Stateful Service Failover in Cloud Logical Networks
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Solution Overview
Problem
In public multi-tenant clouds, high availability logical network gateways face challenges in maintaining stateful services across active and standby instances operating in different physical locations, as the active and standby instances have different network addresses, leading to invalid connection states and service rule inconsistencies when the active instance fails.
Innovation Solution
The centralized routing components store mappings between public network addresses and their respective interface addresses, and the standby instance maps connection state data from the active instance to its own interface addresses, ensuring that stateful service rules and connection states are valid when the standby instance takes over.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active and standby gateway instances are deployed in different physical locations for high availability, then network reliability is improved, but connection state validity and service rule consistency deteriorate due to different network addresses
Solution Approach 1:
The patent introduces a control plane as an intermediary that manages the mapping between different network addresses (public IP addresses) and private network identifiers. This control plane enables the standby gateway to correctly interpret connection states from the active gateway by translating between their different address spaces, thus maintaining connection state validity across geographically separated instances.
Solution Approach 2:
The system performs preliminary actions by pre-establishing and maintaining mapping tables in the control plane that associate public IP addresses with private network identifiers before failover occurs. When failover is needed, these pre-configured mappings enable the standby gateway to immediately understand the connection states without requiring real-time translation or state reconstruction.
2Adaptability or versatility
If centralized routing components are deployed in gateway appliances within data compute nodes, then service functionality is improved, but system complexity increases due to multiple routing components managing different physical locations
Solution Approach 1:
The patent segments the routing functionality into distinct components: a control plane that manages logical routing decisions and address mappings, and data planes (gateway appliances) that execute forwarding operations. This segmentation allows each component to have specialized functionality, reducing the complexity burden on individual routing components while enabling versatile service deployment across multiple physical locations.
Solution Approach 2:
The control plane serves multiple functions including address mapping management, connection state translation, and routing decision coordination across different physical locations. This multi-functionality consolidates what would otherwise require separate specialized components, reducing overall system complexity while maintaining versatile service deployment capabilities.
Data Source
AI summary
Some embodiments provide a method for a network controller that manages a logical network spanning multiple physical locations. For each physical location hosting data compute nodes (DCNs) belonging to the logical network, the method defines a centralized routing component for processing data messages between the DCNs hosted at the physical location and networks external to the logical network, assigns an active instance of the centralized routing component to operate at the physical location, and assigns a standby instance of the centralized routing component to operate at one of the other physical locations.