Hardware Shadow CPU Failover for Network Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for CPU failover in network elements are inefficient due to the complexity and time required to build and maintain a standby software index, which can lead to version problems and downtime, especially when the active CPU fails.
Innovation Solution
A hardware shadow is used to facilitate the failover process by copying data from shadow tables to corresponding hardware tables, allowing the standby CPU to take control without rebuilding the entire index, and using a partial software index for large tables to reduce reconciliation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a standby software index is built and maintained prior to CPU failure, then control plane downtime is removed, but the process becomes complicated and leads to version problems
Solution Approach 1:
The patent uses a hardware shadow that is a direct copy of the hardware tables in the hardware forwarding engine. This copy allows the standby CPU to access current forwarding data without needing to maintain a complex software index, thereby eliminating version problems while maintaining zero downtime.
Solution Approach 2:
The hardware shadow acts as an intermediary between the hardware forwarding engine and the standby CPU. Instead of the standby CPU directly maintaining and accessing a software index, it accesses the hardware shadow which is automatically kept synchronized, simplifying the failover process.
2Ease of manufacture
If a standby software index is built from scratch upon CPU failure, then implementation is simpler, but control plane functionality is interrupted for a long time
Solution Approach 1:
The hardware shadow is prepared in advance and kept synchronized with the hardware forwarding engine during normal operation. When CPU failure occurs, the standby CPU can immediately use the pre-prepared hardware shadow without needing to build anything from scratch, thus achieving both simplicity and zero downtime.
3Stability of the object's composition
If the standby CPU accesses hardware tables directly, then version consistency is maintained, but access complexity and time increase
Solution Approach 1:
Instead of the standby CPU directly accessing hardware tables, the patent creates a hardware shadow that is a copy of these tables. This copy maintains version consistency while providing a simplified access path for the standby CPU, reducing access complexity.
Data Source
AI summary
A method and apparatus of a device that uses a hardware shadow for a central processing unit failover is described. In an exemplary embodiment, a device receives a signal that the active central processing unit has failed, where the active central processing unit controls the processing functions of the network element and the network element includes a hardware forwarding engine and a hardware shadow. The hardware shadow additionally includes multiple shadow tables. For each shadow table, the device copies data from that shadow table to a corresponding table in the hardware forwarding engine, where the hardware shadow is a copy of the data stored in hardware tables for the hardware forwarding engine. In response to the copying, the device further switches control of the network element processing functions from the active central processing unit to a standby central processing unit.