What is the difference between an L4 and L7 load balancer?

The L4 load balancer operates at the transport layer (TCP/UDP). It makes routing decisions based on IP addresses and ports without analyzing packet contents. This provides high performance and low latency but limits balancing capabilities.

The L7 load balancer operates at the application layer (HTTP, HTTPS, etc.). It analyzes request contents — headers, URLs, cookies, etc., allowing for more intelligent decisions, such as routing requests by URL, performing SSL termination, caching, authentication.

Example:

• The L4 load balancer directs all TCP packets to servers based on IP and port.
• The L7 load balancer can route requests to different servers depending on the URL path or content type.