Computer Networks

Networking concepts every backend developer should be able to explain.

• What is Computer Networking? — What networking is, why it exists, and real examples from everyday apps.
• OSI Model — The 7 OSI layers and what each layer is responsible for.
• TCP/IP Model — The practical 4-layer networking model used by the Internet.
• OSI vs TCP/IP & Encapsulation — How OSI maps to TCP/IP and how encapsulation moves data through layers.
• IP Addressing — What an IP address is and how it identifies devices on a network.
• Network ID & Host ID — How an IP address is split into network and device parts.
• Subnet Mask — How devices know which part of an IP address is the network part.
• CIDR — The slash notation used to describe network size, such as /24.
• Public vs Private IP — Why local devices use private IPs and servers use public IPs.
• Router & Default Gateway — How traffic leaves your local network.
• NAT — How many private devices share one public IP address.
• DHCP — How devices automatically receive IP configuration.
• ARP — How local networks resolve IP addresses to hardware addresses.
• TCP — Handshake, termination, sequence numbers, acknowledgements, retransmission, flow control, and congestion control.
• UDP — Difference from TCP, when to use UDP, and real-world examples.
• TCP vs UDP — Reliability, speed, ordering, error recovery, and use cases.
• DNS — DNS lookup process, caching, recursive resolvers, and why DNS is needed.
• DNS Records Explained Simply — A, AAAA, CNAME, MX, TXT, NS, SOA, CAA, SRV and TTL, with real examples for Vercel, Google Workspace and Resend.
• HTTP — Request/response, headers, methods, status codes, cookies, sessions, and keep-alive.
• HTTPS — SSL/TLS, certificates, encryption, and HTTPS request flow.
• REST API — REST principles, statelessness, resources, idempotency, and HTTP methods.
• WebSockets — Why HTTP is not enough, full-duplex communication, handshakes, and real-time apps.
• CORS — Same Origin Policy, preflight requests, and Access-Control-Allow-Origin.
• Cookies vs Sessions vs JWT — Authentication state mechanisms and when each one fits.
• Authentication vs Authorization — Identity verification versus permission checks.
• Load Balancer — Why load balancers are needed, round robin, least connections, and health checks.
• Reverse Proxy — Nginx and why backend servers use reverse proxies.
• CDN — Why images load faster, edge servers, and caching.
• Ports — How network services share one machine through numbered ports.
• Socket Programming — The programming interface behind network communication.