Label control method and apparatus for virtual private LAN segment networks

• US 7,260,097 B2
• Filed: 10/08/2002
• Issued: 08/21/2007
• Est. Priority Date: 01/30/2002
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Casey, Liam
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): CHURNET, DARGAYE H
• Application Number:
  US10/265,621
• Publication Number:
  US 20030142674A1
• Time in Patent Office: 1,778 Days
• Field of Search: 370/408, 370/238, 370/236, 370/401, 370/393, 370/389, 709/249
• US Class Current: 370/392
• CPC Class Codes: H04L 12/4633 Interconnection of networks using encapsulation techniques, e.g. tunneling
• CPC Class Codes: H04L 12/4641 Virtual LANs, VLANs, e.g. virtual private networks [VPN] LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272
• CPC Class Codes: H04L 45/502 Frame based

Abstract

A network can be organized for providing virtual private LAN segment (VPLS) services to customers into a network core and an associated number of logical provider edges. Each logical provider edge is partitioned into a plurality of Edge-PEs and a Core-PE. Customers connect to the Edge-PE. The Edge-PE maintains a context (a virtual bridge) for each customer VPLS it serves, VPLS service is realized by a full mesh of so called virtual circuit (VC) tunnels between virtual bridge ports. Each VC tunnel is identified by 3 VC labels in each direction, the first label is used in the encapsulation of customer traffic from the ingress Edge-PE to the ingress Core-PE, the second from ingress Core-PE to egress Core-PE and the third from egress Core-PE to Egress Edge-PE. The mechanisms for the allocation of the label values to and how the label values are used provide a realization of VPLS service that is scalable and easy to administer.

Claims

1. A method for providing virtual private LAN segment (VPLS) service in a network comprising a core network and a plurality of logical provider edges (LPEs), the method comprising the steps of:

establishing a full mesh of tunnels between a second plurality of Edge-PEs, each of the second plurality of Edge-PEs having at least one customer site attached thereto, the customer sites being members of a VPLS;

each of the second plurality of Edge-PEs further being part of one of the plurality of LPEs;

each of the plurality of LPEs having at least one Core-PE, forming a third plurality of Core-PEs;

each of the full mesh of tunnels comprising;

a first tunnel segment between a first Edge-PE and a first Core-PE of a first LPE,

a second tunnel segment between the first Core-PE and a second Core-PE, the second tunnel segment traversing the core network, and

a third tunnel segment between the second Core-PE and a second Edge-PE of a second LPE;

receiving at the first Edge-PE, a customer LAN packet from a first customer site having a source address associated with the first customer site and a destination address associated with a second customer site;

encapsulating the customer LAN packet with a first label at the first Edge-PE, the first label being indicative of the first tunnel segment;

forwarding the customer LAN packet on the first tunnel segment to the first Core-PE;

swapping the first label for a second label associated with the second tunnel segment at the first Core-PE;

forwarding the customer LAN packet on the second tunnel segment to the second Core-PE;

swapping the second label for a third label associated with the third tunnel segment at the second Core-PE; and

forwarding the customer LAN packet on the third tunnel segment to the second Edge-PE;

examining the destination address and forwarding to a customer port at the second Edge-PE.

2. The method as claimed in claim 1, further comprising the steps of:

notifying the first Core-PE the identity of the VPLS and an address of the first Edge-PE associated therewith;

generating at the first Core-PE an identifier for inclusion in the first label associated with the first tunnel segment.

building at the first Edge-PE a first association table for associating the identifier with a port, the port connected to a customer sits of the VPLS.

3. The method as claimed in claim 2, wherein the identifier is exclusive in the first LPE to the labels associated with all tunnel segments between the first Edge-PE and the Core-PE.

4. The method as claimed in claim 2, further comprising the step of associating the identifier with a broadcast label for encapsulating multicast or unknown customer LAN packets at the first Edge-PE.

5. The method as claimed in claim 2, wherein a first group of Edge-PEs of the VPLS is connected to the first Core-PE and a second group of Edge-PEs of the VPLS is connected to the second Core-PE, and wherein the first label is an LPE label, the second label is a core label, further comprising the steps of:

establishing a fourth plurality of core tunnel segments between the first Core-PE and the second Core-PE, the fourth plurality being the product of the number of Edge PEs in the first group times the number of Edge PEs in the second group;

associating core labels for each of the fourth plurality of core tunnel segments, the core labels comprising a first core label and a second core label

generating at the first Core-PE distinct LPE labels, one for each of the fourth plurality of core tunnel segments;

building a second association table at the first Core-PE for mapping each LPE label to an associated first core label; and

building a third association table at the first Core-PE for mapping each second core label to an associated LPE label.

6. The method as claimed in claim 5, further comprising the step of participating in an auto-discovery protocol exchange by the first Core-PE to learn the address of every other member of the third plurality of Core-PEs.

7. The method as claimed in claim 5, further comprising the step of provisioning in the first Core-PE the address of every other member of the third plurality of Core-PEs.

8. The method as claimed in claim 5, wherein the customer LAN packet received at the first Edge-PE is multicast or unknown customer LAN packet, further comprising the steps of

encapsulating the customer LAN packet with the broadcast label at the first Edge-PE;

transmitting copies of the customer LAN packet from the first Core-PE, on every core tunnel associated with the identifier in the customer LAN packet label, each transmitted copy being encapsulated with the second label for the core tunnels;

determining at each of the Core-PEs for encapsulating the customer LAN packet for the third tunnel, based on the second label;

forwards customer LAN packet on the third tunnel;

examining the source address of the customer LAN packet,

learning an association between the source address and the label in the customer LAN packet at the second Edge-PE; and

extracting the identifier from the customer LAN packet to determine a customer port on the second Edge-PE for forwarding a second customer LAN packet in the direction from the second Edge-PE to the first Edge-PE.

9. The method as claimed in claim 5, wherein an endpoint of the first tunnel in the first Edge-PE is associated with the destination address of the customer LAN packet and The first label is a learnt label, further comprising the steps of:

encapsulating the customer LAN packet with the learnt label at the first Edge-PE;

determining the third label for encapsulating the customer LAN packet for the third tunnel based on the second label, at the second Core-PE; and

examining the source address of the customer LAN packet,

learning an association between the source address and the label in the customer LAN packet at the second Edge-PE;

end

extracting the identifier from the customer LAN packet to determine a customer port on The second Edge-PE for forwarding a second customer LAN packet in the direction from the second Edge-PE to the first Edge-PE.

10. The method as claimed in claim 1, wherein an end point of the first tunnel is a virtual port of a Virtual Bridge bridging the customer LAN packet from the at least one customer site, the virtual bridge defined by a context of the VPLS, further comprising the step of directly forwarding the customer LAN packet destined to a second customer site connected to the first Edge-PE.

11. The method as claimed in claim 4, wherein a switched Ethernet transport (SET) provides layer 2 transport between the Edge-PE and the Core-PE and between Edge-PEs within an LPE and wherein the customer LAN packet received at the first Edge-PE is multicast or unknown customer LAN packet, further comprising the steps of:

encapsulating the customer LAN packet with the broadcast label at the first Edge-PE;

broadcasting the encapsulated packet to all Edge-PEs and Core-PEs in the LPE;

receiving the encapsulated customer LAN packet at a third Edge-PE;

examining the broadcast label to determine the customer LAN packet being part of the VPLS;

examining the source address of the customer LAN packet,

learning an association between the source address of the customer LAN packet and the address of the first Edge-PE, the address of the first Edge-PE being the source address of encapsulating packet;

extracting the identifier from the customer LAN packet to determine a customer port on the second Edge-PE for forwarding a second customer LAN packet in the direction from the second Edge-PE to the first Edge-PE.

12. The method as claimed in claim 5 wherein the core network is a multi-protocol label switching (MPLS) transport network, and the second label is transported as the innermost or a VC label of an MPLS packet and the step of establishing a third plurality of core tunnel segments further comprises the step of:

communicating with the second Core-PE by the first Core-PE using the Label Distribution Protocol (LDP) to agree on the label value for a core tunnel segment for MPLS encapsulated packets travelling from the first Core-PE to the second Core-PE.

13. The method as claimed in claim 12 wherein the second Core-PE initiates the LDP exchange towards the first Core-PE to agree on the second core label used in the third association table of the first PE and for MPLS encapsulated packets travelling in the direction from the second Core-PE to the first Core-PE.

14. The method as claimed in claim 1 wherein the first, second and third labels comprise information carried in the encapsulation of packets, and wherein the information in the third label is used by the second Edge-PE to generate the first label for LAN packets being transported as part of the same VPLS in the direction from the second Edge-PE to the first Edge-PE.

15. The method as claimed in claim 1 further comprising the steps of forwarding reverse LAN packets in a direction from the second Edge-PE to the first Edge-PE;

wherein the third label is associated with a tunnel from the second Edge-PE to the second Core-PE, and the first label is associated with the tunnel from first Core-PE to first Edge-PE.

16. The method as claimed in claim 10 further comprising the step of storing an actual label of the customer LAN packet arriving on the virtual port as part of a table associating egress port with learned customer MAC address.

17. The method as claimed in claim 2, wherein the identifier is Virtual Bridge Label Prefix (VBLabel Prefix) and is a first part of the first label.

18. The method as claimed in claim 17 where the first label further comprises a second part for serving at the first Core-PE as an index into the second association table for the second label for the second tunnel.

19. The method as claimed in claim 18 wherein the identifier is a set of higher order bits and the second part is a set of lower order bits, further comprising the steps of interpreting the identifier as an reference for a virtual bridge of the context of the VPLS by the first Edge-PE, and interpreting the second part as a reference to the second tunnel between the first Core-PE and the second Core-PE.

21. The method as claimed in claim 11 wherein the broadcast destination of the encapsulated customer LAN packet is confined to only those Edge-PEs that serve customer sites of the VPLS, further comprising the steps of:

generating an Ethernet multicast address and associating it with the VLPS;

configuring a network hardware of the Core-PE and only those Edge-PE which serve the same VPLS to receive packets with the multicast address;

using the multicast address as the destination address for encapsulated broadcast and unknown Customer packets.

22. The method as claimed in claim 3, wherein a switched Ethernet transport (SET) provides a layer 2 transport between the Edge-PE and the Core-PE and between Edge-PEs within an LPE and wherein the first Edge-PE has learnt an association of the destination address of the customer LAN packet with the address of a third Edge-PE in the same LPE as itself, further comprising the steps of:

encapsulating the customer LAN packet with the broadcast label at the first Edge-PE;

transmitting the packet over the SET with the learned address of the third Edge-PE as the encapsulating packet'"'"'s destination address

learning an association between the source address source address of the customer LAN packet and the source address of the first Edge-PE, being the source address or the encapsulating packet.

20. A method for providing virtual private LAN segment (VPLS) service in a network comprising a core network and a plurality of logical provider edges (LPEs), the method comprising the steps of:

establishing a tunnel an Edge-PE having at least one customer site attached thereto, the customer sites being members of a VPLS;

the Edge-PE being part of an LPE having a first Core-PE, the tunnel comprising;

a first tunnel segment between the Edge-PE and the first Core-PE, and

a second tunnel segment between the first Core-PE and a second Core-PE, the second tunnel traversing the core network;

receiving at the Edge-PE, a customer LAN packet from a customer site having a source address associated with the customer site and a destination address;

encapsulating the customer LAN packet with a first label at the Edge-PE, the first label being indicative of the first tunnel segment;

forwarding the customer LAN packet on the first tunnel segment to the first Core-PE;

swapping The first label for a second label associated with the second tunnel segment at the first Core-PE; and

forwarding the customer LAN packet on the second tunnel segment to the second Core-PE.