US 5550984

Patent Overview: US 5,550,984 A

Title: Security system for preventing unauthorized communications between networks by translating communications received in IP protocol to non-IP protocol to remove address and routing services information.

Patent number: US 5,550,984 A. Application: US 08/350,541. Inventor: Edward J. Gelb. Original assignee: Matsushita Electric Corp. of America (current assignee listed as Panasonic Corp of North America). Prior art date / filing date: 1994-12-07. Publication (grant) date: 1996-08-27. Status: Expired – Fee Related; anticipated expiration 2014-12-07.

Purpose: To prevent unauthorized communications between computer networks — specifically unauthorized access to a private network from a public network such as the Internet, and between related private networks (e.g., company branch LANs/WANs). The system also aims to protect Unix and MVS hosts from unauthorized access by private-network users.

Plain-language scope (per the supplied text): The security system uses first and second network motherboards, each with a network interface adapter for communicating with its respective network, plus matched, identical transfer adapters for passing communications from one motherboard's network interface adapter to the other's. All components are described as available standard hardware and software, requiring no special coding or hardware, and the system is contained entirely within one unit.

Security is achieved by translating communications received in IP protocol to non‑IP protocol, removing original IP datagram headers and disabling routing services (IP packet forwarding; RIP, ARP, and ICMP) between each network interface adapter and its transfer adapter. This inhibits unauthorized users from obtaining IP and corresponding physical addresses needed for direct communication with nodes on the other network. The second motherboard may provide API shim and client/server software (or Dynamic Link Library software) for communication services, and sets up a domain name, IP address, and subnetwork mask so users of the second network can communicate. Private-network TCP/IP addresses and subnetwork masks can be established independently of the public Internet's registration procedures.

Source: https://patents.google.com/patent/US5550984/en

Not established by this excerpt: the full specification (claims, drawings, detailed embodiments and omitted text), exact claim language, and the identity or content of any prior art references. It also does not establish the relationship among the listed foreign priority filings beyond what is shown.