Network Device Sub-Cluster Selection for Roaming Session Continuity
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Solution Overview
Problem
In a network arrangement with controller clusters, a cluster split leads to different access points connecting to different sub-clusters, causing loss of session information and non-seamless traffic handling for client devices during roaming, due to unsynchronized sub-clusters.
Innovation Solution
Network devices use a common set of criteria to select the same sub-cluster after a cluster split, ensuring consistent sub-cluster selection by sending node lists and bucket maps to access points, maintaining session continuity for client devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cluster split occurs in controller cluster, then network device can continue operating with sub-clusters, but session information is lost and traffic handling becomes non-seamless
Solution Approach 1:
The system performs preliminary actions by establishing node lists and bucket maps before the cluster split occurs. These data structures are prepared in advance and distributed to network devices, enabling them to maintain session continuity even after the split. The node lists identify which controllers belong to which sub-cluster, while bucket maps associate client devices with specific controllers, allowing seamless traffic routing without session information loss.
Solution Approach 2:
The system implements feedback mechanisms where controllers continuously update node lists and bucket maps based on the current cluster topology. After a split occurs, controllers send updated information to network devices, enabling dynamic adaptation. This feedback loop ensures that network devices have the most current mapping information to route traffic appropriately across sub-clusters, maintaining session continuity throughout the split and recovery process.
2Adaptability or versatility
If different access points connect to different sub-clusters after split, then network can accommodate split topology, but traffic handling becomes non-seamless for roaming clients
Solution Approach 1:
The system introduces dynamic adaptability by enabling access points to flexibly select which sub-cluster to connect to based on real-time conditions. Rather than being rigidly assigned to specific controllers, access points can dynamically adjust their connection based on node list information and traffic requirements. This dynamic approach allows the network to adapt to various topological configurations while maintaining reliable traffic handling through coordinated bucket map updates.
Solution Approach 2:
The system uses node lists and bucket maps as intermediary data structures that mediate between the cluster split and traffic handling. These intermediaries translate the abstract sub-cluster topology into concrete routing instructions. Node lists provide the mapping between access points and sub-clusters, while bucket maps provide the mapping between client devices and controllers, enabling seamless traffic handling even when access points are distributed across different sub-clusters.
3Difficulty of detecting and measuring
If sub-clusters are formed without synchronization, then cluster split can be detected and responded to, but session information is lost and traffic may be sent to wrong destinations
Solution Approach 1:
The system prepares node lists and bucket maps in advance as synchronization mechanisms. Before the cluster split fully impacts operations, these data structures are established and distributed to all network devices. This preliminary preparation ensures that when a split occurs, all devices already have the necessary mapping information to maintain sessions correctly, preventing information loss and wrong destination routing.
Solution Approach 2:
The system implements comprehensive feedback mechanisms where controllers continuously broadcast node lists and bucket maps to all network devices. This feedback ensures that every access point and network device receives synchronized information about the current cluster topology and controller assignments. The feedback loop detects split conditions and automatically updates all devices with consistent mapping information, preventing session information loss and ensuring traffic is routed to correct destinations.
Data Source
AI summary
In some examples, a network device determines that a cluster split has occurred in which a controller cluster of controllers is split into a plurality of sub-clusters. The network device receives, from the plurality of sub-clusters, information associated with controllers of the plurality of sub-clusters. The network device selects, from among the plurality of sub-clusters, a sub-cluster to which the network device is to connect using a specified criterion.