1. This is a research project 2. Project has next parts: 1) Research/investigation 2) Modelling/analysis 3) Implementation
мы рассматриваем клиентские сети
Only dynamic routing can allow and make use of redundante links. A router is able to make decisions about which link to use based on a set of configurable measures. Once the redundant links exist, if a link goes down, an alternative path around the failed node will be automatically found and used. Even if links do not actually go down, the routers can distribute the traffic load across the available paths in proportion to the bandwidth available on each path. Routers' reports about what they are doing make it easy to produce good statistics about network utilisation which would allow us to hilight areas of heavy traffic, for example, and plan acordingly. Using routers at a backbone level would allow people running Access Point to run pretty much networking software and formats. Routers can aggregate routes to subnets that are part of the same larger network into a single route to advertise to the rest of the world.
http://www.cse.unsw.edu.au/~nrl/researchprojects.htm#jqadir On Reducing Routing Overhead in MANET Ph.D Candidate: Quan Jun (Jerry) Chen Description: Reducing Routing overhead is one of the most important tasks in wireless network. Particularly, in Mobile Adhoc Network (MANET), where topology changes frequently, routing protocols may generate considerable routing overhead when conquering the uncertainty of mobile nodes. Excessive routing overhead consumes valuable resources, such as bandwidth and power, and causes frequent packet collisions, which finally degrade network throughput and end-to-end delay. In our work, we decompose routing protocols into two fundamental building blocks: 1) beacon broadcasting (route maintenance) and 2) flooding rebroadcasting (route discovery), and we propose two frameworks respectively to reduce routing overhead occurred. For the first one, we propose the framework of “Adaptive Beacon Broadcasting (ABB)”, which adapts beacon broadcasting to nodes mobility and traffic load. For the second one, by exploiting the relationship between flooding distance and the number of hops, we propose “Distance-based Flooding Restriction (DFR)”. Both frameworks are evaluated by theoretical model and simulation. The results show ABB and DFR can significantly reduce routing overhead without compromising other performance metrics.
Pro-active This type of protocols maintains fresh lists of destinations and their routes by periodically distributing routing tables throughout the network. The main disadvantages of such algorithms are - 1. Respective amount of data for maintenance. 2. Slow reaction on restructuring and failures. Reactive This type of protocols finds a route on demand by flooding the network with Route Request packets. The main disadvantages of such algorithms are - 1. High latency time in route finding. 2. Excessive flooding can lead to network clogging. Flow-Oriented This type of protocols finds a route on demand by following present flows. One option is to unicast consecutively when forwarding data while promoting a new link The main disadvantages of such algorithms are - 1. Takes long time when exploring new routes without a priori knowledge. 2. May refer to entitative existing traffic to compensate for missing knowledge on routes. Adaptive This type of protocols combines the advantages of proactive and of reactive routing. The routing is initially established with some proactively prospected routes and then serves the demand from additionally activated nodes through reactive flooding. Some metrics must support the choice of reaction. The main disadvantages of such algorithms are - 1. Advantage depends on amount of nodes activated. 2. Reaction to traffic demand depends on gradient of traffic volume. Hybrid This type of protocols combines the advantages of proactive and of reactive routing. The routing is initially established with some proactively prospected routes and then serves the demand from additionally activated nodes through reactive flooding. The choice for one or the other method requires predetermination for typical cases. The main disadvantages of such algorithms are - 1. Advantage depends on amount of nodes activated. 2. Reaction to traffic demand depends on gradient of traffic volume.
Restrict routing area. Efficient routing area definition. Optimal routing inside the effective routing area. Not guaranteed — outside. Change optimization radius to control network services' QoS. Limit routing overhead externally in order to provide this requirement. Trade-off between traffic overhead and routes quality.
Арность дерева — число несвязанных узлов в дереве, с которыми связан каждый узел дерева Дерево — худший из возможных вариантов маршрутизации
Общая идея такая: чем большее число узлов каждый маршрутизатор (node в данном случае) будет использовать для поиска маршрута, тем большие накладные расходы
d(v i ,v j ) – distance between v i and v j - min hop count With right R i number nodes will have all necessary information for optimal route definition. Calculation expenses for effective route search algorithms are low.
OLPC Mesh networking improvements
OLPC Mesh network improving Arina Rudakova (Saint-Petersburg Elelectrotechnical University «LETI») 3rd FRUCT seminar Saint-Petersburg 23 May 2008
Agenda Introduction Problem definition Domain analysis Solution Project timeline
One Laptop Per Child Home: http://laptop.org The mission of the One Laptop per Child association is to develop a low-cost laptop—the "XO Laptop"— to revolutionize how we educate the worlds children. Goal is to provide children around the world with new opportunities to explore, experiment, and express themselves.
XO laptops hardware Dimensions: 242mm × 228mm × 32mm CPU x86-compatible processor AMD Geode LX-700 433 Mhz, 64KB each L1 I and Dcache; at least 128KB L2 cache DRAM memory: 256 MiB dynamic RAM BIOS: 1024KiB SPI-interface flash ROM Mass storage: 1024 MiB SLC NAND flash, high-speed flash controller Display: Liquid-crystal display: 7.5” dual-mode TFT display Keyboard: 80+ keys, 1.0mm stroke; sealed rubber-membrane key-switch assembly Gamepad: Two sets of four-direction cursor-control keys Touchpad: Dual capacitance/resistive touchpad; supports written-input mode Audio: AC’97 compatible audio subsystem Integrated color video camera: 640 x 480 resolution at 30 FPS Wireless Networking: Integrated 802.11b/g (2.4GHz) interface; 802.11s (Mesh)networking supported; dual adjustable, rotating antennas support diversity reception;capable of mesh operation when CPU is powered down;
Neighborhood:Collaboration interface The Neighbourhood view displays all the connected XO laptops within a child’s community, and what activities they are sharing. Each child is represented by a different colour If there is a shared document or activity being collaborated on by a number of children, it will show up within this view.
XO Mesh goals Ability to act as a mesh point when laptops main CPU is off. Support for asymmetric links/paths. Incremental releases—mesh networking is available immediately on XO; Upgrades will continue to improve functionality and adherence with standards. Simultaneously acts as a mesh point and an infrastructure node. Standards Compliance: follow 802.11s draft when possible.
Mesh network types Infrastructure wireless mesh networks: Mesh routers form an infrastructure for clients. Client wireless mesh networks: Client nodes constitute the actual network to perform routing and configuration functionalities. Hybrid wireless mesh networks: Mesh clients can perform mesh functions with other mesh clients as well as accessing the network
Routing overhead reasons Nodes number influence on the amount of control traffic Network changes dynamics influence on the amount of control traffic Route length influence on the amount of control traffic
Ad-hoc Routing types Pro-active or Table-driven Reactive Routing or On-demand Flow Oriented Adaptive Routing or Situation-Aware Hybrid (Pro-Active and Reactive)
Industrial and open source implementations AWDS (Ad-hoc Wireless Distribution Service) http://awds.berlios.de/ DSDV (Highly Dynamic Destination-Sequenced Distance Vector routing protocol) – based on Bellman-Ford Routing Protocol AODV (Ad-hoc On-demand Distance Vector) Mobile Ad-hoc On-Demand Data Delivery Protocol MPRDV (Multipoint Relay Distance Vector protocol) SSR (Signal Stability Routing protocol) PLBR (Preferred link based routing) TORA (Temporally-Ordered Routing Algorithm routing protocol) HRPLS (Hybrid Routing Protocol for Large Scale Mobile Ad-Hoc Networks with Mobile Backbones) HSLS (Hazy Sighted Link State routing protocol) ZRP (Zone Routing Protocol)
Solution components Routing area restriction Dynamic selection of optimization radius External definition of routing overhead
Routing overhead chart m — tree arity n — nodes number R — dynamics
Possible reasons of routing overhead increase Number of nodes increase Network dynamics increase Network radius increase Using aggressive updating strategy
Routing area restrictionFor effective routing area definition we should introduce some definitions.G(t)=<V,E>, where V – set of nodes, E – archesG(t) describes network topologyd(vi,vj) – distance between vi and vjvi: Ri>0, G (vi , Ri ) ⊂ G (t ), d (vi , v j ) ≤ RiChoose Ri with regard to time needed for collection of information about G(vi,Ri)G(vi,Ri) - effective routing area for vi, G (vi , Ri ) ≡ R(vi )
External and internal routing records External routing records (only in edge nodes) Internal routing records (always true)
Routing optimization area Local optimization Global optimization Optimization in restricted area
Local sample Information collection – 1 hop Route defining – 1 hop «Trust» zone – 1 hop Control traffic is minimum
Global sample Information collection – whole net Route defining – whole net «Trust» zone – whole net Control traffic is maximum
Restricted sample Information collection is restricted with R Route defining – within R radius «Trust» zone – within R radius Control traffic is restricted
Failure detection At first only one router knows about a route failure After the message to sender about the impossibility of passing, the whole effective routing area is informed The sender gets informed when its timer is over
Global planThe past 2007 Autumn, generic task definition, domain investigation 2008 Winter, getting XO devices, experience XO system programmingThe future 2008 Summer, public presentation our of solution ideas (conference proceedings or paper) 2008 Autumn, implement modules for NS2 and simulations 2008 Winter, contribute some code for XO laptops 2009 Spring, defence of the master thesises at LETI