What is an L4 Switch?
An L4 switch is a type of network switch, which is a device used to relay data on a network. Switches are categorized based on the protocol layer they operate on, and the L4 switch functions at Layer 4, the transport layer, which includes protocols like TCP.
L4 switches can analyze and modify information contained in the transport layer, such as port numbers and session sequence numbers, when relaying data (packets). This capability allows them to perform tasks such as traffic load balancing, bandwidth control, session optimization, and WAN acceleration.
Other types of switches include L2 switches (Layer 2 switches), which operate at the data link layer (e.g., Ethernet), L3 switches (Layer 3 switches), which function at the network layer (e.g., IP), and L7 switches (Layer 7 switches), which operate all the way up to the application layer (e.g., HTTP). The term "switch" generally refers to L2 or L3 switches. L4 and L7 switches, however, offer advanced features related to application delivery and are collectively referred to as Application Delivery Controllers (ADC).
F5 provides the F5 BIG-IP, which includes advanced ADC functionality.