Hitless Wireless Switch Restart via Database Synchronization
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Solution Overview
Problem
Large Wireless Local Area Networks (WLANs) face challenges in managing and restarting wireless switches, particularly when they fail, leading to disruptions in network connectivity and IP address management across multiple subnets, which affects seamless roaming of wireless client devices.
Innovation Solution
The implementation of a control plane L3 mobility module and data plane module within the wireless switch, allowing for synchronized databases across peer switches to ensure seamless restart and maintenance of client connections by transmitting restart messages, updating databases, and refreshing stale entries, thus maintaining network stability and client connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wireless switch fails and restarts in a traditional WLAN, then the switch can be restored to operational status, but network connectivity disruptions and client roaming interruptions occur
Solution Approach 1:
The patent implements preliminary actions by maintaining synchronized databases across peer switches before the failing switch restarts. The home wireless client database (HWCDb) is pre-synchronized with peer switches, and stale entry tracking is established in advance, enabling the network to immediately resume normal operation upon restart without connectivity disruptions.
Solution Approach 2:
The patent applies beforehand cushioning by creating redundant database copies at peer switches before the failure occurs. When the wireless switch fails and restarts, these pre-positioned database copies act as a cushion, allowing the network to maintain client connectivity throughout the restart process without interruption to data forwarding.
2Reliability
If the wireless switch restarts and re-establishes peering sessions with peer switches, then the control plane can be restored, but data forwarding interruptions occur during the re-establishment process
Solution Approach 1:
The patent segments the switch functionality into control plane and data plane operations. The control plane can restart and re-establish peering sessions independently while the data plane continues forwarding packets using the pre-synchronized HWCDb at peer switches, eliminating the need for coordinated restart and reducing interruption duration to near zero.
Solution Approach 2:
The patent introduces the peer switches as intermediaries that hold synchronized copies of the HWCDb. When the original switch restarts, these intermediary peer switches continue to forward data packets using their local database copies, mediating between the restarting control plane and the data forwarding requirements.
3Stability of the object's composition
If the wireless switch resets its home wireless client database (HWCDb) with information from its data plane wireless client database (KWCDb), then the database consistency is restored, but synchronization time is required
Solution Approach 1:
The patent performs preliminary synchronization of the HWCDb with peer switches before any failure occurs. This pre-synchronization ensures that when the switch resets its database, the peer switches already have current copies, eliminating the need for time-consuming re-synchronization after restart and reducing synchronization time to minimal updates.
4Ease of operation
If peer wireless switches store information from the HWCDb and mark wireless client devices as stale entries, then the restart process can proceed, but additional database management overhead is created
Solution Approach 1:
The patent implements self-service by having peer switches automatically track and manage stale entries in their own databases without requiring complex coordination with the restarting switch. The stale entry mechanism is a self-managing system where peer switches independently identify and refresh entries based on simple criteria, reducing overall database management complexity.
Data Source
AI summary
Techniques and technologies are provided for restarting a first wireless switch when the first wireless switch fails. For example, after the first wireless switch fails, the first wireless switch transmits a restart message to its peer wireless switches to begin re-establishing peering sessions with peer wireless switches. The first wireless switch resets its home wireless client database (HWCDb) with information from its data plane wireless client database (KWCDb), and transmits the updated information in its HWCDb to its peer wireless switches. The peer wireless switches store this information in their respective control plane wireless client databases (CPWCDbs), and initially mark the wireless client devices in the respective CPWCDbs as stale entries. Each of the wireless switches then exchanges information from their respective HWCDbs with the first wireless switch (and other peer wireless switches) so that each wireless switch eventually has a wireless client database (WCDb) comprising each of the wireless client devices in the mobility domain.