Device, network, and system for forwarding frames between geographically dispersed user networks

• US 20030142680A1
• Filed: 12/30/2002
• Published: 07/31/2003
• Est. Priority Date: 01/28/2002
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Oguchi, Naoki
• Granted Patent: US 7,596,101 B2
• Time in Patent Office: Days
• US Class Current: 370/400
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04L 45/18 Loop-free operations

Abstract

A frame forwarding system which has a plurality of frame forwarding devices and links to transport frames between external networks that belong to a particular group. This system is designed to prevent backbone links from being blocked even when there is a backdoor link that forms a potential loop in the network. A system state sharing unit in a frame forwarding device shares system state information with other frame forwarding devices. This information sharing enables all the frame forwarding devices and inter-node links to behave as a single virtual device for forwarding frames between external networks that belong to a particular group. A frame forwarding processor forwards received frames according to the system state information shared among all the frame forwarding devices in the system.

Claims

1. A frame forwarding system comprising:

a plurality of frame forwarding devices that transport frames between external networks that belong to the same group;

a plurality of links that interconnect the plurality of frame forwarding devices;

system state sharing means, disposed in each frame forwarding device, for sharing system state information with other frame forwarding devices, whereby the frame forwarding devices and the links behave as a single virtual device for forwarding frames between the external networks;

frame forwarding means, disposed in each frame forwarding device, for forwarding received frames according to the system state information shared among all the frame forwarding devices; and

system state updating means, disposed in each frame forwarding device, for updating the system state information managed in the system state sharing means when a given STP BPDU necessitates a change in the system state information.

2. The frame forwarding system according to claim 1, wherein:

the system state updating means updates the system state information when the STP BPDU is received from one of the external networks; and

the system state sharing means transmits the system state information to other frame forwarding devices.

3. The frame forwarding system according to claim 1, wherein:

the system state updating means updates the system state information when the STP BPDU is received from one of the external networks; and

the system state sharing means transmits the STP BPDU to other frame forwarding devices.

4. The frame forwarding system according to claim 1, further comprising connectivity testing means, disposed in each frame forwarding device, for testing connectivity with other forwarding units by sending a predefined message at predetermined intervals and checking whether the other frame forwarding devices respond to the predefined message.

5. The frame forwarding system according to claim 1, further comprising a server that manages the system state information in a centralized manner.

6. The frame forwarding system according to claim 5, wherein the server comprises system state updating means for updating the system state information when there is a change in the state of the frame forwarding system.

7. The frame forwarding system according to claim 6, wherein the system state updating means updates the system state information according to the STP BPDU.

8. The frame forwarding system according to claim 5, wherein the server further comprises connectivity testing means for testing connectivity between the server and the frame forwarding devices by sending a predefined message at predetermined intervals and checking whether the frame forwarding devices respond to the predefined message.

9. The frame forwarding system according to claim 1, wherein the system state information includes port parameters, bridge parameters, and port state parameters.

10. A frame forwarding device for use as a node in a frame forwarding system which has a plurality of nodes and links to transport frames between external networks that belong to the same group, comprising:

system state sharing means for sharing system state information with other nodes in the frame forwarding system, whereby the nodes and links behave as a single virtual device for forwarding frames between the external networks; and

frame forwarding means for forwarding received frames according to the system state information shared among all the nodes in the frame forwarding system.

11. A network system, comprising:

a plurality of LAN segments;

an intermediary network interconnecting the LAN segments;

virtual bridging means for making the intermediary network work as a single bridge device; and

loop preventing means for preventing a logical loop from being formed on a physical loop in the network system, while ensuring use of logical paths on the intermediary network.

12. An edge network device on an intermediary network that interconnects a plurality of LAN segments to form a network system, comprising:

frame forwarding means for forwarding an incoming frame to other network devices on the intermediary network, when the incoming frame contains information for detecting a physical loop on the network system and avoiding loop traffic on the physical loop; and

loop preventing means for preventing a logical loop from being formed on the physical loop, while maintaining logical paths on the intermediary network, based on the information contained in the incoming frame and parameters that characterize the intermediary network as a single virtual bridge device.