Electrical computers and digital processing systems: multicomput – Network computer configuring
Reexamination Certificate
1999-02-24
2002-04-30
Choules, Jack M. (Department: 2177)
Electrical computers and digital processing systems: multicomput
Network computer configuring
C709S203000, C370S355000
Reexamination Certificate
active
06381638
ABSTRACT:
FIELD OF INVENTION
This invention relates to computer networks. More specifically, it relates to a system and method for an Options Based Address Reuse (“OBAR”) for computer networks.
BACKGROUND OF THE INVENTION
Internet Protocol (“IP”) is an addressing protocol designed to route traffic within a network or between networks. Current versions of IP, such as IP 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 U.S. Pat. No. 4,294,967,296, or greater than 4 billion possible addresses. A unique IP number is typically assigned to network devices and a network using IP, whether or not the network is connected to the Internet. Most organizations, such as corporations and universities have multiple networks using IP, with multiple network devices each assigned an IP address. With the explosive growth of the Internet and intranets, IP addresses using a 32-bit address-field may soon be exhausted. IP 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 nodes, will still be using older versions for IP with a 32-bit address space for many years to come. For more information on IP, see Internet Engineering Task Force (“IETF”) Request For Comments (“RFC”) RFC-791, specifically incorporated herein by reference.
Transmission Control Protocol (“TCP”) is a connection-oriented, end-to-end reliable protocol designed to fit into a layered hierarchy of protocols which support multi-network applications. For more information on TCP, see RFC-793, specifically incorporated herein by reference. Transmission Control Protocol/Internet Protocol (“TCP/IP”) is a common and well-known networking protocol comprised of TCP and IP that provides communication across interconnected networks, between computers with diverse hardware architectures and various operating systems. TCP/IP requires each network device to have its own globally routable, globally unique IP address, and each TCP/IP connection or socket is unique for, and characterized by, a quadruple of source-address/source-port/destination-address/destination-port.
Typical TCP/IP Session
FIG. 1
illustrates a typical TCP/IP session between a Host
1
and a Server
1
over the Internet and through Router A and Router B. As is known in the art, a router translates differences between network protocols and routes data packets to an appropriate network node or network device. While only traffic between Host
1
and Server
1
is shown in
FIG. 1
for ease of illustration, it should be understood that there may be multiple Hosts and Servers connected to Router A and Router B, respectively. In setting up the session, Host
1
and Server
1
each have their own globally routable, globally unique IP address, and TCP port. For the example shown in
FIG. 1
, Host
1
has a globally routable and unique IP address of “Host 1” and a TCP port of 1029, and Server
1
has a globally routable and unique IP address of “Server
1
” and a TCP port of 80.
Although Router A and Router B also have at least one of their own globally routable and unique IP addresses, they need not be mentioned for purposes of this example, since Router A and Router B simply act as forwarding agents during the session. In other words, each packet that arrives at either Router A or Router B is simply forwarded out the appropriate interface, depending on the destination IP address indicated in the packet. Because packets from the Internet are forwarded to the network devices (i.e., Host
1
and Server
1
) by their respective routers (i.e., Router A and Router B) based on a destination IP address, however, it is critical that each of the network devices have a globally routable, globally unique IP address. Otherwise, the routers would not know to which network device to send the packets.
FIG. 1
illustrates the typical steps involved with setting up, conducting, and terminating the TCP/IP session. Host
1
creates a TCP/IP socket in computer memory for the connection between itself and Server
1
. This socket holds state information for the TCP/IP connection, such as sequence number, acknowledgement number, and round-trip calculation (see, e.g., W. R. Stevens,
TCP/IP Illustrated, Vol.
1, Addison-Wesley, 1994). The unique quadruple characterizing the TCP/IP socket created by Host
1
is Host
1
/
1029
/Server
1
/
80
. Host
1
sends a TCP-SYN packet to Server
1
to begin TCP transmission. The IP header of the TCP-SYN packet, as well as any other data packet sent by Host
1
to Server
1
, contains a source address of Host
1
, a source port of 1029, a destination address of Server
1
, and a destination port of 80.
Assuming a listen socket exists on the TCP port for which the TCP request refers, Server
1
creates a TCP/IP socket for the connection between itself and Host
1
. This socket holds information similar to that held by the TCP/IP socket at Host
1
. In addition, the unique quadruple characterizing the TCP/IP socket created by Server
1
is Server
1
/
80
/Host
1
/
1029
.
Server
1
then sends a TCP-SYN-ACK packet to Host
1
to acknowledge the TCP transmission. The IP header of the TCP-SYN-ACK packet, as well as any other data packet sent by Server
1
to Host
1
, contains a source address of Server
1
, a source port of 80, a destination address of Host
1
, and a destination port of 1029. Host
1
responds with a TCP-ACK packet to acknowledge the acknowledgement sent by Server
1
, and data is exchanged between Server
1
and Host
1
. Assuming the host closes the TCP/IP session first, Host
1
sends a TCP-FIN packet to Server
1
to initiate termination of the TCP/IP session. Finally, the session ends when Server
1
sends a TCP-FIN-ACK packet to Host
1
to acknowledge receipt of the termination request.
Network Address Translation
Network address translation (“NAT”) has been proposed to extend the lifetime of IPv
4
and earlier versions of IP by allowing a small home office or small network to exist behind one or more IP addresses. The one or more IP addresses are used for communication with external networks such as the Internet. Internally, the small home office or small network uses private addressing. When a device or node using private addressing desires to communicate with the external world, a private address is translated to a common IP address used for communication with an external network by a NAT-enabled device, such as a NAT router.
There are several problems associated with using NAT to extend the life of IP. NAT interferes with the end-to-end routing principal of the Internet which recommends that packets flow end-to-end between network devices without changing the contents of any packet along a transmission route (see e.g., C. Huitema,
Routing in the Internet,
Prentice Hall, 1995). Current versions of NAT replace a private network address in a data packet header with an external network address on outbound traffic, and replace an external address in a data packet header with a private network address on inbound traffic. In addition, NAT typically replaces an internal network device's port number in a data packet header with a corresponding external port number on outbound traffic, and replaces an external port number in a data packet header with a corresponding internal network device's port number on inbound traffic. This type of address and port translation is computationally expensive, causes security problems by preventing certain types of encryption from being used, or breaks a number of existing applications in a network that cannot do NAT (e.g., File Transfer Protocol (“FTP”)).
Current versions of NAT may not gracefully scale beyond a small network containing a few dozen nodes or devices because of the computational and other resources required. NAT potentially requires support for many different internal network protocols to be specifically programmed into a translation mechanism for external protocols in a NAT device, such
Borella Michael S.
Grabelsky David
Mahler Jerry J.
Sidhu Ikhlaq S.
3Com Corporation
Choules Jack M.
Lewis Cheryl
McDonnell & Boehnen Hulbert & Berghoff
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