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Configurable Routing in Ad-Hoc Networks

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Configurable Routing in Ad-Hoc Networks Configurable Routing in Ad-Hoc Networks Nadine Shillingford and Christian Poellabauer Department of Computer Science and Engineering University of Notre Dame Notre Dame, IN 46556 fnshillin, [email protected] Abstract— The actual use of a wireless ad-hoc network or run across the network, will be unknown a-priori. Further, ad- its operational parameters may be unknown before deployment hoc networks may be accessed by varying numbers of clients or they may change during the life time of a network. This (users), with different applications and differing expectations requires that an ad-hoc network be configurable to the unique needs of a client and that multiple clients can configure the on QoS. Therefore, it will be essential to make configurability network simultaneously. The QoS metric(s) used in the selection and customizability of future ad-hoc networks a key design of routes in an ad-hoc routing protocol can strongly affect the feature. network’s performance. Unfortunately, the majority of existing Toward this end, this work introduces the CMR (Con- routing protocols support only one or two fixed metrics in route figurable Mesh Routing) toolkit which provides an easy-to- selection. We conducted a survey of over 40 routing protocols published from 1994-2007 which indicated that 90% of the use API for ad-hoc networks, allowing applications or users protocols use one or two metrics and only 10% use three to to implement their own routing protocols and QoS metrics. four metrics in route selection. Toward this end, we propose a While our prototype implementation supports four of the most modular routing toolkit for ad-hoc networks, where users and popular QoS metrics, it is easily extensible and we expect that applications can initiate route discoveries that best suit their QoS future versions will cover a large variety of QoS metrics. requirements. To achieve this, we introduce CMR (Configurable Mesh Routing), which enables network users to initiate route The main contribution of this work is the introduction of discoveries that establish routes customized to their unique needs the concept of configurable ad-hoc network routing design (including multi-path routes with different QoS specifications for and implementation of a toolkit supporting such configuration. each path). Our experiments on a 20-node mesh testbed illustrate While CMR will enable us to configure, re-configure, and the ability of CMR to produce routes that mimic the behavior of existing protocols as well as its usefulness in deploying novel, customize an ad-hoc network after deployment, it will also be customized, multi-QoS routes. a valuable tool for rapid prototyping, testing, and comparison of novel routing protocols and for teaching the differences I. INTRODUCTION and inner workings of routing in wireless networks. We have The vast majority of routing protocols for ad-hoc networks implemented CMR as a middleware tool and used it to develop such as Dynamic Source Routing (DSR) [9], Dynamic Des- numerous routing protocols on a network of Linux-based tination Sequence Distance-Vector Routing (DSDV) [18], and wireless mesh routers. Zone Routing Protocol (ZRP) [6] establish routes based on a single Quality-of-Service (QoS) metric, giving the network II. RELATED WORK (and all its users) little choice or flexibility in route establish- ment. Only a few protocols consider multiple metrics, e.g., Routing protocols for ad-hoc networks have received signif- Admission Control enabled On demand Routing (ACOR) [10] icant attention over the last several years. Most ad-hoc network and Ad-hoc QoS on-demand Routing (AQOR) [23] attempt to routing protocols consider one or two QoS metrics only and include the metrics bandwidth and end-to-end delay in route all applications and clients in such a network must use the selection. We conducted a study of more than 40 routing same protocol and metrics. Once a network is deployed, these protocols for ad-hoc networks, which indicated that 90% of metrics can only be changed by modifying the routing layer the protocols use only one or two metrics in route selection. on each network node. We have studied numerous routing The other 10% use three to four metrics in route selection. protocols that have been proposed from 1994-2007 and Table I However, these routing protocols provide little flexibility be- shows a list of popular routing protocols and the QoS metrics yond their supported QoS metrics. that they implement. The protocols proposed by [1], [15], [25], While we move toward commercial-off-the-shelf available and [2] are abbreviated since no acronyms are specified and easily deployable ad-hoc networks, it will increasingly in the literature. The vast majority of protocols support a be the case that operational parameters of the network, such single metric; only 10% of these routing protocols implement as physical environment, network topology, potential interfer- more than two QoS metrics. Three of the routing protocols ences and hazards, and even the exact type of applications to investigated in our study [13, 17, 10] indicate that they can be extended to allow more QoS metrics (indicated by a ‘+’ This work is supported in part by NSF under grant number CNS- 0545899 and by the Army Research Office under grant number W911NF- sign in Table I), but these papers suggest the extensions as 06-1-0120. future work and still remain to be completed. Table II gives a summary of the number of protocols which implement the extendable and it has been used to implement different routing six main metrics identified during our study. protocols such as ClickDSR [3]. In contrast, CMR purely focuses on the customized deployment of routing layers in Metric Protocol ad-hoc networks and provides the mechanisms to support Shortest path DSDV, CGRS, WRP, DFR, IARP, MMRP, multiple QoS metrics simultaneously. While CMR has been OLSR, TBRPF, AODV, DSR, TORA, ARA, Ariande, AOMDV, BSR, CHAMP, DYMO, developed as middleware tool for Unix systems, it could also DNVR+, IERP, LUNAR, MOR, DQSRa, be implemented by extending Click (which will be considered ZRP, GSR, FSR+, CBRP, LQSR, STAR in our future work). Link quality/strength Babel, Guesswork, SSA, LQSR, QuaSAR, DQSRb Other configuration tools such as the x-kernel [8], Net- Reliability Guesswork, BSR, LBR, ABR graph [4], and the Active Network Research projects [20, b Bandwidth LSQR , ACOR+, AQOR, QuaSAR, 21] offer flexibility and reusability. In the x-kernel, one can DQSRb, FQMM, OLSMQc, QRP using TDMAd create different protocols out of a library of components. Latency LSQRb, ACOR+, AQOR, QuaSAR, However, x-kernel needs to be configured and executed in b DQSR , HSR addition to programming of the individual protocols. CMR Energy/Battery power QuaSAR, Guesswork is focused mainly on routing protocols and does not require aDistributed QoS Routing protocol (abbr.). any additional configuration except the starting of a service bA link-state QoS routing protocol (abbr.). on each network node. The ANTS [22] toolkit is based on cThe On-Demand Link-State Multi-path QoS Routing Protocol (abbr.). the concept of active networks. In ANTS a protocol is defined d QoS Routing Protocol for Ad-Hoc Networks using TDMA (abbr.). as a collection of related code groups that are treated as a TABLE I single unit of protection by the active nodes. The focus of ROUTING PROTOCOLS BY QOSMETRICS ANTS is on programmable networks, whereas CMR’s goal is the customization of the routing layer in ad-hoc networks. The XORP project [7] is a modular routing kit which pro- vides open source implementations of major Internet protocols QoS Metric Number of Protocols Shortest Path 28 such as BIP and OSPF. XORP offers extensibility and also Bandwidth 7 promises the user the ability to implement new protocols. Latency 6 However, compiling of XORP takes up to an hour and requires Reliability 5 Link Quality/Capacity 6 1.4GB of free disk space. In addition, XORP does not have its Energy 2 own forwarding system but instead depends on the forwarding TABLE II system of the underlying operating system. Although, the goal ROUTING METRICS IN NUMBERS of XORP is similar, CMR offers a more compact system for implementing routing protocols in less time and with its own forwarding system. In the QuaSAR [14] protocol, the authors implement four In comparison to these previous efforts, an important design different QoS metrics (battery power, signal strength, band- feature of CMR is its easy deployment and ease-of-use, e.g., it width, and latency). The route discovery algorithm selects does not require dynamic code distribution or reconfiguration routes based on these collected metrics and a precedence/rank- of a kernel and the QoS-metrics for route discovery are ing passed down from the application (if the application does determined using a simple rule language. not specify a precedence, then the default metric precedence is battery power, signal strength, bandwidth, and latency). While III. PRELIMINARIES QuaSAR supports the largest number of QoS metrics of the investigated protocols, it is still inflexible in that an application CMR is designed for wireless ad-hoc networks, including can only give a precedence for route selection and not add or mesh networks, mobile ad-hoc networks (MANETs), and eliminate metrics. sensor networks. An ad-hoc network is a self-configuring The RSVP [24] protocol is used by a host to request specific network that does not have a fixed infrastructure. Nodes in QoS from the network. It is also used by routers to deliver QoS such networks can be dedicated (mesh) routers, sensor devices, requests to all nodes along the downstream paths. RSVP estab- gateway devices, and numerous end devices such as laptops, lishes and maintains state to provide the requested service. It handhelds, or cell phones.
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