luokai0 Computer Networks Expert
Before Starting
- Which OSI layer?
- LAN, WAN, or internet-scale?
- Protocol design or troubleshooting?
Core Expertise Areas
OSI and TCP/IP Models
OSI 7 layers: physical, data link, network, transport, session, presentation, application. TCP/IP 4 layers: network access, internet, transport, application. Encapsulation: each layer adds header wrapping data from layer above.
Network Layer
IP addressing: IPv4 32-bit, IPv6 128-bit, CIDR notation, subnetting. Routing: distance vector (RIP, Bellman-Ford), link state (OSPF, Dijkstra), BGP path vector. NAT: network address translation, maps private to public addresses. ARP: maps IP address to MAC address on local network.
Transport Layer
TCP: connection-oriented, reliable, ordered, flow control, congestion control. TCP 3-way handshake: SYN, SYN-ACK, ACK. TCP congestion control: slow start, congestion avoidance, fast retransmit, CUBIC. UDP: connectionless, unreliable, low overhead, for latency-sensitive applications. QUIC: UDP-based, 0-RTT, multiplexed streams, used by HTTP/3.
Application Layer
HTTP/1.1: persistent connections, pipelining, text-based. HTTP/2: binary, multiplexed, header compression, server push. HTTP/3: QUIC-based, eliminates head-of-line blocking. DNS: hierarchical, recursive and iterative resolution, TTL, caching. TLS: record protocol, handshake, certificates, symmetric encryption.
Network Security
Firewalls: stateless packet filter, stateful inspection, application layer gateway. DDoS: volumetric, protocol, application layer attacks, mitigation strategies. VPN: IPSec tunnel mode, SSL/TLS VPN, WireGuard. Zero trust: never trust always verify, microsegmentation, identity-based access.
Best Practices
- Always capture packets when debugging network issues
- Understand MTU and fragmentation at each layer
- Test both IPv4 and IPv6 code paths
- Monitor round-trip time and packet loss separately
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Confusing latency and bandwidth | Latency is delay, bandwidth is capacity |
| Ignoring TCP buffers in throughput | Buffer size limits throughput on high-latency links |
| DNS TTL too short or long | Balance freshness vs DNS load |
| Not handling partial TCP reads | Always loop until full message received |
Related Skills
- operating-systems-expert
- devsecops-expert
- websockets-expert