Virtual IP Address Mapping for NAS Controller Cluster Failover
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Solution Overview
Problem
In network environments with a NAS controller cluster, failures of the active controller can lead to erroneous communication with the External Authentication Server (EAS) due to the lack of automatic updates of the standby controller's IP address, resulting in requests being sent to the failed controller instead of the new active one, especially during events like RADIUS Change of Authorization/Disconnect or XML add/authenticate/delete commands.
Innovation Solution
Implementing virtual IP addresses for the NAS controller cluster, where each controller is mapped to multiple virtual IP addresses with different priorities, allowing for N−1 times more parallelism compared to single VIP approaches, ensuring that messages from the EAS are correctly routed to the active or standby controllers, thereby preventing miscommunication after a failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single Virtual IP address is used for the NAS controller cluster, then communication simplicity is improved, but controller identification precision deteriorates causing requests to be sent to the wrong controller after failure
Solution Approach 1:
The single Virtual IP address is segmented into multiple Virtual IP addresses, with each controller in the cluster being assigned one or more specific Virtual IP addresses. This segmentation allows the EAS to identify and communicate with the correct controller by targeting its specific Virtual IP address, thereby resolving the ambiguity that occurs with a single shared Virtual IP address after controller failure.
Solution Approach 2:
Each controller is assigned unique local qualities in the form of specific Virtual IP addresses that distinguish it from other controllers in the cluster. This local quality assignment ensures that communication requests from the EAS can be precisely directed to the intended controller based on its unique Virtual IP address, preventing misrouting to failed or incorrect controllers.
2Measurement precision
If multiple Virtual IP addresses are assigned to each controller, then controller identification precision is improved, but system complexity increases
Solution Approach 1:
The Virtual IP address system is designed with multi-functionality where Virtual IP addresses serve multiple purposes: they uniquely identify controllers, enable precise routing of communication requests, and provide a standardized interface for the EAS to interact with the cluster. This universal approach simplifies the overall system architecture compared to implementing entirely separate identification and communication mechanisms.
Solution Approach 2:
The Virtual IP addresses act as intermediaries between the EAS and the physical controllers. Rather than the EAS directly managing complex controller states or physical addresses, it communicates through the Virtual IP address layer, which handles the complexity of controller identification, failover, and request routing automatically, thereby reducing the perceived system complexity.
3Reliability
If the active controller fails without updating the EAS, then system reliability deteriorates causing erroneous communication, but implementing automatic update mechanisms increases device complexity
Solution Approach 1:
The system performs preliminary actions by pre-assigning unique Virtual IP addresses to each controller and pre-configuring the mapping between Virtual IP addresses and controllers. When a controller fails, the EAS can immediately identify the correct active controller using these pre-established Virtual IP address mappings, eliminating the need for complex real-time update mechanisms and maintaining communication reliability.
Solution Approach 2:
The controller cluster implements a feedback mechanism where controllers monitor each other's status and automatically update their Virtual IP address assignments when failures occur. This feedback loop ensures that the EAS receives accurate information about the current active controller through the Virtual IP address system, maintaining communication reliability without requiring complex manual intervention or centralized management.
Data Source
AI summary
Examples described herein include a method and system for determining a number of controllers in a Network Authentication Server (NAS) controller cluster, wherein each of the controllers in the NAS controller cluster includes a unique Physical Internet Protocol (PIP) address; creating a number of unique Virtual Internet Protocol (VIP) addresses for use by an external authentication server (EAS) to communicate with the controllers in the NAS controller cluster, wherein the number of VIP addresses is to be proportional to the number of PIP addresses; and mapping each controller in the NAS controller cluster to a plurality of VIP addresses, wherein the VIP addresses are to have different priorities for different controllers in the NAS controller cluster.