PTAB

IPR2018-00099

RPX Corp v. Parity Networks LLC

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1. Case Identification

2. Patent Overview

  • Title: System Performance In A Data Network Through Queue Management Based On Ingress Rate Monitoring
  • Brief Description: The ’848 patent describes a method to improve network performance by managing congestion. It proposes an enhancement to the standard Random Early Detection (RED) packet-dropping algorithm to discriminate between different data flows. The system monitors the ingress rate of each flow against a "flow profile," marks packets based on their compliance with bandwidth thresholds in the profile, and then applies a corresponding drop probability, preferentially dropping packets from non-compliant flows.

3. Grounds for Unpatentability

Ground 1: Claims 1, 4-5, 8-10, 12-19, and 21-23 are obvious over Feng in view of the Admitted Prior Art RED Algorithm.

  • Prior Art Relied Upon: Feng (a May 1997 IEEE publication) and the Admitted Prior Art RED Algorithm (as described in the ’848 patent specification, originating from a paper by Floyd).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Feng, a paper published two years before the patent's filing, taught the core of the invention. Feng disclosed a method for optimizing network performance by using a "traffic envelope" or "Tspec" (analogous to the patent's "flow profile") to define bandwidth parameters for a connection. Feng monitored traffic against this profile using a "token bucket," marked packets as "conformant" or "unmarked," and used an Enhanced RED (ERED) algorithm where conformant packets have a lower drop probability. The Admitted Prior Art RED Algorithm, which the patent itself incorporated, supplied the standard details for the drop functions, such as being zero below a minimum queue threshold (min_th) and positive above it, thereby teaching limitations [D] and [E] of claim 1. The combination also allegedly taught dependent claim limitations, such as Feng's Tspec specifying an "average rate," "peak rate," and "burst size" (claims 12-13), and the linearity of the drop function (claims 9, 18) being taught by the admitted prior art's description of RED.
    • Motivation to Combine: A POSITA would have been motivated to combine these references because Feng explicitly described its ERED system as a "minor modification to the original RED algorithm" and cited the foundational Floyd paper. To understand and implement Feng's system, a POSITA would have naturally consulted the well-known RED algorithm (admitted as prior art) for the underlying details of the drop mechanism, including the use of minimum and maximum thresholds.
    • Expectation of Success: A POSITA would have had a high expectation of success because Feng's ERED was an incremental improvement designed to add flow discrimination to the standard RED algorithm. The combination represented a straightforward application of known techniques to solve a known problem, yielding predictable results.

Ground 2: Claims 11, 20, and 24-31 are obvious over Feng in view of the Admitted Prior Art RED Algorithm and Ferguson.

  • Prior Art Relied Upon: Feng (a May 1997 IEEE publication), the Admitted Prior Art RED Algorithm, and Ferguson (a March 1998 IETF Internet-Draft).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground asserted that adding Ferguson to the combination of Ground 1 rendered the remaining claims obvious. Ferguson was introduced to teach a system with more than two levels of service priority. While Feng taught a binary "marked" versus "unmarked" system, Ferguson disclosed using a three-bit field in the packet header to create multiple levels of "drop preference" (e.g., from "highest" to "lowest"). Ferguson suggested using multiple token-buckets with different bit-rate thresholds to mark packets and explicitly recommended using Feng's "modified RED behavior" to apply different drop probabilities for each priority level. Petitioner contended this combination rendered obvious claims 11, 20, and 24, which require three levels of marking ("low," "normal," and "high"), as a POSITA would naturally apply these labels to Ferguson's disclosed priority levels.
    • Motivation to Combine: A POSITA seeking to improve Feng's binary system with more granular, multi-level service differentiation would have been motivated to incorporate Ferguson's teachings. Ferguson itself cited Feng and presented its multi-level drop preference mechanism as a suitable enhancement for such systems, providing an explicit reason to integrate the two.
    • Expectation of Success: The combination was presented as straightforward and predictable. Ferguson provided a clear roadmap by suggesting the use of its multi-level marking scheme in conjunction with Feng's modified RED algorithm, removing any need for undue experimentation.

4. Key Technical Contentions

  • "Flows" vs. "Connections": Petitioner contended that a POSITA would understand Feng's use of "connections" and "sessions" to be interchangeable with the ’848 patent's claimed "flows." The argument was that Feng's system, which monitored unidirectional data transfers like FTP or streaming video, functionally operated on "flows" from a source to a destination, even if different terminology was used.
  • "Leaky-Bucket" vs. "Token-Bucket": Petitioner argued that the "token-bucket" algorithm disclosed in Feng for monitoring ingress rates is technically equivalent and interchangeable with the "leaky-bucket" algorithm required by claims 14 and 23. The petition asserted that these were well-known, interchangeable models for rate monitoring, differing only in the direction of the counter. Feng's own citation to the Rathgeb reference, which describes a "leaky bucket," was presented as further evidence of this direct equivalence.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1, 4-5, and 8-31 of Patent 6,252,848 as unpatentable under 35 U.S.C. §103.