Glossary term
What is L4 / L7 (Layer 4 / Layer 7)?
L4 / L7 stands for Layer 4 / Layer 7.
L4 = transport (IP + port). L7 = application (HTTP: URLs, headers). Example: An L4 load balancer sees "port 443"; an L7 one sees "GET /api/orders".
Learn it properly · System DesignLesson 12: Load Balancers: L4 vs L7 and Balancing AlgorithmsOne address, many servers, and one of them just crashed at 2 AM. How load balancers spread traffic, L4 vs L7, the balancing algorithms and when each wins, and why a “deep” health check can take everything down at once.