Obviousness

An analysis of the obviousness of US patent 7061859 under 35 U.S.C. § 103 requires identifying combinations of prior art references that would render the claims obvious and explaining why a person having ordinary skill in the art (PHOSITA) would have been motivated to combine them. The core novelty of US7061859, as identified previously, resides in its specific mask-based approach for rapid fault protection:

1. Constructing a "general mask" (preferably bitmap) indicating unreachable segments due to a fault.
2. Constructing a "specific mask" (preferably bitmap) for each data flow indicating its desired path.
3. "Superimposing" these two distinct masks (e.g., via a Boolean operation) to rapidly determine one of three specific dispositions for the data flow: convey over the desired path, steer over an alternative path, or stop conveying.

A PHOSITA in 2001 (the filing date of US7061859) would be well-versed in bidirectional ring network topologies, the critical need for fast fault recovery (e.g., the 50 ms standard mentioned in the patent's background), and common network management practices like fault detection and traffic rerouting. Furthermore, a PHOSITA would possess fundamental computer science knowledge, including the use of efficient data structures like bitmaps for representing sets or binary states, and the application of Boolean logic operations for comparing or combining such data.

The problem US7061859 aims to solve is enabling network nodes to "decide rapidly, with minimal computational cost, on the course of action that makes optimal use of the network resources remaining after the fault" [US7061859, Description].

Obviousness Argument: US6820210B1 in view of general knowledge of efficient data processing techniques

Primary Reference: US6820210B1, titled "System and method for fault recovery for a two line bi-directional ring network," assigned to Cisco Technology, Inc., with a filing date of April 27, 1998, preceding US7061859.

Disclosure of US6820210B1:
US6820210B1 describes a fault recovery system for bidirectional ring networks where nodes maintain "routing tables for primary and secondary paths" and switch traffic from a failed primary path to a standby "protection path" (secondary path) upon fault detection. The patent also notes that a "routing information field" can indicate the status of network elements or segments.

Motivation for Combination/Modification:
A PHOSITA, aiming to enhance the speed and computational efficiency of the fault recovery mechanisms taught by US6820210B1—particularly to achieve rapid decision-making necessary for high-speed packet rings to meet performance requirements like the 50 ms recovery standard—would be motivated to implement compact data representations and efficient logical operations. The desire for "fast rerouting" and "optimal use of network resources" [US7061859, Summary] would lead a PHOSITA to consider highly optimized processing methods. Bitmaps and Boolean operations were well-established and standard techniques in computing for representing and efficiently manipulating sets of binary states by 2001.

Reasoning for Obviousness (Applying KSR v. Teleflex considerations):

1. Constructing a general mask (Claims 1 & 7): US6820210B1 teaches that a "routing information field" can indicate segment status. To improve computational efficiency in fault detection and recovery, a PHOSITA would find it an obvious design choice to represent the status of network segments (i.e., which segments are unreachable due to a fault) using an ordered bitmap, or "general mask." In this mask, each bit would correspond to a specific network segment, with a '1' indicating an unreachable segment and '0' indicating a reachable one. This is a straightforward and efficient method to encode and query binary state information for a fixed set of network elements.

2. Constructing a specific mask (Claims 1 & 7): US6820210B1 describes the concept of "primary and secondary paths" for data flows. For a given data flow, its desired path consists of a specific set of network segments. Applying the same principles of computational efficiency, a PHOSITA would find it obvious to represent this desired path as a "specific mask" in bitmap form. Each bit in this specific mask would correspond to a network segment, with a '1' indicating that the flow was intended to traverse that segment had no fault occurred.

3. Superimposing the general and specific masks using a Boolean operation (Claims 1 & 7): With both the general network fault state and the specific data flow path represented as bitmaps, determining the impact of a fault on a particular flow becomes a simple and highly efficient logical operation. A PHOSITA would recognize that a Boolean conjunction (AND) operation between the general mask and the specific mask would effectively reveal the overlap between the unreachable segments and the flow's intended path. This is a fundamental and efficient operation for computing set intersection.

4. Determining the disposition of the flow based on the superimposed masks (Claims 3-6 & 9-12): The outcomes of the Boolean AND operation would predictably lead to the three dispositions claimed in US7061859:

   • If the combined mask is null (all zeros): This predictably means there is no overlap between the flow's desired path and the unreachable segments. Therefore, the obvious disposition is to "convey the data flow over the desired path" (i.e., no steering required).
   • If the combined mask corresponds exactly to the general mask: This predictably means that all unreachable segments lie directly on the flow's intended path. In a bidirectional ring network, the obvious response is to "steer the data flow over an alternative path" (i.e., in the opposite direction around the ring) to bypass all failed segments.
   • If the combined mask is neither null, nor does it correspond to the general mask: This predictably indicates a partial overlap between the flow's desired path and unreachable segments, or that the fault segments might isolate the destination node despite partial path availability. Given the motivation to "avoid wasting network bandwidth" [US7061859, Description], the obvious disposition would be to "stop conveying the data flow" (e.g., discard or delay packets) because the destination might be unreachable or an alternative path might not be viable or optimal. This decision leverages a PHOSITA's understanding of ring topologies and the implications of segment failures for connectivity.

Therefore, a PHOSITA, seeking to improve the efficiency and speed of fault recovery in bidirectional ring networks as taught by US6820210B1, would have been motivated to represent network segment status and data flow paths using bitmaps and to employ standard Boolean logic to rapidly determine the appropriate disposition of data flows, with predictable results. This combination of US6820210B1 and general knowledge would render independent claims 1 and 7, and their dependent claims, obvious.