Microsoft Corp v. Proxyconn Inc

1. Case Identification

• Case #: IPR2013-00109
• Patent #: 6,757,717
• Filed: January 11, 2013
• Petitioner(s): Microsoft Corporation
• Patent Owner(s): Proxyconn, Inc.
• Challenged Claims: 6, 7, 9, 11, 12, and 14

2. Patent Overview

• Title: System and method for data access in a packet-switched network
• Brief Description: The ’717 patent describes a method to reduce redundant data transmission over a network by comparing digital fingerprints (e.g., MD5 digests) of data. If a receiver already possesses data with a matching digest to data a sender intends to transmit, the actual data transfer is avoided.

3. Grounds for Unpatentability

Ground 1: Anticipation - Claims 6, 7, 9, 11, 12, and 14 are anticipated by HTTP DRP.

• Prior Art Relied Upon: HTTP DRP (“The HTTP Distribution and Replication Protocol,” W3C Note, Aug. 1997).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that HTTP DRP, a proposed supplement to the standard HTTP protocol, disclosed every element of the challenged claims. For system claims 6, 7, and 9, HTTP DRP described standard network configurations with client and server computers (acting as caching computers and gateways) that calculate, store, and compare MD5 digests to avoid redundant data transmission. For method claims 11, 12, and 14, HTTP DRP disclosed a client receiving an index file of MD5 digests from a server and responding with signals that constitute the claimed "positive" (using a local copy when digests match), "negative" (sending a GET request for the full file when no match exists), and "partial" (sending a "differential GET" request when a different version is cached) indications.

Ground 2: Anticipation - Claims 6, 7, and 9 are anticipated by Mattis.

• Prior Art Relied Upon: Mattis (Patent 6,292,880).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Mattis disclosed a web proxy caching computer with a network cache that uses an MD5-digest-based file system. This system inherently performs the functions of the "caching computer" in claim 6, including calculating MD5 digests on cached data objects and comparing them to a second MD5 digest. Petitioner contended that Mattis disclosed that this second digest could be derived from a client request or received from an origin server, with the latter explicitly anticipating the limitation of receiving a digest over the packet-switched network. The dependent claims were likewise disclosed as inherent functionalities of the described caching system.

Ground 3: Obviousness - Claims 6, 7, 9, 11, 12, and 14 are obvious over Mattis and HTTP DRP.

• Prior Art Relied Upon: Mattis (Patent 6,292,880) and HTTP DRP (W3C Note, Aug. 1997).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that Mattis taught an MD5-digest-based cache file system, and HTTP DRP taught a communication protocol using MD5 digests. The combination of these two complementary references allegedly disclosed every element of the challenged claims. HTTP DRP provided the protocol for clients to request objects via MD5 digests, directly supplying the "digest received from said packet-switched network" that Mattis's caching system was capable of comparing. The combination provided a complete, functional system and method as claimed.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine the references because they addressed the exact same problem (reducing network and storage redundancy), proposed the same algorithmic solution (comparing MD5 digests), and applied it to the same application (web content distribution via HTTP). Petitioner argued it would have been a natural and obvious step to implement the HTTP DRP protocol using the robust caching system described in Mattis.
  • Expectation of Success: Success was predictable because the references were complementary and designed to operate in the same environment. Mattis explicitly contemplated that client requests could identify an object by its MD5 digest, which is precisely what HTTP DRP defined. Therefore, combining them required no modification and involved a predictable application of known technologies.

• Additional Grounds: Petitioner asserted that claims 6 and 7 are anticipated by Yohe (Patent 5,835,943). Petitioner also asserted an additional obviousness challenge against claims 6, 7, and 9 based on the combination of HTTP DRP, Mattis, Yohe, and Admitted Art, arguing Yohe explicitly taught the "fast local network" connection if it were found lacking in the primary combination.

4. Key Claim Construction Positions

• "a caching computer" (claims 6, 7, 9): Petitioner proposed this term meant any computer or computers, including connected storage devices, capable of caching, and was not limited to a single machine.
• "positive, partial or negative indication signal" (claims 11, 12, 14): Petitioner noted its disagreement with a Board decision in a related IPR (IPR2012-00026) that required the issuance of all three alternative signals. However, for the purposes of this petition, Petitioner applied the Board's more stringent interpretation and argued that the prior art still met the limitation.
• Means-Plus-Function Terms: For terms like "means for calculating a digital digest" and "means for comparison," Petitioner adopted the Board's constructions from the related IPR, such as construing "means for comparison" as "any general purpose computer," to demonstrate unpatentability even under those interpretations.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that the statutory one-year time bar under 35 U.S.C. §315(b) did not apply to this second petition, even though it was filed more than one year after Microsoft was served with an infringement complaint. The reasons provided were that the Board had already instituted an inter partes review on a timely first petition (IPR2012-00026), this second petition was accompanied by a motion for joinder under §315(c), and the Patent Owner had consented to the joinder.

6. Relief Requested

• Petitioner requested the institution of an inter partes review for claims 6, 7, 9, 11, 12, and 14 of the ’717 patent on all asserted grounds and the ultimate cancellation of these claims as unpatentable.