Summary after reading the first chapter of tcp/ip protocol
The difference between the network layer and the transport layer is the most critical: the network layer (ip) provides point-to-point services, while the transport layer (tcp and udp) provides end-to-end services
On an Internet, each interface is identified by an ip address, although users are accustomed to using hostnames instead of ip addresses. The domain name system provides dynamic mapping between host names and ip addresses. Port numbers are used to identify applications that communicate with each other. The server uses a well-known port number, while the customer uses a temporary port number.
