Inter-autonomous-system virtual private network with autodiscovery and connection signaling

• US 7,733,876 B2
• Filed: 08/31/2005
• Issued: 06/08/2010
• Est. Priority Date: 02/11/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Rosen, Eric C, Martini, Luca, Davie, Bruce S.
• Primary Examiner(s): Sefcheck; Gregory B
• Assistant Examiner(s): Kang; Suk Jin
• Application Number:
  US11/216,963
• Publication Number:
  US 20060182122A1
• Time in Patent Office: 1,742 Days
• Field of Search: 370/395.53
• US Class Current: 370/395.53
• CPC Class Codes: H04L 12/2854 Wide area networks, e.g. public data networks

Abstract

A layer-2 virtual-private-network (L2-VPN) service with automatic discovery and connection establishment is provided within a wide-area, multiple-autonomous-system (AS) network according to one of two approaches. In the first approach, inter-AS tunnels are used to connect pairs of provider edge (PE) routers of different ASes, and the PE routers then establish signaling connections to each other which are used to create pseudowires that implement the layer-2 connectivity. A second approach utilizes so-called “pseudowire switching” in which separate pseudowires are created within each AS and between ASes, and then the separate pseudowires are stitched together to form end-to-end connections. The first approach has the benefit of transparent operation provided by the tunnel, while the second approach requires fewer inter-AS signaling connections.

Claims

1. A method of providing layer-2 virtual private network (L2-VPN) services in a multiple-autonomous-system network, comprising:

(1) initially performing an auto-discovery process including;

(i) in a first provider edge (PE) router of a first autonomous system (AS), sending a first internal routing Information (R-I) message to a first border router of the first AS, the first internal R-I message including network layer reachability information (NLRI) for a first L2-VPN forwarder operating within the first PE router, the NLRI including an identifier of a VPN and an identifier of the first L2-VPN forwarder;

(ii) in the first border router in response to receiving the first internal R-I message, sending a first external R-I message along a path between the first AS and a second AS, the first external R-I message forwarding the NLRI of the first L2-VPN forwarder and identifying the first border router as a router through which the first L2-VPN forwarder can be reached;

(iii) in a second border router of the second AS, receiving the first external R-I message, the first external R-I message including the NLRI of the first L2-VPN forwarder and identifying the first border router along the path between the first and second ASes as a router through which the first L2-VPN forwarder can be reached; and

(iv) in the second border router in response to receiving the first external R-1 message, sending a second internal R-1 message to a second PE router of the second AS, the second internal R-1 message including the NLRI of the first L2-VPN forwarder and identifying the second border router as a router through which the first L2- VPN forwarder can be reached; and

(2) subsequently performing a pseudowire establishment process including;

(i) within each of the first and second ASes, establishing respective direct internal signaling connections and internal pseudo wires between the respective PE router and border router of the respective ASes; and

(ii) at each of the first and second border routers, (a) establishing respective external signaling connections and external pseudowires along the path between the first and- second ASes and (b) stitching the respective external and internal pseudowires together to form at least part of an end-to-end connection between the first L2-VPN forwarder and a second L2-VPN forwarder in the second PE router over which communications of the VPN are to be carried, the first and second border routers stitching the respective external and internal pseudowires using endpoint identifiers learned from a border gateway protocol (BGP),

wherein the first AS is different than the second AS.

2. A method according to claim 1, wherein (1) the first and second ASes are neighboring ASes, (2) the first and second external R-I messages are both a single external R-I message sent from the first border router to the second border router, (3) the respective external signaling connections of the first and second border routers are both a single signaling connection between the first and second border routers, and (4) the stitched-together external and internal pseudowires form the complete end-to-end connection between the first L2-VPN forwarder and the second L2-VPN forwarder.

3. A method according to claim 1, wherein (1) the first and second ASes are non-neighboring ASes separated by one or more transit ASes, (2) the first external R-I message is sent to a third border router of a first one of the transit ASes, and the second external R-I message is sent by a fourth border router of a second one of the transit ASes and identifies the fourth border router as the border router through which the first L2 VPN forwarder can be reached, (3) the external signaling connections and external pseudowires of the first border router extend to the third border router, and the external signaling connections and external pseudowires of the second border router extend to the fourth border router, and (4) the complete end-to-end connection between the first L2-VPN forwarder and the second L2-VPN forwarder includes the stitched-together external and internal pseudo wires as well as additional pseudo wires within and among the transit ASes.

4. A method according to claim 3, wherein the first and second transit ASes are a single transit AS.

5. A method according to claim 3, wherein the first and second transit ASes are separate transit autonomous systems.

6. A method according to claim 1, wherein the VPN is a virtual-private-LAN-service (VPLS) VPN and the L2-VPN forwarders are virtual switching instances (VSIs) of the VPLS VPN.

7. A method according to claim 1, wherein the VPN is a virtual-private-wire-service (VPWS) VPN, and wherein the NERI for each L2-VPN forwarder includes a pool number for a respective pool of attachment circuits associated with the VPWS VPN.

8. A method of providing layer-2 virtual private network (L2-VPN) services in a multiple-autonomous-system network, comprising:

(1) initially participate in an auto-discovery process including;

(i) receiving, from a first provider edge (PE) router of a first autonomous system (AS), a first internal routing information (R-I) message, the first internal R-I message including network layer reachability information (NLRI) for a first L2-VPN forwarder operating within the first PE router, the NLRI including an identifier of a VPN and an identifier of the first L2-VPN forwarder; and

(ii) in response to receiving the first internal R-I message, sending a first external R-I message along a path between the first AS and a second border router of a second AS, the first external R-I message forwarding the NLRI of the first L2-VPN forwarder and identifying a first border router as a router through which the first L2-VPN forwarder can be reached; and

(2) subsequently participate in a pseudowire establishment process including;

(i) establishing an internal signaling connection and an internal pseudowire to the first PE router;

(ii) establishing direct external signaling connection and an external pseudowire along the path between the first and second ASes; and

(iii) stitching the external and internal pseudo wires together to form at least part of an end-to-end connection between the first L2-VPN forwarder and a second L2-VPN forwarder in the second PE router over which communications of the VPN are to be carried, the first and second border routers stitching the respective external and internal pseudowires using endpoint identifiers learned from a border gateway protocol (BGP), wherein the first AS is different than the second AS.