• Define an information and communications network and classify LAN, wireless LAN, WAN and the Internet, with the devices that connect them.
• Compare client–server with peer-to-peer use of a network, and circuit switching with packet switching.
• Read an IPv4 address, explain address exhaustion and DNS, and follow the TCP/IP steps of a transmission.
• Explain how a web page and an e-mail travel, calculate transfer time from speed and size, and use cloud services and generative AI correctly.

Computer Networks, Cloud and Prompt Engineering
├── First: networks (concept, types, connection devices)
├── Second: patterns of network use (client-server, peer-to-peer)
├── Third: connection methods (circuit / packet switching)
├── Fourth: IP addresses and domain names (DNS)
├── Fifth: communication protocols and the TCP/IP layers
├── Sixth: how web pages work (URL and browsing steps)
├── Seventh: how e-mail works (SMTP, POP, IMAP)
├── Eighth: data transfer speed and its calculations
├── Ninth: cloud computing and its advantages
└── Tenth: generative AI and prompt engineering

The IP address

• An IP address is a unique identifying number given to every device connected to the Internet; it is the device’s “address” on the network.
• IPv4 is divided into four blocks of 8 bits each, separated by a dot and written in decimal from 0 to 255 — for example 192.168.0.1.
• Public addresses are reachable on the Internet and are assigned by the authority; private addresses are used inside a local network and are not routable on the Internet.
• With the rapid spread of the Internet, new IPv4 addresses are almost exhausted — the solution is IPv6, whose 128-bit addresses give an enormous space, together with address-sharing techniques.

Domain names and DNS

• A domain name is the human-readable substitute for an IP address, made of parts read right to left: the top-level (organisation or country), then the second-level name, then the host label such as “www”.
• Examples of generic top levels .com commercial, .edu education, .gov government, .org organisation; country codes: .eg Egypt, .jp Japan, .kr South Korea, .cn China.
• The DNS (Domain Name System) is the server that translates a domain name into its IP address, and can answer the reverse query.

Units and constants

• Transfer speed is the number of bits transmitted in one second, measured in bps.
• 1 Kbps = 1000 bps, 1 Mbps = 1000 Kbps, 1 Gbps = 1000 Mbps.
• 1 Byte = 8 bits; 1 KB = 1000 B, 1 MB = 1000 KB, 1 GB = 1000 MB.
• Transfer time (s) = data size in bits ÷ speed in bps ; data size = speed × time; and actual speed = connection speed × transfer efficiency.

• A 1 GB file over a 100 Mbps link whose efficiency is 0.8: actual speed = 100 × 0.8 = 80 Mbps = 80,000,000 bps; size = 1 × 1000 × 1000 × 1000 × 8 = 8,000,000,000 bits; time = 8,000,000,000 ÷ 80,000,000 = 100 seconds.
• Always convert megabytes to megabits by multiplying by 8 — forgetting that factor is the classic error.

💡 High-yield traps

• In circuit switching the path is reserved before sending; in packet switching no path is reserved and each packet may take another route.
• Every IPv4 block is 8 bits and therefore runs 0–255 — a block of 256 is invalid.
• Private addresses are not reachable over the Internet; they belong inside the LAN.
• DNS does the name → address translation; the router does not.
• TCP/IP has four layers, not seven (that is the OSI model).
• Transfer speed uses bits while file size is given in bytes multiply the size by 8.
• Use 1000, not 1024, for Kbps/Mbps/Gbps and KB/MB/GB in this syllabus.
• Actual speed = connection speed × efficiency; a question on “why did the download take longer?” expects this relation.
• POP downloads then deletes; IMAP keeps messages on the server — swap them and the answer is wrong.
• SMTP sends, it does not receive.
• A URL’s country code is the last meaningful label (.eg, .jp); read the domain right to left.
• Generative AI predicts text from statistics; it does not look up a verified database of facts.