Overview of Layer 4 Switching

What is Layer 4 Switching ?

Layer 4, is the Transport layer in OSI model, which takes care of things like flow control and reliable and accurate delivery of the data to the next layer, uses protocols such as TCP and UDP. These protocols include the port number information in the header, which helps identify what application the packet is being used .A Layer 4 switch can identify this information, together with the IP address that is identified on Layer 3, it not only knows where the data needs to go, but also what application will use it. The combination of a Layer 4 TCP or UDP port number and the Layer 3 address is called a socket.

Layer 4 can be used to enhance the features of a Layer 3 switch, which essentially performs packet routing at high speeds by means of hardware, by allowing it to filter network traffic and perform switching based on the application the data is intended for. So, a Layer 4 switch has the ability to not only examine the IP address, but also to control the traffic based on the port numbers located at Layer 4 of the OSI model.