State of HTTP2
Jun 13, 2020
The HTTP2 spec was published as an Internet Draft May 30th, 2015. Five years later and the capabilities seem to vary wildly across libraries. With HTTP3 fast approaching I was curious the current state of play for some of the bigger libraries I encounter regularly.
This document aims to identify what capabilities exist for the libraries.
The implementation details of HTTP2 start at section 3 in the spec. I will aim to document compatibility of the following libraries over the coming weeks. Starting with server compatibility and then client compatibility. Server compatibilty should be relatively easy using h2spec.
Server Libraries
- Go golang.org/x/net/http2.
- Project Reactor.
- Java 11 stdlib.
- Netty.
Client Libraries
- Go stdlib.
- Netty.
- OK HTTP.
- Project Reactor.
- Java 11 stdlib.
Legend
- ✓ - success.
- ⚠ - partial failure.
- ✖ - failure.
| no. | Title | 1 |
| 3. | Starting HTTP/2 | |
| 3.1 | HTTP/2 Version Identification | |
| 3.2 | Starting HTTP/2 for “http” URIs | |
| 3.2.1 | HTTP2-Settings Header Field | |
| 3.3 | Starting HTTP/2 for “https” URIs | |
| 3.4 | Starting HTTP/2 with Prior Knowledge | |
| 3.5 | HTTP/2 Connection Preface | ⚠ |
| 4.1 | Frame Format | ✓ |
| 4.2 | Frame Size | ⚠ |
| 4.3 | Header Compression and Decompression | ✓ |
| 5.1 | Stream States | ✓ |
| 5.1.1 | Stream Identifiers | ✓ |
| 5.1.2 | Stream Concurrency | ✓ |
| 5.2.2 | Appropriate Use of Flow Control | ✓ |
| 5.3.1 | Stream Dependencies | ✓ |
| 5.3.2 | Dependency Weighting | ✓ |
| 5.3.3 | Reprioritization | ✓ |
| 5.3.4 | Prioritization State Management | ✓ |
| 5.3.5 | Default Priorities | ✓ |
| 5.4 | Error Handling | ✓ |
| 5.4.1 | Connection Error Handling | ✓ |
| 5.4.2 | Stream Error Handling | ✓ |
| 5.4.3 | Connection Termination | ✓ |
| 5.5 | Extending HTTP/2 | ✓ |
| 6. | Frame Definitions | ✓ |
| 6.1 | DATA | ✓ |
| 6.2 | HEADERS | ✓ |
| 6.3 | PRIORITY | ✓ |
| 6.4 | RST_STREAM | ✓ |
| 6.5 | SETTINGS | ✓ |
| 6.5.1 | SETTINGS Format | ✓ |
| 6.5.2 | Defined SETTINGS Parameters | ✓ |
| 6.5.3 | Settings Synchronization | ⚠ |
| 6.6 | PUSH_PROMISE | - |
| 6.7 | PING | ✓ |
| 6.8 | GOAWAY | ✓ |
| 6.9 | WINDOW_UPDATE | ✓ |
| 6.9.1 | The Flow-Control Window | ✓ |
| 6.9.2 | Initial Flow-Control Window Size | ✓ |
| 6.9.3 | Reducing the Stream Window Size | ✓ |
| 6.10 | CONTINUATION | ✓ |
| 7. | Error Codes | ✓ |
| 8. | HTTP Message Exchanges | ✓ |
| 8.1 | HTTP Request/Response Exchange | ✓ |
| 8.1.1 | Upgrading from HTTP/2 | ✓ |
| 8.1.2 | HTTP Header Fields | ⚠ |
| 8.1.3 | Examples | |
| 8.1.4 | Request Reliability Mechanisms in HTTP/2 | |
| 8.2 | Server Push | ✓ |
| 8.2.1 | Push Requests | |
| 8.2.2 | Push Responses | |
| 8.3 | The CONNECT Method | |
| 9. | Additional HTTP Requirements/Considerations | |
| 9.1 | Connection Management | |
| 9.1.1 | Connection Reuse | |
| 9.1.2 | The 421 (Misdirected Request) Status Code | |
| 9.2 | Use of TLS Features | |
| 9.2.1 | TLS 1.2 Features | |
| 9.2.2 | TLS 1.2 Cipher Suites |