1. OK. Let's focus on TCP/IP's network layer. What else can you tell me about it besides what was already presented in Chapter 2?

The network layer transfers user messages from a source host to a destination host. In TCP/IP, the heart and soul of this layer is the Internet Protocol, which is the IP of TCP/IP. IP receives data bits from the lower layer, assembles the bits into packets (called IP datagrams), and selects the "best" route based on some metric to route the packets between nodes. ( Note: A metric is a description of the "cost" of a route used by routing hardware and software to select the best possible route. See Chapter 7 for more information.)

IP is connectionless, which implies that every datagram must contain the address of the destination node. This address, called an Internet or IP address, is assigned to a node's network interface as part of the node's initial network configuration. An IP address uniquely identifies a host similar to the way a social security number uniquely identifies a person. It is used by the network layer as a road map to locate a host within the Internet by determining what path a datagram is to follow en route to its final destination. Datagrams destined for a host connected to the same local network as the sending host are delivered directly by the sending host. To transfer datagrams destined for a host connected to a remote network,...