CHAPTER 13 Routing and Peering 325 performance guarantees in terms of bandwidth, delay, and so on cannot be enforced from end to end because packets often follow different paths through the network. A good example of a router-based network is the global, public Internet. CONNECTION-ORIENTED AND CONNECTIONLESS NETWORKS Many layers of a protocol stack, especially the lower layers, offer a choice of connection- oriented or connectionless protocols. These choices are often independent. We've seen that connectionless IP can use connection-oriented PPP at Layer 2. But what is it that makes a network connectionless? Not surprisingly, it's the implantation of the network layer. IP, the Internet protocol suite's network layer protocol, is connectionless, so TCP/IP networks are connectionless. Connection-oriented networks are sometimes called switched networks, and con- nectionless networks are often called router-based networks. The signaling protocol messages used on switched networks to set up SVCs are themselves routed between switches in a connectionless manner using globally unique addresses (such as tele- phone numbers). These call setup messages must be routed, because obviously there