Cisco Systems Inc v. Portsmouth Network Corp

1. Case Identification

• Case #: IPR2024-00505
• Patent #: 6,917,986
• Filed: January 30, 2024
• Petitioner(s): Cisco Systems, Inc.
• Patent Owner(s): Portsmouth Network Corp.
• Challenged Claims: 1-2, 4-7, 9-14, 16-19, and 21-24

2. Patent Overview

• Title: Methods and Devices for Fault-Resistant Network Access
• Brief Description: The ’986 discloses methods for providing reliable access in computer networks configured with redundant communication links. The technology centers on a network architecture with an "edge switch" connected to one or more "access switches" via primary (active) and secondary (standby) links, using a protocol like Spanning Tree Protocol (STP) to prevent data loops. The purported invention is a method for an edge switch to respond to a failure on the active link by activating the standby link and sending "dummy frames" to downstream switches to rapidly update their filtering databases and re-route traffic.

3. Grounds for Unpatentability

Ground 1: Obviousness over Gai (Downstream Embodiment) - Claims 1-2, 4-7, 9-14, 16-19, and 21-24 are obvious over Gai

• Prior Art Relied Upon: Gai (Patent 6,032,194).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Gai teaches a network architecture analogous to that of the ’986 patent. Specifically, Gai’s backbone switch 124 functions as the claimed "edge switch," which is connected via redundant links to access switches 115 and 116. Consistent with standard STP principles also used in the ’986 patent, Gai discloses placing one link in a forwarding state and the redundant link in a blocking state. Upon failure of the active link, Gai teaches activating the backup link to maintain network connectivity.
  • Motivation to Modify: Petitioner asserted that although Gai's primary example describes sending "dummy" multicast messages upstream toward the network's root switch after a failure, a person of ordinary skill in the art (POSITA) would be motivated to apply the same technique in a downstream direction. The fundamental goal in Gai is rapid network reconfiguration following a topology change. A POSITA would recognize that if a failure occurred on the edge switch's active port, the same logic would apply: the edge switch would need to inform the downstream access switches of the new active path. Therefore, a POSITA would combine Gai's teachings by having the edge switch send dummy traffic over the newly activated link downstream to the access switches.
  • Expectation of Success: A POSITA would have a reasonable expectation of success in this modification. Sending dummy messages to update filtering databases is a known and effective technique disclosed in Gai. Applying this established method to a downstream failure scenario is a predictable application of the same principle to solve the same problem of updating network topology information.

Ground 2: Obviousness over Gai (Upstream Embodiment) - Claims 1-2, 4-7, 9-14, 16-19, and 21-24 are obvious over Gai

• Prior Art Relied Upon: Gai (Patent 6,032,194).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Gai’s explicit teachings render the challenged claims obvious without modification. Gai expressly describes an access switch (e.g., switch 114) that detects a failure on its active forwarding port (its "root port"). In response, the switch immediately transitions one of its backup ports from a blocked state to a forwarding state. The switch then transmits "dummy multicast messages" upstream through this newly active port to inform other devices in the network of the new topology, causing them to update their filtering databases. Petitioner argued this process directly maps onto the limitations of the independent claims.
  • Motivation to Combine: This ground asserted direct anticipation or, at a minimum, obviousness based on Gai's express teachings, requiring no combination of references. Petitioner argued that the Patent Owner distinguished Gai during prosecution by narrowly characterizing it as an "upstream" solution, while framing the ’986 patent as a "downstream" invention. However, Petitioner contended that the broadest challenged claims (e.g., independent claim 1) are not limited to a specific direction of traffic flow (downstream or upstream).
  • Key Aspects: This ground directly challenges the distinction made during prosecution, arguing the examiner erred by overlooking that Gai’s explicit "upstream" embodiment falls within the scope of the broader, direction-agnostic claims of the ’986 patent.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under 35 U.S.C. §314(a) based on Fintiv factors would be inappropriate. The petition asserted that the parallel district court litigation is in its early stages, with minimal investment and a trial date (June 2025) that is proximate to the statutory deadline for a Final Written Decision (FWD). Petitioner also stipulated that it will not pursue in district court any invalidity ground on which an IPR is instituted.
• Petitioner further argued that discretionary denial under 35 U.S.C. §325(d) is unwarranted. Although the Gai reference was before the examiner in an Information Disclosure Statement (IDS), Petitioner contended that the examiner committed a material error by failing to appreciate its most relevant teachings. The petition alleged the examiner overlooked that Gai's explicit upstream failure-response mechanism rendered the broad claims obvious and that Gai's principles would have made a downstream application of the same mechanism obvious to a POSITA.

5. Relief Requested

• Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-2, 4-7, 9-14, 16-19, and 21-24 of the ’986 patent as unpatentable.