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Networking

Notes on networking for system design — organized to go broad (one place for the whole landscape) and deep on each topic, with primary sources: specs/RFCs, engineering blogs, conference talks, and papers.

Each topic gets its own page as I write it up. This page is the map.

Written

gRPC
RPC over HTTP/2 + Protocol Buffers.
GraphQL
Client-specified queries + federation across services.
Planned topics

The stack (fundamentals)

  • OSI / request lifecycle — layers 3/4/7; what happens on GET example.com (DNS → TCP handshake → HTTP → teardown)
  • L3 — Network: IP addressing, routing, public vs private, NAT, DHCP

L4 — Transport protocols

  • TCP — 3-way handshake, streams, ordering, flow & congestion control, head-of-line blocking
  • UDP — connectionless, best-effort; when loss is acceptable (media, gaming, VoIP)
  • QUIC / HTTP/3 — TCP+TLS reimagined over UDP; 0-RTT; per-stream loss recovery

L7 — Application protocols

  • REST — resources/verbs, idempotency, status codes, pagination
  • HTTP evolution — HTTP/1.1 → /2 (multiplexing, HPACK) → /3 (QUIC); keep-alive
  • Realtime family (the “how do I push to a client?” decision):
    • SSE — EventSource, reconnection, Last-Event-ID, proxy buffering gotchas
    • WebSockets — HTTP upgrade, bidirectional, framing; infra pain (LBs/proxies/firewalls)
    • Long polling — the fallback; how it differs from SSE
    • WebRTC — P2P over UDP; STUN/TURN/ICE, signaling, NAT traversal
    • Realtime decision — polling vs long-poll vs SSE vs WebSocket vs WebRTC (tradeoff table)

Load balancing & proxies

  • Load balancing — L4 vs L7, client-side vs dedicated, algorithms, health checks, failover
  • Envoy — modern L7 proxy; the xDS APIs (LDS/RDS/CDS/EDS); basis of service meshes
  • API Gateway — auth, TLS termination, rate limiting, routing; vs plain LB

Datacenter & cloud networking

  • North-south vs east-west — ingress/egress vs service-to-service traffic
  • Sidecar & service mesh — sidecar pattern, Envoy dataplane, Istio/Linkerd, mTLS
  • Kubernetes networking — Pod IPs, ClusterIP / NodePort / LoadBalancer, kube-proxy, CNI, Ingress
  • iptables & the packet path — netfilter hooks, DNAT/SNAT, conntrack
  • eBPF — programmable kernel dataplane; Cilium (iptables replacement), Katran (L4 LB), XDP
  • DNS deep dive — resolution, records, TTLs, GeoDNS, DNS as load balancing

Latency, reliability & failure

  • Regionalization & CDN — speed-of-light latency, data locality, edge, regional partitioning
  • Failure patterns — timeouts, retries + exponential backoff + jitter, idempotency keys, circuit breakers, thundering herd
  • TLS — handshake, termination points, mTLS

Cross-cutting references (to fold into topic pages)