Connection::app_limited to PathData::app_limited (#580)
## Description - Does what the PR title says - Also some small cleanups in `poll_transmit_path_space`, if I may. Context for what `app_limited` is: > When bytes in flight is smaller than the congestion window and sending is not pacing limited, the congestion window is underutilized. This can happen due to insufficient application data or flow control limits. When this occurs, the congestion window SHOULD NOT be increased in either slow start or congestion avoidance. https://www.rfc-editor.org/rfc/rfc9002.html#section-7.8 I.e. when `app_limited` is `true`, the congestion controller doesn't increase the congestion window. You can see this in `Cubic::on_ack` where it outright immediately bails, doing nothing, when `app_limited` is `true`. Because all paths have their own congestion window, they need to track whether they're application limited separately. Otherwise it's possible that there's a situation where one path is never exercised fully (e.g. a backup path), while another path is saturated with application data. Previously, the application data path would set the connection-wide `app_limited` to `false`, causing the backup path (that never experiences congestion) to inflate its congestion window. With this change, the backup path would know it's not application limited and pass that correct information to the congestion controller.
noq
General purpose implementation of the QUIC transport
protocol in pure
Rust. Noq is built as an async-friendly API in the noq crate on top
of a sans-io protocol library in noq-proto.
Noq started out as a fork of the excellent Quinn project. The main focus of development has been towards adding support for more QUIC (draft) extensions:
Features
- Easy to use futures-based async API.
- Client and server server functionality.
- 0-RTT and 0.5-RTT data support.
- Ordered and unordered stream reads.
- Custom and zero-length connection identifiers.
- Fully pluggable crypto API with a Rustls implementation using ring or aws-lc-rs provided by default for convenience.
- Broad platform support, including Linux, Windows, macOS, android, iOS and wasm.
Standards
The noq library aims to be correct implementation of various QUIC standards:
- Supports the core QUIC specifications:
- The standardised QUIC extensions:
- Draft extensions:
- qlog: Structured Logging for Network Protocols.
- QUIC Multipath.
- With experimental qlog support.
- QUIC Address Discovery (QAD).
- Using QUIC to traverse NATs (QNT).
Getting started
Examples at https://github.com/n0-computer/noq/blob/main/noq/examples
$ cargo run --example server ./
$ cargo run --example client https://localhost:4433/Cargo.toml
This launches an HTTP 0.9 server over the QUIC transport on the loopback address serving the current working directory, with the client fetching ./Cargo.toml. By default, the server generates a self-signed certificate and stores it to disk, where the client will automatically find and trust it.
License
Copyright 2025 The quinn developers Copyright 2025 N0, INC.
This project is licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.