Mesh Networking Sebastian Büttrich, wire.less.dk edit: March

Agenda What is a mesh network? Why and where to deploy mesh networks? Mesh routing protocols Mesh Hardware Planning and implementing a mesh network Mesh case stories

Lab Agenda Lab: Flashing a wireless router Lab: Building a Freifunk Mesh (OLSR) - The 3 Villages Mesh Lab: Adding OpenWRT based mesh nodes (OLSR) – on mixed hardware (Linksys WRT54G, Ubiquiti NanoStation & Bullet,...)) plus optionally: Trying B.A.T.M.A.N., olsrd and batmand on laptops/phones, mesh potato

What is a mesh network? A mesh network is a network that employs one of two topologies: full mesh topology or partial mesh topology. In the full mesh topology, each node is connected directly to each of the others. In the partial mesh topology, nodes are connected to only some, not all, of the other nodes.

What is a mesh network? full mesh topology

What is a mesh network? Partial mesh topology

What is a mesh network? A network that handles many-to-many connections and is capable of dynamically updating and optimizing these connections In a wireless mesh network, all wireless cards are in ad-hoc mode (not infrastructure) Note: A mesh does not have to be (very) dynamic! Other terms: Mobile ad-hoc network (MANET)

Mesh - why and where? Mesh networks are ideal in all situations where central architecture is not suited Mesh networks can help avoid the need for expensive high towers Mesh networks are … – robust – dynamic – self healing – suited for user networks as well as infrastructure and long distance networks

Mesh - why and where?

Mesh networks make good use of community resources through sharing Lend itself nicely to favourable social models: – sharing – distributed responsibility – personal interest = shared interest Self-configuring and easy to set up – well... that may be argued :)... we will see in the Lab

Mesh - why and where?

Another field of mesh networking are Wireless Sensor networks Motes/sensors are often deployed over wide and inaccessible areas Strengths of mesh routing are essential in this case – self organization, self healing – no need for line of sight to central node

Mesh - why and where?

Quick quiz: mesh basics Radio cards are in what mode? Antennas – what type is good? Do we run DHCP? What wireless settings do we have to agree on?

Mesh routing Routing protocols are the engines or brains of mesh networking Routing protocols take care of... – Node discovery – Border discovery – Link metrics – Route calculation – IP address management – Uplink/backhaul management

Mesh routing Mesh routing for wireless networks is fundamentally different from routing for wired networks In wired networks, the best path is usually that with the smallest number of hops – see e.g. OSPF protocol Wired hops are typically either available or not available – i.e. the quality is 0% or 100%

Mesh routing In mesh routing, the state of a link can be anything inbetween 0% and 100% available Measuring link quality and calculating metrics is of central importance Expected Transmission Count (ETX) is a significantly better approach to metrics and routing than OSPF Routing protocols differ in how exactly the metrics and routes are calculated and kept

Mesh routing protocols Proactive: – OLSR (Optimized Link State Protocol) – B.A.T.M.A.N. (Better Approach to Mobile Ad-Hoc Networking) Reactive: – AODV (Ad-hoc on Demand Distance Vector) – SrcRR (MIT Roofnet) Hybrid: – HSLS (Hazy Sighted Link State Routing, CuWin) These are just some of the most relevant protocols in our context... there are many more!

Mesh routing: OLSR pure RFC-compliant OLSR simply minimizes the number of hops – however, that might not be the best choice for wireless networks Thus, ETX-based metrix were introduced: – Periodically send HELLO messages to everybody. – Record packet loss. – Calculate how many resends you would need for a succesful trip along any route. – This value = metric (cost) of the route.

Mesh routing: OLSR The success probability is NLQ x LQ, where NLQ is the Neighbour Link Quality of the link and LQ is its link quality. For example, if we have a NLQ of 60% and a LQ of 70%, the probability of a successful round trip is 60% x 70% = 0.6 x 0.7 = 0.42 = 42%. in the above case of NLQ x LQ = 42%, we expect on average 1 / 0.42 = 2.38 transmission attempts for a packet until it gets through. The value 1 / (NLQ x LQ) is called the Expected Transmission Count or ETX. Source:

Mesh routing: B.A.T.M.A.N. How does B.A.T.M.A.N. calculate routes? Rather than maintaining knowledge about all the nodes across the network, each node perceives and maintains only the information about the best next hop towards all other nodes. Thereby the need for a global knowledge about local topology changes becomes unnecessary. So, B.A.T.M.A.N. only remembers which direct neighbour gives the best chances to reach a certain destination.

Hardware for Mesh In principle, any computing device with the necessary CPU power and wireless interface can take part in a mesh network For example: Desktop or laptop PCs Dedicated mesh hardware, e.g. Fonera, Meraki, Meshnode a.o. Off-the-shelf, inexpensive wireless routers, reconfigured Mobile phones, PDAs, etc

The GPL firmware of the original Linksys WRT54 has been improved and forked into many types of firmware, e.g. OpenWRT, Freifunk, X-WRT, ROBIN (ROuting Batman Inside).. Examples of Hardware suitable for OpenWRT and Freifunk Firmware: Linksys WRT54G(L) Ubiquiti Asus WL500G Buffalo WHR-G54S D-Link DIR-300 Firmware for Wireless routers

Who can mesh? An up-to-date list of hardware compatibility is here: The list is long! Hardware for OpenWRT

Who can mesh? Pay attention to Hardware revisions if using OpenWRT/Freifunk on Linksys! Tested versions: Linksys WRT54G-v1.x|2.0|2.2|3.0|3.1|4.0 NOT 5.0 and up (wrong chipset, lack of memory) WRT54GL-v1.0| Price: circa EUR 60 The Linksys WRT54G

Dedicated mesh hardware Type: mesh node Price: from USD 40 = Accton Centralized management “Plug and Play” Open-mesh.com

Dedicated mesh hardware... not always quite so open Fonera & Meraki

Planning a mesh Planning a mesh is in equal parts a technical and an organizational/social process Questions of Implementation / Support / Maintenance / Ownership need to be carefully considered Distributed ownership models benefit from social gatherings (e.g. Organisation, device configuration, antenna soldering, etc) IP distribution via DHCP is missing in mesh networks – this demands focus on planning and communication

Planning a mesh IP planning

Planning a mesh Planning helps

Mesh cases Community network started in Berlin/Germany, to fill a gap in broadband (DSL/fiber) access Home of the Freifunk Firmware Number of Nodes: 500+ Berlin, many more cities with several 100s The Freifunk movement

Mesh cases The Freifunk movement 180 nodes (Oct 2005) this = graphviz visualization

Mesh cases Guifi.net 180 nodes (Oct 2005) this = graphviz visualization Spain Freifunk based > 6000 working nodes

Mesh cases Guifi.net 180 nodes (Oct 2005) this = graphviz visualization

Mesh cases Athens Wireless

Mesh cases Dharamsala / India 180 nodes (Oct 2005) this = graphviz visualization Using Linksys WRT54G with OpenWRT firmware Using OLSR with ETX Connecting non-profit organizations Developed by Dharamsala Information Technology Group / TibTec

Mesh cases Peebles Valley, Mpumalanga, South Africa Meraka Institute, CSIR Pretoria Using FreifunkFirmware < 10 nodes right now, but growing First node was the Aids care training and support (ACTS) clinic

Mesh cases Sengerema, Tanzania Sengerema Telecenter First shared mesh network in Tanzania Freifunk Firmware / Linksys WRT54GL Started in October 2008 with 12 clients To be extended Lakezone Wireless Expert Group

Mesh cases Sengerema: Reach

Mesh cases Sengerema: Planning

Mesh cases Sengerema: Site Survey

Mesh cases Sengerema: Node hardware

Mesh cases Sengerema: Installation

Mesh cases Sengerema: Installation

Mesh cases Sengerema: Opening

Mesh cases Sengerema: Customers

Further Reading OpenWRT Firmwarehttp://OpenWRT.org Good OpenWRT guidehttp://nbd.name/openwrt Freifunk Firmware and projecthttp://freifunk.net B.A.T.M.A.N. Dharamsala meshhttp://drupal.airjaldi.com/ Guifi.net, Spainhttp:// Many articleshttp://wikipedia.org Mesh networking URLs

Further Reading Mesh networking Books Corinna “Elektra” Aichele: Mesh Open Source Press 2007 available in english soon... maybe

“As a net is made up by a series of knots, so everything in this world is connected by a series of knots. If anyone thinks that the mesh of a net is an independent, isolated thing, he is mistaken. It is called a net because it is made up of a series of connected meshes, and each mesh has its place and responsibilities to other meshes.”

That was it... Thank you! Sebastian Büttrich, wire.less.dk edit: March