Networking Exam Ultimate Study Guide.

Network Devices

  • Host Devices (End Devices): Devices situated at the network edge hosting applications (such as email clients and web browsers) that provide services directly to users.

  • Switch: Intermediary hardware that connects multiple local devices within a network.

  • Router: Intermediary device that forwards data packets between disparate networks.

  • Wireless Router: Integrates access point functionality to connect wireless hosts and typically incorporates a switch for wired connections.

  • Access Point (AP): Connects to a router or network infrastructure to extend wireless coverage.

  • Modem: Connects a home or small office network to the Internet service provider infrastructure.

Network Types and Topologies

  • LAN (Local Area Network): Encompasses devices connected over a limited geographic area; managed wholly by an individual or an enterprise IT department.

  • VLAN (Virtual Local Area Network): Segments switch ports logically to function as multiple discrete switches, isolating traffic and permitting administrative grouping across different physical floors or locations.

  • WLAN (Wireless Local Area Network): Connects endpoints wirelessly using radio frequencies within a small geographic range.

  • PAN (Personal Area Network): Interconnects devices (such as smartphones, tablets, mice, keyboards, and printers) within an individual's personal workspace, predominantly using short-range Bluetooth technology.

  • WMN (Wireless Mesh Network): Employs interconnected access points across residences, businesses, or municipalities to expand WLAN coverage dynamically.

  • MAN (Metropolitan Area Network): Spans across a city or educational/corporate campus using fiber-optic cabling or wireless links.

  • WAN (Wide Area Network): Links multiple distinct networks over large geographic separations through contracted service providers; the Internet serves as the largest global WAN.

  • VPN (Virtual Private Network): Establishes an encrypted, secure tunnel over insecure public infrastructure (such as the Internet) to provide teleworkers with remote access to corporate private networks.

Internet Access Technologies

  • Analog Telephone (Dial-up): Employs an internal or external USB analog modem plugged into an RJ-11 telephone wall jack and mapped to a software COM port; requires dialing configurations including area codes and outside-line prefixes.

  • ISDN (Integrated Services Digital Network): Multi-channel broadband standard capable of carrying voice, video, and data concurrently across traditional copper lines at speeds greater than dial-up.

  • Broadband: Multiplexes concurrent signals across different transmission frequencies on a single shared medium.

  • DSL (Digital Subscriber Line): Always-on connection carrying voice and data over copper phone lines on separate frequencies; uses a physical filter to isolate voice frequencies.

    • VDSL (Very High-Speed DSL): Supports symmetric speeds up to 26 Mbps26\,\text{Mbps}, or asymmetric transfers up to 52 Mbps52\,\text{Mbps} download and 6 Mbps6\,\text{Mbps} upload.

    • VDSL2: Supports bidirectional throughput up to 100 Mbps100\,\text{Mbps}.

  • Cable: Delivers network access, voice, and television transmissions simultaneously via coaxial television infrastructure linked to a cable modem.

  • Fiber: Transmits high-speed network traffic as pulses of light over optical fiber lines.

  • Satellite: Utilized primarily in rural regions lacking wired cable or DSL infrastructure.

  • Cellular, Tethering, and Hotspots: Cellular networks use distributed transmission towers; tethering links an external device to a cellular phone to borrow its data link, while mobile hotspots specifically configure a smartphone to broadcast Wi-Fi connectivity.

Transport Layer Port Addressing

  • Port Identification: TCP and UDP associate logical port numbers with application layer sessions rather than physical hardware ports.

  • Source Port: Dynamically assigned by the local originating system to isolate multiple concurrent sessions of the same application (such as individual browser tabs).

  • Destination Port: Fixed, well-known port number mapping to the target server-side daemon or application service.

Common Network Application Protocols and Ports

  • DNS (Domain Name Service) - Ports 53 (TCP, UDP): Resolves human-readable domain names into IP addresses; requests typically use UDP, while larger transfers and responses use TCP.

  • HTTP - Port 80 (TCP): Unencrypted hypertext transfer protocol serving web pages and multimedia.

  • HTTPS - Port 443 (TCP, UDP): Encrypted, authenticated hypertext transport serving secure web content.

  • SMTP (Simple Mail Transfer Protocol) - Port 25 (TCP): Handles client-to-server outbound email dispatch and server-to-server mail relaying.

  • POP3 (Post Office Protocol 3) - Port 110 (TCP): Downloads stored email messages directly from a mail server.

  • IMAP (Internet Message Access Protocol) - Port 143 (TCP): Advanced protocol facilitating remote synchronization and management of email messages on a server.

  • LDAP (Lightweight Directory Access Protocol) - Port 389 (TCP, UDP): Centralized directory querying, identity validation, and access control across shared enterprise networks.

  • FTP (File Transfer Protocol) - Ports 20 (Data) and 21 (Control) (TCP): Unencrypted client/server file transfer; SSH File Transfer Protocol (SFTP) over port 22 is the secure replacement.

  • TFTP (Trivial File Transfer Protocol) - Port 69 (UDP): Low-overhead, connectionless file transfer.

  • SMB/CIFS (Server Message Block / Common Internet File System) - Port 445 (TCP, UDP): Standard Microsoft client/server file, directory, and printer sharing mechanism.

  • AFP (Apple Filing Protocol) - Port 548 (TCP, UDP): Proprietary Apple protocol delivering file services across macOS environments.

  • SSH (Secure Shell) - Port 22 (TCP): Authenticated, encrypted command-line terminal access to remote hosts.

  • Telnet - Port 23 (TCP): Unencrypted, plain-text remote command-line access.

  • RDP (Remote Desktop Protocol) - Port 3389 (TCP, UDP): Microsoft proprietary protocol providing full remote graphical user interface desktop control.

  • DHCP (Dynamic Host Configuration Protocol) - Ports 67 (Server) and 68 (Client) (UDP): Automates client IP addressing, subnet masking, and gateway assignments.

  • NetBIOS over TCP/IP (NetBT) - Ports 137–139 (TCP, UDP): Enables legacy NetBIOS application communication over modern TCP/IP networks.

  • SNMP (Simple Network Management Protocol) - Ports 161 and 162 (UDP): Transmits centralized monitoring metrics and management alerts for network infrastructure.

  • SLP (Service Location Protocol) - Port 427 (TCP, UDP): Dynamically advertises and identifies available local network shared services without requiring manual configuration.