Equal-cost source-resolved routing system and method

• US 20050041590A1
• Filed: 12/24/2003
• Published: 02/24/2005
• Est. Priority Date: 08/22/2003
• Status: Active Grant

• Current Assignee: Proven Networks, LLC
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Rao, Kishore C., Olakangil, Joseph, Dighe, Sahil
• Granted Patent: US 8,018,852 B2
• Time in Patent Office: Days
• US Class Current: 370/238
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00

Abstract

A method and system for augmenting routing decisions in a network switching device with topology information acquired using source learning are disclosed. In the preferred embodiment, the method of selecting a port to transmit an outbound flow from a first node to a second node comprises the steps of identifying a plurality of ports associated with minimal equal-cost paths from the first node to the second node, and if an inbound flow from the second node is detected on a first port of the plurality of ports of the first node, then transmitting the outbound flow from the first port. In the absence of an inbound flow from the second node, the first node generally selects the port for the outbound flow from the plurality of minimal equal-cost paths. The present invention allows a switching device to take advantage of the path determination made at another router in the network while avoiding inconsistencies between conventional route selection operations and IP source learning in switching devices adapted to perform bridging on IP address.

Claims

1. A equal-cost source-resolved (ECSR) port selection method for transmitting an outbound flow from a first node to a second node in a distributed network comprising one or more routing devices, the method comprising the steps of:

(a) identifying a plurality of ports associated with minimal equal-cost paths from the first node to the second node; and

(b) if an inbound flow from the second node is detected on a first port of the plurality of ports of the first node, then transmitting the outbound flow from the first port.

2. The ECSR port selection method of claim 1, wherein the minimal equal-cost paths are derived from route information exchanged between the first node and the one or more routing devices in the distributed network.

3. The ECSR port selection method of claim 1, wherein the method further includes, after the inbound flow from the second node is detected, the step of retaining a network address associated with the inbound flow at a forwarding database maintained by the first node.

4. The ECSR port selection method of claim 3, wherein the forwarding database comprises entries relating one or more network addresses to an associated inbound port of the plurality of ports.

5. The ECSR port selection method of claim 1, wherein the inbound flow from the second node is detected using a network address source learning.

6. The ECSR port selection method of claim 5, wherein the source learning associates a source IP address retrieved from one or more inbound protocol data units (PDUs) with the port on which the one or more inbound PDUs is received.

7. The ECSR port selection method of claim 1, wherein the method further includes the step of, if an inbound flow from the second node is not detected on the plurality of ports, transmitting the outbound flow from a port selected from the plurality of ports associated with the minimal equal-cost paths.

8. The ECSR port selection method of claim 7, wherein the selected port is chosen using round robin.

9. The ECSR port selection method of claim 7, wherein the port on which the outbound flow is transmitted is reassigned from the selected port to the first port after the inbound flow from the second node is detected.

10. A equal-cost source-resolved (ECSR) switching device for transmitting an outbound flow to a second node, the switching device adapted for:

(a) identifying a plurality of ports associated with a minimal equal-cost path from the switching device to the second node;

(b) if an inbound flow from the second node is not detected on the plurality of ports of the first node, then transmitting the outbound flow from a port selected from the plurality of ports associated with the minimal equal-cost path;

(c) monitoring for an inbound flow from the second node on the plurality of ports associated with the minimal equal-cost path; and

(d) if the inbound flow from the second node is detected on a first port of the plurality of ports, then transmitting the outbound flow from the first port.

11. A method for selecting a port on a first node of a communication network for carrying an outbound flow, the method comprising the steps of:

(a) identifying a plurality of ports on the first node associated with minimal equal-cost paths to a second node;

(b) determining whether an inbound flow from the second node is present on a first port of the plurality of ports; and

(c) selecting the first port for carrying the outbound flow in response to determining that an inbound flow from the second node is present on the first port.

12. The port selection method of claim 11, wherein the minimal equal-cost paths are derived from route information exchanged between the first node and one or more routing devices in the network.

13. The port selection method of claim 11, wherein the method further comprises the step of retaining a network address associated with the inbound flow in a forwarding database maintained by the first node.

14. The port selection method of claim 13, wherein the forwarding database comprises entries associating network addresses with ports.

15. The port selection method of claim 11, wherein the determining step includes detecting the inbound flow using address source learning.

16. The port selection method of claim 15, wherein the address source learning associates a source address from an inbound PDU with a port on which the inbound PDU is received.

17. The port selection method of claim 11, further comprising the step of selecting, using round-robin, a port for carrying the outbound flow in response to determining that an inbound flow from the second node is not present on the first port.

18. The port selection method of claim 17, further comprising the step of reassigning the outbound flow from the round-robin-selected port to the first port in response to determining that an inbound flow from the second node has become present on the first port.