The most important aspect of satisfying an ISP customer is to ensure the customer has realistic expectations, and then to satisfy those expectations. Many customer desires center around "high availability," but there is an unfortunate tendency to focus on only one technology (e.g., multihomed BGP) to solve these problems.

This tutorial reviews how to define your customer requirements with respect to availability and scalability. It identifies the capabilities and limitations of a wide range of complementary functions at multiple OSI layers, from physical diversity to virtual server farms. It also considers the issues of communicating with customers while problems occur. Previous related tutorials include Berkowitz' NANOG14 tutorial on address management for ISPs and their customers (Atlanta, 1998).