Method and system for allocating persistent private network...

Details Method and system for allocating persistent private network... Method and system for allocating persistent private network...

1999-10-26

2004-08-24

Patel, Alit (Department: 2664)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S353000, C370S355000, C370S401000

Reexamination Certificate

active

06781982

ABSTRACT:

FIELD OF INVENTION
This invention relates to computer networks. More specifically, it relates to a method and system for allocating persistent private network addresses between private networks.
BACKGROUND OF THE INVENTION
The Internet Protocol (“IP”) is an addressing protocol designed to facilitate the routing of traffic within a network or between networks. The Internet Protocol is used on many computer networks including the Internet, intranets and other networks. Current versions of Internet Protocol such as Internet Protocol version-4 (“IPv4”) are becoming obsolete because of limited address space. With a 32-bit address-field, it is possible to assign 2
32
different addresses, which is 4,294,967,296, or greater than 4 billion globally unique addresses.
However, with the explosive growth of the Internet and intranets, Internet Protocol addresses using a 32-bit address-field may soon be exhausted. Internet Protocol version-6 (“IPv6”) proposes the use of a 128-bit address-field for IP addresses. However, a large number of legacy networks including a large number of Internet subnets will still be using older versions for Internet Protocol with a 32-bit address space for many years to come.
Network Address Translation (“NAT”) has been proposed to extend the lifetime of Internet Protocol version 4 by allowing subnets with private Internet Protocol addresses to exist behind a single or small number of globally unique Internet Protocol addresses (see e.g., Internet Engineering Task Force (“IETF”) RFC-2663, “IP Network Address Translator (“NAT”) Terminology and Considerations,” P. Srisuresh and M. Holdrege, August 1999). Multiple private hosts use a single global Internet Protocol address for communication with external networks such as the Internet.
Internally, a sub-network (“subnet”) uses local private addressing. Local addressing may be any addressing scheme that is different from public Internet Protocol addressing, or a private non-unique use of Internet Protocol addresses. In either case, local addresses on a subnet are not used on a external, global Internet Protocol network. When a device or node using local addressing desires to communicate with the external world, its local address is translated to a common external Internet Protocol address used for communication with an external network by a network address translation device. That is, network address translation allows one or more global Internet Protocol addresses to be shared among network devices using a larger number of local private addresses.
There are several problems associated with using network address translation to extend the life of the Internet Protocol. Network address translation interferes with the end-to-end routing principal of the Internet that recommends that packets flow end-to-end between network devices without changing the contents of any packet along a transmission route (see e.g., “Routing in the Internet,” by C. Huitema, Prentice Hall, 1995, ISBN 0-131-321-927).
Current versions of network address translation replace a local network address in a data packet header with an external global network address on outbound traffic, and replace an external global network address in a data packet header with a local private network address on inbound traffic. This type of address translation is computationally expensive, causes security problems by preventing certain types of encryption from being used, or breaks a number of existing applications that cannot coexist with network address translation (e.g., File Transfer Protocol (“FTP”)).
Current versions of network address translation may not gracefully scale beyond a small subnet containing a few dozen nodes or devices because of the computational and other resources required. Network address translation potentially requires support for many different application layer network protocols be specifically programmed into a translation mechanism device such as a network address translation router.
Computational burdens placed on a network address translation router may be significant and degrade network performance, especially if several network address translation-enabled sub-networks share the same network address translation router. In a worst case scenario, a network address translation router translates every inbound and outbound data packet.
The Internet Engineering Task Force (“IETF”) has assigned three sets of private Internet Protocol addresses: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. The number after the “/” indicates a number of bits used as a private network identifier. For example, the “/8” indicates that the first eight bits are used as a private network identifier. A network address represented as “network address
-network bits” indicates that the first n-network bits represent a network identifier. The number of bits remaining represent the number of available host network addresses. For example, if a total of 32 bits are used for a network address (e.g., 32-its for IPv4 addresses) and a “network address/8” notation is used, then 32−8=24 bits remain for host network addresses. In this example at most 2
24
host network addresses are available. Thus, the three sets of private Internet Protocol addresses: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 include at most 2
24
, 2
20
, and 2
16
addresses respectively. A private network may use any of these addresses without consulting any official Internet administrative entity. However, these private addresses are not routable to/from the public Internet. Thus, more than one private network may reuse the same address without creating an addressing or routing ambiguity.
In many instances, network devices using private address spaces are connected to the public Internet Protocol network such as the Internet or an intranet with a network address translation router. The network address translation router changes a source Internet Protocol address of outbound data packets leaving the private address space to a public Internet Protocol address., For inbound data packets, the network address translation router changes a public Internet Protocol address of data packets entering the private address space to an appropriate private Internet Protocol address. However, this network address translation in a network address translation router suffers from the problems described above.
Some of the problems associated with network address translation of private network addresses into public network addresses have been overcome with Distributed Network Address Translation (“DNAT”) described in co-pending applications Ser. Nos. 09/035,600, 09/270,967 and 09/271,025 assigned to the same Assignee as the present application. See also “Distributed Network Address Translation”, by Michael Borella, David Grabelsky, Ikhlaq Sidhu, and Brian Petry, IETF Internet Draft, <draft-borella-aatn-dnat-01.txt>, October 1998. Distributed Network Address Translation is also called “Realm Specific Internet Protocol” (“RSIP”) by the IETF. For more information on Realm Specific Internet Protocol see “Realm Specific IP Framework,” by M. Borella and J. Lo, IETF draft, <draft-ieft-nat-rsip-framework-02.txt>, October 1999, and “Realm Specific IP: Protocol Specification,” by M. Borella and J. Lo, IETF draft, <draft-ietf-nat-rsip-protocol-02.txt>, August 1999.
Distributed Network Address Translation is used with private small office network, home office networks or other private stub networks or subnets that have multiple network devices with private network addresses using a common external global public network address to communicate with an external network such as the Internet.
As multimedia devices on private networks use the Internet or other Internet Protocol Networks for services such as audio and/or video conferencing (e.g., H.323, H.324, CUSeeME, RealAudio, Internet Relay Chat, Voice over Internet Protocol (“VoIP”), etc.) there is a need to maintain the privacy of multimedia endpoint devices. If the Internet Protocol address of a multimedia device is publicly available, a device, a device&ap

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