Network having at least two routers, each having conditional filter so one of two transmits given frame and each transmits different frames, providing connection to a subnetwork

• US 5,737,526 A
• Filed: 12/30/1994
• Issued: 04/07/1998
• Est. Priority Date: 12/30/1994
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Systems, Inc.
• Inventors: Pandian, Gnanaprakasam, Lowry, David, Naderi, Ramin, Clark, Wayne, Bordonaro, Frank, Periasamy, Ravi
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Chen, Anderson I.
• Application Number:
  US08/366,713
• Time in Patent Office: 1,194 Days
• Field of Search: 395/200.02, 395/200.03, 395/200.1, 395/200.2, 370/16, 370/94.3, 364/940, 364/990.92, 364/990.61, 364/990.64, 364/990.67
• US Class Current: 709/241
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing

Abstract

A hierarchical wide-area network architecture which conforms to the DLSw protocol is provided, in which multiple routers having a logical connection to one another are designated as a peer group. At least one router in each peer group is designated as a border peer, and functions as a gateway between the members of its group and other peer groups. The peer group structure reduces broadcast traffic on slow links by changing the source of the broadcast from a small access router with a relatively slow link to another, more powerful router, with a faster link on the network. More than one border peer can be included in each group, to share the transmission workload and act as a backup. The border peers can share information about the groups that they service and can cooperate to provide a single-point broadcast service to all of the users of the service. When two or more routers are connected to a network in parallel to provide back-up facilities, conditional filters are employed to prevent redundant operations. Different types of frames are handled by the two different routers, so that they share the communication load between them and make the most effective use of the available bandwidth.

Claims

1. A wide-area network, comprising:

a plurality of subnetworks, wherein each subnetwork contains at least one network node;

a plurality of routers that are respectively connected to said plurality of subnetworks, for providing a logical connection from a node in one subnetwork to a node in another subnetwork, and wherein at least one of said subnetworks has at least two routers connected to it in parallel; and

a conditional filter in each of said two routers that are connected to said one subnetwork, said conditional filter causing said routers to selectively transmit or drop frames of data that are sent to said routers from said one subnetwork in parallel, so that only one of said two routers transmits a given frame of data from one subnetwork and each of said two routers transmits different respective frames of data from said one subnetwork.

2. The wide-area network of claim 1 wherein the conditional filter in one of said two routers causes said router to transmit frames of a first type and to drop frames of a second type, and the conditional filter in the other of said two routers causes said other router to drop frames of said first type and to transmit flames of said second type.

3. The wide-area network of claim 2 wherein said first and second types of frames respectively relate to different network transmission protocols.

4. The wide-area network of claim 1 further including means in each of said two routers for determining the operational state of the other router, and for interrupting the function of the conditional filter if the other router is determined to be non-operational, such that all frames of data from said one subnetwork are transmitted by the operational router.

5. The wide-area network of claim 1 further including means in the other routers of said wide-area network for selecting one of said two routers for conducting communications with said one subnetwork.

6. The wide-area network of claim 5 wherein said selection is made on an arbitrary basis.

7. The wide-area network of claim 5 wherein said selection is made on the basis of the cost of communicating with each of said two routers.

8. The wide-area network of claim 1, wherein said network conforms to the Data Link Switching protocol.