Layer 4
In plain terms
The transport layer of the network model.
Going deeper
Layer 4 handles end-to-end data transport via protocols like TCP and UDP, managing ports, reliability, and flow. It sits below the application layer.
Under the hood
Layer-4 load balancers route by IP/port without inspecting content, making them fast but less smart than L7.
Examples
TCP/UDP, port-based load balancing, transport protocols, firewalls.
Think of it like...
Like the postal service ensuring packages get delivered, without reading the letters inside.