MASQUE Tunneling: UDP & IP Proxying over HTTP/3
🎯 What You'll Learn
This guide explains the IETF MASQUE protocol suite and its implications for privacy infrastructure. We cover the why behind protocol design decisions and when MASQUE outperforms traditional VPN solutions — essential knowledge for building censorship-resistant systems.
Why MASQUE Changes Everything
MASQUE (Multiplexed Application Substrate over QUIC Encryption) represents a paradigm shift in how we think about tunneling. Traditional VPN protocols (WireGuard, OpenVPN, IPsec) have distinct traffic signatures that Deep Packet Inspection (DPI) can identify and block.
MASQUE solves this fundamental problem by making tunneled traffic indistinguishable from normal HTTPS:
- Unblockable by design — Uses standard HTTP/3 on port 443
- Multiplexed efficiency — Multiple tunnels share one QUIC connection
- No TCP-over-TCP — Native QUIC datagrams eliminate meltdown
- IETF standardized — RFC 9298 (CONNECT-UDP), RFC 9484 (CONNECT-IP)
Protocol Architecture
Understanding the architectural relationship between client, proxy, and target is essential for proper deployment. The proxy acts as a protocol translator, converting HTTP/3 streams into native UDP or IP traffic.
│ Client │ HTTP/3 │ MASQUE │ UDP │ Target │
│ │◄───────►│ Proxy │◄───────►│ Server │
└─────────────┘ QUIC └─────────────┘ └─────────────┘
│
│ Indistinguishable from
│ normal HTTPS traffic
▼
┌───────────┐
│ Firewall │ ✓ Passes inspection
└───────────┘
CONNECT-UDP vs CONNECT-IP
The MASQUE specification defines two primary modes, each suited for different use cases:
| Feature | CONNECT-UDP | CONNECT-IP |
|---|---|---|
| RFC | RFC 9298 | RFC 9484 |
| Scope | Single UDP flow | Full IP tunnel |
| Protocols | UDP only | Any (TCP, UDP, ICMP) |
| Target | Specific host:port | Any destination |
| Use Case | DNS, QUIC proxy | Full VPN replacement |
| Complexity | Lower | Higher |
CONNECT-UDP Deep Dive
CONNECT-UDP establishes a bidirectional UDP proxy to a specific target. The client specifies the destination in the request path, and the proxy forwards datagrams transparently. This is ideal for proxying specific services like DNS or game traffic.
CONNECT-UDP Implementation
Complete Go client implementation with HTTP/3 transport and QUIC datagram handling.
CONNECT-IP Full Tunnel
CONNECT-IP creates a virtual network interface capable of any IP protocol. Unlike CONNECT-UDP which targets specific flows, CONNECT-IP gives you a complete tunnel supporting TCP, UDP, ICMP, and custom protocols. This is the foundation for building full VPN replacements.
CONNECT-IP Tunnel Setup
Server-side configuration, IP assignment, and routing table integration.
Security Considerations
MASQUE's invisibility is a double-edged sword. The same properties that protect legitimate users also enable malicious actors. Proper deployment requires careful consideration of:
- Authentication — Who can establish tunnels through your proxy?
- Rate limiting — Preventing resource exhaustion attacks
- Logging — Balancing privacy with abuse prevention
- Exit policies — What traffic is allowed to egress?
Production Security Configuration
Authentication middleware, rate limiting strategies, and exit policy implementation.
Performance Characteristics
MASQUE inherits QUIC's performance benefits while adding minimal overhead. Key factors affecting throughput include:
- Datagram MTU — Larger datagrams reduce per-packet overhead
- Connection coalescing — Multiple tunnels share handshake cost
- 0-RTT resumption — Previously established connections reconnect instantly
- Congestion control — QUIC's modern algorithms adapt quickly
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Request Access Browse DocumentationExternal Resources
- RFC 9298 — CONNECT-UDP specification
- RFC 9484 — CONNECT-IP specification
- MASQUE Working Group — IETF documents
- QUIC Working Group — Transport layer specs