PTAB

IPR2018-01719

Metaswitch Networks Ltd. v. Sonus Networks, Inc.

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1. Case Identification

  • Case #: IPR2018-01719
  • Patent #: 7,158,627
  • Filed: September 20, 2018
  • Petitioner(s): Metaswitch Networks Ltd. and Metaswitch Networks Corporation
  • Patent Owner(s): James J. Lu
  • Challenged Claims: 1-20

2. Patent Overview

  • Title: Method and System for Inhibiting Softswitch Overload
  • Brief Description: The ’627 patent describes a method and system for preventing overload in a telecommunications softswitch. The system monitors operational criteria of the computer running the softswitch, such as CPU usage, memory usage, or the number of active calls, and limits or blocks new incoming calls if any criterion exceeds a predefined threshold.

3. Grounds for Unpatentability

Ground 1: Obviousness over Li - Claims 1, 3, 5-7, 9-12, 14, 15, 17, 18, and 20 are obvious over Li.

  • Prior Art Relied Upon: Li (Patent 6,591,301).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Li teaches every element of the challenged claims. Li discloses a system for handling overload in a telecommunications network node (a gatekeeper) that functions as a softswitch. This system uses "overload control routines" that are triggered by "processing load monitors," which measure metrics like CPU capacity. When an overload condition is detected (e.g., CPU usage exceeds a 90% threshold), Li’s system limits the number of calls processed by rejecting new incoming messages until the load returns to an acceptable level. This directly maps to the ’627 patent’s method of monitoring a computer criterion and limiting calls based on the monitoring.
    • Motivation to Combine (for §103 grounds): This ground is based on a single reference.
    • Expectation of Success (for §103 grounds): This ground is based on a single reference.

Ground 2: Obviousness over Kohli in view of Li - Claims 1, 3-7, 9-12, 14, 15, 17, 18 and 20 are obvious over Kohli in view of Li.

  • Prior Art Relied Upon: Kohli (Patent 7,213,068) and Li (Patent 6,591,301).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Kohli discloses a full-featured, distributed softswitch system with multiple signaling subsystems (e.g., SS7, H.323, SIP) for translating between different network protocols, thus teaching the softswitch environment of the ’627 patent. While Kohli discloses the softswitch architecture, Li provides the specific overload control mechanism that Kohli lacks. Li teaches monitoring processor load and rejecting new calls when a threshold is exceeded. The combination of Kohli's comprehensive softswitch and Li's specific overload control method renders the claims obvious.
    • Motivation to Combine: A POSITA would have been motivated to apply Li's known overload control methods to Kohli's softswitch to solve the well-known problem of processor overload in telecommunications switches. The ’627 patent itself admits that CPU overload is a known potential problem for softswitches.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because Li’s gatekeeper and Kohli’s softswitch perform analogous functions (call signaling and control). Applying a known overload control technique from one call-control system to another would have been a straightforward and predictable implementation.

Ground 3: Obviousness over Lakshmi in view of Korner - Claims 1-20 are obvious over Lakshmi in view of Korner.

  • Prior Art Relied Upon: Lakshmi (“The Lucent Technologies Softswitch-Realizing the Promise of Convergence,” Bell Labs Technical Journal, 1999) and Korner (“Overload Control of SPC Systems,” 1991).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Lakshmi discloses a commercial softswitch (the Lucent Softswitch™) with multiple signaling subsystems (SS7, ISDN, SIP), satisfying the system elements of the claims. Korner, which addresses overload in predecessor Stored Program Control (SPC) switching systems, teaches the claimed overload control methods. Specifically, Korner discloses monitoring three distinct criteria: processor load (Load Measure Control), memory/queue length (Queue Length Control), and the number of incoming calls (Call Count Control). Korner teaches throttling or blocking new calls via a "gate" when any of these monitored criteria exceed a threshold.
    • Motivation to Combine: A POSITA would combine Lakshmi and Korner to implement efficient overload control on a modern softswitch. Overload was a known issue, and Lakshmi itself notes the need for "congestion control." A POSITA would naturally look to established principles, like those in Korner for the predecessor SPC systems, to solve this problem.
    • Expectation of Success: Because softswitches are the direct technological evolution of SPC systems and often use similar switching algorithms, a POSITA would reasonably expect that overload control principles proven in SPC systems would be successfully applicable to softswitches.

  • Additional Grounds: Petitioner asserted an additional challenge that claims 1-20 are obvious over Li (or Kohli in view of Li) further in view of Volftsun (Patent 6,707,792). This ground argued for adding Volftsun’s teachings on memory-based overload control (monitoring message queue capacity) to the processor-based control taught by Li.

4. Key Claim Construction Positions

  • "Softswitch" (All Claims): Petitioner argued this term should be construed simply as "a system that provides switching of telephone calls through software." This construction is based on the patent's own description and is consistent with extrinsic sources. The construction is important because it is broad enough to encompass prior art systems, like Li's "gatekeeper," which perform the same function but may not use the specific "softswitch" label, thereby preventing the Patent Owner from arguing non-anticipation based on nomenclature alone.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of the ’627 patent as unpatentable.