System and method for providing support for multipoint L2VPN services in devices without local bridging

1. A method of processing a packet sent to a service provider network, comprising:

receiving the packet from a cable modem;

identifying a cable interface and cable service identifier associated with the cable modem;

inserting a layer 2 network identifier into the packet, the layer 2 (L2) network identifier comprising inner and outer Service Provider Virtual Local Area Network (SP-VLAN) tags, wherein the inner SP-VLAN tag represents a service flow on a destination node in a point-to point L2 Virtual Private Network (VPN) service or a customer VPN in a multipoint L2VPN service and wherein the outer SP-VLAN tag represents the destination node in the point-to-point L2VPN service or a single attachment circuit on a Cable Modem Termination System (CMTS); and

transmitting the double SP-VLAN tagged packet to an upstream network device, the upstream network device forwarding and routing the SP-VLAN tagged packet.

2. The method of claim 1 , further comprising:

mapping the inner SP-VLAN tag to a virtual private network; and

mapping the outer SP-VLAN tag to the cable interface and the cable service identifier associated with the cable modem.

3. The method of claim 1 , wherein forwarding and routing the SP-VLAN tagged packet comprises:

identifying a virtual trunk interface based on the outer SP-VLAN tag, wherein the virtual trunk interface is associated with the cable service identifier;

removing the outer SP-VLAN tag to form a single SP-VLAN tagged packet; and

forwarding the single SP-VLAN tagged packet to a downstream network device based on the inner SP-VLAN tag.

4. The method of claim 3 , wherein the upstream and downstream network devices comprise a same device.

5. The method of claim 1 , wherein the upstream network device is an aggregation device.

6. The method of claim 1 , wherein the upstream network device interprets the outer SP-VLAN tags as a virtual trunk in the virtual private network, the upstream network device providing bridging among virtual trunks.

7. The method of claim 1 , wherein the upstream network device interprets the inner SP-VLAN tag as a broadcast group of virtual private networks, the upstream network device performing bridging within the broadcast group.

8. The method of claim 1 , wherein the packet received includes a customer VLAN tag.

9. The method of claim 1 , wherein the packet received does not include a customer VLAN tag.

10. A method of processing a packet received from a service provider network, comprising:

receiving the packet having an inner SP-VLAN tag;

drawing an outer SP-VLAN tag from a plurality of outer SP-VLAN tags wherein the outer SP-VLAN tags of the plurality each correspond to an attachment circuit for a VPN corresponding to a same CMTS;

inserting the outer SP-VLAN tag into the received packet to form a double SP-VLAN tagged packet; and

forwarding the double SP-VLAN tagged packet to an egress network device, the egress network device routing the packet to an appropriate cable modem in the VPN.

11. The method of claim 10 , wherein routing the packet comprises:

associating a cable interface and cable service identifier with a cable modem;

identifying a virtual trunk interface based on the outer SP-VLAN tag, wherein the virtual trunk interface is associated with the cable service identifier;

identifying the VPN based on the inner SP-VLAN tag;

removing the SP-VLAN tags; and

transmitting the packet to the cable modem in the VPN.

12. The method of claim 10 , wherein the egress network device is a provider edge device not having a bridging functionality.

13. The method of claim 10 , wherein the egress network device is a cable modem termination system.

14. The method of claim 10 , wherein the packet received includes a customer VLAN tag.

15. The method of claim 10 , wherein the packet received does not include a customer VLAN tag.

16. A network device, comprising:

a cable connection to allow the network device to exchange data with at least one cable modem;

a processor to:

receive a packet from a cable modem;

associate a cable interface and cable service identifier with the cable modem; and

insert a layer 2 network identifier into the packet, the identifier comprising inner and outer SP-VLAN tags, wherein the inner SP-VLAN tag represents a service flow on a destination node in a point-to-point L2VPN service or a customer VPN in a multi-point L2VPN service and wherein the outer SP-VLAN tag represents the destination node in a point-to-point L2VPN service or a single attachment circuit on a Cable Modem Termination System (CMTS); and

a network interface to allow the device to send and receive traffic across a network.

17. The network device of claim 16 , wherein the network device has no bridging functionality.

18. The network device of claim 16 , the processor further to:

receive a double SP-VLAN tagged packet through the network interface;

forward the packet to an appropriate downstream device in a VPN.

19. The network device of claim 18 , the processor further to:

identify a virtual trunk interface based on the outer SP-VLAN tag, wherein the virtual trunk interface is associated with the cable service identifier;

identify the virtual private network based on the inner SP-VLAN tag;

remove the SP-VLAN tags; and

transmit the packet to the cable modem in the private virtual network.

20. The network device of claim 16 , further comprising a memory to store network identifiers and cable service identifiers associated with the cable modem.

21. A network device, comprising:

means for allowing the network device to exchange data with at least one cable modem;

means for receiving a packet from a cable modem;

means for associating a cable interface and cable service identifier with the cable modem;

means for inserting a layer 2 network identifier into the packet, the identifier comprising inner and outer SP-VLAN tags, wherein the inner SP-VLAN tag represents a service flow on a destination node in a point-to point L2VPN service or a customer VPN in a multipoint L2VPN service and wherein the outer SP-VLAN tag represents the destination node in a point-to-point L2VPN service or a single attachment circuit on a Cable Modem Termination System (CMTS); and

means for allowing the network device to send and receive traffic across a network.

22. The network device of claim 21 , further comprising:

means for receiving the double SP-VLAN tagged packet;

means for identifying a virtual trunk interface based on the outer SP-VLAN tag, wherein the virtual trunk interface is associated with the cable service identifier;

means for identifying a virtual private network based on the inner SP-VLAN tag;

means for removing the SP-VLAN tags; and

means for transmitting the packet to the cable modem in the private virtual network.

23. The network device of claim 21 , further comprising means for storing network identifiers and cable service identifiers associated with the cable modem.

24. An article of computer-readable media containing instructions embedded in the computer readable media that, when executed, cause a computer to:

receive a packet from a cable modem;

associate a cable interface and cable service identifier with the cable modem;

insert a layer 2 network identifier into the packet, the layer 2 network identifier comprising inner and outer SP-VLAN tags, wherein the inner SP-VLAN tag represents a service flow on a destination node in a point-to point L2VPN service or a customer VPN in a multipoint L2VPN service and wherein the outer SP-VLAN tag represents the destination node in the point-to-point L2VPN service or a single attachment circuit on a Cable Modem Termination System (CMTS); and

transmit the SP-VLAN tagged packet across a network through a network interface.

25. The article of claim 24 , the instructions, when executed, further causing the computer to:

receive a packet having an SP-VLAN tag in the packet;

insert an outer SP-VLAN tag into the received SP-VLAN tagged packet to form a double SP-VLAN tagged packet; and

forward the double SP-VLAN tagged packet to a network device; and

route the packet to an appropriate cable modem in a virtual private network.

26. The article of claim 25 , wherein the instructions for routing the packet to the cable modem comprise instructions, when executed, further cause the computer to:

associate a cable interface and cable service identifier with a cable modem;

identify a virtual trunk interface based on the outer SP-VLAN tag, wherein the virtual trunk interface is associated with the cable service identifier;

identify a virtual private network based on the inner SP-VLAN tag;

remove the SP-VLAN tags; and

transmit the packet to the cable modem in the private virtual network.

27. A cable network, comprising:

a transmitting device to assign a network identifier to traffic and to transmit the traffic, the network identifier comprising outer and inner SP-VLAN tags inserted into a packet, wherein the outer SP-VLAN tag is selected from a plurality of outer SP-VLAN tags each corresponding to an attachment circuit for a VPN, the VPNs each associated with a single CMTS; and

a receiving device to receive the packet and to:

associate the network identifier with a cable modem in a virtual private network;

remove the SP-VLAN tags; and

route the packet to the cable modem in the virtual private network.

28. The cable network of claim 27 , the transmitting device to assign a network identifier further comprising the transmitting device to:

map virtual private networks to inner SP-VLAN tags; and

map virtual trunk interfaces associated with cable modems to outer SP-VLAN tags.