Invalidity dossier
US 6141755
Firewall security apparatus for high-speed circuit switched networks
Current assignee: GOVERNMENT OF UNITED STATES AS REPRESENTED BY DIR NAT SECURITY AGENCY
Added 9/21/2026, 4:01:25 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 6,141,755 B1
Title: Firewall security apparatus for high-speed circuit switched networks
Patent number / application: US 6,141,755 A / US 09/059,041
Inventors: Patrick William Dowd; John Thomas McHenry
Assignee: Government of the United States as represented by the Director, National Security Agency (original assignee: National Security Agency)
Dates: Priority/filing date 1998-04-13; granted/publication date 2000-10-31; anticipated expiration 2018-04-13; legal status listed as "Expired – Lifetime"
Purpose: The patent addresses network security for signaling-based circuit switched networks, framed as a concern that could otherwise stall wide-scale deployment, including residential broadband (RBB) and small-business/home environments where low cost is essential. It seeks strong flow selectability without sacrificing the performance benefits of high-speed circuit switched networks, at low cost and complexity, across rates from narrowband ISDN (kilobits per second) to broadband above gigabits per second.
Plain-language scope: Rather than validating each individual packet, the invention validates the flow — a communication session between two network endpoints used to transfer Protocol Data Units. Suitability of flows is determined in real time during initial connection negotiations; once a connection is established as suitable, datagrams belonging to that flow pass through the firewall without performance degradation. The description relates to information processing system organization and to security using active connection management with authentication. It is stated to work with any signaling-based circuit switched network protocol and with a multitude of hardware and software protocols; ATM and Frame Relay are named as current examples, with ATM used as the explanatory exemplar (53-byte cells; 5-byte header; VPI/VCI identifiers defined per link, not end-to-end). Classifications include H04L63/02 (firewalls), H04L63/0227 (filtering policies), H04L63/0254 (stateful filtering), and H04L63/08 (authentication).
Source: https://patents.google.com/patent/US6141755/en
What this excerpt does not establish: It supplies no claims text, abstract, detailed description, or drawing content; no specific claim limitations, authentication mechanism details, or implementation architecture can therefore be confirmed from it. The legal-status, priority-date, and assignee listings are expressly stated in the source to be assumptions, not legal conclusions. The excerpt also omits any prior-art comparison beyond what is quoted here.
Generated 10/1/2026, 10:02:38 PM
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Litigation summary
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Proceedings on file (0)
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PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
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Obviousness
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Extensions
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Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.