Networking
A beginner to advanced computer networking library: OSI and TCP/IP, subnetting, NAT and routing, TCP, UDP and QUIC, DNS, HTTP/2 and HTTP/3, TLS 1.3, proxies, load balancers, CDNs, network security, a troubleshooting toolkit, and an interview playbook.
Start here for networking prep, from "what is a MAC address" to "why does gRPC need an L7 load balancer".
The pages follow the stack from the bottom up, then cover the infrastructure between clients and servers, security, and how to debug real problems.
Subnet examples were verified with Python's ipaddress module, and recent changes (HTTP/3 and QUIC adoption, post-quantum TLS key exchange, shorter certificate lifetimes) are included where they matter.
- 01Networking Fundamentals
Beginner networking concepts: what a network is, LAN vs WAN, topologies, the OSI and TCP/IP models, encapsulation, MAC vs IP vs port addressing, devices (hub, switch, router), bandwidth vs latency vs throughput, and the numbers worth memorizing.
Beginner - 02IP Addressing and Routing
IPv4 and IPv6 addressing, CIDR and subnetting with worked examples, private ranges, NAT and its types, ARP and NDP, DHCP, ICMP, routing tables and longest prefix match, static vs dynamic routing, OSPF vs BGP, anycast, and cloud VPC networking.
Beginner to mid - 03TCP, UDP, and QUIC
The transport layer in depth: ports and sockets, UDP, the TCP header, three-way handshake, connection teardown and TIME_WAIT, the state machine, reliability with sequence numbers and retransmission, flow control, congestion control (Reno, CUBIC, BBR), Nagle and delayed ACK, head-of-line blocking, and QUIC.
Mid to advanced - 04DNS, HTTP, and TLS
The application-layer trio behind every web request: DNS resolution, record types, caching and TTLs, DNSSEC and encrypted DNS; HTTP/1.0 to HTTP/3 at the wire level, keep-alive, multiplexing, HPACK and QPACK; TLS 1.3 handshake, certificates and chains of trust, mTLS, SNI and ECH, and HTTPS pitfalls.
Mid - 05Application Protocols and Infrastructure
Real-time and RPC protocols (polling, long polling, SSE, WebSockets, WebRTC, gRPC), other everyday protocols (SSH, email, FTP and SFTP, NTP), and the network infrastructure between client and server: forward and reverse proxies, L4 vs L7 load balancers, load balancing algorithms, CDNs, API gateways, service meshes, and connection pooling.
Mid to advanced - 06Network Security
Network security for engineers: the CIA triad, firewalls (stateless, stateful, WAF), network segmentation and zero trust, VPNs (IPsec, WireGuard, SSL VPN), common attacks by layer (sniffing, spoofing, MITM, DNS attacks, DDoS, SSRF), DDoS mitigation, and a practical hardening checklist.
Mid to advanced - 07Troubleshooting and Tools
A practical networking toolkit: a layer-by-layer troubleshooting method, ping, traceroute and mtr, dig and nslookup, curl timing, ss and netstat, lsof, tcpdump and Wireshark, openssl s_client, nc, ip and ifconfig, iperf, plus a symptom-to-cause table for timeouts, resets, 502s, and slow requests.
Mid - 08Networking Interview Playbook
Networking interview rehearsal: the full 'what happens when you type a URL' answer with a diagram, a 50-question bank from beginner to senior with pointers, scenario questions, cheat sheets for ports, layers, and subnets, common mistakes, and a 7-day study plan.
All levels
Reading Path
Pick Your Level
| You are | Read in this order |
|---|---|
| New to networking | Fundamentals, IP and Routing, TCP, UDP, and QUIC |
| Preparing for a mid-level loop | Add DNS, HTTP, and TLS, Infrastructure |
| Preparing for senior, SRE, or infra roles | Add Security, Troubleshooting |
| One week left | The Interview Playbook study plan |
Related Sections
- Operating Systems explains sockets, file descriptors, and I/O multiplexing from the kernel side.
- Backend covers HTTP semantics, APIs, authentication, and caching in application code.
- System Design uses DNS, CDNs, load balancers, and real-time protocols as building blocks.