Wireless Client Traffic Continuity Across Controller Failover
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Solution Overview
Problem
In wireless communication networks, when a primary controller handling a client's transmissions enters an inactive state, the client device loses encryption keys, necessitating de-authentication and re-authentication, which disrupts ongoing sessions and can lead to connectivity issues and unnecessary roaming attempts.
Innovation Solution
Implementing a standby controller that stores session information and encryption keys, allowing seamless transition and maintaining connectivity without the need for de-authentication and re-authentication by synchronizing state information and handling network traffic when the primary controller becomes inactive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary controller handles client network traffic, then network connectivity is established, but when the primary controller becomes inactive, the client loses encryption keys and must undergo de-authentication and re-authentication, disrupting ongoing sessions
Solution Approach 1:
The standby controller pre-synchronizes encryption keys and session information from the primary controller before the primary controller becomes inactive. This preliminary action ensures that when failover occurs, the standby controller already possesses the necessary authentication credentials and session state, eliminating the need for de-authentication and re-authentication processes and maintaining continuous network connectivity for the client device
Solution Approach 2:
The standby controller maintains a copy of the encryption keys and session information that the primary controller uses to communicate with the client device. By replicating these critical authentication and session elements, the standby controller can immediately assume the primary controller's role without requiring the client to re-authenticate, thus preventing session disruption and maintaining reliability during controller failover
2Reliability
If de-authentication and re-authentication processes are performed when controller failover occurs, then new encryption keys can be established, but all current session information is lost including SSH sessions, FTP sessions, and audio or video communications
Solution Approach 1:
The standby controller pre-synchronizes not only encryption keys but also complete session information including SSH sessions, FTP sessions, and audio or video communication states from the primary controller before failover occurs. This preliminary synchronization ensures that when the standby controller takes over, it already possesses all active session data, allowing seamless continuation of all client sessions without information loss while maintaining security through valid encryption keys
Solution Approach 2:
The standby controller maintains comprehensive copies of both encryption keys and all session information from the primary controller. By replicating the complete operational state including active sessions, the standby controller enables immediate takeover that preserves both security credentials and session continuity, preventing loss of any session information while ensuring valid encryption keys are available for secure communication
3Adaptability or versatility
If a client device receives de-authentication notifications from an access point, then the client may attempt to associate with a different access point, but this may not be beneficial to the wireless communication network and/or the client device
Solution Approach 1:
The standby controller acts as an intermediary that absorbs the de-authentication event internally without propagating it to the client device. When the primary controller becomes inactive, the standby controller seamlessly takes over the client's session, maintaining the appearance of continuous service to the client. This intermediary action prevents the client from receiving de-authentication notifications that would trigger unnecessary roaming attempts, thereby maintaining connectivity stability while preserving the client's ability to select access points when genuinely needed
Data Source
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Figure 2
Figure 3A~3B
AI summary
A non-transitory computer readable medium comprising instructions which causes performance of operations comprising: receiving, by a second network coordination device, current state information of a client device, including a transmit counter and a receive counter, from a first network coordination device, wherein the first network coordination device is a primary network coordination device for the client device and the second network coordination device is a standby coordination device for the client device; and responsive to detecting a particular event, the second network coordination device (i) transitioning to be the primary network coordination device for the client device, (ii) incrementing the transmit counter by an offset, and (iii) transmitting a message to the client device including the incremented transmit counter is shown.