Granted Patent B2

US 7,715,403 · App. 11/594,568 · Granted May 11, 2010

Abstract

Claims (34)

1. A method for load balanced and symmetric shortest-path-first (SPF) path selection from a source IP device to a destination IP device through a network, the method comprising:

(a) advertising, from a source IP device, at least a portion of which is implemented in hardware, an output interface cost in a first direction over a first network segment between the source IP device and a destination IP device that is different from an output interface cost advertised in a second direction over the first network segment;

(b) identifying, by the source IP device, a plurality of available network paths between the source IP device and the destination IP device

(c) calculating, by the source IP device, a path cost for each of the available network paths from the source IP device to the destination IP device, wherein calculating a path cost includes, for paths that include the first network segment, substituting the output interface cost advertised in the first direction with the output interface cost advertised in the second direction;

(d) ranking, by the source IP device, the paths based on the calculated costs;

(e) selecting, by the source IP device, from the ranked paths, a lowest cost path; and

(f) assigning both directions of a media session to the lowest cost path.

2. The method of claim 1 wherein calculating the path costs includes calculating the costs using an Open Shortest Path First (OSPF) protocol.

3. The method of claim 2 wherein the output interface cost advertised in the first direction is assigned for traffic engineering purposes.

4. The method of claim 1 wherein the output interface cost advertised in the first direction of the first segment is at least one order of magnitude greater than the output interface cost advertised in the second direction of the first segment.

5. The method of claim 1 wherein the output interface cost advertised in the first direction over the first network segment is at least one order of magnitude less than the output interface cost advertised in the second direction of the first network segment.

6. The method of claim 1 wherein the output interface cost advertised in the first direction over the network segment comprises a cost for reaching a voice over IP host in the source IP device and wherein the cost advertised in the second direction over the first network segment includes a cost for reaching a voice over IP host in the destination IP device.

7. The method of claim 1 wherein the source and destination IP devices each comprises a media gateway.

8. The method of claim 1 wherein assigning both directions of the media session to the lowest cost path comprises:

(a) at the source IP device, assigning media packets associated with the session that are output from the source IP device to the lowest cost path; and

(b) at the destination IP device, assigning media packets associated with the session that are output from the destination IP device to the lowest cost path.

9. A system for obtaining a symmetric shortest-path-first (SPE) path selection from a source IP device to a destination IP device through a network, the system comprising:

a source IP device, at least a portion of which is implemented in hardware, the source IP device including:

(a) means in the source IP device for advertising an output interface cost in a first direction over a first network segment between the source IP device and a destination IP device that is different from an output

(b) means in the source IP device for identifying a plurality of available network paths between the source IP device and the destination IP device;

(c) means in the source IP device for calculating a path cost for each of the available network paths from the source IP device to the destination IP device, wherein calculating a path cost includes, for paths that include the first network segment, substituting the output interface cost advertised in the first direction with the output interface cost advertised in the second direction;

(d) means in the source IP device for ranking the paths based on the calculated costs;

(e) means in the source IP device for selecting, from the ranked paths, a lowest cost path; and

(f) means for assigning both directions of a media session to the lowest cost path.

10. The system of claim 9 wherein the source and destination IP devices each comprises a media gateway.

11. A computer program product comprising computer-executable instructions embodied in a computer-readable medium for performing steps comprising:

(a) advertising an output interface cost in a first direction over a first network segment between a source IP device and a destination IP

(a) advertising an output interface cost in a first direction over a first network segment between a source IP device and a destination IP device that is different from an output interface cost advertised in a second direction over the first network segment;

(b) identifying a plurality of available network paths between the source IP device and the destination IP device;

(c) calculating a path cost for each of the available network paths from the source IP device to the destination IP device, wherein calculating a path cost includes, for paths that include the first network segment, substituting the output interface cost advertised in the first direction with the output interface cost advertised in the second direction;

(d) ranking the paths based on the calculated costs;

(e) selecting, from the ranked paths, a lowest cost path; and

(f) assigning both directions of a media session to the lowest cost path.

12. The computer program product of claim 11 wherein the source and destination IP devices each comprises a media gateway.

Assignments (16)