GSoC 2019 – Building a Network Simulator for qaul.net

qaul.net allows spontaneous, ad-hoc networks to form between any wireless-enabled devices over whatever medium is available. Currently, the project is undergoing a Rust rewrite, which will provide enhanced security, modularity, and performance.

As with any rewrite, testing is a major component of the process. In the case of qaul.net, that requires a fairly sophisticated model of the underlying network protocols in use and even some of the physics behind them (like jitter, also known as “lag spikes”, which has the potential to foul up any routing protocol).

Project Overview

The problem of building a simulator is a common one, but in this case it is somewhat complicated by its dual use here, in both automated testing and as a way to quickly provide (fake) data to new applications, UIs, and other software components.

The simulator needs to be able to quickly simulate a network of hosts communicating over various media, accurately portray a qaul.net network complete with cryptographic identity management, and finally provide a HTTP API mirroring that of the real qaul.net service, so applications can develop against a known-good testing state.

Quickly simulating a network of hosts is relatively easy. Using an existing graph datastructure library (petgraph), along with ancillary data structures, the simulator will build a world state model representing hosts as vertices and connections (over Wi-Fi, Bluetooth, and even Internet overlay connections) as edges. Then, the simulator will provide a “tick”-based simulation model in which messages are passed from host to host via each medium in a simulated timestep.

Accurately portraying a qaul.net network is a little harder, but not much more so. With the network simulator built up, each host needs only to be given a small amount of behavior and a cryptographic identity to begin to act like a real qaul.net network. This behavior will be parametric, so testing all kinds of scenarios (including adversarial ones) will be possible.

Providing a HTTP API mirroring the real qaul.net service is the final step, and will probably mean wrapping the simulator in an asynchronous shell so that a Futures-based HTTP library can run alongside it. Once this is complete, the webserver can be spun up and applications can be pointed to it as though it were a real network!

Progress So Far

Up to now, I’ve spent my time getting comfortable in the qaul.net Zulip chat and evaluating the fundamental abstractions that I’ll use to build the simulator core. I currently have about a hundred lines of code written, in addition to a few “spike” components that I wrote just to test out various concepts. Starting today, though, the real code is happening!

About Me

I’m Leonora, a computer science student at Beloit College. I’ve written a lot of Rust and really like the language, but I’ve spent most of the last two years working on data analysis applications like the Open Energy Dashboard and CancerIQ. I’m super excited to be working on the next generation of qaul.net and the open, decentralized internet!

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