Requirements for a radio to join a load balancing group

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The access capability of an AP is limited. If a large number of STAs exist in a hotspot area, the user deploys multiple APs in this area to meet requirements of the STAs. In this case, certain APs may be connected to multiple STAs whereas other APs to only a few STAs, resulting in imbalance. To solve this problem, load balancing is used. In load balancing mode, AP radios in a hotspot area are added to a group. When the load is unbalanced in the group, STAs are automatically associated with lightly loaded AP radios but not heavily loaded radios.

The requirements for a radio to join a load balancing group are as follows:

- A radio can join only one load balancing group.

- The newly added radios must be of the same type as other radios in the load balancing group.

Radios in a hotspot area must be of the same type. Otherwise, load balancing cannot be achieved.

The type of radios in a load balancing group is determined by the type of the first added radio.

- The channel of a new radio must be different from channels of other radios in the load balancing group.

If the channel of a new radio is the same as channels of other radios in the load balancing group, a radio signal collision occurs. To improve coverage areas and minimize collisions, APs in a hotspot area must be configured with different channels.

To detect channel collisions, check the configured channel and actual channel of the radio.

- More radios can be added to a load balancing group if it is not full.

In a load balancing group, radios must be configured with different channels and all these radios must be of the same type. In addition, radios of the same type support limited and fixed channels. Therefore, the number of radios in a load balancing group is limited.

Other related questions:
The traffic information about radios is incorrect when checking the information about the load balancing group
Perform the following operations to locate the fault: 1. Check whether the radios operate normally, and whether the uplink and downlink services are interrupted. 2. Check whether the AP reports traffic information periodically (at a fixed period of 30s). In versions earlier than V200R006, run the display load-balance-group all command to view the configuration result. In V200R006 and later versions, run the display sta-load-balance static-group command to view the configuration result. 3. Check whether traffic information in the packets reported by the AP is correct. 4. Check whether the AC receives the packets containing traffic information reported by the AP and whether the packets are processed correctly.

How to configure load balancing in a link aggregation group
Run the load-balance { dst-ip | dst-mac | src-ip | src-mac | src-dst-ip | src-dst-mac } command in the Eth-Trunk view. The default load balancing mode of the S3700HI, S5700HI, S5706, and S6700 is src-dst-ip; the default load balancing mode of other switches is src-dst-mac.

Load balancing
The functions and meanings of load balancing are described as follows: When multiple routes have the same routing protocol preference and metric, these routes are called equal-cost routes, among which load balancing can be implemented. Routers support the multi-route mode, allowing you to configure multiple routes with the same destination and preference. If the destinations and costs of multiple routes discovered by the same routing protocol are the same, load balancing can be performed among the routes. Run the maximum load-balancing number command in the views of various protocols to implement load balancing. Load balancing falls into the following two modes: -Packet-by-packet When the packet-by-packet load balancing is configured, firewalls at the network layer forward packets to the same destination through various equal-cost paths. That is, switches always choose the next hop address that is different from the last one to send packets. -Session-by-session When session-by-session load balancing is configured, firewalls forward packets according to the source address, destination address, source port, destination port, and protocol contained in the packets. When the five factors are the same, firewalls always choose the same next hop address as the last one used to send the packets.

How load balancing is implemented on S series switches when link aggregation is configured
For S series switches (except the S1700), there are two load balancing modes: per-packet load balancing and per-flow load balancing. 1. Per-packet load balancing mode When there are multiple physical links between the two devices of the Eth-Trunk, the first data frame of a data flow is transmitted on one physical link, and the second data frame is transmitted on another physical link. In this case, the second data frame may arrive at the peer device earlier than the first data frame. As a result, packet mis-sequencing occurs. 2. Per-flow load balancing mode This mechanism uses the hash algorithm to calculate the address in a data frame and generates a hash key value. Then the system searches for the outbound interface in the Eth-Trunk forwarding table based on the generated hash key value. Each MAC or IP address corresponds to a hash key value, so the system uses different outbound interfaces to forward data. This mechanism ensures that frames of the same data flow are forwarded on the same physical link and implements flow-based load balancing. Per-flow load balancing ensures the correct sequence of data transmission, but cannot ensure the bandwidth usage. Notes: Currently, S series switches support only per-flow load balancing mode, including the following: 1. Load balancing based on the source MAC address of packets; 2. Load balancing based on the destination MAC address of packets; 3. Load balancing based on the source IP address of packets; 4. Load balancing based on the destination IP address of packets; 5. Load balancing based on the source and destination MAC addresses of packets; 6. Load balancing based on the source and destination IP addresses of packets; 7. Enhanced load balancing for L2, IPv4, IPv6, and MPLS packets based on the VLAN ID and source physical interface number. When you configure load balancing modes, follow these guidelines: The load balancing mode only takes effect on the outbound interface of traffic. If load is unevenly distributed on the inbound interfaces, change the load balancing mode on the uplink outbound interfaces. Configure load balancing to ensure data flow is transmitted on all active links instead of only one link, preventing traffic congestion and ensuring normal service operation. For example, if data packets have only one destination MAC address and IP address, you are advised to configure load balancing based on the source MAC address and IP address. If you implement load balancing based on the destination MAC address and IP address, the data flow may be transmitted on only one link, causing traffic congestion.

Principles of AP load balancing
Load balancing can evenly distribute AP traffic loads to ensure high bandwidth for each STA. The load balancing function applies to wireless networks with high user densities to ensure proper access of STAs. Depending on whether a load balancing group needs to be manually created, load balancing is classified into static and dynamic load balancing. For details about the principles, see: V200R005: Configuring Load Balancing V200R006: Configuring Load Balancing

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