As we discussed in Chapter 12, "Fundamentals of Secure Perimeter Design," performance is an important element to include in the design of a network. Networks that do not offer acceptable performance to their users are frequently not used. It is also important to consider performance when designing the security infrastructure for a network because many techniques that are used to protect networks have performance impacts. Managing these impacts in your design is essential if you hope to deliver a secure network that is acceptable to its users. This can be difficult because performance issues can be hard to quantify prior to implementation, and adding security might decrease performance. This chapter discusses performance issues as they apply to security. We provide you with guidance on how different elements of your security infrastructure can contribute to performance problems and how you can reduce or eliminate the performance impacts of your design decisions.