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This project is a PoC for building a P2P mesh with focus in the browser, using webrtc connections. Authors: @agusaldasoro @hugoArregui

The concept is simple:

  • Extend the use of a webrtc signaling server in order to perform peer discovery and mesh status updates.
  • Peers will discover each other using the mesh status updates, and will connect randomly to each other. Using the mesh knowledge they obtain from the updates, each peer will maintain a view of the mesh in the form of an adjacency matrix. To broadcast a message, peers will take the graph described by the adjacency matrix and calculate the minimum spanning tree (MST) using Prism Algorithm (that is: a tree starting from the current peer and describing the path to every other peer in the mesh, reaching every other peer only once). Then, a package will be sent using the path described by the MST, including both the payload and the route to follow. The peers receiving the message will relay the message, if necessary, according to the packet's own rules.

Project structure

  • lib/: this is the P2P mesh library that runs in the peer
  • server/: the server implementation
  • simulation/: this is an example using the P2P mesh library
  • chat/: this is a web example using the P2P mesh library

See it on action: running the simulation

make install
make build

Start the server:

cd server
npm run start

Start some clients:

cd simulation
bin/spawn.sh

open localhost:8000 in your browser, there every client will have a link to see their adjacency matrix, their connection status and so on, it's also possible to view a graph like this:

Graph

Showing a picture of how peers are connected and, marked in red, the MST paths.

See it on action: chat example

The server must be runnning for this example, most browsers will prevent a websocket connection to localhost, so you may need to deploy the server somewhere or use a tool like ngrok

cd chat
npm ci
make start

This example has been tested in Chrome.

Open questions

  • Security: the server will share the mesh updates, so the server must be trusted to relay the information in a reliable way. Otherwise the security must be built-in using in the application protocol, by using encryption for example.
  • Network partitions: since each peer picks its connections at random, is possible (although very unlikely), to end up in a network partition in which a group of peers are isolated from another group. Since we are able to detect this case, we can use the server as a fallback mechanism. Other strategies are possible, like explicitly trying to connect to them, but they are out of the scope of this PoC.
  • Amount of connections: each peer will attempt to connect to the number of targetConnections, but will accept maxConnections. This values varies according to different use cases, since the browsers will not handle a big number of connections, so it's important to reach a balance between what the browser can handle, and an effective amount. Having more connections means the communication will be faster in the mesh, and the MST will be shorter.