🌐 Networking

Core → Advanced

• OSI vs TCP/IP model; what L4 and L7 mean (matters for load balancers)
• IP, subnets/CIDR, NAT, private ranges (needed for VPCs in AWS)
• TCP: 3-way handshake, flow control, congestion control, TIME_WAIT, Nagle, keep-alive
• UDP and when to use it; QUIC
• DNS resolution chain, TTLs, record types (A, AAAA, CNAME, SRV, TXT)
• HTTP/1.1 (keep-alive, head-of-line blocking) → HTTP/2 (multiplexing, HPACK) → HTTP/3 (QUIC)
• TLS 1.3 handshake, certificates, CA chain, mTLS, SNI
• Load balancing: L4 vs L7, algorithms (round robin, least-conn, consistent hashing), health checks
• CDNs, anycast, edge caching, cache headers (Cache-Control, ETag)
• WebSockets, SSE, long polling (Realtime (WebSockets, SSE))
• Proxies: forward vs reverse, connection pooling, timeouts (Envoy, Gateways & Service Mesh)

🧪 Labs (🟢 warm-up → 🟡 core → 🔴 hard → ⚫ boss)

• 🟢 dig +trace, curl -v --http2, curl -w timing breakdown; explain every line
• 🟡 HTTP/1.1 server from raw TCP in Go (keep-alive, chunked encoding)
• 🟡 Wireshark + SSLKEYLOGFILE: decrypt TLS 1.3 and read HTTP/2 frames
• 🔴 An L7 load balancer in Go (codingchallenges.fyi): health checks, round robin, least-conn
• 🔴 A DNS resolver in Go that walks from the root servers
• ⚫ A TCP proxy with connection pooling; measure the latency win vs no pooling

🧠 Cognitive tasks

• Blank-page: “what happens when you type a URL” in 15 min at full depth
• Predict → verify: time saved per request by connection reuse from Mumbai to us-east-1
• First-principles: why does HTTP/2 still have head-of-line blocking?

🛰️ Orbit integration

• SSE streaming through proxies (buffering, idle timeouts) for orbit-stream
• gRPC load balancing between orbit-api and the engine (why L4 fails)

Go deeper

⚙️ Network Stack Internals · Envoy Internals

Resources

• High Performance Browser Networking (Grigorik, free at hpbn.co): ⭐ best practical book
• Computer Networking: A Top-Down Approach (Kurose & Ross): reference
• Beej’s Guide to Network Programming
• Cloudflare Learning Center (free and excellent)

Interview questions interview-q

• What happens when you type google.com and press Enter? (Go deep: DNS → TCP → TLS → HTTP → LB → server → render)
• Why does HTTP/2 still suffer from head-of-line blocking at the TCP level?
• L4 vs L7 load balancer?