Networking & Internet Study Guide

Introduction

Computer networking allows computers, phones, servers, printers, smart devices, and other systems to exchange information. Networks can be as small as two computers in one room or as large as the Internet, which connects networks across the world.

The Internet is often described as a network of networks. Instead of relying on one enormous central computer, millions of interconnected networks exchange data using standardized communication rules called protocols.

Understanding networking means learning how devices are identified, how data is divided into packets, how routers choose paths, how domain names become IP addresses, and how protocols such as TCP, UDP, HTTP, and TLS work together. These concepts form the foundation of web browsing, streaming, cloud computing, online gaming, email, messaging, and many modern technologies.

Learning Objectives

After studying this guide, you should be able to:

·         Explain what computer networks and the Internet are.

·         Distinguish LANs, WANs, wired networks, and wireless networks.

·         Explain IP addresses, MAC addresses, ports, packets, and routing.

·         Describe the roles of routers, switches, access points, and firewalls.

·         Compare TCP and UDP.

·         Explain DNS, HTTP, HTTPS, and TLS.

·         Describe how a web request travels from a device to a server and back.

What Is a Computer Network?

A computer network is a group of devices connected so they can exchange information or share resources.

Devices on a network may include:

·         Desktop computers

·         Laptops

·         Smartphones

·         Servers

·         Printers

·         Routers

·         Smart televisions

·         Security cameras

·         Internet of Things devices

Networks can share files, printers, Internet connections, applications, databases, and other services.

A device connected to a network is often called a host or node, depending on the context.

Major Types of Networks

Networks can be classified according to their geographic size and purpose.

Personal Area Network

A PAN, or Personal Area Network, covers a very small area around an individual.

Bluetooth connections between phones, headphones, keyboards, and smartwatches are common examples.

Local Area Network

A LAN, or Local Area Network, connects devices within a limited area such as:

·         A home

·         School

·         Office

·         Laboratory

·         Building

Home Wi-Fi networks are examples of LANs.

Wide Area Network

A WAN, or Wide Area Network, connects networks across much larger geographic areas.

A company may operate offices in several cities and connect their LANs through a WAN.

The Internet itself can be thought of as an enormous collection of interconnected networks spanning the globe.

Wired and Wireless Networks

Networks can transmit information through several physical technologies.

Ethernet

Ethernet is widely used for wired local networking.

Devices commonly connect through cables to switches or routers.

Wired connections can provide:

·         High speed

·         Consistent performance

·         Low latency

·         Reduced interference compared with some wireless environments

Wi-Fi

Wi-Fi allows devices to communicate using radio signals rather than physical network cables.

A wireless access point connects wireless devices to a network.

Many home devices combine several functions in one box, including routing, switching, wireless access, and sometimes modem functions.

Network Devices

Several types of equipment perform different networking tasks.

Router

A router connects different networks and forwards packets toward their destinations.

For example, a home router connects a private home network with an Internet service provider's network.

Routers make forwarding decisions based mainly on IP addressing and routing information.

Memory Tip

Router = connects networks

Switch

A switch primarily connects devices within the same local network.

It examines network-layer or link-layer information depending on the type of switch, but ordinary Ethernet switches mainly use MAC addresses to determine where Ethernet frames should be forwarded.

Memory Tip

Switch = connects devices inside a LAN

Modem

A modem connects a user's equipment to certain types of communication service provided by an Internet service provider.

The exact technology varies.

Examples include:

·         Cable

·         DSL

·         Cellular

·         Fiber equipment

In modern home networking, some devices combine modem and router functions.

Wireless Access Point

A wireless access point allows wireless devices to join a wired or broader local network using Wi-Fi.

Firewall

A firewall controls network traffic according to security rules.

NIST describes a firewall as a device or program that controls network traffic between networks or hosts with different security requirements.

Firewalls may allow some traffic while blocking other traffic based on factors such as addresses, ports, applications, or connection state.

How Network Data Travels

Information sent across networks is usually divided into smaller units.

At different networking layers, these units may be called:

·         Frames

·         Packets

·         Datagrams

·         Segments

The exact term depends on the protocol being discussed.

For beginners, packet is often used as a general term for a small unit of network data.

Suppose a computer downloads a large image. The entire image does not normally travel across the Internet as one enormous transmission. Data is divided into manageable pieces that can travel through networks and later be reassembled.

Packet Switching

The Internet mainly uses packet switching.

Data is divided into packets, and network devices forward those packets toward their destination.

Packets from the same communication do not always have to travel through exactly the same physical path.

Packet switching allows network resources to be shared efficiently among many users.

Protocols

A protocol is a set of rules governing communication between systems.

Protocols define questions such as:

·         How is data formatted?

·         How is a destination identified?

·         How are errors handled?

·         How does communication begin and end?

·         What does a particular message mean?

Different protocols perform different jobs.

Examples include:

·         IP

·         TCP

·         UDP

·         DNS

·         HTTP

·         TLS

Modern Internet communication works because many independent devices follow compatible protocol standards.

Network Models

Networking concepts are often organized into layers.

Each layer performs particular functions while relying on services provided by lower layers.

OSI Model

The OSI model contains seven conceptual layers:

1.      Physical

2.      Data Link

3.      Network

4.      Transport

5.      Session

6.      Presentation

7.      Application

The OSI model is especially useful for learning and troubleshooting.

For example:

·         Ethernet operates mainly around the physical and data-link levels.

·         IP operates at the network layer.

·         TCP and UDP are transport protocols.

·         HTTP operates at the application layer.

TCP/IP Model

Real Internet systems are often discussed using the simpler TCP/IP model.

A common version contains:

1.      Link

2.      Internet

3.      Transport

4.      Application

Layering allows technologies to change independently.

For example, HTTP can operate whether a user's local connection reaches the Internet through Ethernet, Wi-Fi, or another networking technology.

MAC Addresses

A MAC address, or Media Access Control address, identifies a network interface for communication at the local link level.

Ethernet and Wi-Fi networks use link-layer addressing when moving information across the local network.

MAC addresses and IP addresses perform different jobs.

A simplified distinction is:

MAC address = local network delivery

IP address = delivery across interconnected networks

IP Addresses

IP stands for Internet Protocol.

An IP address identifies an interface or network location for Internet Protocol communication.

Two important versions are IPv4 and IPv6.

IPv4

IPv4 uses 32-bit addresses.

A familiar IPv4 address looks like:

192.0.2.25

Because IPv4 has a limited address space, techniques such as Network Address Translation became widely used.

IPv6

IPv6 uses 128-bit addresses, providing vastly more address space than IPv4. The IPv6 standard was designed as IPv4's successor and expanded IP addressing from 32 bits to 128 bits.

An IPv6 address might look like:

2001:db8::25

IPv6 also includes changes designed to improve extensibility and simplify parts of packet processing.

Public and Private IP Addresses

Not every IP address used inside a network is directly reachable from the public Internet.

Public IP Address

A public IP address is used for communication through the public Internet.

Private IP Address

Private address ranges are commonly used within homes, offices, and other internal networks.

A home might contain dozens of devices with private addresses while the router communicates externally through a smaller number of public addresses.

Network Address Translation

Network Address Translation, or NAT, modifies network addressing information as packets pass between networks.

Home routers commonly use NAT so multiple private devices can share an Internet connection associated with a public IPv4 address.

NAT and firewalls are related concepts but are not identical.

NAT changes addressing information.

A firewall applies traffic-control policies.

Subnets

A subnet is a logical subdivision of an IP network.

Subnetting allows administrators to divide a larger network into smaller sections.

Possible reasons include:

·         Organization

·         Security

·         Traffic management

·         Efficient address use

·         Separating departments or device types

A subnet mask in IPv4, or prefix length in both IPv4 and IPv6 notation, identifies which portion of an address represents the network.

Default Gateway

When a device needs to send traffic outside its local network, it usually sends that traffic toward a default gateway.

In many home networks, the router functions as the default gateway.

Think:

Local destination → send directly

Remote destination → send toward gateway/router

Routing

Routing is the process of selecting paths for packets through interconnected networks.

Routers maintain information about which destinations can be reached through different interfaces or neighboring networks.

A packet traveling across the Internet may pass through many routers before reaching the destination.

Each router does not need to know the entire history of the packet. It mainly needs enough routing information to determine an appropriate next step.

TCP

TCP, or Transmission Control Protocol, is an important Internet transport protocol.

The modern TCP standard describes TCP as providing a reliable, in-order byte-stream service. It uses mechanisms such as sequence information, error detection, and retransmission to deal with lost data.

TCP is connection-oriented.

Before ordinary data transfer, endpoints establish a connection.

TCP is useful when correct and ordered delivery is important.

Examples traditionally associated with TCP-based communication include many:

·         Web connections

·         Email services

·         File transfers

·         Remote-login services

Application protocols can change which transports they use over time, so a particular application should not always be assumed to use TCP.

UDP

UDP, or User Datagram Protocol, provides a simpler datagram-based transport service.

The original Internet standard describes UDP as providing application programs with a way to send messages using a minimum amount of protocol mechanism.

UDP does not itself provide TCP-style guarantees that every packet will arrive or arrive in order.

This reduced overhead can be valuable when an application prefers speed, low delay, or its own reliability mechanism.

UDP may be used in applications involving:

·         Real-time communication

·         Streaming

·         Online games

·         DNS traffic

·         Modern protocols built above UDP

TCP vs. UDP

A useful memory aid is:

TCP = reliability

UDP = simplicity and speed

This is simplified, but it captures the main beginner-level distinction.

Ports

An IP address identifies a network destination, but a computer can run many network applications simultaneously.

Port numbers help transport protocols identify particular application endpoints.

Imagine an apartment building:

IP address = building address

Port number = apartment number

TCP and UDP each use port numbers.

Some services have commonly assigned ports, but programs are not physically required to use only those familiar values.

DNS

Humans prefer names such as:

example.com

Computers use network addresses.

The Domain Name System, or DNS, connects these worlds by resolving domain names into information such as IP addresses.

ICANN describes DNS as the system that allows people to use text-based domain names instead of having to remember numerical IP addresses.

DNS is hierarchical and distributed rather than one giant global file. Its original design explicitly uses a distributed database and a tree-structured namespace.

Simplified DNS Process

When you enter a domain name:

1.      Your device needs an address for that name.

2.      It asks a DNS resolver.

3.      The resolver may use cached information.

4.      If necessary, DNS servers are consulted through the hierarchy.

5.      An appropriate record is returned.

6.      Your device can then communicate with the destination address.

Memory Tip

DNS = Internet naming system

It is often compared with an address book, although real DNS performs more functions than that analogy suggests.

Domain Names

A domain name has a hierarchical structure.

For:

www.example.org

·         .org is the top-level domain.

·         example is a lower level beneath .org.

·         www may identify a host or subdomain beneath example.org.

ICANN coordinates important parts of the Internet's global system of unique domain names and numerical identifiers.

DHCP

DHCP, or Dynamic Host Configuration Protocol, allows devices to receive network configuration automatically.

A DHCP service may provide information such as:

·         IP address

·         Subnet information

·         Default gateway

·         DNS server addresses

Without automatic configuration, network administrators might have to configure every device manually.

HTTP

HTTP stands for Hypertext Transfer Protocol.

It is a major application-layer protocol used by the World Wide Web.

The current HTTP semantics standard describes HTTP as a stateless application-level request-and-response protocol.

A simple web interaction looks like:

Client request → Server

Server response → Client

Common HTTP request methods include:

·         GET

·         POST

·         PUT

·         DELETE

The exact meaning and permitted behavior depend on the protocol specification and application.

HTTP vs. HTTPS

HTTP describes communication semantics for web resources.

HTTPS indicates HTTP communication protected using a secure transport mechanism.

Modern HTTPS uses TLS, or Transport Layer Security.

TLS 1.3 is designed to provide a secure communication channel with properties including authentication, confidentiality, and protection against tampering.

A simplified relationship is:

HTTP + TLS = HTTPS

This is useful as a learning model, although modern HTTP versions can use different underlying transport arrangements.

Encryption

Encryption transforms readable information into a protected form that requires appropriate cryptographic information to recover.

Encryption helps protect data such as:

·         Passwords

·         Financial information

·         Private messages

·         Authentication data

However, encryption alone does not solve every security problem.

An encrypted connection to a malicious website can still be dangerous.

Client-Server Networking

Many Internet services use the client-server model.

A client requests a service.

A server provides the service.

Examples:

·         Browser → web server

·         Email application → mail server

·         Mobile app → API server

One server may serve enormous numbers of clients.

Peer-to-Peer Networking

In peer-to-peer, or P2P, networking, devices can communicate more directly and may act as both service consumers and providers.

P2P architectures can distribute work among participating systems rather than relying entirely on one central server.

Bandwidth, Throughput, and Latency

These terms describe different aspects of network performance.

Bandwidth

Bandwidth describes a communication link's capacity to carry data.

It is commonly expressed in bits per second.

Examples:

·         Mbps — megabits per second

·         Gbps — gigabits per second

Throughput

Throughput is the amount of useful data actually transferred during a period.

Real throughput may be lower than a link's theoretical capacity because of protocol overhead, congestion, interference, and other factors.

Latency

Latency is delay.

A network can have high bandwidth but still have noticeable latency.

This distinction matters for applications.

Downloading a large file benefits heavily from high throughput, while online games and interactive calls are highly sensitive to delay.

Memory Tip

Bandwidth = how much

Latency = how long

Packet Loss

Packet loss occurs when network packets fail to reach their intended destination.

Possible causes include:

·         Congestion

·         Wireless interference

·         Hardware problems

·         Faulty connections

·         Routing problems

TCP can retransmit missing information, but retransmission can increase delay.

Real-time applications may sometimes prefer to continue rather than wait for missing data.

Network Security

Network security aims to protect systems, communications, and data.

Major goals commonly include:

Confidentiality

Information should be available only to authorized parties.

Integrity

Data should not be improperly modified.

Availability

Systems and services should remain accessible when needed.

These are sometimes called the CIA triad:

Confidentiality — Integrity — Availability

Common Network Threats

Examples include:

·         Malware

·         Phishing

·         Eavesdropping

·         Spoofing

·         Unauthorized access

·         Denial-of-service attacks

·         Misconfigured services

Security therefore requires more than one tool.

Organizations may combine:

·         Firewalls

·         Encryption

·         Authentication

·         Software updates

·         Network segmentation

·         Monitoring

·         Backups

Cloud Computing and Networking

Cloud computing provides computing resources through network-accessible infrastructure.

Cloud services can include:

·         Virtual servers

·         Storage

·         Databases

·         Applications

·         Networking

·         AI services

Cloud computing does not mean that data exists somewhere abstractly outside physical systems. Cloud services run on real computers located in data centers and connected through networks.

Content Delivery Networks

A Content Delivery Network, or CDN, distributes content across multiple locations.

Instead of every user downloading a file from one distant server, copies may be served from infrastructure closer to users.

CDNs can help improve:

·         Loading speed

·         Availability

·         Scalability

They are widely used for websites, images, software downloads, and video delivery.

How Loading a Website Works

Suppose you enter a website address into a browser.

A simplified process is:

1.      Connect to a network: Your device joins a wired or wireless network.

2.      Obtain configuration: It has an IP address, gateway, and DNS configuration.

3.      Resolve the name: DNS determines the address associated with the domain.

4.      Route packets: Routers forward traffic toward the destination.

5.      Establish transport/security: The systems create the required transport and, for HTTPS, secure communication.

6.      Send HTTP request: The browser requests a resource.

7.      Server responds: The server sends an HTTP response containing content or instructions.

8.      Browser processes content: The browser renders the page and may request additional images, scripts, fonts, or data.

Many of these steps happen in fractions of a second.

Internet vs. World Wide Web

The Internet and the World Wide Web are not the same thing.

The Internet is the underlying network infrastructure and protocols connecting systems.

The Web is one service that operates over the Internet using technologies such as:

·         URLs

·         HTTP

·         HTML

·         Web browsers

·         Web servers

Other Internet services include email, messaging, file transfer, online games, and voice communication.

Memory Tip

Internet = network infrastructure

Web = service using that infrastructure

Common Mistakes

Mistake 1: Wi-Fi and Internet Mean the Same Thing

False.

Wi-Fi is a local wireless networking technology. A Wi-Fi network can exist without Internet access.

Mistake 2: A Router and Switch Are the Same

False.

A switch typically connects devices within a network, while a router connects different networks and forwards IP packets between them.

Mistake 3: DNS Is the Internet

False.

DNS is an important naming system used by Internet applications, but it is only one part of Internet infrastructure.

Mistake 4: HTTPS Means a Website Is Trustworthy

False.

HTTPS protects communication with the identified endpoint. It does not guarantee that the organization or content itself is honest or safe.

Mistake 5: IPv6 Is Just a Longer Way to Write IPv4

False.

IPv6 is a distinct version of the Internet Protocol with 128-bit addressing and several protocol-design changes.

Mistake 6: More Bandwidth Always Eliminates Lag

False.

Latency, congestion, packet loss, server performance, and routing also affect network responsiveness.

Memory Tips

Remember the devices:

Switch = local devices

Router = networks

Access point = wireless connection

Firewall = traffic control

For core addressing:

MAC = local

IP = network location

Port = application endpoint

For Internet services:

DNS = name to network information

TCP = reliable ordered transport

UDP = lightweight datagrams

HTTP = web communication

TLS = secure channel

And remember:

Internet ≠ Web

The Web runs on the Internet.

Summary

Computer networking connects devices so they can communicate and share resources. Small local networks may connect devices in a home or office, while wide-area networks connect systems over much larger distances.

The Internet is built from many interconnected networks using common protocols. IP provides addressing and packet delivery across networks. Routers forward packets between networks, while switches help devices communicate within local networks.

TCP provides reliable, ordered communication, while UDP offers a simpler datagram service with less built-in reliability. Ports allow multiple applications to use the same computer's network connection.

DNS translates human-friendly domain names into information needed for network communication. HTTP provides the request-and-response system used by the Web, while HTTPS uses security technologies such as TLS to protect communications.

Understanding networking ultimately means understanding layers. Ethernet or Wi-Fi can carry IP packets; IP can carry transport protocols such as TCP or UDP; those transport systems can support application protocols such as HTTP. Each layer solves a different part of the communication problem.

FAQ

1. What is a computer network?

A computer network is a group of connected devices capable of exchanging data or sharing resources.

2. What is the Internet?

The Internet is a global system of interconnected networks communicating through standardized Internet protocols.

3. What does a router do?

A router forwards packets between different networks based on network addressing and routing information.

4. What is an IP address?

An IP address identifies an interface or network location used for communication through the Internet Protocol.

5. What is DNS?

DNS is a distributed hierarchical naming system that allows domain names to be associated with information such as IP addresses.

6. What is the difference between TCP and UDP?

TCP provides reliable, ordered byte-stream communication. UDP provides a simpler datagram service without TCP's built-in delivery and ordering guarantees.

7. What is the difference between HTTP and HTTPS?

HTTP defines web request-and-response communication. HTTPS protects HTTP communication through a secure mechanism such as TLS.

8. What is the difference between bandwidth and latency?

Bandwidth concerns data-transfer capacity, while latency concerns communication delay.

9. Is Wi-Fi the Internet?

No. Wi-Fi connects devices wirelessly to a local network. That network may or may not have an Internet connection.

10. What is a firewall?

A firewall controls network traffic according to security policies, allowing or blocking communication based on defined rules.

Key Takeaways

·         The Internet is a global collection of interconnected networks rather than one central network.

·         Routers connect networks, switches connect local devices, and access points provide wireless network access.

·         IP addresses identify network locations, while ports identify application communication endpoints.

·         TCP emphasizes reliable ordered delivery, while UDP provides lightweight datagram communication.

·         DNS, HTTP, TLS, routing, and layered protocols work together to make modern Internet communication possible.

References

1.      Internet Engineering Task Force / RFC Editor. RFC 9293: Transmission Control Protocol (TCP). RFC Editor — TCP (RFC 9293)

2.      Internet Engineering Task Force / RFC Editor. RFC 768: User Datagram Protocol. RFC Editor — UDP (RFC 768)

3.      Internet Engineering Task Force / RFC Editor. RFC 8200: Internet Protocol, Version 6 (IPv6) Specification. RFC Editor — IPv6 (RFC 8200)

4.      Internet Engineering Task Force / RFC Editor. RFC 9110: HTTP Semantics. RFC Editor — HTTP Semantics (RFC 9110)

5.      Internet Engineering Task Force / RFC Editor. RFC 1034: Domain Names — Concepts and Facilities. RFC Editor — DNS Concepts (RFC 1034)

6.      Internet Engineering Task Force / RFC Editor. RFC 9846: The Transport Layer Security (TLS) Protocol Version 1.3. RFC Editor — TLS 1.3 (RFC 9846)

7.      Internet Corporation for Assigned Names and Numbers. The Domain Name System. ICANN — The Domain Name System

8.      Internet Corporation for Assigned Names and Numbers. About ICANN. ICANN — Internet Identifiers and DNS Coordination

9.      National Institute of Standards and Technology. Firewall — CSRC Glossary. NIST — Firewall Definition

10.  Internet Corporation for Assigned Names and Numbers. DNSSEC — What Is It and Why Is It Important? ICANN — DNSSEC Overview