Networking Basics and Protocols

ARPANET

First packet switching network, created by the Department of Defense in 1969.

Bit

A single binary digit representing 0 or 1.

Byte

A unit of digital information consisting of 8 bits.

Half-duplex

Communication mode where only one side sends data at a time.

Full-duplex

Communication mode where both sides send and receive simultaneously.

Modem

Converts data between digital formats and transmission formats.

Router

Forwards data packets between different networks using a routing table.

Switch

Forwards data packets between specific devices within the same network.

Hub

Bridges multiple devices together and broadcasts messages to all connected devices.

Network Interface Controller (NIC)

Hardware component connecting a device to a network, featuring a unique MAC address.

Coaxial Cable

Cable with an inner conductor surrounded by a concentric conducting shield.

Twisted Pair

Pairs of wires twisted together to reduce interference and crosstalk.

Optical Fiber

Transparent fibers transmitting light data, immune to electromagnetic interference.

Radio Waves

Unguided broadcast transmission using line-of-sight propagation.

MAC Address

A 48-bit unique physical address permanently assigned to a NIC.

IPv4

A 32-bit address standard using dotted quad notation.

IPv6

A 128-bit address standard providing a massive supply of addresses.

NAT (Network Address Translation)

Converts private IP addresses to public IP addresses and vice versa.

DNS (Domain Name System)

Translates human-readable domain names into IP addresses.

DHCP

Protocol that dynamically assigns and leases IP addresses on a network.

Subnetting

Splitting an IP network into logical divisions using subnet masks.

CIDR

Classless Inter-Domain Routing notation indicating network mask bits.

OSI Model

A seven-layer reference model defined by the ISO.

DoD Model

A four-layer network model consisting of Network Access, Internet, Host-to-Host, and Process.

Encapsulation

Wrapping data with layer headers and footers down the protocol stack.

ARP

Protocol that maps IP addresses to MAC addresses at the Data Link Layer.

ICMP

Network layer management protocol used for tools like ping and traceroute.

TCP

Reliable, connection-oriented transport layer protocol with guaranteed delivery.

UDP

Unreliable, connectionless transport layer protocol without handshakes.

TCP Three-Way Handshake

Connection establishment sequence consisting of SYN, SYN-ACK, and ACK.

SYN Flooding

Denial of service attack exploiting incomplete TCP handshakes.

ARP Poisoning

Injecting false ARP replies to associate an attacker's MAC with an IP address.

DNS Poisoning

Injecting false routing or IP mapping information into a DNS server.

Proxy Server

Masks client identity, filters content, and improves performance via caching.

Firewall Ruleset

A list of rules processed top-to-bottom to allow or block traffic, ending with a default deny.

Stateful Inspection

Firewall technology that incorporates layer-4 connection states into screening decisions.

Intrusion Detection System (IDS)

Passively monitors network traffic and alerts on suspicious activity without blocking.

Intrusion Prevention System (IPS)

An inline security device that detects and actively blocks malicious traffic.

Virtualization

Running one or more software-based virtual machine instances on a physical host.

Virtual Desktop Infrastructure (VDI)

Separates the user desktop environment from the physical access device for enhanced security.

Virtual Private Network (VPN)

Extends a private network securely across a public network using tunneling and encryption.

Private Network

10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16

Loopback

127.0.0.0/8

Link local

169.254.0.0/16

Broadcast

255.255.255.255

TCP 25

SMTP

UDP 53

DNS

TCP 80

HTTP

TCP 443

HTTPS

TCP 21

FTP

TCP 22

SSH/SFTP

TCP/UDP 3389

RDP

TCP 23

Telnet