Method and system for automatically interconnecting IPv4 networks across an IPv6 network

• US 20060209885A1
• Filed: 09/12/2005
• Published: 09/21/2006
• Est. Priority Date: 03/21/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ward, David D., Hain, Anthony
• Granted Patent: US 7,609,691 B2
• Time in Patent Office: Days
• US Class Current: 370/465
• CPC Class Codes: H04L 61/251 between different IP versions
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/167 Adaptation for transition between two IP versions, e.g. between IPv4 and IPv6 translation of Internet protocol [IP] addresses H04L61/2503

Abstract

A method and system for automatically interconnecting IPv4 networks across an IPv6 network are disclosed. The method includes receiving an IPv4 packet at an ingress router in the IPv6 network and finding the longest match IPv4 routing entry for IPv4 addresses in the received packet to identify an egress router in the IPv6 network. The IPv4 packet is encapsulated to create an IPv6 packet, wherein destination and source addresses of the encapsulated packet identify a subnet router anycast corresponding to the ingress router and the egress router in the IPv6 network. The encapsulated packet is forwarded to the egress router.

Claims

1. A method for automatically interconnecting IPv4 networks across an IPv6 network, the method comprising:

receiving an IPv4 packet at an ingress router in the IPv6 network;

finding the longest match IPv4 routing entry for IPv4 addresses in the received packet to identify an egress router in the IPv6 network;

encapsulating the IPv4 packet to create an IPv6 packet, wherein destination and source addresses of the encapsulated packet identify a subnet router anycast corresponding to the ingress router and the egress router in the IPv6 network; and

forwarding the encapsulated packet to the egress router.

2. The method of claim 1 further comprising concatenating a prefix with the longest match IPv4 routing entry to create a IPv6 prefix value.

3. The method of claim 2 further comprising setting remaining bits in IPv6 address to zero.

4. The method of claim 1 wherein the encapsulated packet includes a traffic-class field, payload-length field and hop-count field.

5. A method for transmitting packets from a first IPv4 network to a second IPv4 network across an IPv6 network, the method comprising:

forwarding an IPv4 packet from the first IPv4 network to an ingress router in the IPv6 network;

creating a tunnel in the IPv6 network for transferring the packet across the IPv6 network, comprising defining tunnel endpoint addresses as an IPv6 subnet router anycast corresponding to the ingress router and an egress router;

encapsulating the IPv4 packet to create an IPv6 packet;

forwarding the encapsulated packet to the egress router;

decapsulating the packet at the egress router; and

forwarding the packet to the second IPv4 network.

6. The method of claim 5 wherein defining tunnel endpoints further comprises finding the longest match IPv4 routing entry corresponding to destination and source IPv4 addresses in the received IPv4 packet.

7. The method of claim 5 wherein decapsulating the packet comprises removing an IPv6 header.

8. The method of claim 5 further comprising copying a hop-count from an IPv6 header in the encapsulated header to an IPv4 time-to-live field.

9. The method of claim 5 further comprising concatenating a prefix with the longest match IPv4 routing entry to create a IPv6 prefix value.

10. The method of claim 5 wherein encapsulating the IPv4 packet comprises encapsulating ICMP messages originating in the IPv4 network.

11. The method of claim 5 wherein the logical link MTU is 1280 bytes.

12. A computer program product for automatically interconnecting IPv4 networks across an IPv6 network, the product comprising:

code that finds the longest match IPv4 routing entry for IPv4 addresses in a received IPv4 packet to identify an egress router in the IPv6 network;

code that encapsulates the IPv4 packet to create an IPv6 packet, wherein destination and source addresses of the encapsulated packet identify a subnet router anycast corresponding to the ingress router and the egress router in the IPv6 network;

code that forwards the encapsulated packet to the egress router; and

a computer-readable medium that stores the codes.

13. The computer program-product of claim 12 further comprising code that creates a locally defined prefix and connects the prefix with the longest match IPv4 routing entry to create an IPv6 prefix value.

14. Apparatus for automatically interconnecting IPv4 networks across an IPv6 network, the apparatus comprising:

means for receiving an IPv4 packet at an ingress router in the IPv6 network;

means for finding the longest match IPv4 routing entry for IPv4 addresses in the received packet to identify an egress router in the IPv6 network;

means for encapsulating the IPv4 packet to create an IPv6 packet, wherein destination and source addresses of the encapsulated packet identify a subnet router anycast corresponding to the ingress router and the egress router in the IPv6 network; and

means for forwarding the encapsulated packet to the egress router.

15. The apparatus of claim 14 further comprising means for creating a locally defined prefix and connecting the prefix with the longest match IPv4 routing entry to create an IPv6 prefix value.