The Internet and Its Protocols

372 Chapter 8 Traffic Engineering

Figure 8.3 A tunnel carries a collection

of flows from one point in the network to another by a path

that may not be the shortest.

Tunnels may run from one edge of the network to another, or may be used

to bypass an area of congestion. The simplest way to achieve a tunnel is to

impose a source route on each datagram that enters the tunnel. In this way the

router at the head end of the tunnel determines the path of the datagram until it

reaches the end of the tunnel. Other, more sophisticated, IP tunneling techniques

are described in Section 15.1. Note that tunnels ...