13 Best Free and Open Source Load Balancers
Layer 4 (L4) load balancers work at the transport level. That means they can make routing decisions based on the TCP or UDP ports that packets use along with their source and destination IP addresses. L4 load balancers perform Network Address Translation but do not inspect the actual contents of each packet. Layer 7 (L7) load balancers act at the application level, the highest in the OSI model. They can evaluate a wider range of data than L4 counterparts, including HTTP headers and SSL session IDs, when deciding how to distribute requests across the server farm.
L7 load balancing is more CPU‑intensive than packet‑based L4 load balancing, but rarely causes degraded performance on a modern server. L7 load balancing enables the load balancer to make smarter load‑balancing decisions, and to apply optimizations and changes to the content.
Load balancers can be hardware-based or software-based.
The ratings chart below summarizes our verdict. Only free and open source software is eligible for inclusion here.