Network Load Balancing (NLB)

Often, when I hear people discussing redundancy on their servers, the conversation includes many instances of the word cluster, such as, "If we set up a cluster to provide redundancy for those servers..." or "Our main website is running on a cluster..." While it is great that there is some form of resiliency being used on the systems to which these conversations pertain, it is often the case that clustering is not actually involved anywhere. When we boil down the particulars of how their systems are configured, we discover that it is NLB doing this work for them. We will discuss real clustering further along in this chapter, but first I wanted to start with the more common approach to making many services redundant. NLB distributes traffic at the TCP/IP level, meaning that the server operating systems themselves are not completely aware of or relying on each other, with redundancy instead being provided at the network layer. This can...