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🌐 Computer Networks

How data moves across the world. 50 topics, from beginner to advanced.

Computer networks explain how devices exchange data across the internet. The topics follow data down the layers of the network stack, from application protocols such as HTTP and DNS, through TCP and IP routing, to the physical link. Knowing these layers makes it easier to debug slow pages, lost connections and security issues.

Who this area is for

Students of networking and web development, system administrators, and developers who need to debug why a request is slow or fails.

Real-world use cases

Diagnosing why a website loads slowly by inspecting DNS lookups and TCP handshakes.
Choosing between TCP and UDP for a file transfer versus a live video call.
Configuring firewall rules that allow web traffic and block everything else.
Finding out why a website loads slowly by checking DNS lookup time and the number of round trips.
Opening a firewall port for one service without exposing the rest of the machine.

Topics in Computer Networks

Beginner (17)

What is a Network — A set of devices connected to share data and resources.
Network Topologies — Layouts such as bus, star and mesh.
LAN, WAN and MAN — Networks classified by geographic scale.
OSI Model — Seven-layer conceptual framework for network functions.
TCP/IP Model — Four-layer practical protocol suite of the Internet.
IP Addresses — Numeric labels identifying devices on a network.
IPv4 vs IPv6 — Older 32-bit and newer 128-bit addressing schemes.
Subnetting — Dividing a network into smaller logical segments.
MAC Addresses — Hardware identifiers burned into network interfaces.
Ethernet — Dominant wired LAN technology using frames.
Switches and Hubs — Devices forwarding frames within a local network.
Routers — Devices forwarding packets between networks.
DNS — Distributed system translating names to IP addresses.
DHCP — Protocol automatically assigning addresses to hosts.
HTTP — Application protocol for requests and responses on the web.
Ports and Sockets — Endpoints identifying services and connections on hosts.
Packet Switching — Splitting data into independently routed packets.

Intermediate (17)

Wi-Fi — Wireless LAN technology based on IEEE 802.11.
TCP — Reliable ordered connection-oriented transport protocol.
UDP — Lightweight connectionless transport without delivery guarantees.
Three-Way Handshake — Exchange establishing a TCP connection.
Flow Control — Preventing a fast sender from overwhelming a receiver.
Congestion Control — Adapting send rate to avoid overloading the network.
Sliding Window Protocol — Allowing multiple outstanding unacknowledged packets.
Error Detection and Correction — Using checksums and codes to find and fix corrupted bits.
CRC — Polynomial-based checksum for detecting burst errors.
ARP — Protocol mapping IP addresses to MAC addresses.
ICMP and Ping — Control messages and the tool testing reachability.
NAT — Translating private addresses to public ones.
Routing Algorithms — Methods determining best paths such as distance-vector and link-state.
RIP and OSPF — Common interior routing protocols.
BGP — Protocol exchanging routes between autonomous systems.
VLANs — Logical separation of networks on shared switches.
HTTPS and TLS — Encrypted web communication using certificates.

Advanced (16)

Email Protocols — SMTP, IMAP and POP3 for sending and retrieving mail.
FTP and SSH — File transfer and secure remote login protocols.
CDN — Geographically distributed caches speeding content delivery.
Load Balancers — Devices spreading traffic across servers.
Proxies — Intermediaries forwarding requests on behalf of clients or servers.
Firewalls — Filters permitting or blocking traffic by rules.
VPN — Encrypted tunnels extending private networks over public ones.
QUIC and HTTP/3 — UDP-based multiplexed encrypted transport.
WebSockets — Persistent full-duplex channels between browser and server.
Software-Defined Networking — Separating control logic from forwarding hardware.
Network Virtualization — Overlay networks abstracted from physical links.
MPLS — Label-based forwarding technique in carrier networks.
5G Networks — Fifth-generation cellular standard with low latency and high bandwidth.
Network Performance — Latency, bandwidth, jitter and throughput metrics.
Multicast and Anycast — One-to-many and nearest-of-many addressing methods.
Network Programming with Sockets — Writing programs that communicate via the socket API.

How to study Computer Networks

Run the networking tools in the DevOps area on your own machine: ping, traceroute and a packet capture. Trace one request from your browser to a server, naming each layer it passes through. Compare what you expect with what the tools show.

Frequently asked questions

What is the difference between TCP and UDP?

TCP guarantees ordered, reliable delivery by retransmitting lost packets, at the cost of extra latency. UDP sends datagrams without those guarantees, which suits real-time media and games.

What happens when I type a URL into a browser?

The browser resolves the domain with DNS, opens a TCP and TLS connection to the server, sends an HTTP request, and renders the response. Each step is a topic in this area.

What does an IP address do?

An IP address identifies a device on a network so routers can forward packets to it. IPv4 uses 32-bit addresses and IPv6 uses 128-bit addresses.

What is the difference between a network and the internet?

A network is any set of connected devices that can exchange data. The internet is a global network of networks that uses shared protocols, such as IP, to connect them.

Why do networks use layers?

Layers let each part solve one problem, such as reliable delivery or addressing, without knowing how the others work. This separation makes the network easier to build, test and change.

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