Cluster Load Balancing

Cluster load-balancing is achieved through the features, Client load-balancing and AP load-balancing. Both these features are explained in this section.

Active Client Load Balancing

The client load balancing feature ensures that clients are evenly distributed across the cluster members, thereby using the system resources efficiently.

If the system detects a distorted distribution of load, it balances the load on the managed devices by changing the UAC of these clients. The load across all the managed devices is balanced in the cluster regardless of the type of platform.

The cluster manager calculates the ratio of the existing number of clients on a managed device and its maximum capacity. Based on this ratio and additional threshold triggers, client load balancing is triggered.

When any new managed device, including the managed device that comes up after a failover, is added to an existing cluster, it is considered for load balancing and accordingly, APs and clients are moved to balance the load in the cluster.

Threshold Triggers

• AP Total Load Balance threshold—The total load balance threshold is set to 40%. This is the default value and cannot be configured.

Bucket Based Client Load Balancing

ArubaOS 8.11.0.0 now supports the bucket based client load balancing feature that distributes the buckets based on the platform capacity in a cluster. In bucket based client load balancing, the cluster manager intermittently checks for the proportionate distribution of the bucketmap among the cluster nodes, and if required, re-balances 8 buckets of one ESSID Extended Service Set Identifier. ESSID refers to the ID used for identifying an extended service set. in one iteration. The periodicity of rebalancing of the buckets among the cluster nodes is at every 20 seconds.

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command displays the current bucket distribution for all the ESSIDs Extended Service Set Identifier. ESSID refers to the ID used for identifying an extended service set..

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command displays the current bucket distribution for a specific ESSID Extended Service Set Identifier. ESSID refers to the ID used for identifying an extended service set..

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command displays the details of the bucketmap publish counters.

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command clears the details of the bucketmap publish counters.

AP Load Balancing

The AP load balancing feature ensures that the cluster leader manages the load balancing based on the platform capacity. The AP is dynamically assigned an AAC when it connects to a cluster. Here, instead of client load, AP load is considered.

Both active and standby APs are considered for load balancing.

Following is the AP load balancing criteria if a managed device is newly added:

• When an AP threshold is already met in the cluster nodes, if a new managed device is added, the Active AP table of the new managed device is filled first based on AP count set.
• When the threshold is not met, APs are moved to standby AP table of the newly added managed device.
• The count of these APs will increment based on the AP count set only after the stabilization of the cluster, however, the APs that were moved during this phase cannot be always based on AP Count.

The active AP load balancing is performed using VRRP Virtual Router Redundancy Protocol. VRRP is an election protocol that dynamically assigns responsibility for a virtual router to one of the VRRP routers on a LAN. for L2 connection and the switch IP of one cluster member for L3 connection. The AP Total Load Balance threshold is set to 40% and active AP load balancing threshold value is set to 20%. This is the default value.

The cluster leader considered the AP load on each cluster member and assigned the cluster member with least total AP load as the AAC.

For initial load balancing, cluster leader evaluates if the managed device with the least active AP load percentage can accommodate additional APs. If yes, return this managed device as the candidate AAC.

For periodic load balancing, the cluster leader performs load balancing based on the following conditions:

1. Finds the managed devices with maximum and minimum active load percentage.
2. Finds the managed devices with maximum and minimum total load percentage
3. Checks if the max active load percentage is more than the active load percentage threshold. Also, checks if the difference between the maximum and minimum loaded managed devices is more than the unbalance threshold.
4. Moves the active APs from maximum loaded managed devices to minimum loaded managed device. However, if it is unable to move the Active APs, it will re-balance the standby load by moving the standby APs from the maximum load percentage managed device to minimum load percentage managed device.

After APs are listed on a cluster member, the cluster manager periodically recalculates the load of the cluster members to balance the load. For example, when a new managed device joins the cluster.

Listed below are the advantages of AP load balancing

• Easy scaling of cluster nodes.
• Eliminates manual distribution through the LMS Local Management Switch. In multi-controller networks, each controller acts as an LMS and terminates user traffic from the APs, processes, and forwards the traffic to the wired network. -IP.

Configuring Cluster Load Balancing

The following procedure describes how to configure load balancing for a cluster:

1. In the Managed Network node hierarchy, navigate to the Configuration > Services > Clusters tab.
2. In the Clusters table, select a cluster to configure AP load balancing.
3. In the Cluster Profile > <cluster name> window, expand the Advanced accordion.
4. Configure the active AP load balancing settings described in table below.
5. Click Submit.
6. Click Pending Changes.
7. In the Pending Changes window, select the checkbox and click Deploy changes.

Table 1: Active AP Load Balancing Parameters

Parameter	Description
Redundancy	Enable redundancy. When the redundancy mode is enabled, the capacity of the cluster is reduced to half and only 8000 clients are considered to reach the threshold.
Heartbeat threshold	Minimum heartbeat threshold is set in milliseconds. The default setting is based on the latency determined between each pair of managed devices and the cluster. It also depends on the connection type between managed device and distribution switch (single ethernet cable, or port channel, and so on).

The following procedure describes how to configure the AP and client load balancing values:

1. In the Managed Network node hierarchy, navigate to the Configuration > System tab.
2. Click Profiles.
3. Expand the Cluster accordion and click Classic Controller Cluster.
4. Click + to create a cluster profile.
5. Add the AP load balancing values and Client Load Balancing values.
6. Click Submit.
7. Click Pending Changes.
8. In the Pending Changes window, select the checkbox and click Deploy changes.

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. commands configure load balancing for a cluster:

Following is an example of Active AP load balancing:

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command checks if Active AP load balancing for IPv4 is enabled or disabled:

 

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command checks if Active AP load balancing for IPv6 is enabled or disabled:

The following CLI Command-Line Interface. A console interface with a command line shell that allows users to execute text input as commands and convert these commands to appropriate functions. command displays the number of times a managed device published APs on the AP channel for A-AAC assignment:

The following command displays the number of times the AP tried to connect to the cluster leader and needed the cluster leader to assign an A-AAC for this AP: