Load Balancer Types

Generally speaking, load balancers fall into three categories:

• DNS Round Robin (rarely used): clients get a randomly-ordered list of IP addresses.
  • pros: easy to implement and free
  • cons: hard to control and not responsive, since DNS cache needs time to expire
• Network (L3/L4) Load Balancer: traffic is routed by IP address and ports.L3 is network layer (IP). L4 is session layer (TCP).
  • pros: better granularity, simple, responsive
• Application (L7) Load Balancer: traffic is routed by what is inside the HTTP protocol. L7 is application layer (HTTP).