Module 2 & 9 – Internet, Online Communication, Networks & Security (Comprehensive Study Notes)

Communication and Network Foundations

  • The concept of a network: system of two or more devices linked via wired, wireless, or telecommunication systems to share hardware, software, data, and information.
    • Requires both hardware (NICs, cables, routers, WAPs, etc.) and software (OS networking components, apps, protocols).
    • Forms the backbone of global digital communication via the Internet.
  • Digital communications: transfer of data, instructions & information between devices.
    • Sending & receiving devices can be any computer/mobile device.
    • Transmission media: wired (copper, fiber) or wireless (RF, IR, satellite).
  • Core communication system components (Table 9-1 recap):
    • Sending device → Communications device → Transmission medium → Communications device → Receiving device.

The Internet: Evolution & Key Concepts

  • Began as ARPANET (1969) by U.S. DoD’s ARPA.
    • Objectives: (1) resource sharing among geographically separated scientists, (2) survivability under disaster.
    • Original 4 hosts: UCLA, UCSB, Stanford Research Institute, Univ. of Utah.
  • Internet = global collection of millions of interlinked networks providing abundant goods, services & info.
  • Bandwidth: channel capacity (higher bandwidth → more/faster data).
  • Net neutrality: principle that every website has equal priority; ISPs must deliver the same service level regardless of content.
  • Internet Service Provider (ISP): company selling Internet access; obligated (in theory) to uphold net-neutral traffic.

World Wide Web Essentials

  • The Web (WWW) = service on Internet consisting of websites stored on webservers.
    • Web page: specially-formatted document (HTML) containing text, graphics, audio, video & hyperlinks.
    • Static page → identical on every visit.
    • Dynamic page → regenerated each display (e.g., weather, stock quotes).
    • Hyperlinks (links): clickable text/graphics navigating to other web resources.
  • Website: collection of related pages + associated items (docs, images) stored on a single webserver.
    • One server may host multiple sites.
    • Responsive Web Design: layout adapts automatically to screen size.
  • Core web technologies
    • HTML (Hypertext Markup Language): defines page structure & content.
    • CSS (Cascading Style Sheets): controls design & appearance.
    • Together enable modern, device-adaptive sites.

Web Browsers & Navigation Tools

  • Popular browsers (Table 2-1): Apple Safari, Google Chrome, Microsoft Edge, Mozilla Firefox.
  • Browser features
    • Address bar shows URL; navigation bar holds Back/Forward (tracks breadcrumbs).
    • Cookies: small text files created by server to store session data (items viewed, login status, etc.).
  • URL Components (Fig 2-6):
    • Protocol (e.g., http or https) —> Server/domain —> Pathname —> File name.
  • IP address: unique numeric identifier; IPv4 = four octets 0–255 (e.g., 69.32.132.255). IPv6 provides vastly larger address space.
  • Domain Name System (DNS): translates domain names to IPs via DNS servers (often operated by ISPs).

Connecting to the Internet

  • Hot spot: wireless AP providing Internet (public or personal).
    • Mobile hot spot: phone/device sharing cellular data.
  • Cellular networks: 4 ext{G} widely available, 5 ext{G} offers higher-bandwidth.
  • Wi-Fi networks: public locations (coffee shops, hotels) or home/office routers.
  • Tethering: smartphone/tablet shares its data connection with other devices.

Online Activities & Web Services

  • Information/Research sites: libraries, encyclopedias, dictionaries.
  • Education: LMS platforms, MOOCs.
  • Business sites: branding, e-commerce.
  • Government: forms, census data (Fig 2-16 U.S. Census site).
  • Blogs: time-stamped posts in reverse chronological order.
  • Health/Fitness, Science, Entertainment portals.
  • Bookmarking & tagging: organize/share links & media (tags are descriptive keywords).
  • Social media: myriad interaction channels (posting, sharing, messaging).
  • Online banking/trading: remote financial management.
  • Web Apps: apps executed in browser; pros (device-agnostic, collaboration, no installs) vs cons (must be online, security, provider dependence, fewer features).

Online Safety & Security

  • Secure website: uses encryption; URL begins with https (Hypertext Transfer Protocol Secure).
    • Encryption scrambles data in transit; decrypted by intended recipient.
  • Digital certificate: third-party-signed credential verifying site identity.
  • Safety tips: verify sites, disable location sharing, clear history, avoid storing passwords, phishing filters, pop-up blockers, private browsing, proxy servers.

Communicating Online

  • Email: original Internet service enabling global asynchronous communication.
  • Internet messaging services (real-time): notify when contacts are online; provide text, file exchange, private chatrooms.
  • Messaging app common features: text, multimedia, voice, voice-to-text, group discussions (e.g., Facebook Messenger).
  • Social networks (types & examples)
    • Social networking: Facebook, LinkedIn, Instagram.
    • Blogging/microblogging: Twitter, WordPress.
    • Media sharing: YouTube, Flickr.
    • Collaborative projects: Wikipedia, forums.
    • Social curation/bookmarking/news: Reddit, Digg.
    • File sharing: Dropbox, WeTransfer.
  • Security practices: cautious registration, profile management, friend limits, minimal personal info, skepticism of urgent requests.

Information Literacy & Web Searches

  • Search engine uses spiders/crawlers to build index of web content.
  • Query: user-entered search term(s).
  • Search tools also include subject directories (alphabetized topical guides).
  • Search strategy steps (Fig 2-35): question → keywords → choose tool → use keywords → add/remove terms → search operators.
  • Boolean / search operators
    • Quotes "phrase" → exact match.
    • OR (|) → either term.
    • Hyphen (-) → NOT.
    • Asterisk * → wildcard.
    • Range #..# → numeric interval.

Using Online Content Responsibly & Ethically

  • Internet lacks guaranteed accuracy; apply CARS checklist (Credible, Accurate, Reasonable, Supportable).
  • Citation: formal reference for non-common-knowledge sources (Word can auto-manage and build bibliography, Fig 2-37).
  • Intellectual property rights: protect creators of photos, art, writing, music.
  • Digital Rights Management (DRM): tech preventing unauthorized copying (authentication, watermarks, encryption).
  • Public domain: works free of copyright; Creative Commons: retains copyright while allowing specified uses.
  • Ethics fundamentals: cite others’ ideas, avoid plagiarism, respect licenses.

Network Classifications & Environments

  • Home networks: single building, easy setup, few users (share Internet, printers, files, gaming).
  • Business networks: many users, multiple buildings, central data access.
  • Business-specific environments
    • Intranet: internal, private network using Internet tech.
    • Extranet: grants controlled intranet access to outsiders (suppliers/clients).
    • VPN: encrypted tunnel allowing secure remote access over public Internet.

Wired vs Wireless Networks

  • Wired: data via physical cables; faster & more secure; installation through walls/floors.
  • Wireless: data via airwaves; easier installation & mobility; can be less secure.
  • Cellular (3G/4G/5G) extends wireless access regionally via towers.

Communications Software

  • Establishes connections, manages data transfer, provides user interface for communication.

Network Topologies, Architectures & Geography

  • Topologies (physical layouts)
    • Bus: all devices share central cable (bus). Single cable failure → network down.
    • Ring: sequential data path; device failure can halt network (obsolete).
    • Star: devices connect to central hub/switch; hub failure critical; device failure isolated. Multiple stars + bus → tree.
    • Mesh: devices interconnect; alternate routes improve fault tolerance (full vs partial mesh).
  • Architectures
    • Client/Server: dedicated servers provide resources, controlled by admin.
    • Peer-to-Peer (P2P): ≤10 computers share resources equally; no admin; includes Internet file-sharing (legal only for non-copyright material).
  • Geographic reach
    • LAN (Local Area Network) — limited area.
    • WLAN — wireless LAN.
    • WAN — large region (e.g., Internet backbone).
    • MAN — city/county.
    • PAN — personal devices (Bluetooth).
    • BAN — biosensors in body.

Network Standards & Protocols

  • Standard: guideline for hardware, speeds, media.
  • Protocol: rules for data format, addressing, error handling, sequence.
  • Key wired standard: Ethernet.
  • TCP/IP suite:
    • TCP: routes data reliably.
    • IP: assigns unique addresses (IPv4 / IPv6).
  • Short-range / wireless standards (Table 9-3 & 9-4)
    • Wi-Fi (IEEE 802.11 a/b/g/n/ac/ax): 11\text{ Mbps} → 7\text{ Gbps}.
    • Bluetooth: ≤3\text{ Mbps} over ≈30\text{ ft}.
    • UWB: high-speed, short-range, penetrates obstacles.
    • IrDA: infrared, line-of-sight remotes.
    • RFID: tags + readers (inventory, tolls — Fig 9-8 workflow).
    • NFC: RFID-based; very close range (payments, tags, tickets).
    • LTE/5G: cellular data standards.

Network Connection Hardware

  • Node: any addressable device.
  • Hub: broadcasts data to all ports.
  • Switch: forwards data only to intended recipient (preferred).
  • Router: connects multiple networks & routes packets.
  • Modems (digital/broadband): convert signals for ISP link; types
    • Cable (via coax, Fig 9-10), DSL, ISDN.
  • Dedicated lines (always-on): cable, DSL/ADSL, ISDN, FTTP (fiber), ATM, T-carrier (T1/T3) with multiplexing for multiple signals.

Setting Up a Home/SOHO Network

  • Minimum hardware: modem + router (or combo) + wireless access point + client devices.
  • Basic steps
    1. Install modem/router & connect to ISP service.
    2. Enable Wi-Fi, assign SSID & strong key.
    3. On each device, enable Wi-Fi, select SSID, enter key.
  • Adding wireless printer: place within range, connect to Wi-Fi, install vendor app/drivers (Fig 9-12).
  • Improve signal: fully extend/replace antennas, centralize router, add boosters/repeaters (Fig 9-13).

Securing Networks

  • Common risks (Table 9-6): adware, spyware, virus, worm, trojan, ransomware, rootkit.
  • Protective measures
    • Change default router credentials, SSID, enable strong encryption (WPA2/WPA3), limit MAC addresses.
    • Monitor connected devices via admin interface.
    • Encryption of data in transit.
    • Authentication: usernames/passwords, biometrics.
    • Firewalls: block unauthorized inbound/outbound traffic.
    • Network-Attached Storage (NAS): central secure storage.
    • Network monitoring software: traffic analysis, bandwidth usage, alerts.
    • Packet sniffers: legitimate diagnostics vs malicious hijacking.
    • Stealth mode & router firewall to reduce visibility.
    • Steps to detect intruders: log in → count devices → secure → enable firewall/stealth.

Professional & Ethical Considerations

  • Network administrator: plans, designs, procures equipment, deploys, secures & maintains networks; holds position of trust (Fig 9-15).
  • Professional code topics: professionalism, social responsibility, personal integrity, privacy, legal compliance, clear communication, system integrity, continuous education.
  • USENIX: non-profit supporting sysadmins & researchers since 1975.
  • Ethics: maintain security, respect privacy, follow laws/policies, stay informed on evolving threats & standards.