Network Security Principles and Practices

Composition of IPsec

IPsec combines three main protocols to form a cohesive security framework:

• Internet Key Exchange (IKE) protocol

• Encapsulating Security Payload (ESP) protocol

• Authentication Header (AH) protocol

Of these three protocols, IKE and ESP are the ones that are mostly deployed together. Although AH is also an important component of the IPsec protocol suite, not that many deployments of IPsec have this protocol turned on for use. In general, much of AH's functionality is embedded in ESP. Therefore, in our discussions in the rest of this chapter, we will focus our attention on ESP, and much of the discussion will assume that we are talking about ESP unless otherwise stated. For example, while discussing quick-mode exchanges in the following ...