csit 220 no.2

Internet

A global network of networks that allows devices (computers, phones, servers) to communicate and share data.

Protocol

A set of rules that defines how data is formatted, sent, and received across a network.

Host (End System)

Any device connected to the Internet that runs applications (ex: computers, smartphones, servers).

Client

A device or software that requests services or data from another device (server).

Server

A device or program that provides data or services to clients.

ISP (Internet Service Provider)

A company that provides users with Internet access (ex: Verizon, Comcast).

Router

A network device that forwards data packets between networks.

Access Network

The part of the network that connects end systems to the Internet (Wi-Fi, cable, fiber, 5G).

Packet Switching

Data is divided into packets that travel independently across the network and are reassembled at the destination.

Circuit Switching

A dedicated communication path is established between sender and receiver for the entire session.

Propagation Delay

The time it takes for a signal to physically travel across a link.

Transmission Delay

Time required to push all bits of a packet onto the wire.

Queuing Delay

Time a packet spends waiting in a router’s queue.

Packet Loss

When a router’s buffer is full and incoming packets are dropped.

Throughput

The rate at which data is successfully transferred over a network (in bits per second).

Protocol Stack

The structure of network layers used by the Internet: Application, Transport, Network, Link, Physical.

Application Layer

The top layer where network applications and protocols (like HTTP, DNS, and SMTP) operate.

Client-Server Architecture

A model where a client requests and a server provides data or services.

Peer-to-Peer (P2P)

A network model with no central server — peers act as both clients and servers.

Process

A program running on a host (a web browser, mail client, etc.).

Socket

The interface between the application and the transport layer, where data is sent or received.

Transport Services

The type of communication a network provides, like reliable delivery or low latency.

HTTP (HyperText Transfer Protocol)

The protocol used by web browsers and servers to transfer web pages. Example: Visiting https://www.wikipedia.org uses HTTP (or HTTPS for secure version).

HTTPS (HyperText Transfer Protocol Secure)

HTTP combined with encryption (SSL/TLS) for secure web communication. Example: Online shopping or banking sites use HTTPS.

DNS (Domain Name System)

Translates domain names (like google.com) into IP addresses. Example: When you type “youtube.com,” DNS finds its IP (like 142.250.190.14).

SMTP (Simple Mail Transfer Protocol)

Used to send emails between mail servers. Example: Gmail uses SMTP to send outgoing emails.

POP3 (Post Office Protocol v3)

Downloads email from a mail server to a local client. Example: Outlook uses POP3 to retrieve your mail.

IMAP (Internet Message Access Protocol)

Lets users view and manage email directly on the mail server. Example: Gmail’s app uses IMAP to sync mail.

FTP (File Transfer Protocol)

Used to transfer files between computers over a network. Example: Uploading files to a web host using an FTP client.

DHCP (Dynamic Host Configuration Protocol)

Automatically assigns IP addresses to devices on a network. Example: Your router gives your laptop an IP using DHCP.

Transport Layer

Provides logical communication between processes on different hosts.

Multiplexing

Combining data from multiple applications into one stream for transmission.

Demultiplexing

Delivering received data to the correct application process based on port numbers.

Port Number

A 16-bit number identifying which process or service to deliver data to (ex: port 80 for HTTP, 25 for SMTP).

TCP (Transmission Control Protocol)

Provides reliable, connection-oriented data transfer with error checking, flow control, and congestion control. Example: Used by HTTP, HTTPS, FTP, SMTP, and DNS (in some cases).

UDP (User Datagram Protocol)

Provides connectionless, unreliable, but fast communication with minimal overhead. Example: Used by streaming apps, online games, and VoIP (like Zoom).

Connection-Oriented

A communication type where a connection must be established before data is sent (like a phone call). TCP uses this approach.

Connectionless

Data is sent without setting up a dedicated connection (like sending a letter). UDP uses this approach.

Reliable Data Transfer (RDT)

Ensures that all data arrives correctly and in order. TCP provides reliability.

Flow Control

Prevents a sender from overwhelming a receiver with too much data at once. Handled by TCP.

Congestion Control

Prevents too much data from entering the network, which could cause packet loss. TCP automatically adjusts sending rate.

Checksum

A small value used to detect errors in transmitted data. Used in UDP and TCP headers.

Source Port

The port number of the sending process.

Destination Port

The port number of the receiving process.

Length

Total length of the UDP header and data.

Checksum

Used for error detection in the packet.