Working outside in, the XYZ website has a single web server. A recent outage has suddenly identified available budget money for redundant components at each layer of the current design. By the way, every company is one major outage away from adding budget money for redundancy plans. One web server is currently used in the design. To add redundancy, we must horizontally scale the web server layer by adding additional web servers, eliminating the single point of failure. How will traffic be passed to both servers? How does the packet on the wire know which web server to go to and which path to take in and out, and how is all of this physically connected?

Load balancing is a major design component when adding redundancy to designs. A single load balancer will help delegate traffic across multiple servers, but a single load balancer creates another single point of failure. For redundancy, two or more load balancers are added to designs. Load balancers control traffic patterns. There are many interesting configurations to consider when deciding how to control and distribute traffic. Distribution may relate to traffic type, content, traffic patterns, or the ability of the servers to respond to requests. Load balancers help to handle traffic logically; how is the traffic handled at the physical layer?