PTAB

IPR2026-00180

Microsoft Corp v. Sandpiper CDN LLC

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Content Delivery Networks
  • Brief Description: The ’173 patent relates to methods for distributing content in a content delivery network (CDN). The purported novelty is a "late-binding" caching policy, where a CDN node determines the currently applicable cache policy at the time content is requested, rather than when the content was first cached, to ensure the latest policy is always used.

3. Grounds for Unpatentability

Ground 1: Obviousness over O’Rourke - Claims 1-2, 4-6, 8-9, and 11-13 are obvious over O’Rourke

  • Prior Art Relied Upon: O’Rourke (Patent 7,912,921)
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that O’Rourke disclosed all limitations of the independent claims. O’Rourke taught a cache server in a CDN that responds to a content request by first determining if the content is stored locally. If so, the server uses a set of cache policies to determine if the stored version is "acceptable." These policies, which can be modified by a user at any time, dictate whether to serve the cached content or download a new version. Petitioner contended that using the policy in effect at the time of the request is equivalent to the ’173 patent’s "current cache policy." The policies in O’Rourke that determine if a version is "acceptable" (e.g., based on staleness) inherently comprise a time period for expiration.
    • Key Aspects: Petitioner asserted that while O’Rourke’s flowchart shows identifying applicable policies before checking for the local cache, it would have been an obvious and trivial design choice for a person of ordinary skill in the art (POSITA) to perform these steps in the reverse order as claimed, as the functions are not dependent on each other.

Ground 2: Obviousness over O’Rourke and MS-MSSO - Claims 3 and 10 are obvious over O’Rourke in view of MS-MSSO

  • Prior Art Relied Upon: O’Rourke (Patent 7,912,921) and MS-MSSO (a 2009 Microsoft technical document on media streaming protocols).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed dependent claims requiring the request to be an HTTP request and the content to comprise one or more resources. Petitioner argued that O’Rourke explicitly taught that its cache server could be a Windows Media Server. MS-MSSO, in turn, described the standard protocols for Windows Media Servers, including the Windows Media HTTP Streaming Protocol. This protocol explicitly used HTTP for transferring multimedia data, which inherently consists of one or more resources (e.g., audio and video).
    • Motivation to Combine: A POSITA implementing O’Rourke’s flexible cache server as a Windows Media Server (an embodiment suggested by O’Rourke) would be motivated to consult a document like MS-MSSO to understand the server's standard protocols. MS-MSSO highlighted the advantages of using HTTP streaming for compatibility with proxies and firewalls, providing a clear reason to implement this known protocol.
    • Expectation of Success: Petitioner argued a POSITA would have a high expectation of success, as the combination involved implementing a standard, well-documented protocol (from MS-MSSO) on a server platform (Windows Media Server) expressly contemplated by the primary reference (O’Rourke).

Ground 3: Obviousness over O’Rourke and Blumofe - Claims 7 and 14 are obvious over O’Rourke in view of Blumofe

  • Prior Art Relied Upon: O’Rourke (Patent 7,912,921) and Blumofe (Application # 2012/0096106).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground addressed dependent claims requiring the cache policy to also relate to caching content outside the CDN. While O’Rourke’s cache policies managed content within its CDN, Blumofe taught a "CDN Extender"—a caching proxy deployed beyond the CDN's edge (e.g., in a mobile network) that serves CDN-provisioned content. Blumofe taught that the main CDN supplies and controls the caching policies used by this external extender.
    • Motivation to Combine: A POSITA seeking to apply O'Rourke's customizable CDN to a wider range of network environments, such as the wireless networks O'Rourke does not address, would be motivated to incorporate Blumofe's solution. Blumofe was designed to solve this exact problem by extending a CDN's reach and policy enforcement into networks that cannot host full CDN servers, thereby improving performance for users on those networks.
    • Expectation of Success: Success would be expected because Blumofe’s extender was designed to work with existing CDNs like O'Rourke's. The combination would predictably allow O'Rourke's system to enforce its customizable cache policies on caches located both inside and outside the primary CDN infrastructure.

  • Additional Grounds: Petitioner asserted a parallel set of obviousness challenges against the same claims based on Middleton (Application # 2011/0060812) alone and in combination with MS-MSSO and Blumofe, arguing Middleton taught an extensible CDN platform with a revalidation process that determined a current cache policy at request time.

4. Relief Requested

  • Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-14 of the ’173 patent as unpatentable.