In the bump in the wire (BITW) method, we add a hardware device that provides
IPsec services. For example, suppose we have a company with two sites. Each has a
network that connects to the Internet using a router that is not capable of IPsec
functions. We can interpose a special IPsec device between the router and the
Internet at both sites, as shown in Figure 29-3. These devices will then intercept
outgoing datagrams, add IPsec protection to them, and strip it off incoming
datagrams