Computer Networks and Internet Basics
Computer Networks and Internet Basics covers how devices are connected, how data is addressed and routed, and how common Internet services work. Expect topology comparisons, protocol matching and IP address reasoning.
Networks and topologies
A LAN covers one site, a MAN a city and a WAN spans countries; the Internet is a network of networks. Star topology uses a central switch, which isolates faults easily but is a single point of failure. Bus topology shares one backbone cable, ring passes a token, and mesh gives redundant paths at high cabling cost. A hub broadcasts to all ports, a switch forwards by MAC address, and a router forwards between networks by IP address.
Protocol stack
TCP/IP is the practical suite. IP delivers packets best-effort; TCP adds connection setup, sequencing and retransmission; UDP is connectionless and suits streaming. Application protocols include HTTP/HTTPS for the web, SMTP for sending mail, POP3 or IMAP for retrieving it, FTP for file transfer, and DNS to resolve names into IP addresses.
Worked example. Host 192.168.1.10 with mask 255.255.255.0 (/24). The network address is 192.168.1.0 and the broadcast address is 192.168.1.255, leaving 254 usable host addresses. Reasoning: the mask fixes the first three octets as the network part, while the host bits are all zero for the network address and all one for broadcast.
Traps. A MAC address is physical and fixed to the network card; an IP address is logical and can change. Bandwidth is capacity, throughput is what is actually achieved. DNS resolves names but encrypts nothing; HTTPS relies on TLS.