s rather than trying to implement fail-safe routers, which is a much harder job. Figure 2-8 shows the chain of events when a router fails between A and B, and traffic between both nodes must be redirected. Failure in the router does not break the traffic flow between both end systems. Chapter 2 Figure 2-8 Router failure. ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER Router Failure ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER ROUTER Datagrams are routed through an alternative path. Note that although it is correct to state that IP networks do not store state, this doesn't imply that they are stateless. Some state is always needed in order to be able to route datagrams. For instance, when routing protocols distribute new routes to different destinations, the routers must Packet Switching, IP, and the IETF store this information. Another example where state information is stored in the network is header compression in low-bandwidth point-to-point links. Both ends of the link store information in order to perform the header transfer. This happens, for instance, when encoded voice is transferred through a radio interface. In general, however, IP networks tend to keep the state information stored inside the network at minimum in order to scale better and to be more robust. End-to-End Protocols The presence of an IP layer common to all nodes and the concentration of intelligence in the end systems make IP an excellent platform for service creation, and a wide range of applications is already implemented on top of IP. Application development has as many approaches as practitioners, but in order to take full advantage of all the good features IP offers as a plat- form, developers are often advised to follow certain general design rules, which constitute the so-called IP way. At this point, I want to emphasize that the importance of IP and the Internet (the largest worldwide IP network) is in part a function of its design rules and the way Internet standards are developed. I