The design of PaMaNet the Paderborn mobile ad-hoc network

Abstract

Wireless connectivity is state of the art for local area networks. Currently, most W-LAN networks rely on a centralized design with access points routing all inner and outbound traffic. These access points are intrinsic communication bottlenecks. Mobile Ad Hoc Networks (MANET) overcome this problem, because every participant serves as a simple node as well as a router. Current MANETs are restricted in scalability, because they rely on ooding mechanisms or complete routing tables. Other approaches, providing better scalability use clustering, yet network performance deteriorates in case of high node mobility.We describe the design of a PaMaNet, the Paderborn Mobile Ad Hoc Network, a MANET overcoming these problems providing scalability and reliability in a mobile scenario. When implemented, PaMaNet works with standard W-LAN IEEE 802.11 radio devices, provides IPv6 communication interfaces and works on personal computers under a standard Linux distribution.First, we present current routing protocols and classify them with respect to scalability and stability in dynamically evolving MANETs. Then, we discuss related research in the area of distributed hash tables and consistent hashing, used for relieving hot spots in the Web, storage area networks and peer-to-peer networks, which inspires the design of PaMaNet.PaMaNet consists of three main components: First, the embedding of the routing layer into IEEE 802.11 and IPv6 by using techniques used at the ad hoc support library (aslib) by Gupta et al. Second, the routing layer which combines a landmark routing, hierarchical clustering, consistent hashing for providing location dependent addresses and lookup-service for the location of nodes. Third, a peer-to-peer data storage system based on egoistic distributed caches enabling hop and traffic efficient data access on replicated data partitions.The routing layer incorporates a variety of new approaches. Link distances re ect the failure probability of links, which is estimated by the reciprocal age of the link. Then, we combine a landmarking system on this metric with the hierarchical layer graph yielding small landmark addresses and small routing tables. To balance the load of the distributed lookup-service for landmark addresses, a hierarchical weighted consistent hashing scheme is used. This ensures that each node receives an equal part of all landmark addresses. Using these mechanisms (regularly and on demand) PaMaNet adjusts IPv6 routing tables such that short stable routes are preferred.For the distribution of control data like landmark information PaMaNet uses a message box system interface to provide fast one-hop communication. On top of this system, PaMaNet provides a peer-to-peer data storage and lookup system that realizes time, traffic, and load efficient access using egoistic caches and data segmentation strategies.