Method and apparatus for MAC address learning

• US 20080240106A1
• Filed: 03/26/2008
• Published: 10/02/2008
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Schlenk, Ralph
• Granted Patent: US 8,295,282 B2
• Time in Patent Office: Days
• US Class Current: 370/392
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 45/54 Organization of routing tables
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches

Abstract

The invention includes a method and apparatus for synchronizing line card forwarding databases. A method includes receiving a data packet at a line card, generating a control packet for each of at least one other line card to enable an address update operation thereat, and propagating the at least one control packet toward the at least one other line card. The control packet, or packets, is generated in response to a determination to perform an address update operation for the received data packet. The address update process may be implemented as an ingress address update process or an egress address update process. This address update process performed in conjunction with an address aging process.

Claims

1. A method for synchronizing line card forwarding databases, comprising:

receiving a data packet at a line card;

in response to a determination to perform an address update operation for the received data packet, generating a control packet for each of at least one other line card to enable an address update operation thereat; and

propagating the at least one control packet toward the at least one other line card.

2. The method of claim 1, wherein determining whether to perform an address update operation for the data packet comprises:

determining a source address of the data packet;

determining whether an entry for the source address exists in a forwarding database of the line card at which the data packet is received.

3. The method of claim 2, further comprising:

if an entry for the source address does not exist in the forwarding database, performing an address learning operation comprising adding a new entry for the source address to the forwarding database, wherein the new entry for the source address comprises the source address, an associated egress port, and an aging timestamp; and

if an entry for the source address exists in the forwarding database, determining whether an egress port included in the entry for the source address matches an egress port associated with the received data packet.

4. The method of claim 3, further comprising:

if the egress ports match, determining whether to perform an address refresh operation, wherein determining whether to perform the address refresh operation comprises determining whether an aging timestamp of the entry for the source address satisfies a refresh threshold and, in response to the aging timestamp satisfying the refresh threshold, performing the address refresh operation, wherein performing the address refresh operation comprises resetting the aging timestamp of the entry for the source address;

or

if the egress ports do not match, performing an address relearning operation, wherein performing the address relearning operation comprises updating an egress port of the entry for the source address and resetting an aging timestamp of the entry for the source address.

5. The method of claim 1, wherein generating a control packet comprises:

generating a copy of the data packet; and

modifying the copy of the data packet to mark the copy of the data packet as the control packet.

6. The method of claim 1, further comprising:

running an address aging process on each of the line cards, each aging process comprising;

for each of a plurality of entries of an associated forwarding database, determining whether an address aging timestamp associated with the entry satisfies an aging threshold;

for each of the plurality of entries for which the associated address aging timestamp does not satisfy the aging threshold, incrementing the address aging timestamp associated with the entry; and

for each of the plurality of entries for which the associated address aging timestamp satisfies the aging threshold, invalidating the table entry.

11. The method of claim 5, wherein modifying the copy of the data packet comprises one of:

setting one or more bits of an internal header of the copy of the data packet;

or

setting one or more bits of a data packet header of the copy of the data packet.

12. The method of claim 5, wherein modifying the copy of the data packet comprises:

removing a payload of the copy of the data packet.

13. The method of claim 1, wherein propagating the at least one control packet toward the at least one other line card comprises:

propagating the at least one control packet toward the at least one other line card using a data forwarding path.

14. The method of claim 1, further comprising:

receiving the at least one control packet at the at least one other line card;

identifying the at least one control packet as being a control packet; and

performing the address learning operation to update a forwarding database of the receiving line card.

15. The method of claim 1, further comprising:

determining a destination address for the received data packet;

determining whether an entry for the destination address exists in the forwarding database of the line card which receives the data packet;

if the entry for the destination address does exist, determining an egress port associated with the destination address and forwarding the data packet to one of the other line cards on which the egress port is disposed; and

if the entry for the destination address does not exist, forwarding the data packet to each of the other line cards.

7. An apparatus for synchronizing a plurality of forwarding databases of a respective plurality of line cards, comprising:

means for receiving a data packet at a line card;

means for generating, in response to a determination to perform an address update operation for the received data packet, a control packet for each of at least one other line card to enable an address update operation thereat; and

means for propagating the at least one control packet toward the at least one other line card.

8. The apparatus of claim 7, wherein the means for determining whether to perform an address update operation for the data packet comprises:

means for determining a source address of the data packet;

means for determining whether an entry for the source address exists in a forwarding database of the line card at which the data packet is received;

means for performing an address learning operation comprising adding a new entry for the source address to the forwarding database if an entry for the source address does not exist in the forwarding database, wherein the new entry for the source address comprises at least the source address, an associated egress port, and an aging timestamp;

means for determining, if an entry for the source address exists in the forwarding database, whether an egress port included in the entry for the source address matches an egress port associated with the received data packet;

means for performing, if the egress ports do not match, an address relearning operation comprising updating an egress port of the entry for the source address and resetting an aging timestamp of the entry for the source address; and

means for determining, if the egress ports match, whether to perform an address refresh operation by determining whether an aging timestamp of the entry for the source address satisfies a refresh threshold; and

means for performing, in response to the aging timestamp satisfying the refresh threshold, the address refresh operation by resetting the aging timestamp of the entry for the source address.

9. The apparatus of claim 7, further comprising:

means for running an address aging process on each of the line cards, comprising;

means for determining, for each of a plurality of entries of an associated forwarding database, whether an address aging timestamp associated with the entry satisfies an aging threshold;

means for incrementing the address aging timestamp of each of the plurality of entries for which the associated address aging timestamp does not satisfy the aging threshold; and

means for invalidating each of the plurality of entries for which the associated address aging timestamp satisfies the aging threshold.

16. The apparatus of claim 7, wherein the means for generating a control packet comprises:

means for generating a copy of the data packet; and

means for modifying the copy of the data packet to mark the copy of the data packet as the control packet.

17. The apparatus of claim 16, wherein the means for modifying the copy of the data packet comprises at least one of:

means for setting one or more bits of an internal header of the copy of the data packet; and

means for setting one or more bits of a data packet header of the copy of the data packet.

18. The apparatus of claim 16, wherein the means for modifying the copy of the data packet comprises:

means for removing a payload of the copy of the data packet.

19. The apparatus of claim 7, wherein the means for propagating the at least one control packet toward the at least one other line card comprises:

means for propagating the at least one control packet toward the at least one other line card using a data forwarding path.

20. The apparatus of claim 7, further comprising:

means for receiving the at least one control packet at the at least one other line card;

means for identifying the at least one control packet as being a control packet; and

means for performing the address learning operation to update a forwarding database of the receiving line card.

10. A method for maintaining a plurality of forwarding databases on a respective plurality of line cards, comprising:

for each of the forwarding databases, storing a plurality of address entries, each address entry comprising an address value, a port value, and an address aging timestamp; and

for each of the forwarding databases, periodically running an address aging process on each of the stored address entries, comprising;

determining whether the address aging timestamp associated with the entry satisfies an aging threshold;

if the address aging timestamp does not satisfy the aging threshold, incrementing the address aging timestamp associated with the entry; and

if address aging timestamp satisfies the aging threshold, invalidating the table entry.