Prior art

V. Analysis of Prior Art Cited in Prosecution

This section details the prior art references cited by the USPTO examiner during the prosecution of the application that led to US Patent 7,969,880. These references were considered by the examiner but the claims of the '880 patent were ultimately deemed patentable over them. An analysis of each reference provides insight into the novel aspects of the '880 patent.

A. U.S. Patent Documents

• US 6,954,435 B2 - "Method and apparatus for selecting a link from a link aggregate group"

  • Full Citation: Roberts, Edward P., et al. Method and apparatus for selecting a link from a link aggregate group. U.S. Patent 6,954,435 B2, filed March 19, 2002, and issued October 11, 2005.
  • Brief Description: This patent describes a method for distributing data frames across multiple links in a link aggregate group (LAG). It discloses using a hash function on packet header information (such as source and destination addresses) to select a specific link within the LAG for transmission. The goal is to balance the traffic load across the available links.
  • Potential Anticipation of Claims: This reference appears to disclose several key elements of the '880 patent, particularly concerning claim 1. It teaches the use of a "computing module" (a hash function) that uses "seed information" (packet header data) to select a physical port from a plurality of "candidate ports" (the links in the LAG). However, the '880 patent is distinguished by its inclusion of a "modifying module" that is "configured to modify the computational expression." The '435 patent does not appear to explicitly teach or suggest a mechanism for dynamically or manually changing the hash function itself to alter the traffic distribution pattern once it is set.

• US 7,058,054 B2 - "System and method for load balancing in a link aggregation group"

  • Full Citation: Basso, Claude, et al. System and method for load balancing in a link aggregation group. U.S. Patent 7,058,054 B2, filed September 30, 2002, and issued June 6, 2006.
  • Brief Description: The '054 patent discloses a system for load balancing traffic across a Link Aggregation Group (LAG). It describes using a hash function based on packet header fields to select an outgoing port. The patent focuses on providing a more granular and flexible selection of fields within the packet header to be used as input for the hash function, allowing for better traffic distribution.
  • Potential Anticipation of Claims: This patent, similar to the '435 patent, teaches the core concept of using a hash function on packet data to select a port from a group of candidate ports. It advances the idea by allowing more user control over what "seed information" is used in the hash calculation. However, it appears to fall short of anticipating the key inventive step of the '880 patent: the ability to modify the computational expression (the hash function) itself. The '054 patent allows for changing the input to the function, but not the function itself.

• US 7,200,145 B2 - "System and method for link aggregation using flow-based hashing"

  • Full Citation: Edsall, Thomas J., et al. System and method for link aggregation using flow-based hashing. U.S. Patent 7,200,145 B2, filed June 30, 2003, and issued April 3, 2007.
  • Brief Description: This patent details a method for distributing traffic in a link aggregation environment by using a hash function. It emphasizes maintaining the order of packets within a single "flow" (a sequence of packets between the same source and destination) by ensuring they are all sent over the same link. The selection of the link is based on a hash of flow-identifying information in the packet headers.
  • Potential Anticipation of Claims: This reference strongly relates to the '880 patent's description of using source and destination information as "seed information" for a computational process to select a physical port from a group of candidate ports (the aggregated links). The '145 patent, however, does not describe or suggest a "modifying module" to change the hash function itself. The focus is on the consistent application of a single hash function to maintain flow integrity, not on the dynamic alteration of the load-balancing algorithm.

• US 2005/0251590 A1 - "Method for path selection in a multiple path network"

  • Full Citation: Ambe, Shekhar, et al. Method for path selection in a multiple path network. U.S. Patent Application Publication 2005/0251590 A1, filed May 6, 2004, and published November 10, 2005.
  • Brief Description: This patent application describes a method for selecting one of a plurality of available paths for a data flow in a network. The selection is made based on a hash value generated from information in the packet header. The system aims to distribute flows across multiple paths to balance the load.
  • Potential Anticipation of Claims: This application describes the fundamental process of using a hash function on packet information to select an output path (which corresponds to a port or group of ports). It is relevant to both claims 1 and 9. However, like the other references, it does not appear to disclose the key element of a "modifying module" that can alter the "computational expression" (the hash function). This ability to change the core logic of the distribution is what distinguishes the '880 patent.

B. Foreign Patent Documents

• JP 2005-252758 A - "Packet Transfer Device"

  • Full Citation: Yano, Hiroki. Packet Transfer Device. Japanese Patent Application Publication No. 2005-252758 A, published September 15, 2005.
  • Brief Description: As noted in the '880 patent's background section, this reference discloses a method for distributing communication load by using a function to convert packet header information into an output value, which is then used to select a transmission queue corresponding to one of several links.
  • Potential Anticipation of Claims: This reference appears to be highly relevant as it describes a similar load-balancing mechanism. The key distinguishing feature of the '880 patent, however, remains the "modifying module" and the explicit ability to "modify the computational expression." Without a detailed translation and analysis of the full JP 2005-252758 A document, it is difficult to definitively state whether it anticipates this feature. However, given that the '880 patent was granted over this reference, it is presumed that the examiner found the "modifying module" to be a novel and non-obvious improvement.

• JP 2006-5437 A - (Title not provided in '880 patent data)

  • Full Citation: Japanese Patent Application Publication No. 2006-5437 A, published January 5, 2006.
  • Brief Description: This document is cited as related technology in the '880 patent. The specific content and its relevance can only be fully assessed by reviewing the document itself. Based on its context, it likely pertains to network packet relaying and load distribution.
  • Potential Anticipation of Claims: Similar to the other Japanese reference, a complete analysis is not possible without the full text. However, the '880 patent's core invention lies in the modifiability of the computational expression used for load balancing. It is likely this specific feature that was found to be novel over the teachings of JP 2006-5437 A.

VI. Summary of Prior Art Analysis

The prior art cited during the prosecution of US Patent 7,969,880 establishes that the general concept of using hash functions on packet header data (source/destination addresses, etc.) to distribute traffic across aggregated links or multiple paths was well-known before the '880 patent's filing date. References such as US 6,954,435 B2, US 7,058,054 B2, and US 7,200,145 B2 all describe this fundamental technique.

The inventive concept of the '880 patent, which allowed it to be granted over this prior art, is the inclusion of a "modifying module" with the specific function of "modifying the computational expression." This introduces a dynamic and adaptable element to the load-balancing mechanism. Instead of being locked into a single, static hash function, the network device described in the '880 patent can change the algorithm itself, either manually or automatically, to respond to changing network conditions or to counteract traffic imbalances that might arise from a particular hash function's characteristics. This modification of the core distribution logic is the key point of novelty and non-obviousness that distinguishes the '880 patent from the cited references.