What is Balancer

Load balancing means that concurrent access requests and data traffic are evenly distributed among multiple devices, greatly improving service processing capabilities. Load balancing devices in the Cache system are classified into load balancing subsystems (LBSs) and global load balancers (GLBs) based on deployment scenarios. -- An LBS is used in in-band policy-based routing (PBR) deployment scenarios. PBR on a router of the live network is added to direct upstream and downstream HTTP traffic to the F5. The traffic is then load balanced to the Cache system by the LBS. -- A GLB is used in in-band DNS redirection deployment scenarios. DNS requests of intranet users are parsed into HTTP proxy IP addresses and are then redirected to the Cache system.

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.

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.

By default, Eth-Trunks work in manual load balancing mode.

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