INTEGRATING PEER-TO-PEER FUNCTIONALITIES AND ROUTING IN MOBILE AD-HOC NETWORKS Grant Millar (grant@seednet.eu) 1 , Alexandros Ladas (A.Ladas@kingston.ac.uk) 2 , Olayinka Adigun (O.Adigun@kingston.ac.uk) 2 , and Christos Politis (C.Politis@kingston.ac.uk) 2 1 Cylo Tech Ltd, Essex, United Kingdom 2 Wireless Multimedia and Networking (WMN) Research Group, Kingston University London, KT1 2EE London, United Kingdom ABSTRACT Mobile Ad-hoc Networks (MANETs) impose strict require- ments in terms of battery life, communication overhead and network latency, therefore optimization should be made to ap- plications and services such as domain name service (DNS), dynamic host configuration protocol (DHCP) and session ini- tiation protocol (SIP) if they are to be considered for use on MANETs. Due to the decentralized and self-organizing nature of MANETs, such applications could utilize a distributed name resolution/data storage service. Distributed Hash Tables (DHTs) enable these features by virtually organizing the network topol- ogy in a peer-to-peer (P2P) overlay. P2P overlays have been de- signed to operate on the application layer without knowledge of the underlying network thus causing poor performance. To address this problem, we propose and evaluate two different DHTs integrated with MANET routing in order to optimize the overall performance of MANET communications when P2P ap- plications and services are used. Both architectures share the same functionality such as decentralization, self-reorganization, and self-healing but differ in MANET routing protocol. Per- formance evaluation using the NS2 simulator shows that these architectures are suited to different scenarios namely increasing network size and peer velocity. Comparisons with other well- known solutions have proven their efficiency with regard to the above requirements. 1. INTRODUCTION P2P networks can be defined as decentralized application layer overlay networks where traffic flows on top of the physical net- work such as the Internet. Such networks are formed dynam- ically on-the-fly and rely on no fixed infrastructure such as servers. Distributed Hash Table (DHT) is a class of a decentral- ized distributed system and are widely used today on the Inter- net in various peer-to-peer systems for example providing name look-up services such as P2PSIP [1] or keeping track of peers in a file sharing system such as BitTorrent [2]. MANETs are physical networks consisting of wireless de- vices (normally Wi-Fi i.e. IEEE 802.11) or nodes such as smartphones, tablets, laptops, and sensor equipment among others. These devices are able to dynamically form wireless networks amongst themselves and thus akin to P2P networks, have no fixed or centralized infrastructure, instead rely on self- configuration. P2P overlays and MANETs share a common no- tion of rapid network setup, thus MANETs can be vital in sce- narios where an instant network deployment is needed. Such scenarios include ubiquitous computing, providing instant net- work and disaster recovery during emergency scenarios. One of the main challenges related to the real-world deployment of MANETs is efficient routing. Due to nodes physically moving in a 3-Dimensional spatial area, the most efficient route in terms of a specific metric (such as the fastest or most reliable route) may be constantly changing, therefore routes need to be re-evaluated regularly and route failures must be dealt with in a swift manner in order to reduce the impact. One can see that even on the surface both P2P networks and MANETs share some common properties such as being decen- tralized and self-organizing, as well as participants sharing their network resources to relay packets for others. The algorithms for routing in both technologies are focused on searching the net- work. In MANETs, the focus is searching for a route to a specific destination IP, whereas in P2P networks the focus is on search- ing for a route to a specific destination key and retrieving the data associated with the key. To achieve the former, MANETs use routing protocols running on the network layer whereas P2P networks can use DHTs to achieve key look-up. Many routing protocols have been proposed for MANETs, with most pertaining to a certain group determined on whether they proactively or reactively (or a hybrid) search the network for routes to a destination. Proactive MANET routing protocols build up a picture of the entire network by exchanging informa- tion about the network topology so that every node will even- tually know the shortest path to any destination in the network. The main overhead in this case is disseminating this topology information as it must be flooded in the network to all nodes. Re- active MANET routing protocols will remain idle until a packet is to be sent from a node. Before transmission of the packet, the route to the destination will be found usually by utilizing a one-off flooding algorithm to find the shortest or quickest path.