Cloud Hub:  Yet another implementation of wireless mesh networks

Introduction

This is an implementation of wireless mesh networks.  It is intended to be a firmware upgrade for inexpensive wireless routers such as the Linksys WRT54G.  The idea is to make it easy to build up wireless coverage throughout large homes, office buildings, and multiple-building campuses by setting up inexpensive routers that will configure themselves into optimal wireless meshes.  Clients can then gain access to the internet either by attaching cat-5 cable to one of the boxes, or by joining the mesh as an "ad-hoc leaf node" which requires no special software or drivers.

Cloud hub is a link-level implementation, meant to be thought of as a single large "ethernet hub".

From the user's perspective, a hub is a simple device:  plug it in, and then attach cat-5 cables to it.

The goal of the cloud hub project is to make a wireless mesh close to this level of simplicity:

Get a new wireless box, install the cloud hub firmware, plug it in, and it finds your other cloud hub boxes by itself.  Connect your computer to it with a cat-5 cable, or set your computer's wifi card to ad-hoc mode, and you're done.  (Well, almost.  If you want, you can access a simple internal configuration web page and set wifi parameters such as SSID and WEP to your preferences.)

Configuration, to the extent that it is necessary, is uncluttered and simple.

This project represents an experiment in system design philosophy: Do just one task, and do it in a simple, clean, understandable, and reliable way.  Have different boxes do different things.  This firmware provides a simple, clean and minimal configuration web interface.  A collection of routers with this firmware collectively implement a single collision domain.  The individual cloud boxes do not have IP addresses.  In cloud mode, the boxes do not provide DHCPD service; have another box do that.  No firewalls; have another box do that.  No NAT; have another box do that.  (Maybe have a single non-cloud server box, or even your DSL/cable modem, do all of these things.)  Cloud hub provides a single conceptually simple service: a collision domain implemented wirelessly over an extended area.

Use Cat-5 cable to connect one of your cloud boxes to a DSL or cable modem, or a LAN that is connected to the internet.

The wireless routers continuously sense wireless signal strength.  They update their connectivity among themselves automatically to optimize overall signal quality.

In addition to wireless connections, the cloud hub boxes sense each other via cat-5 connections.  So, if you have more than one cloud hub box that happens to be attached to your LAN, those boxes will find each other that way and integrate with each other via the cat-5 connection.

The cloud hub software uses wifi ad-hoc mode.  It permits standard unmodified ad-hoc devices to integrate into the mesh as leaf nodes.  In other words, you can use a wifi-equipped laptop computer or beige box with a wifi card in it.  After configuring such a device into ad-hoc mode, it will be integrated into the wireless mesh and gain access to the network.

Ad hoc clients can roam throughout the mesh, and are dynamically handed off to the nearest, best-signal cloud box.

The cloud boxes create a spanning tree of connections among themselves, but make an effort to communicate parsimoniously to reduce wireless traffic.  Additional non-local arcs are added to the graph in those cases where signal quality permits it.  Each node has the responsibility to make sure that its spanning-tree neighbors have messages propagated to them, but if a node can construct a proof that its neighbor has the message (having overheard it from some other box in the cloud), it will refrain from redundantly transmitting it.

The internal web server has a display that shows a continuously updated picture of the topology of the entire cloud.

The web server has a display of the wireless environment of the entire cloud.  Each node monitors its immediate environment for other wifi access points and activity.  About once per minute it transmits this information throughout the cloud.  So, every cloud box can show the user all of the wifi activity seen by every node throughout the cloud.

From the internal configuration web server of a single cloud box, it is possible to update the wifi parameters of all of the boxes in the cloud.  (As a security check, this will only work for boxes that share the same administrator password and current wifi parameters.)

Security is currently 64-bit or 128-bit WEP.

The indicator lights on the front of the WRT54G blink so as to provide a handy picture of mesh status.  The lights on the front of a particular WRT54G blink out the number of boxes in the cloud of which it is a member, and how many of those boxes it can sense directly with adequate signal strength.

In sum, the cloud hub project embodies few novel ideas for mesh networking combined with attention to detail to create reliable, easy-to-deploy wireless infrastructure.