Mesh Networks Sri Edupuganti
Internet ETHERNET WIRELESS The Wireless Paradox: Lots of Wires Expensive, difficult to install, and long installation time, especially in outdoor deployments
Traditional vs Ad-hoc Network Traditional Mobile Ad-hoc
Evolution of Mesh • It takes a lot of wires to build a wireless network • If all you have is a hammer every problem looks like a nail • i.e. AP’s alone are not the answer • The original embodiment of mesh as a wireless peer to peer version of the Internet is incomplete: We moved the mesh “one node in”. • i.e. clients are not part of the mesh • Wireless backhaul Mesh is not the same as WiFi • Mesh can be the glue to join separate networks together
What is Wireless Mesh Network? • A wireless mesh network is a mesh network created through the connection of wireless access points installed at each network user's locale. • Each network user is also a provider, forwarding data to the next node. • The networking infrastructure is decentralized and simplified because each node need only transmit as far as the next node. • Wireless mesh networking could allow people living in remote areas and small businesses operating in rural neighborhoods to connect their networks together for affordable Internet connections.
Mesh topology definition • A mesh network is a network that employs one of two connection arrangements, 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." Full and Partial Mesh Network
Access Point and Backhaul Routerof Mesh Network Like any Wi-Fi access point, the access point in the mesh router serves the mobile users in the area. The backhaul side of the device wirelessly relays the traffic from router to router until it reaches a gateway that connects to the Internet or other private network via a wired or other wireless connection.
Network Architecture of Wireless Mesh Network • In the wireless mesh network, a node can send and receive messages, and it also functions as a router and can relay messages for its neighbors. Multiple nodes cooperate to relay a message to its destination. • Through the relaying process, a packet of wireless data will find its way to its destination, passing through intermediate nodes with reliable communication links • The mesh topology enhances the overall reliability of the network, which is particularly important when operating in harsh industrial environments.
Configuration of Mesh Network • Networks can be configured in one of several ways such as: (1) All the BSs, and only the BSs, are gateways to the wireless network, (2) none of the BSs are gateways (3)the BSs are gateways (possibly with a limited capacity) along with other specific gateways, (4)Every BSs and the MUsit serves are an IP-subnet and all these subnets form a single IP-network.
Mesh networks –motivations & expectations • Until now, mesh networks have most often proposed for urban scenarios and municipality networks • But there is big potential for rural and remote connectivity scenarios
Advantages of Mesh Networks • Decreased need for Internet gateways • Collaborative redundant backup technology, which insures data security in the event of disk failure • The ability to configure routes dynamically • Lower power requirements, which could potentially be met by low-cost or renewable energy sources • Increased reliability: Each node is connected to several other nodes and if one drops out of the network, its neighbors simply find another route. • Since mesh or multi-hop networks use low power transmissions to reach only the nearby nodes there is less interference with radio signals from other nodes.
Why Wireless Mesh Network? Reliable routing Flexible coverage
Mesh Hardware and Software Examples Hardware LinkSys WRT54G Mesh node 4G Access cube Mesh AP Software MeshLinux QuWin Pebble Zebra/Quagga OpenWRT
Single, Dual, Triple Radio Mesh Routers • Mesh routers can employ one, two or three radios. • A single-radio router shares bandwidth between users and the backhaul. • If two radios are used, one is dedicated to the frontside clients and the other to the backhaul. • In three-radio routers, two radios are used for the backhaul and can transmit and receive • simultaneously over different Wi-Fi channels , such as the systems from BelAir Networks • (www.belairnetworks.com) and MeshDynamics (www.meshdynamics.com).
Mesh routing protocols:Elements of mesh routing A major benefit of wireless mesh networks is path diversity, which provides many routes to the central network in case one of the routers fails or its transmission path is temporarily blocked. The choice in routing algorithm is critical, and numerous mesh algorithms have been used over the years. • Node discovery• Border discovery• Link metrics• Route calculation• IP address management• Uplink/backhaul management
Mesh routing protocols: Types Proactive(Tabledriven) • OLSR (Optimized Link State Routing protocol)OLSREXT,QOLSR • TBRPF (Topology Broadcast based on ReversePath Forwarding routing protocol) • HSLS (Hazy Sighted Link State routing protocol) • MMRP (Mobile Mesh Routing Protocol), short: MobileMesh • OSPF (Open Shortest Path First) • Proactive (Tabledriven) Proactive checking of Link state and updating of routing tables – high complexity and CPU load, high performance • Reactive (Ondemand) Reacting on detection problems (nonworking routes) – less demanding on CPU • Lines between types are not strict • More and mixed types exist Reactive (Ondemand) • AODV
Mesh routing protocols OLSR • OLSR is a routing protocol for mobile ad-hoc networks. The protocol is proactive, table driven and utilizes a technique called multipoint relaying (MPR) for message flooding. • OLSRD is meant to be a well structured and well coded implementation that should be easy to maintain, expand and port to other platforms. One of the most promising and stable protocols MMRP(MobileMesh) • Mobile Mesh contains 3 separate protocols, each addressing a specific function Link Discovery – a Simple “Hello” Protocol Routing Link - State Packet Protocol Border Discovery Enables external tunnels • Developed by Mitre (with military interest involved) OSPF • Calls for the sending of linkstate advertisements (LSAs) to all other routers within the same hierarchical area. Information on attached interfaces, metrics used, and other variables included in LSAs. • OSPF routers accumulate linkstate information, use the SPF algorithm to calculate shortest paths AODV • The Ad hoc On Demand Distance Vector (AODV) protocolis a routing protocol designed for mobile ad hoc networks. ...enables dynamic, self starting, multihop routing between computers.
Performance Issues in Mesh Network • Throughput • Latency • Scalability • Security • IP distribution • Latency obviously has to grow with number of hops • • Effects of latency dependent on application • • Example VoIP: latency can be felt from 170ms on, but sometimes walkie talkie with 5 s delay is better than nothing • IP distribution in mesh networks is far from trivial • DHCP in private IP ranges is unproblematic, but what happens when a mesh meets a neighbour mesh? • Ipv6 might solve many issues, but is not implemented widely yet • Ad hoc networks per definition need to talk to clients before they know them this imposes an inherent security challenge! • Vulnerability to Denial of Service attacks • Mesh has not been tested in real life with more than a few dozen nodes • Commercial implementations (200 nodes? 10,000 nodes?) often do not share (true) experience – and are therefore hard to evaluate
Issues in Mesh Networks • Multihop performance degradation • Exponential decay, linear decay, or k-asymptotic? • Multiple Radios and preventing dynamic frequency oscillations in a self aware network • Scalability and bridging • Most meshes are really small, and joined together • IEEE 802 TGs is specifying 32 node maximums! • How to manage disjoint but cooperating meshes • Multiple loop-free Mesh portals (partially solved, but not widely adopted) • Mesh Security (solved) • Compatibility (intra-mesh, and inter-mesh)
DEPLOYMENT ISSUES • Practical deployment experience shows that simple models, while useful, are largely wrong. • Metrics for routing need to take into consideration expected throughput based on network measurement. • Self organization is critical, but currently lacking.
Conclusion • • Mesh networks can handle many to many connections and are capable of dynamically updating and optimizing these connections • • WMN’s are a promising technology for next generation wireless networking. • Many application scenarios are stimulating its rapid development. • However, to strengthen the market penetration and secure the success of WMN’s, more research is needed.
Questions • What are functional components of Mesh Network? Ans: Routing Functionality(L2 or L3), Access point, Gateway Mesh point, Mesh Portal, Base station and Mobile station. • What are advantages of using Mesh Network? Ans: Self forming, Self healing, Self balancing, Increased Performance and coverage, Lower Infrastructure and Operational costs, and Increased Reliability. • What are the issues in Wireless Mesh Networks? Ans:Throughput, Latency, Scalability, Security and IP distribution
References • Kevin DeMartino, “An Architecture for a Seamless Mesh Network”, IEEE Communications Magazine • http://www.itrainonline.org/itrainonline/mmtk/wireless_en/17_Mesh_Networking/17_en_mmtk_wireless_mesh-networking_slides.pdf • http://www.oreillynet.com/pub/a/wireless/2004/01/22/wirelessmesh.html • http://en.wikipedia.org/wiki/Wireless_mesh_network • http://en.wikipedia.org/wiki/Mesh_network • http://en.wikipedia.org/wiki/Ad_hoc_routing_protocol_list • http://wifinetnews.com/archives/003972.html • http://www.sensorsmag.com/articles/0203/38/main.shtml
References • IAN F. AKYILDIZ, GEORGIA INSTITUTE OF TECHNOLOGY,”A survey on wireless mesh network” • Kamlesh Rath, Lalit Kotecha, Howard Persh, Deb Ranjan Das, Dat Ton, “Scalable Connection Oriented Mesh Proposal ” • STEFANO M. FACCIN, MESH WLAN NETWORKS:CONCEPT AND SYSTEM DESIGN • Rainer Baumann, Olga Bondareva, A Macro Mobility and Multihoming Notification Protocol for Wireless Mesh Networks implementing Mobile IP and SHIM6 • http://www.intel.com/technology/comms/cn02032.htm • ieeexplore.ieee.org/iel5/35/32334/01509968.pdf • ieeexplore.ieee.org/iel5/2188/19625/00909581.pdf?arnumber=909581 • www.answers.com/topic/wireless-mesh-network • www.eng.ucy.ac.cy/toumpis/courses/ECE453/papers/mesh2.pdf • www.apricot.net/.../1%20-%20Danny%20Ng/Apricot%202004%20Wireless%20Mesh.pdf • Many IEEE papers on Mesh and Wireless Mesh Networks. • Many documents and links related to Mesh networks and Wireless Mesh Networks in google.com and ask.com