Modern web systems operate across multiple communication models and transport layers to satisfy increasing requirements for security, reliability, latency, and real-time interaction. This document provides a structured syllabus-style overview of the dominant protocols used today, including HTTP, HTTPS, WS/WSS, HTTP/2, QUIC/HTTP/3, MQTT, gRPC, SSE, and emerging standards.

I. Historical Context

Early Web (HTTP/1.x Era)

  • Request–response based
  • Stateless communication
  • Designed for static documents
  • TCP-based handshakes
  • No real-time push capability

Modern Expectations

  • Real-time updates
  • Low latency
  • Bi-directional channels
  • Mobile network resilience
  • End-to-end encryption
  • Efficient media streaming
  • Edge & CDN acceleration

These requirements shaped the emergence of newer and more specialized transport protocols.

II. Core Protocols and Characteristics

1. HTTP (Hypertext Transfer Protocol)

Role: Document and API retrieval

  • Stateless
  • Request-driven
  • TCP transport
  • No built-in encryption

Use cases: REST APIs, static assets, browsing

2. HTTPS (HTTP Secure)

Enhancements: TLS encryption, authentication, and integrity

  • Confidentiality by encrypted transport
  • Integrity verification
  • Endpoint authentication

Required for: Payments, login, modern browser APIs, secure data handling

3. WebSockets (WS)

Role: Real-time full-duplex communication

  • Persistent connection
  • Bi-directional messaging
  • TCP-based
  • Low overhead

Examples: Chat, trading dashboards, multiplayer gaming, collaborative editing

4. WebSocket Secure (WSS)

WS + TLS for secure real-time messaging

  • Complies with browser mixed-content policies
  • Suitable for financial & sensitive communication
  • Standard for encrypted market data feeds

5. HTTP/2

Primary improvement: Performance optimization

  • Multiplexed streams
  • Binary framing
  • Header compression
  • Server push

Note: Still TCP-based, inherits head-of-line blocking.

6. QUIC & HTTP/3

Transport redesign optimized for mobile & global traffic

  • UDP-based transport
  • Built-in TLS 1.3
  • Zero-RTT reconnection
  • Stream multiplexing without blocking
  • Connection migration across networks (Wi-Fi ↔ LTE)

Beneficiaries: CDNs, streaming platforms, mobile clients

7. MQTT

Role: Lightweight publish/subscribe communication for IoT

  • Minimal overhead
  • Low power consumption
  • Persistent sessions
  • Efficient on unreliable networks

8. gRPC

Role: High-performance microservice RPC framework

  • HTTP/2-based
  • Binary Protocol Buffers serialization
  • Supports streaming

9. Server-Sent Events (SSE)

Model: Unidirectional server → client streaming

  • Persistent event stream
  • Auto-reconnect behavior
  • Ideal for dashboards, feeds, and notifications

III. Comparative Tables

A. Transport Layer Comparison

Protocol Transport Security Direction Persistence
HTTP TCP Optional Client → Server No
HTTPS TCP+TLS Yes Client → Server No
WS TCP Optional Bi-Directional Yes
WSS TCP+TLS Yes Bi-Directional Yes
HTTP/2 TCP+TLS Yes Client → Server Streamed
QUIC/H3 UDP+TLS Yes Client → Server Streamed
MQTT TCP Optional Pub/Sub Yes
SSE TCP Optional Server → Client Yes
gRPC TCP+TLS Yes Bi/Uni Direction Yes

B. Domain Suitability Mapping

Application Preferred Protocol
REST APIs HTTPS
Market Feeds WSS
Messaging/Chat WSS
IoT Sensors MQTT
Video Streaming QUIC/H3
Notifications SSE
Microservices gRPC
Collaborative Editing WSS/WebRTC
Browser Media WebRTC

IV. Architectural Considerations

Transport Layer

  • TCP: Reliable, ordered, but higher latency
  • UDP: Lower latency, best-effort, enhanced by QUIC's reliability layer

Security Layer

TLS transitioned from optional to effectively mandatory due to browser security policies, compliance frameworks, and industry norms.

Network Mobility

  • QUIC supports connection migration
  • Benefits mobile clients switching networks
  • Reduces session disruption

V. Real-Time Interaction Models

Three primary paradigms define modern interaction:

  1. Request/Response: REST/HTTPS (pull model)
  2. Publish/Subscribe: MQTT/NATS (event distribution)
  3. Full-Duplex Sessions: WebSockets/WebRTC (low-latency collaboration)

VI. Cloud & CDN Alignment

HTTP/3 Adoption is accelerating due to support from:

  • Google
  • Meta
  • Cloudflare
  • Fastly
  • Akamai

Motivations include latency reduction, mobile resilience, and global edge distribution.

VII. Future Trends

  • Expansion of QUIC beyond HTTP semantics
  • WebTransport for low-latency streams
  • WebCodecs for media pipeline access
  • WebRTC for real-time audio/video data
  • 5G enabling ultra-low-latency connectivity
  • Edge computing for proximity execution
  • IoT scaling with MQTT and alternatives

The evolution from HTTP to HTTPS, WSS, QUIC, and beyond reflects a broader transformation of the web into a secure, interactive, and real-time communication environment. Speed, responsiveness, and privacy have become standard expectations rather than optional enhancements.