SYNCHRONIZING ROUTING TABLES IN A DISTRIBUTED NETWORK SWITCH

• US 20130195105A1
• Filed: 11/28/2012
• Published: 08/01/2013
• Est. Priority Date: 02/01/2012
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Basso, Claude, Shedivy, David A., Verrilli, Colin B., Walk, Bruce M., Wind, Daniel
• Granted Patent: US 8,885,518 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/72 Routing based on the source address

Abstract

Techniques are provided for routing table synchronization for a distributed network switch. In one embodiment, a first frame having a source address and a destination address is received. If no routing entry for the source address is found in a routing table of a first switch module, routing information is determined for the source address and a routing entry is generated. An indication is sent to a second switch module, to request a routing entry for the source address to be generated in the second switch module, based on the routing information.

Claims

1. A computer-implemented method for routing table synchronization in a distributed network switch that includes a first switch module and a second switch module, wherein the method comprises:

receiving, by the first switch module, a first frame having a source address and a destination address, wherein each switch module comprises a plurality of bridge elements and a routing table, wherein the routing table in each switch module is shared among the plurality of bridge elements in the respective switch module; and

upon determining that the routing table of the first switch module does not include a routing entry for the source address;

determining routing information for the source address;

generating the routing entry for the source address in the routing table of the first switch module, based on the routing information; and

sending, to the second switch module, an indication to generate a corresponding entry in the routing table of the second switch module for the source address, based on the routing information.

2. The computer-implemented method of claim 1, wherein a broadcast domain of the first switch module is flooded with the first frame, and wherein the routing table of the second switch module is updated to include the corresponding entry for the source address, without flooding a broadcast domain of the second switch module with any response frame.

3. The computer-implemented method of claim 2, wherein a response frame from the destination address and destined for the source address is received by the second switch module subsequent to the second switch module being updated to include the corresponding entry for the source address.

4. The computer-implemented method of claim 3, further comprising:

receiving, by the first switch module, the response frame from the second switch module; and

sending, by the first switch module, the response frame to the source address.

5. The computer-implemented method of claim 1, wherein the first frame comprises at least one of a multicast frame and a broadcast frame, wherein the first switch module is configured to store the indication in at least one bit of a frame header of the first frame, and wherein the indication is sent to the second switch module without any synchronization frame other than the first frame to be sent.

6. The computer-implemented method of claim 1, wherein each routing table is managed according to one or more aging rules, and wherein the method further comprises:

upon determining that a routing entry for the destination address does not exist in the routing table of the first switch module, sending an indication to the second switch module to refresh a routing entry for the destination address in the routing table of the second switch module, wherein refreshing the routing entry of the destination address comprises at least one of generating the routing entry of the destination address and reducing an extent to which the routing entry of the destination address is considered to have aged, and wherein refreshing the routing entry of the destination address further comprises sending, to the first switch module, an indication to generate a routing entry for the destination address in the routing table of the first switch module.

7. The computer-implemented method of claim 6, wherein the routing entry of the destination address is refreshed only upon determining that the second switch module owns the destination address, wherein owning the network address comprises being configured to first generate the routing entry for the destination address, prior to any other switch module, wherein the routing entry for the network address in each switch module includes a flag indicating whether the respective switch module owns the routing entry, and wherein the first switch module is further configured to send an invalidate frame to other switch modules, the invalidate frame indicating to invalidate a routing entry for a specified network address.