The document discusses HTTP/3 and QUIC support in .NET 7.0, with HTTP/3 providing benefits for unreliable networks and mobile scenarios. It also covers HTTP/2 WebSockets, which allow reusing the HTTP/2 connection at the client level but require an API change. Additionally, it introduces YARP as an open source reverse proxy library built on .NET, highlighting how reverse proxies are useful for load balancing and other scenarios in microservices architectures.

1. Networking in .NET 7.0 and
YARP
WUG Days Brno 2022
Karel Zikmund – @ziki_cz

2. Agenda
• HTTP/3 and QUIC
• Evolution from HTTP/1.1 and HTTP/2 – key differences
• Advantages
• .NET 7.0 implementation
• Future in .NET 8.0+
• HTTP/2 WebSockets
• YARP – Yet Another Reverse Proxy
• What is Reverse Proxy
• When you need Reverse Proxy?
• YARP in production

3. HTTP versions
• What’s difference between:
• HTTP/1.1
• HTTP/2
• What’s difference between:
• HTTP/2
• HTTP/3

4. HTTP/1.1
• HTTP vs. HTTPS
• Textual protocol
• Multiple connections
• 3-way handshake (3 RTT)
• TCP – 1 RTT – SYN/ACK
• TLS 1.2 – 2 RTTs (Hello + Key)
• TLS 1.3 (2 RTT)
• TCP slow start – Window ramp up
• HTTP Pipelining

5. HTTP/2
• Binary protocol (packets with frames)
• Multiplexing streams on 1 connection
• TCP-based
• 3 RTT (or 2 RTT with TLS 1.3)
• Can be technically without SSL, unencrypted
• Head of the line blocking
• Packet loss blocks all streams, not just the one with lost packet

6. HTTP/3
• Binary protocol (packets with frames)
• Multiplexing streams on 1 connection
• QUIC-based
• QUIC = UDP + TLS
• 1 RTT
• 25.1% of all websites
• Major browsers – https://caniuse.com/http3

7. HTTP/3 – Advantages
• Unreliable networks – last mile network
• No head of the line blocking
• Improved loss recovery
• 0-RTT
• Keys from previous connection
• Dangerous – replay attacks
• Idempotent requests (e.g. harmless GET)
• Connection ID
• Transfer between networks
• Requires server support – by default in .NET

8. QUIC – Pros and Cons
• Multi-path … also for HTTP/3
• RFC in progress
• Increase bandwidth (multiple routes)
• Decrease latency (duplicated traffic) – streaming
• Unreliable delivery
• Not in .NET yet
• Extensible and versioned
• Network appliances (routers, proxies) – problems with UDP

9. HTTP/3 & QUIC – .NET support
• msquic-based – http://github.com/microsoft/msquic
• OSS, x-plat
• HTTP/3
• .NET 7.0 – full support (client and server) on Windows and Linux
• Performance – on par with HTTP/2
• QUIC APIs
• .NET 7.0 – GA quality
• API shape is Preview (reserve right to change it in .NET 8.0)
• Looking for consumers to validate

10. .NET Usage
• HTTP/3 opt-in
• HttpClient – defaults to HTTP/1.1
• HttpRequestMessage.Version = 3.0
• QUIC: EnablePreviewFeatures

11. .NET 8.0+
• HTTP/3 enabled by default in Kestrel
• More Performance work
• Finalize QUIC API shape
• Additional non-critical features
• 0-RTT (as opt-in)
• Support macOS, Mobile platforms (iOS, Android)
• Additional protocols and extensions
• gRPC over HTTP/3
• Multi-path
• WebTransport
• QUIC Datagram

12. HTTP/2 WebSockets
• Same WebSocket protocol, just over HTTP/2
• Pros:
• Reuse HTTP/2 connection – better perf
• Client:

13. HTTP/2 WebSockets
• Chrome and Edge – enabled by default
• Uses CONNECT word instead of GET – routes may need update

14. WebSockets Future
• HTTP/3 WebSockets
• WebTransport – WebSockets done right
• Session with multiple QUIC streams
• Multiple sessions on HTTP/3 connection
• Prototype in progress

15. YARP
• Yet Another Reverse Proxy
• https://microsoft.github.io/reverse-proxy
• OSS: https://github.com/microsoft/reverse-proxy
• Layer-7 proxy – terminates & re-issues requests
• Other popular reverse proxies: Nginx, HAProxy, Envoy, Ocelot, …

16. YARP and reverse proxies
• Who used YARP?
• Who used some Reverse Proxy?
• Who knows what a reverse proxy is?

17. What is a reverse proxy
• Public endpoint
• Load balancing between backend servers
• Can offload work from backend servers: Encryption, Auth, Compression, Caching
Reverse
proxy
contoso.com/orders
contoso.com/store
woodgrovebank.com
Public Internet Private Network

18. Reverse proxies – Why to use them?
• Load balancing
• A/B testing, or Version rollout
• Health checks, health status
• Indirection between URL-space and backend implementation
• API Management – consistent API surface for customers
• Offloading from backend
• Auth, compression, encryption, static files (like CDN)
• Authentication migration
• Cloud to On-prem reverse tunnel (*)
• Route local traffic to remote servers (single point of control and config)
• k8s and Service Fabric ingress control
• .NET Framework migration to .NET Core

19. YARP
• Library, not EXE
• 2 releases: 1.0 & 1.1
• .NET 5.0+ support
• Extensibility in C#, layered
• x-plat
• Great perf
• Latest protocols (gRPC , HTTP/3, HTTP/2 WebSockets)
• Drives innovation and perf improvements into .NET

20. YARP – docs
https://microsoft.github.io/reverse-proxy

21. YARP – Azure App Service
• Blog post
• 160B+ requests/day … 1.9M RPS
• 14M+ host names
• .NET 6.0 + YARP
• Why?
• Perf improvements
• 80% in throughput in perf tests
• Lower CPU usage
• More extensibility points
• New customer scenarios:
• gRPC, HTTP/3, per-host cipher suite config, custom error pages, …

22. YARP – Dynamics 365
• Announced 2021 November at .NET Conf
• >100B requests/month ... 38.5K RPS
• >7.5PB/month … transferred data
• ~700 instances of YARP
• Original authors
• Started on .NET Core 3.1

23. YARP – Architecture with pipeline
ASP.NET
Routing
TLS Termination
Auth2
Static Files
Other routes
Config
Session
Affinity
Load
Balancing
Request
Transformations
Http
Forwarder
Destination
Enumeration
HttpClient*
Health
checks
Specific
destination
server
http(s)
http(s)
Proxy process
Kestrel
Passive
Health
Checks

24. YARP – Architecture Http Forwarder
ASP.NET
Routing†
TLS Termination
Auth2
Static Files
Other routes
Http
Forwarder
HttpClient*
Specific
destination
server
http(s)
http(s)
Proxy process
Kestrel
Your custom
handler(s)
Request
Transformations
Site Information
/ Cache
Load balancing
Health checks

25. Summary
• HTTP/3 and QUIC support in .NET 7.0
• GA quality
• QUIC API shape may change in .NET 8.0
• Pro: Unreliable networks, Mobile scenarios
• HTTP/2 WebSockets
• Client needs new API call to reuse connection
• Server needs ConnectMethod change
• YARP
• Library, extensible via C#
• Micro-services world needs reverse proxies
@ziki_cz