What are L4-L7 (load balancing levels)?

L4 and L7 are levels of the OSI model at which different types of load balancers operate.

• L4 (Transport Layer) — balancing occurs at the TCP/UDP level. The load balancer looks at IP addresses and ports without analyzing the contents of packets. This allows for quick traffic distribution but without deep understanding of protocols.

• L7 (Application Layer) — balancing at the application level, such as HTTP/HTTPS. The load balancer can analyze request contents, headers, cookies, URLs, and make decisions based on this data. This enables more complex routing rules, for example, directing requests to different services based on the URL path.

Example: An L4 load balancer can route traffic based on IP and port, while an L7 can route based on URL or HTTP headers.