Computer Networks Glossary

Welcome to the definitive glossary for Computer Networks. This is designed to act as your one-stop quick reference for essential networking concepts covered throughout the course. From basic OSI model layers to advanced SDN concepts, each definition bridges theoretical learning with practical, real-world examples.

Use this glossary to solidify your intuition, quickly refresh concepts before interviews, or bridge any knowledge gaps.

Note: This glossary provides core definitions to accelerate your learning. Refer to the specific modules for deep-dive explanations, interactive architecture maps, and hands-on examples.

C

CSMA/CD

Carrier Sense Multiple Access with Collision Detection. An algorithm used in half-duplex Ethernet networks to manage when devices can transmit data on a shared medium and how to recover if two devices transmit simultaneously causing a “collision”.

  • Analogy: Polite conversation rules in a dark room. You listen if someone is speaking (Carrier Sense). If quiet, you talk. If you hear someone else start talking at the same time (Collision Detection), both stop, wait a random amount of time, and try again.

D

DHCP (Dynamic Host Configuration Protocol)

A network management protocol used to dynamically assign an IP address and other network configuration parameters (like subnet mask and default gateway) to each device on a network so they can communicate.

  • Mechanism: DORA process (Discover, Offer, Request, Acknowledge).

DNS (Domain Name System)

The “phonebook” of the Internet. It translates human-readable domain names (like www.example.com) into machine-readable IP addresses (like 192.0.2.1).

  • Analogy: Looking up a contact’s name in your phone to find their actual phone number.

H

HTTP/HTTPS (Hypertext Transfer Protocol / Secure)

The foundational protocol for transmitting hypermedia documents (like HTML) across the Web. HTTPS uses TLS to encrypt the data.

  • Mechanism: A stateless, request-response protocol between a client (browser) and a server.

I

IP Address (Internet Protocol)

A logical, hierarchical address assigned to devices connected to an IP network.

  • Usage: Used to route packets across different networks globally (like a postal address identifying city, street, and house). Includes IPv4 (32-bit, e.g., 192.168.1.1) and IPv6 (128-bit).

M

MAC Address (Media Access Control)

A unique 48-bit hardware address permanently assigned to a network interface card (NIC) by the manufacturer.

  • Usage: Used to deliver frames locally on a shared segment (like finding a specific desk in an office building). It is a “flat” address, unchangeable, and looks like 00:1A:2B:3C:4D:5E.

N

NAT (Network Address Translation)

A process used by a router to modify the source or destination IP addresses in packet headers. Typically used to map multiple private IP addresses (inside a local network) to a single public IP address before accessing the Internet.

  • Why it matters: It delayed IPv4 exhaustion and adds a layer of security by hiding internal network structures.

O

OSI Model

The Open Systems Interconnection (OSI) model is a conceptual framework that standardizes the functions of a communication system into seven distinct layers.

  • Analogy: Think of it like a mailing system—each department (layer) performs a specific task (packaging, addressing, routing) before passing it down or up the chain.
  • Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.

R

Routing Protocols (BGP & OSPF)

  • OSPF (Open Shortest Path First): An Interior Gateway Protocol (IGP) used to route traffic within a single autonomous system (like routing paths inside a university campus). Uses link-state algorithms to find the fastest path.
  • BGP (Border Gateway Protocol): The Exterior Gateway Protocol (EGP) that powers the Internet. It routes traffic between different autonomous systems (like routing paths between different internet service providers).

S

SDN (Software-Defined Networking)

An architectural approach that decouples the network control plane (the “brains” deciding where traffic goes) from the data plane (the underlying hardware forwarding the traffic).

  • Why it matters: Enables centralized, programmable management of the entire network structure via software APIs rather than configuring individual hardware switches manually.

Subnetting and CIDR

The practice of dividing a larger network into smaller logical networks (subnets). CIDR (Classless Inter-Domain Routing) uses a flexible slash notation (e.g., /24) to denote the subnet mask, rather than strict IP classes (A, B, C).

  • Analogy: Taking a large piece of land and drawing fences to create separate, manageable plots, determining exactly how many houses can fit in each plot.

T

TCP (Transmission Control Protocol)

A connection-oriented transport protocol that provides reliable, ordered, and error-checked delivery of a stream of bytes between applications.

  • Key Features: Three-way handshake (SYN, SYN-ACK, ACK), Flow Control (Sliding Window), and Congestion Control.
  • Analogy: Sending a tracked package where the receiver must sign for every single item.

TCP/IP Model

A more practical, four-layer networking model upon which the actual Internet operates. It closely mirrors real-world protocol implementations.

  • Layers: Network Access (Link), Internet, Transport, Application.

TLS/SSL Handshake

The process that kicks off an HTTPS session. The client and server agree on cryptographic algorithms, authenticate the server (usually with a certificate), and securely exchange a symmetric session key before transmitting actual data.

U

UDP (User Datagram Protocol)

A connectionless, lightweight transport protocol that sends independent packets (datagrams) without guaranteeing delivery, ordering, or duplicate protection.

  • Key Features: Fast, low overhead.
  • Use cases: Real-time applications where speed is preferred over perfection (e.g., VoIP, online gaming, live video streaming).

V

VPN (Virtual Private Network)

Creates a secure, encrypted “tunnel” over a public network (like the Internet), allowing users to send and receive data as if their devices were directly connected to a private network.

Next Steps: With these core concepts mastered, you are now ready to tackle the architectural case studies. Head over to the specific modules to explore how these protocols operate in large-scale production environments.