Network address translation in a network having multiple overlapping address domains

• US 6,888,837 B1
• Filed: 03/23/1999
• Issued: 05/03/2005
• Est. Priority Date: 03/23/1999
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Patel, Manish, Meehan, Thomas, Cunningham, Timothy
• Primary Examiner(s): Rao, Seema S.
• Assistant Examiner(s): ABELSON, RONALD B
• Application Number:
  US09/274,940
• Time in Patent Office: 2,233 Days
• Field of Search: 370/389, 370/392, 370/400, 370/401, 370/393, 370/395.54, 370/410, 370/438, 370/465, 370/474, 370/475, 709/238, 709/245
• US Class Current: 370/401
• CPC Class Codes: H04L 61/2514 between local and global IP addresses
• CPC Class Codes: H04L 61/2535 Multiple local networks, e.g. resolving potential IP address conflicts
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]

Abstract

A technique for translating addresses in a communication network having multiple overlapping address domains involves mapping an overlapping local address from a first address domain to a unique global address that is specific to a second address domain. The unique global address is used by any device in the second address domain to reference the device in the first address domain having the overlapping local address. Furthermore, a packet sent from a source host in the first address domain to a destination host in the second address domain requires at least a source address translation in order to translate the source host local address used within the first address domain into a source host global address that is used within the second address domain, and may also require a destination address translation in order to translate the destination host global address used within the first address domain into a destination host local address used within the second address domain.

Claims

1. A method of translating addresses in a communication network having multiple overlapping address domains, the method comprising the steps of:

receiving an overlapping local address from an inbound address domain, wherein the overlapping local address is a destination host local address from a destination address domain;

receiving a translation request message as part of a domain name resolution procedure, wherein the translation request message includes the overlapping local address and further specifies an outbond address domain; and

translating an overlapping local address from the inbound address domain into a unique global address that is specific to a specified outbound address domain, wherein the step of translating the overlapping local address from the inbound address domain into the unique global address that is specific to the specified outbound address domain comprises the steps of;

selecting the unique global address from among a number of available global network addresses; and

mapping the unique global address to the overlapping local address from the inbound address domain exclusively for the specified outbound address domain.

2. The method of claim 1, wherein the step of translating the overlapping local address from the inbound address domain into the unique global address that is specific to the specified outbound address domain comprises the steps of:

maintaining a number of address translation entries, each address translation entry mapping a local address from one of a number of overlapping inbound address domains to a corresponding global address that is specific to one of a number of overlapping outbound address domains;

finding an address translation entry mapping the overlapping local address from the inbound address domain to the unique global address that is specific to the specified outbound address domain; and

extracting the unique global address from the address translation entry.

3. The method of claim 2 wherein each address translation entry comprises an inbound local address field, an outbound address domain field, and an outbound global address field, and wherein the step of maintaining the number of address translation entries comprises:

selecting a network address from among a number of available network addresses; and

creating an address translation entry having the inbound local address field equal to the local address, the outbound address domain field equal to the specified outbound address domain, and the outbound global address field equal to the selected network address.

4. The method of claim 2 wherein each address translation entry comprises an inbound local address field, an outbound address domain field, and an outbound global address field, and wherein the step of finding the address translation entry mapping the overlapping local address from the inbound address domain to the unique global address that is specific to the specified outbound address domain comprises finding the address translation entry having the inbound local address field equal to the overlapping local address and the outbound address domain field equal to the specified outbound address domain.

5. The method of claim 1, wherein the outbound address domain is a source address domain.

6. The method of claim 1, further comprising the step of transmitting a translation response message including the unique global address.

7. The method of claim 1, wherein the step of receiving the overlapping local address from the inbound address domain comprises receiving a packet from a source host in a source (inbound) address domain that is destined for the destination host in the destination (outbound) address domain and includes a source address equal to an overlapping source host local address from the source (inbound) address domain and a destination address equal to a unique destination host global address.

8. The method of claim 7, wherein the step of translating the overlapping local address from the inbound address domain into the unique global address that his specific to the specified outbound address domain comprises the steps of:

maintaining a number of source address translation entries, each source address translation entry mapping a source host local address from one of a number of overlapping source (inbound) address domains to a corresponding source host global address that is specific to one of a number of overlapping destination (outbound) address domains;

determining the source (inbound) address domain for the packet;

determining the destination (outbound) address domain for the packet;

translating the source address in the packet from the overlapping source host local address in the source (inbound) address domain into a unique source host global address that is specific to the destination (outbound) address domain; and

forwarding the translated packet to the destination host over the destination (outbound) address domain.

9. The method of claim 8, wherein the step of translating the source address in the packet comprises the steps of:

selecting the source host global address from a pool of network addresses; and

creating a source address translation entry mapping he overlapping source host local address from the source (inbound) address domain for the packet to the source host global address that is specific to the destination (outbound) address domain for the packet.

10. The method of claim 8, wherein the step of translating the source address in the packet comprises the steps of:

finding a source address translation entry mapping the overlapping source host local address from the source (inbound) address domain for the packet to a unique source host global address that is specific to the destination (outbound) address domain for the packet;

extracting the source host global address from the source address translation entry.

11. The method of claim 10, wherein the step of maintaining the number of source address translation entries comprises maintaining a number of source address translation tables, each source address translation table consisting of those source address translation entries mapping the source host local addresses from a common source (inbound) address domain, and wherein the step of finding the source address translation entry mapping the overlapping source host local address from the source (inbound) address domain for the packet to the unique source host global address that is specific to the destination (outbound) address domain for the packet comprises selecting a source address translation table based upon the source (inbound) address domain for the packet.

12. The method of claim 11, wherein each source address translation entry comprises a source local address field, a destination (outbound) address domain field, and a source global address field, and wherein the step of finding the source address translation entry mapping the overlapping source host local address from the source (inbound) a domain for the packet to the unique source host global address that is specific to the destination (outbound) address domain for the packet comprises finding the source address translation entry having the source local address field equal to the overlapping source host local address and the destination (outbound) address domain field equal to the destination (outbound) address domain for the packet.

13. The method of claim 11, wherein each source address translation entry comprises a source local address field, a source (inbound) address domain field, a destination (outbound) address domain field, and a source global address field, and wherein the step of finding the source address translation entry mapping the overlapping source host local address from the source (inbound) address domain for the packet to the unique source host global address that is specific to the destination (outbound) address domain for the packet comprises finding the source address translation entry having the source local address field equal to the overlapping source host local address, the source (inbound) address domain field equal to the source (inbound) address domain for the packet, and the destination (outbound) address domain field equal to the destination (outbound) address domain for the packet.

14. The method of claim 8, wherein the step of determining the source (inbound) address domain for the packet comprises determining the source (inbound) address domain for the packet implicitly based upon a network interface over which the packet is received.

15. The method of claim 8, further comprising the step of maintaining a number of destination address translation entries, each destination address translation entry mapping a destination host global address that is specific to a source (inbound) address domain to a corresponding destination host local address for a corresponding destination (outbound) address domain.

16. The method of claim 15, wherein each destination address translation entry maps a destination host global address to a corresponding destination (outbound) address domain, and wherein the step of determining the destination (outbound) address domain for the packet comprises the steps of:

finding a destination address translation entry for the destination host global address in the packet; and

extracting the destination (outbound) address domain from the destination address translation entry.

17. The method of claim 15, wherein each destination address translation entry maps the destination host global address to a corresponding source (inbound) address domain, and wherein the step of determining the source (inbound) address domain for the packet comprises the steps of:

finding a destination address translation entry for the destination host global address in the packet; and

extracting the source (inbound) address domain from the destination address translation entry.

18. The method of claim 15, wherein each destination address translation entry maps the destination host global address to a corresponding destination host local address for the destination (outbound) address domain, and wherein the method further comprises the steps of:

finding a destination address translation entry for the destination host global address in the packet;

extracting the destination host local address from the destination address translation entry; and

translating the destination address in the packet from the destination host global address to the corresponding destination host local address extracted from the destination address translation entry.