Networking and The Internet - Quick Reference Notes
2.1 Networking
Key concepts you should know
ARPAnet, WAN, LAN, MAN, PAN
File server, Hub, Switch, Router, Modem, WLAN, WAP, NIC, WNIC
Client-server vs peer-to-peer models
Thin client vs thick client
Bus, Star, Mesh, Hybrid network topologies
Cloud storage (public, private, hybrid) and data redundancy
Wired vs wireless networking (cables, wireless technologies, security, range)
Ethernet and CSMA/CD; data collisions and how they are detected/avoided
Bit streaming (on-demand vs real-time); buffering; bit rate
Internet vs World Wide Web (WWW)
IP addresses (IPv4, IPv6; public vs private); CIDR; NAT
Uniform Resource Locator (URL) structure; Domain Name Service (DNS)
2.1.1 Networking basics
WANs connect multiple LANs across large areas; can be private or public
LANs cover a small area (building); share devices like printers
MANs connect networks across a city (larger than LAN, smaller than WAN)
IP addressing basics: unique identifiers for devices on networks
WNICs and WLANs extend LANs wirelessly; WAPs connect wireless devices to wired networks
Private vs public networks: ownership and access control
2.1.2 Client-server vs peer-to-peer (P2P)
Client-server: dedicated servers; clients access resources; central security and backups; scalable
P2P: each node provides and consumes resources; no central server; simpler, smaller scale; lower security and management
2.1.3 Network topologies
Bus: single central cable; easy to expand; data in one direction; collisions common; single point of failure
Star: central hub/switch; each device has own connection; collisions reduced; hub failure = network down; security can be centralized; hub vs switch affects how data is routed
Mesh: interlinked nodes; routing vs flooding; fault-tolerant; scalable but high cabling and maintenance
Hybrid: combination of topologies; flexible but complex to install/manage
2.1.4 Public and private cloud computing
Cloud storage: data on off-site servers; data redundancy across multiple servers
Public cloud: provider and user are different entities
Private cloud: hosted behind a company firewall; integrated with provider
Hybrid cloud: mix of private and public
Pros: remote access, backups, scalable storage; Cons: security concerns, data privacy, dependency on internet
2.1.5 Wired and wireless networking
Wireless: easier expansion, mobility; potential interference; security concerns; generally slower than wired but improving
Wired: more reliable, higher data rates, fewer dead spots; less mobility
Key wireless techs: Wi‑Fi (IEEE 802.11), Bluetooth (WPAN, ~30 m range, spread-spectrum frequency hopping)
Spread spectrum (frequency hopping) and security measures (WEP/WPA2)
2.1.6 Hardware for LANs/WANs
Hub: multiple devices share a single collision domain; broadcasts to all ports; no intelligence
Switch: forwards frames to specific destination MAC; reduces collisions; can be wired or wireless
Repeater: boosts signal over long distances; creates extended networks; has single collision domain unless used with additional devices
Bridge: connects LANs using the same protocol; reduces broadcast domain size
Router: routes data between networks; can perform protocol translation; determines best path
Gateway: entrance point to another network; can be a router/firewall/server; can connect dissimilar networks
Modem: converts between digital and analogue signals for transmission over phone lines; softmodem = software modem
NIC: network interface card; provides device connectivity; MAC address assigned at factory
WNIC: wireless NIC; connects via radio to WLAN
Cabling basics: twisted pair, coaxial, fibre optic; pros/cons by speed, interference, distance
2.1.7 Ethernet and data handling
Ethernet = IEEE 802.3; frames contain source/destination MACs
IP address conflicts occur when two devices share the same address; usually resolved by rebooting DHCP/routers
CSMA/CD: collision detection; devices sense channel, jam on collision, back off using random timing; prevents simultaneous transmissions
Broadcasts vs collisions: broadcasts go to all devices; collisions occur when two devices transmit at once on the same channel
2.1.8 Bit streaming
Bit streaming = continuous sequence of bits over a network for video/audio
Requires buffering and compression; buffer must keep data ahead of playback
On-demand streaming vs real-time streaming
Pros: immediate playback, no full file download; cons: depends on network stability
2.1.9 The internet vs WWW (brief recap)
Internet: global network of networks using TCP/IP
WWW: collection of web pages accessed via the internet using HTML/HTTP/URLs
2.1.10 IP addressing and NAT basics
IPv4: 32-bit addresses; roughly 4.29 billion addresses; classful addressing (A, B, C, D, E)
CIDR: flexible allocation with suffix like /18 to designate net/host parts
IPv6: 128-bit addresses; hex notation; no NAT required; built-in routing/authentication potential
Private IP address blocks: Class A: 10.0.0.0–10.255.255.255; Class B: 172.16.0.0–172.31.255.255; Class C: 192.168.0.0–192.168.255.255
Public IP addresses are allocated by ISPs
NAT: translates private addresses to a public address to conserve IPv4 space
2.1.11 URLs and DNS
URL = protocol://domain/path/filename; e.g., http(s)://www.example.com/index.html
DNS translates domain names to IP addresses; DNS servers cache mappings
DNS process illustrated: user requests URL → DNS finds IP → browser connects to IP → server responds
Domain names simplify addressing; IPs are not user-friendly
2.2 The Internet
2.2.1 Internet vs WWW (key differences)
Internet: network of networks; uses TCP/IP; global routing and data transfer
WWW: collection of web pages/services accessed via the internet; uses HTML/HTTP/URLs
2.2.2 Hardware and software to support the internet
Devices: computers, tablets, phones
Access methods: PSTN/phone lines, fibre, satellite, cellular data; routers (wired/wireless)
Modems and gateways connect home networks to ISPs; browsers access web content
ISP: provides connectivity and often a gateway/modem; ~ monthly service
Rising use of fibre optic for high-speed broadband; WAPs enable wireless access
2.2.3 IP addressing details (IPv4, IPv6, NAT, CIDR, sub-netting)
IPv4: 32-bit addresses; classful ranges (A, B, C) with network ID vs host ID
Class ranges (summary):
Class A: 0.0.0.0 to 127.255.255.255; 8 netID bits, 24 hostID bits
Class B: 128.0.0.0 to 191.255.255.255; 16 netID bits, 16 hostID bits
Class C: 192.0.0.0 to 223.255.255.255; 24 netID bits, 8 hostID bits
Class D/E for multicast/experimental
Binary representation of networks and host IDs can be used to understand addressing
CIDR: introduces flexible net/host boundaries, e.g., 192.0.2.0/18
NAT: allows multiple private IPs to share a single public IP
IPv6: 128-bit addresses; large address space; hex notation; benefits include no inherent NAT requirement, built‑in auth, and better routing
Zero compression in IPv6 to shorten long addresses (e.g., ::)
Sub-netting: dividing a LAN into smaller subnets to reduce traffic and improve management
Private IP blocks (internal, behind NAT) = 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
Public IPs are routable on the internet; DNS maps hostnames to these addresses
2.2.4 Uniform Resource Locators (URLs) and the web
URL structure: protocol, domain name, path, file
Domain names provide user-friendly addressing; DNS resolves to IPs
2.2.5 Domain Name Service (DNS)
DNS translates domain names to IP addresses; caching improves speed
Typical workflow: browser asks DNS, DNS resolves, IP returned, connection established
2.2.6 Scripting in HTML (intro; not syllabus core but helpful)
JavaScript: client-side scripting; runs in the user’s browser; interacts with HTML
PHP: server-side scripting; runs on the web server; embedded in HTML via .php files
Examples illustrate how dynamic content can be generated and delivered
2.2.7 Cloud and web services (brief recap)
Cloud software: applications hosted remotely; access via browser; updates and security managed by provider
On the client, data can be cached or stored locally if offline; data synced when online
2.2.8 Practical connections
PSTN vs VoIP: PSTN uses circuit switching; VoIP uses packet switching over the internet; VOIP advantages include lower cost and flexible routing
Satellite types (GEO, MEO, LEO) offer different coverage and latency profiles; GEO satellites provide wide coverage and fixed position; LEO/MEO reduce latency but require larger constellations
2.2.9 Quick reference formulas and notes
IPv4 address space: 2^{32} = 4{,}294{,}967{,}296 addresses
IPv6 address space: 2^{128} addresses
Private IPv4 blocks (examples):
Class A: 10.0.0.0/8
Class B: 172.16.0.0/12
Class C: 192.168.0.0/16
CIDR suffixes denote the length of the net prefix, e.g., /18
Binary/networking concepts (netID vs hostID) can be understood via AND masking
End of notes for 2.1 and 2.2