PTAB

IPR2018-01719

Metaswitch Networks Ltd v. Sonus Networks Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

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

3. Grounds for Unpatentability

Ground 1: Obviousness over a Single Reference - 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 asserted that Li discloses all limitations of the challenged claims. Li teaches a system for handling overload in a telecommunications network component, specifically an H.323 gatekeeper. Petitioner argued this gatekeeper, which performs call switching and translation via software, is a "softswitch" as claimed. Li explicitly discloses "overload control routines" that are triggered by "processing load monitors" that measure CPU capacity. When CPU usage exceeds a predetermined threshold (Li suggests 90%), the routines limit calls by rejecting new, incoming messages until the processing load decreases to an acceptable level. This directly maps to the claimed method of monitoring a criterion and limiting calls based on that monitoring.
    • Motivation to Combine (for §103 grounds): Not applicable as this ground is based on a single reference. Petitioner argued Li alone renders the claims obvious because it teaches every element, and any minor differences would have been obvious modifications.
    • Expectation of Success (for §103 grounds): Not applicable.

Ground 2: Obviousness over Full-Featured Softswitch with Overload Control - 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), Li (Patent 6,591,301).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Kohli discloses a full-featured, multi-protocol softswitch with a plurality of signaling subsystems (e.g., SS7, H.323, SIP), meeting a key limitation of the ’627 patent not explicitly detailed in Li. However, Kohli does not expressly teach an overload control mechanism. Li supplies this missing element by teaching overload control routines based on monitoring CPU load. The combination of Kohli’s comprehensive softswitch architecture with Li’s specific overload control method allegedly discloses every element of the challenged claims.
    • Motivation to Combine (for §103 grounds): A person of ordinary skill in the art (POSITA) would be motivated to apply Li's disclosed overload control methods to Kohli's softswitch to solve the well-known problem of processor overload in telecommunication switches. The ’627 patent itself admits that CPU overload was a known potential problem for softswitches.
    • Expectation of Success (for §103 grounds): A POSITA would have a reasonable expectation of success in this combination because both references address telecommunications switching, and applying a known overload control technique (Li) to a standard switch architecture (Kohli) is a predictable and straightforward engineering solution.

Ground 3: Obviousness over a Commercial Softswitch with Predecessor Overload Principles - Claims 1-20 are obvious over Lakshmi in view of Korner.

  • Prior Art Relied Upon: Lakshmi (“The Lucent Technologies Softswitch,” 1999) and Korner (“Overload Control of SPC Systems,” 1991).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Lakshmi describes the Lucent Softswitch, a commercial, software-based switching platform with multiple signaling subsystems (SS7, ISDN, SIP), similar to Kohli. Korner, though directed at earlier Stored Program Control (SPC) switching systems (predecessors to softswitches), explicitly teaches the three overload criteria recited in the ’627 patent claims: Load Measure Control (monitoring CPU usage), Queue Length Control (monitoring memory/queue length), and Call Count Control (monitoring the number of calls). Korner further teaches throttling or blocking new calls when these monitored criteria exceed a threshold.
    • Motivation to Combine (for §103 grounds): A POSITA would combine the teachings because overload was a known issue, and softswitches (Lakshmi) were functionally similar to their SPC-system predecessors (Korner). It would have been obvious to apply the established and fundamental overload control principles described by Korner to the modern softswitch architecture described by Lakshmi to improve its robustness and performance.
    • Expectation of Success (for §103 grounds): The functional similarity between SPC-systems and softswitches would provide a POSITA with a high expectation of success in applying Korner's proven overload control algorithms to Lakshmi's system.

  • Additional Grounds: Petitioner asserted additional obviousness challenges over Li or Kohli/Li in further view of Volftsun (Patent 6,707,792), which teaches overload control based on monitoring memory queue capacity, to explicitly add memory-based monitoring to the processor-based monitoring of Li.

4. Key Claim Construction Positions

  • "Softswitch": Petitioner argued this term, central to all claims, should be construed as "a system that provides switching of telephone calls through software." This construction is critical because it allows prior art references that do not use the word "softswitch" but describe software-based switching components (like Li’s "gatekeeper") to be applied against the claims.

5. Relief Requested

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