, a plurality of medium access control (MAC) address entries are cleared from a MAC address table, wherein the plurality of MAC address entries that are cleared comprise at least one MAC address entry that remains valid after the link failure, and wherein the network apparatus clears the plurality of MAC address entries from the MAC address table regardless of whether or not the network apparatus receives an outside signal signifying that the MAC address table is to be cleared.    
     
     
       23. The network apparatus of claim 22, wherein upon clearing the plurality of MAC address entries from the MAC address table, a discovery process is begun by the network apparatus.  
     
     
       24. The network apparatus of claim 22, wherein the plurality of MAC address entries are cleared by overwriting each entry in the table with a template from a register.  
     
     
       25. The network apparatus of claim 22, wherein the plurality of MAC address entries are cleared by momentarily turning off power within the network apparatus.  
     
     
       26. The network apparatus of claim 22, wherein the network apparatus momentarily drops a link on another port on which the link failure was not detected is momentarily dropped to cause the link failure to propagate to another network apparatus.  
     
     
       27. A network apparatus comprising:
 a plurality of ports, wherein, upon detection of a link failure at a port, the network apparatus is configured to clear a plurality of address entries from an address table, wherein the plurality of address entries that the network apparatus is configured to clear comprise at least one address entry that remains valid after the link failure, and wherein the network apparatus is configured to clear the plurality of address entries from the address table regardless of whether or not the network apparatus receives an outside signal signifying that the address table is to be cleared.    
     
     
       28. The network apparatus of claim 27, wherein the network apparatus is configured to begin a discovery process after clearing the plurality of address entries from the address table.  
     
     
       29. The network apparatus of claim 27, wherein the network apparatus is configured to clear the plurality of address entries by overwriting each entry in the table with a template from a register.  
     
     
       30. The network apparatus of claim 27, wherein the network apparatus is configured to clear the plurality of address entries by momentarily turning off power within the network apparatus.  
     
     
       31. The network apparatus of claim 27, wherein the network apparatus is configured to momentarily drop a link on a port of the network apparatus on which the link failure was not detected to cause the link failure to propagate to another network apparatus.  
     
     
       32. A method of fault recovery by a network apparatus, the method comprising:
 detecting a link failure at a port of the network apparatus; and   clearing a plurality of address entries from an address table of the network apparatus in response to the link failure detection, wherein the plurality of address entries that are cleared comprise at least one address entry that remains valid after the link failure, and wherein the plurality of address entries are cleared from the address table regardless of whether or not the network apparatus receives an outside signal signifying that the address table is to be cleared.    
     
     
       33. The method of claim 32, wherein clearing the plurality of address entries from the address table causes a discovery process to fill the address table to begin.  
     
     
       34. The method of claim 32, further comprising:
 momentarily dropping a link on another port of the network apparatus, wherein momentarily dropping a link comprises stopping transmission of a link signal for a period of time.    
     
     
       35. The method of claim 34, wherein momentarily dropping the link on the other port causes propagation of the link failure to a next network apparatus.  
     
     
       36. The method of claim 34, wherein the link is momentarily dropped for a length of time sufficient for another network apparatus to which the network apparatus is connected to detect the link drop.  
     
     
       37. The method of claim 32, wherein the address table is cleared of all address entries by overwriting each entry in the address table with a template from a register.  
     
     
       38. The method of claim 32, wherein the address table is cleared of all address entries by momentarily turning off power within the network apparatus.