Dynamic retrieval of routing information for inter-AS TE-LSPs

• US 20060209716A1
• Filed: 03/15/2005
• Published: 09/21/2006
• Est. Priority Date: 03/15/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Vasseur, Jean-Philippe, Previdi, Stefano B.
• Granted Patent: US 7,616,574 B2
• Time in Patent Office: Days
• US Class Current: 370/254
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/033 by updating distance vector protocols
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04L 45/50 using label swapping, e.g. multi-protocol label switch [MPLS]
• CPC Class Codes: H04L 47/15 in relation to multipoint traffic arrangements for broadcast or multicast in data networks H04L12/18
• CPC Class Codes: H04L 47/70 Admission control; Resource allocation
• CPC Class Codes: H04L 47/724 at intermediate nodes, e.g. resource reservation protocol [RSVP]
• CPC Class Codes: H04L 47/785 among multiple network domains, e.g. multilateral agreements
• CPC Class Codes: H04L 47/825 Involving tunnels, e.g. MPLS

Abstract

A technique dynamically triggers an exchange of reachability information between a tail-end (remote) domain target node (e.g., a tail-end node) of a traffic engineering (TE) label switched path (LSP) and a local domain head-end node of the TE-LSP in a computer network. The inter-domain information retrieval technique is illustratively based on triggering a Border Gateway Protocol (BGP) session whereby at least a portion of the reachability, i.e., routing, information of the tail-end node is transmitted to the head-end node of the TE-LSP in accordance with BGP. Specifically, once a TE-LSP is established between the head-end node and the tail-end node, the head-end node triggers the tail-end node, e.g., through extensions to a request/response signaling exchange, to establish the BGP session. Establishment of the BGP session enables transmission of the routing information from the tail-end node to the head-end node. The head-end node uses the routing information to calculate routes, i.e., address prefixes and associated attributes, reachable from the tail-end node for insertion into its routing table.

Claims

1. A method for dynamically triggering an exchange of reachability information between a target node of a traffic engineering (TE) label switched path (LSP) and a head-end node of the TE-LSP in a computer network, the method comprising:

establishing a TE-LSP from the head-end node in a local domain to a tail-end node in a remote domain;

triggering, from the head-end node in response to establishing the TE-LSP, the target node to establish a border gateway protocol (BGP) session with the head-end node;

transmitting reachability information of the tail-end node from the target node to the head-end node through the BGP session;

calculating, at the head-end node, routes reachable from the tail-end node using the reachability information; and

inserting the calculated routes into a routing table of the head-end node.

2. The method of claim 1, further comprising:

triggering the BGP session via a request/response signaling exchange.

3. The method of claim 2, further comprising:

issuing a routing information request (RI-REQ) data structure from the head-end node to the target node to trigger the BGP session.

4. The method of claim 3, further comprising:

asserting a BGP request (BGP-REQ) flag in the RI-REQ data structure to trigger the BGP session.

5. The method of claim 2, wherein the request/response signaling exchange is embodied as extensions to Resource ReSerVation Protocol (RSVP) TE signaling messages.

6. The method of claim 1, further comprising:

sending an access control list (ACL) from the head-end node to the target node that limits the amount of reachability information to be returned in the BGP session.

7. The method of claim 1, further comprising:

delaying for a configurable period of time after the establishment of the TE-LSP prior to triggering the BGP session.

8. The method of claim 1, wherein the TE-LSP spans multiple autonomous systems (ASes).

9. The method of claim 1, wherein the BGP session is embodied as a multi-hop BGP session.

10. A system for dynamically triggering an exchange of reachability information of a traffic engineering (TE) label switched path (LSP) in a computer network, the system comprising:

a head-end node in a local domain configured to establish a TE-LSP to a tail-end node in a remote domain and trigger, in response to establishing the TE-LSP, the establishment of a border gateway protocol (BGP) session;

a target node of the TE-LSP configured to receive the trigger, establish the BGP session with the head-end node, and transmit reachability information of the tail-end node to the head-end node through the BGP session;

a routing information base executing in the head-end node and configured to calculate routes reachable from the tail-end node using the reachability information; and

a routing table of the head-end node configured to store the calculated routes.

11. The system of claim 10, further comprising:

a routing information request (RI-REQ) data structure issued from the head-end node to the target node to trigger the BGP session.

12. The system of claim 10, further comprising:

a BGP request (BGP-REQ) flag in the RI-REQ data structure to trigger the BGP session

13. The system of claim 10, further comprising:

a BGP advertisement transmitted from the target node to the head-end node to transmit the reachability information.

14. The system of claim 10, further comprising:

an access control list (ACL) sent from the head-end node to the target node that limits the amount of reachability information to be returned in the BGP session.

15. The system of claim 10, further comprising:

a configurable-length timer, wherein the head-end node begins the timer after the establishment of the TE-LSP and triggers the BGP session after expiration of the timer.

16. An apparatus for dynamically triggering an exchange of reachability information between a target node of a traffic engineering (TE) label switched path (LSP) and a head-end node of the TE-LSP in a computer network, the apparatus comprising:

means for establishing a TE-LSP from the head-end node in a local domain to a tail-end node in a remote domain;

means for triggering, from the head-end node in response to establishing the TE-LSP, the target node to establish a border gateway protocol (BGP) session with the head-end node;

means for transmitting reachability information of the tail-end node from the target node to the head-end node through the BGP session;

means for calculating, at the head-end node, routes reachable from the tail-end node using the reachability information; and

means for inserting the calculated routes into a routing table of the head-end node.

17. A node for dynamically triggering an exchange of reachability information between a target node of a traffic engineering (TE) label switched path (LSP) in a computer network, the node comprising:

a processor adapted to execute software processes;

a memory adapted to store a head-end node process executable by the processor, the head-end node process configured to i) establish a TE-LSP to a tail-end node in a remote domain, and ii) trigger, in response to establishing the TE-LSP, the establishment of a border gateway protocol (BGP) session;

a network interface coupled to the processor to receive reachability information of the tail-end node through the BGP session;

a routing information base process stored in the memory and executed by the processor, the routing information base process configured to calculate routes reachable from the tail-end node using the reachability information; and

a routing table in the memory configured to store the calculated routes.

18. A routing information request (RI-REQ) data structure for dynamically triggering an exchange of reachability information between a target node of a traffic engineering (TE) label switched path (LSP) and a head-end node of the TE-LSP in a computer network, the data structure comprising:

one or more flags, one of the one or more flags indicating that establishment of a border gateway protocol (BGP) session is requested to exchange routing information;

one or more target objects indicating one or more target nodes to which the request is directed; and

an access control list (ACL) to indicate one or more prefixes to which the request is directed.