Selective AP Key Caching for Fast Roaming During Controller Outages
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Solution Overview
Problem
Existing wireless network systems face issues with session key caching when cloud-based servers or local area network controllers become unavailable, leading to increased roaming times and disruptions in applications requiring low latency, such as voice calls and video streaming.
Innovation Solution
Access points (APs) generate and cache session keys locally, determining a set of roaming candidate APs based on proximity and signal strength, and propagate these keys to selected APs without external controller involvement, using existing roam notification protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If cloud-based servers or local area network controllers are used to manage session key caching, then centralized control and coordination are improved, but system reliability deteriorates when these external controllers become unavailable
Solution Approach 1:
The patent segments the centralized key caching function into distributed individual AP caches. Each AP maintains its own session key cache independently, eliminating the single point of failure represented by centralized controllers. This segmentation allows roaming to continue even when external controllers are unavailable, as each AP can independently serve roaming requests using its local cache.
Solution Approach 2:
The patent implements self-service by enabling APs to autonomously cache and retrieve session keys without requiring external controller intervention. When a client device roams between APs, the source AP directly provides the session key to the destination AP from its local cache, bypassing the need for cloud-based servers or local controllers. This self-service mechanism ensures continuous operation during controller unavailability.
2Speed
If all session keys are cached at all access points, then roaming speed is improved, but resource usage and system complexity deteriorate
Solution Approach 1:
The patent applies local quality by having each AP cache only the session keys relevant to its specific roaming context rather than all keys site-wide. Each AP maintains a tailored cache containing keys for clients that are likely to roam to or from that particular AP, based on local roaming patterns and proximity. This selective caching reduces memory and processing requirements compared to universal caching, while still enabling fast roaming for relevant clients.
3Productivity
If session keys are cached at selected access points based on proximity, then roaming efficiency is improved, but key distribution complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-caching session keys at APs before roaming is actually needed. When a client device initially associates with an AP, the session key is immediately cached at that AP and proactively distributed to neighboring APs in the roaming candidate set. This advance caching ensures that when roaming occurs, the keys are already in place, eliminating the need for complex real-time key distribution mechanisms during the roaming event itself.
Data Source
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AI summary
An example system includes a plurality of AP devices configured to provide a wireless network at a site, the plurality of AP devices including a first AP device configured to determine a set of roaming candidates within the site for client devices connected to the first AP device, wherein the set of roaming candidates includes one or more AP devices of the plurality of AP selected according to a selection criteria; in response to establishing a connection with a client device, cache a key associated with the client device in the memory of the first AP device; generate a packet with the key associated with the client device, and a list of APs that includes one or more identifiers of the one or more AP devices within the set of roaming candidates for the first AP device; and transmit the packet to the plurality of AP devices at the site.