MANAGING HOST ROUTES FOR LOCAL COMPUTER NETWORKS WITH A PLURALITY OF FIELD AREA ROUTERS

• US 20130013809A1
• Filed: 07/05/2011
• Published: 01/10/2013
• Est. Priority Date: 07/05/2011
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Vasseur, Jean-Philippe, Hui, Jonathan W., Previdi, Stefano, Shaffer, Shmuel
• Granted Patent: US 8,799,510 B2
• Time in Patent Office: Days
• US Class Current: 709/239
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/64 using an overlay routing layer

Abstract

In one embodiment, a particular field area router (FAR), in a local computer network (e.g., a mesh network) having a plurality of FARs, advertises a common subnet prefix assigned to the local computer network into a global computer network. Each of the plurality of FARs of the local computer network is configured to accept any traffic destined to the local computer network, and a tunnel overlay is built among the plurality of FARs. Upon receiving a packet at the particular FAR destined to a particular device in the local computer network, and in response to the particular FAR not having a host route to the particular device, it forwards the packet on the tunnel overlay to another of the plurality of FARs of the local computer network.

Claims

1. A method, comprising:

advertising, into a global computer network, from a particular field area router (FAR) in a local computer network having a plurality of FARs, a common subnet prefix assigned to the local computer network, wherein each of the plurality of FARs of the local computer network is configured to accept any traffic destined to the local computer network;

building a tunnel overlay among the plurality of FARs of the local computer network;

receiving a packet at the particular FAR destined to a particular device in the local computer network; and

in response to the particular FAR not having a host route to the particular device, forwarding the packet on the tunnel overlay to another of the plurality of FARs of the local computer network.

2. The method as in claim 1, wherein the packet is received at the particular FAR from the global computer network.

3. The method as in claim 1, wherein the packet is received at the particular FAR from another FAR of the local computer network.

4. The method as in claim 1, further comprising:

advertising, into the local computer network and global computer network from the particular FAR, a FAR prefix that falls within the common subnet prefix.

5. The method as in claim 4, wherein one or more devices in the local computer network that communicate through the particular FAR configure their addresses based on the FAR prefix for the particular FAR.

6. The method as in claim 1, further comprising:

discovering, by the particular FAR, each other of the plurality of FARs of the local computer network.

7. The method as in claim 1, further comprising:

in response to the particular FAR having the host route to the particular device, forwarding the packet into the local computer network toward the particular device.

8. The method as in claim 1, wherein the tunnel overlay is fully connected, the method further comprising:

selecting a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR not having already received the packet.

9. The method as in claim 8, further comprising:

maintaining a list of FARs that have already received the packet in the forwarded packet.

10. The method as in claim 1, wherein the tunnel overlay is a ring, the method further comprising:

selecting a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR being a next FAR on the ring.

11. The method as in claim 10, further comprising:

maintaining a time-to-live (TTL) value in the forwarded packet, the TTL configured and maintained to prevent the packet from circling the ring more than once.

12. The method as in claim 1, further comprising:

maintaining an Interior Gateway Protocol (IGP) instance among the plurality of FARs; and

selecting a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR having the host route to the particular device according to the IGP instance.

13. The method as in claim 1, further comprising:

advertising particular host routes to devices of the local computer network from the particular FAR only in response to the corresponding host route being actively utilized.

14. The method as in claim 1, further comprising:

triggering network address renumbering in the local computer network to defragment address space in the local computer network when host route overhead crosses a given threshold.

15. The method as in claim 14, wherein the given threshold is selected from a group consisting of:

link state database (LSDB) size; and

delay.

16. An apparatus, comprising:

a network interface to communicate in a local computer network having a plurality of field area routers (FARs);

a network interface to communicate in a global computer network;

s a processor coupled to the network interfaces and adapted to execute one or more processes; and

a memory configured to store a FAR process executable by the processor, the process when executed operable to;

advertise, into the global computer network, a common subnet prefix assigned to the local computer network, wherein each of the plurality of FARs of the local computer network is configured to accept any traffic destined to the local computer network;

build a tunnel overlay among the plurality of FARs of the local computer network;

is receive a packet destined to a particular device in the local computer network; and

in response to not having a host route to the particular device, forward the packet on the tunnel overlay to another of the plurality of FARs of the local computer network.

17. The apparatus as in claim 16, wherein the process when executed is further operable to:

advertising, into the local computer network and global computer network from the particular FAR, a FAR prefix that falls within the common subnet prefix, wherein one s or more devices in the local computer network that communicate through the particular FAR configure their addresses based on the FAR prefix for the particular FAR.

18. The apparatus as in claim 16, wherein the tunnel overlay is fully connected, and wherein the process when executed is further operable to:

select a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR not having already received the packet.

19. The apparatus as in claim 16, wherein the tunnel overlay is a ring, and wherein the process when executed is further operable to:

select a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR being a next FAR on the ring.

20. The apparatus as in claim 16, wherein the process when executed is further operable to:

maintain an Interior Gateway Protocol (IGP) instance among the plurality of FARs; and

select a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR having the host route to the particular device according to the IGP instance.

21. The apparatus as in claim 16, wherein the process when executed is further operable to:

advertise particular host routes to devices of the local computer network only in response to the corresponding host route being actively utilized.

22. The apparatus as in claim 16, wherein the process when executed is further operable to:

trigger network address renumbering in the local computer network to defragment address space in the local computer network when host route overhead crosses a given threshold.

23. A tangible, non-transitory, computer-readable media having software encoded thereon, the software, when executed by a processor on a particular field area router (FAR) in a local computer network having a plurality of FARs, operable to:

advertise, into a global computer network, a common subnet prefix assigned to the local computer network, wherein each of the plurality of FARs of the local computer network is configured to accept any traffic destined to the local computer network;

build a tunnel overlay among the plurality of FARs of the local computer network;

receive a packet destined to a particular device in the local computer network; and

in response to not having a host route to the particular device, forward the packet on the tunnel overlay to another of the plurality of FARs of the local computer network.

24. The computer-readable media as in claim 23, wherein the software when executed is further operable to select a specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay through a technique selected from a group consisting of:

i) wherein the tunnel overlay is fully connected, and wherein the technique selects the specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR not having already received the packet;

ii) wherein the tunnel overlay is a ring, and wherein the technique selects the specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR being a next FAR on the ring; and

iii) wherein an Interior Gateway Protocol (IGP) instance is maintained among the plurality of FARs, and wherein the technique selects the specific FAR of the plurality of FARs to which to forward the packet on the tunnel overlay based on the specific FAR having the host route to the particular device according to the IGP instance.

25. The computer-readable media as in claim 23, wherein the software when executed is further operable to:

advertise, into the local computer network and global computer network from the particular FAR, a FAR prefix that falls within the common subnet prefix, wherein one or more devices in the local computer network that communicate through the particular FAR configure their addresses based on the FAR prefix for the particular FAR.