Network Device High Availability via Software State Reconstruction
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Solution Overview
Problem
High-availability routers are costly due to the need for redundant hardware components, and they may fail if the number of failing active line cards exceeds the number of redundant line cards.
Innovation Solution
A network device stores a subset of state information associated with software applications, reconstructs data structures, and restarts applications to maintain high availability without using redundant hardware components, allowing it to continue providing routing services even in the event of failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant hardware components are used to provide high availability, then reliability is improved, but device cost increases
Solution Approach 1:
The patent creates software copies of line card functionality rather than using physical hardware copies. The control unit reconstructs line card data structures from stored state information and software applications, providing redundant functionality through software instantiation rather than duplicate hardware components.
Solution Approach 2:
The patent replaces the mechanical hardware-based redundancy system with a software-based system. Instead of physically redundant line cards, the invention uses software applications and data structure reconstruction to provide equivalent failover capabilities, eliminating the need for duplicate physical components.
2Device complexity
If fewer redundant line cards are used to reduce cost, then device cost decreases, but reliability deteriorates when multiple line cards fail
Solution Approach 1:
The control unit is designed to universally handle any line card failure scenario. It stores and reconstructs data structures for multiple line cards and can dynamically instantiate software replacements for any failed line card, providing multi-functional redundancy capabilities within a single component rather than requiring dedicated redundant line cards for each active one.
3Reliability
If redundant hardware components are used, then high availability is achieved, but the device requires more hardware resources
Solution Approach 1:
The patent merges the functionality of multiple redundant line cards into a single control unit. The control unit consolidates state information storage, application execution, and data structure reconstruction capabilities for multiple line cards, eliminating the need for separate physical redundant hardware components while maintaining high availability.
Data Source
AI summary
The principles of the invention allow a network device, such as a router, to maintain a high level of services during a failure without substantially utilizing redundant hardware components. During execution, the network device stores a subset of state information associated with applications executing on the network device. In the event of a failure, the network device reconstructs data structures associated with at least one of the applications based on the stored subset of state information. Next, the network device restarts at least one of the applications to resolve the failure. While restarting, the network device may continue to receive and forward information, such as packets, and, therefore, may continue to provide a high level of access to client devices previously connected to the network device. Thus, because the network device need not transfer control to a redundant hardware component, the network device may provide high availability without utilizing redundant hardware components, thereby potentially reducing the cost of high-availability routers.