Transport Protocols

Table of Contents

🟠 P1 — understanding HTTP/2 is essential for gRPC; WebSocket vs SSE comes up in real-time designs

Problem #

The transport layer determines connection multiplexing, head-of-line blocking, and real-time communication capability.

HTTP Versions #

Feature	HTTP/1.1	HTTP/2	HTTP/3 (QUIC)
Multiplexing	❌ One request per conn	✅ Many streams per conn	✅ Many streams per conn
Head-of-line blocking	TCP-level	TCP-level (still!)	❌ Per-stream (UDP-based)
Header compression	❌ No	✅ HPACK	✅ QPACK
Server push	❌ No	✅ Yes	✅ Yes
Connection setup	TCP + TLS (2-3 RTT)	TCP + TLS (2-3 RTT)	0-1 RTT (QUIC handshake)

Real-time Push Mechanisms #

Mechanism	Direction	Protocol	Use case	Complexity
Long-polling	Server → Client	HTTP/1.1	Legacy real-time	Low
Server-Sent Events	Server → Client	HTTP/1.1+	Notifications, feeds	Low
WebSocket	Bi-directional	WS	Chat, gaming, collaboration	Medium
gRPC streaming	Bi-directional	HTTP/2	Internal service streaming	Medium

Instinct #

HTTP/2 is the default for service-to-service. HTTP/3 is still emerging for backend use. For real-time client features: SSE if you only need server→client push (simpler, works with HTTP/2, auto-reconnect). WebSocket if you need true bi-directional (chat, collaborative editing). Avoid long-polling in new designs.

DDIA 2e Reference #

Chapter 4: Modes of dataflow
Chapter 11: Stream processing (for server-push patterns)

Other references #

digital ocean:http1.1 vs 2