test(proto): Implement bandwidth-limited routing

[matheus23]

Description

• Refactors the RoutingDecision::Deliver case to give it a recv_time: Instant field. This allows Routing to decide when to deliver packets.
• Adds a BwLimitedRouting routing implementation that implements a queue that delays packets the more packets are queued and tail-drops packets at a certain max queue length.
• Adds a throughput test as a quick way of testing noq-proto and its congestion control against BwLimitedRouting.

Breaking Changes

None. Test changes only.

Notes & open questions

Started this work because it might be really useful in catching regressions in congestion control, and to prepare work for when we send on multiple paths simultaneously.

Still draft because this needs a little more work in the test itself (it doesn't actually assert anything yet).

But we can now generate neat pictures from noq-proto itself!

The qlog file for this is generated in 0.2 seconds on my machine, even though it is a simulated 10MB transfer over a 1MB/s connection, so this simulates ~10s of actual time.
The other neat thing about it is that it is fairly deterministic. There's still some sources of randomness in noq, but all of the "measured" transfer speeds fall into a 1% range.

Change checklist

• Self-review.
• Documentation updates following the style guide, if relevant.
• Tests if relevant.
• All breaking changes documented.

[github-actions]

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/noq/pr/720/docs/noq/

Last updated: 2026-06-26T17:21:25Z

[github-actions]

Performance Comparison Report

796d86b12e6a3fb99971fa3de246a15dd55fbbd1 - artifacts

Raw Benchmarks (localhost)

Scenario	noq	upstream	Delta	CPU (avg/max)
large-single	5587.6 Mbps	7896.7 Mbps	-29.2%	95.8% / 100.0%
medium-concurrent	5418.7 Mbps	7983.6 Mbps	-32.1%	94.8% / 99.5%
medium-single	3991.1 Mbps	4615.6 Mbps	-13.5%	98.1% / 151.0%
small-concurrent	3954.0 Mbps	5292.2 Mbps	-25.3%	93.3% / 102.0%
small-single	3600.8 Mbps	4674.9 Mbps	-23.0%	93.7% / 102.0%

Netsim Benchmarks (network simulation)

Condition	noq	upstream	Delta
ideal	N/A	4022.5 Mbps	N/A
lan	N/A	810.4 Mbps	N/A
wan	N/A	83.8 Mbps	N/A

Summary

noq is 26.0% slower on average

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0c79f22c7b2a70f628e475829b347a670890bcb6 - artifacts

Raw Benchmarks (localhost)

Scenario	noq	upstream	Delta	CPU (avg/max)
large-single	5450.5 Mbps	7744.4 Mbps	-29.6%	94.0% / 99.0%
medium-concurrent	5256.1 Mbps	7767.4 Mbps	-32.3%	94.2% / 99.0%
medium-single	3800.0 Mbps	4748.9 Mbps	-20.0%	93.9% / 100.0%
small-concurrent	3835.1 Mbps	5358.7 Mbps	-28.4%	90.8% / 99.1%
small-single	3516.7 Mbps	4798.9 Mbps	-26.7%	89.3% / 97.2%

Netsim Benchmarks (network simulation)

Condition	noq	upstream	Delta
ideal	3086.8 Mbps	4092.4 Mbps	-24.6%
lan	782.4 Mbps	810.4 Mbps	-3.5%
lossy	69.8 Mbps	69.8 Mbps	~0%
wan	83.8 Mbps	83.8 Mbps	~0%

Summary

noq is 27.0% slower on average

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9cedbd99a9c48819bd910f8618c569c92465a93f - artifacts

Raw Benchmarks (localhost)

Scenario	noq	upstream	Delta	CPU (avg/max)
large-single	5450.8 Mbps	8057.1 Mbps	-32.3%	96.7% / 98.2%
medium-concurrent	5469.7 Mbps	7652.7 Mbps	-28.5%	96.7% / 98.0%
medium-single	4089.4 Mbps	4563.3 Mbps	-10.4%	95.9% / 98.3%
small-concurrent	3791.2 Mbps	5214.6 Mbps	-27.3%	97.7% / 100.0%
small-single	3551.4 Mbps	4622.5 Mbps	-23.2%	96.0% / 98.3%

Netsim Benchmarks (network simulation)

Condition	noq	upstream	Delta
ideal	3030.9 Mbps	4064.0 Mbps	-25.4%
lan	782.4 Mbps	803.1 Mbps	-2.6%
lossy	69.8 Mbps	69.8 Mbps	~0%
wan	83.8 Mbps	83.8 Mbps	~0%

Summary

noq is 25.1% slower on average