Support of unidirectional link in IS-IS without IP encapsulation and in presence of unidirectional return path

• US 20070115989A1
• Filed: 11/21/2005
• Published: 05/24/2007
• Est. Priority Date: 11/21/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Roy, Abhay, Mirtorabi, Sina, Ginsberg, Lester
• Granted Patent: US 7,957,380 B2
• Time in Patent Office: Days
• US Class Current: 370/392
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/32 Flooding denial of service attacks H04L63/1458

Abstract

The present invention supports the operation of IS-IS over UDLs without the need for encapsulation of IS-IS PDUs in IP and without the need for a large-scale upgrade of the protocol in the network. The present invention also supports adjacency establishment when the return path from a router at the receive end of a to the router at the transmit end of the unidirectional link is via another unidirectional link.

Claims

1. A method for communicating between a first router and a second router over a unidirectional communication link, the method comprising:

a first router initiating establishment of adjacency by sending point-to-point IS-IS hello (IIH) messages over a unidirectional communication link, the unidirectional link connecting the first router to a second router, the IIH messages containing three-way handshake information;

the first router receiving link state packets (LSPs) containing three-way adjacency information and transitioning to an UP state; and

the first router sending to the second router a complete set of complete sequence number packets.

2. The method of claim 1, further comprising the first router sending the second router LSPs stored on the first router.

3. The method of claim 2, further comprising the first router receiving from the second router LSPs containing encapsulated partial sequence number packets.

4. The method of claim 1, wherein, in IIH messages that the first router transmits over the unidirectional communication link to the second router, the first router includes circuit information related to the second router.

5. The method of claim 1, wherein the first router sends at least one LSP to the second router in an action triggered by the first router receiving an LSP.

6. The method of claim 1, further comprising the first router validating the received link state packets containing three-way adjacency information.

7. A computer-readable medium containing instructions which, when executed by a computer, perform communication between a first router and a second router over a unidirectional communication link, by:

causing a first router to initiate establishment of adjacency by sending point-to-point IS-IS hello (IIH) messages over a unidirectional communication link, the unidirectional link connecting the first router to a second router, the IIH messages containing three-way handshake information;

causing the first router to receive link state packets (LSPs) containing three-way adjacency information and transitioning to an UP state; and

causing the first router to send to the second router a complete set of complete sequence number packets.

8. A router for use in a packet-switched network, comprising:

a first router having a processor configured to;

initiate establishment of adjacency with a second router by sending point-to-point IS-IS hello (IIH) messages over a communication connection to a unidirectional communication link, the unidirectional link connecting the first router to a second router, the IIH messages containing three-way handshake information;

cause the first router to receive link state packets (LSPs) containing three-way adjacency information over the communication connection and transitioning to an UP state; and

cause the first router to send to the second router a complete set of complete sequence number packets.

9. The router of claim 8, wherein the processor is configured to send the second router LSPs stored on the first router.

10. The router of claim 9, wherein the processor is configured to cause the first router to receive from the second router LSPs containing encapsulated partial sequence number packets.

11. The router of claim 8, wherein the processor is configured to, in IIH messages that the first router transmits over the unidirectional communication link to the second router, include circuit information related to the second router.

12. The router of claim 8, wherein the processor is configured to cause the first router to send at least one LSP to the second router in an action triggered by the first router receiving an LSP.

13. The router of claim 8, wherein the processor is configured to validate the received link state packets containing three-way adjacency information.