Showing papers on "Routing table published in 2009"

A case for bufferless routing in on-chip networks

Abstract: Buffers in on-chip networks consume significant energy, occupy chip area, and increase design complexity. In this paper, we make a case for a new approach to designing on-chip interconnection networks that eliminates the need for buffers for routing or flow control. We describe new algorithms for routing without using buffers in router input/output ports. We analyze the advantages and disadvantages of bufferless routing and discuss how router latency can be reduced by taking advantage of the fact that input/output buffers do not exist. Our evaluations show that routing without buffers significantly reduces the energy consumption of the on-chip cache/processor-to-cache network, while providing similar performance to that of existing buffered routing algorithms at low network utilization (i.e., on most real applications). We conclude that bufferless routing can be an attractive and energy-efficient design option for on-chip cache/processor-to-cache networks where network utilization is low.

Pathlet routing

Abstract: We present a new routing protocol, pathlet routing, in which networks advertise fragments of paths, called pathlets, that sources concatenate into end-to-end source routes. Intuitively, the pathlet is a highly flexible building block, capturing policy constraints as well as enabling an exponentially large number of path choices. In particular, we show that pathlet routing can emulate the policies of BGP, source routing, and several recent multipath proposals. This flexibility lets us address two major challenges for Internet routing: scalability and source-controlled routing. When a router's routing policy has only "local" constraints, it can be represented using a small number of pathlets, leading to very small forwarding tables and many choices of routes for senders. Crucially, pathlet routing does not impose a global requirement on what style of policy is used, but rather allows multiple styles to coexist. The protocol thus supports complex routing policies while enabling and incentivizing the adoption of policies that yield small forwarding plane state and a high degree of path choice.

SOAR: Simple Opportunistic Adaptive Routing Protocol for Wireless Mesh Networks

Abstract: Multihop wireless mesh networks are becoming a new attractive communication paradigm owing to their low cost and ease of deployment. Routing protocols are critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along predetermined paths and face difficulties in coping with unreliable and unpredictable wireless medium. In this paper, we propose a simple opportunistic adaptive routing protocol (SOAR) to explicitly support multiple simultaneous flows in wireless mesh networks. SOAR incorporates the following four major components to achieve high throughput and fairness: 1) adaptive forwarding path selection to leverage path diversity while minimizing duplicate transmissions, 2) priority timer-based forwarding to let only the best forwarding node forward the packet, 3) local loss recovery to efficiently detect and retransmit lost packets, and 4) adaptive rate control to determine an appropriate sending rate according to the current network conditions. We implement SOAR in both NS-2 simulation and an 18-node wireless mesh testbed. Our extensive evaluation shows that SOAR significantly outperforms traditional routing and a seminal opportunistic routing protocol, ExOR, under a wide range of scenarios.

Shim6: Level 3 Multihoming Shim Protocol for IPv6

Abstract: This document defines the Shim6 protocol, a layer 3 shim for providing locator agility below the transport protocols, so that multihoming can be provided for IPv6 with failover and load sharing properties, without assuming that a multihomed site will have a provider independent IPv6 address prefix which is announced in the global IPv6 routing table. The hosts in a site which has multiple provider allocated IPv6 address prefixes, will use the Shim6 protocol specified in this document to setup state with peer hosts, so that the state can later be used to failover to a different locator pair, should the original one stop working.

An optimal probabilistic forwarding protocolin delay tolerant networks

Abstract: Due to uncertainty in nodal mobility, DTN routing usually employs multi-copy forwarding schemes. To avoid the cost associated with flooding, much effort has been focused on probabilistic forwarding, which aims to reduce the cost of forwarding while retaining a high performance rate by forwarding messages only to nodes that have high delivery probabilities. This paper aims to provide an optimal forwarding protocol which maximizes the expected delivery rate while satisfying a certain constant on the number of forwardings per message. In our proposed optimal probabilistic forwarding (OPF) protocol, we use an optimal probabilistic forwarding metric derived by modeling each forwarding as an optimal stopping rule problem. We also present several extensions to allow OPF to use only partial routing information and work with other probabilistic forwarding schemes such as ticket-based forwarding. We implement OPF and several other protocols and perform trace-driven simulations. Simulation results show that the delivery rate of OPF is only 5% lower than epidemic, and 20% greater than the state-of-the-art delegation forwarding while generating 5% more copies and 5% longer delay.

Routing in Delay-Tolerant Networks Comprising Heterogeneous Node Populations

Abstract: Communication networks are traditionally assumed to be connected. However, emerging wireless applications such as vehicular networks, pocket-switched networks, etc., coupled with volatile links, node mobility, and power outages, will require the network to operate despite frequent disconnections. To this end, opportunistic routing techniques have been proposed, where a node may store-and-carry a message for some time, until a new forwarding opportunity arises. Although a number of such algorithms exist, most focus on relatively homogeneous settings of nodes. However, in many envisioned applications, participating nodes might include handhelds, vehicles, sensors, etc. These various "classesrdquo have diverse characteristics and mobility patterns, and will contribute quite differently to the routing process. In this paper, we address the problem of routing in intermittently connected wireless networks comprising multiple classes of nodes. We show that proposed solutions, which perform well in homogeneous scenarios, are not as competent in this setting. To this end, we propose a class of routing schemes that can identify the nodes of "highest utilityrdquo for routing, improving the delay and delivery ratio by four to five times. Additionally, we propose an analytical framework based on fluid models that can be used to analyze the performance of various opportunistic routing strategies, in heterogeneous settings.

Making routers last longer with ViAggre

Abstract: This paper presents ViAggre (Virtual Aggregation), a "configuration-only" approach to shrinking the routing table on routers. ViAggre does not require any changes to router software and routing protocols and can be deployed independently and autonomously by any ISP. ViAggre is effectively a scalability technique that allows an ISP to modify its internal routing such that individual routers in the ISP's network only maintain a part of the global routing table. We evaluate the application of ViAggre to a few tier- 1 and tier-2 ISPs and show that it can reduce the routing table on routers by an order of magnitude while imposing almost no traffic stretch and negligible load increase across the routers. We also deploy Virtual Aggregation on a testbed comprising of Cisco routers and benchmark this deployment. Finally, to understand and address concerns regarding the configuration overhead that our proposal entails, we implement a configuration tool that automates ViAggre configuration. While it remains to be seen whether most, if not all, of the management concerns can be eliminated through such automated tools, we believe that the simplicity of the proposal and its possible short-term impact on routing scalability suggest that it is an alternative worth considering.

On Combining Shortest-Path and Back-Pressure Routing Over Multihop Wireless Networks

Abstract: Back-pressure based algorithms based on the algorithm by Tassiulas and Ephremides have recently received much attention for jointly routing and scheduling over multi-hop wireless networks. However a significant weakness of this approach has been in routing, because the traditional back-pressure algorithm explores and exploits all feasible paths between each source and destination. While this extensive exploration is essential in order to maintain stability when the network is heavily loaded, under light or moderate loads, packets may be sent over unnecessarily long routes and the algorithm could be very inefficient in terms of end-to-end delay and routing convergence times. This paper proposes new routing/scheduling back-pressure algorithms that not only guarantees network stability (through-put optimality), but also adaptively selects a set of optimal routes based on shortest-path information in order to minimize average path-lengths between each source and destination pair. Our results indicate that under the traditional back-pressure algorithm, the end-to-end packet delay first decreases and then increases as a function of the network load (arrival rate). This surprising low-load behavior is explained due to the fact that the traditional back-pressure algorithm exploits all paths (including very long ones) even when the traffic load is light. On the otherhand, the proposed algorithm adaptively selects a set of routes according to the traffic load so that long paths are used only when necessary, thus resulting in much smaller end-to-end packet delays as compared to the traditional back-pressure algorithm.

Hyperbolic Embedding and Routing for Dynamic Graphs

Abstract: We propose an embedding and routing scheme for arbitrary network connectivity graphs, based on greedy routing and utilizing virtual node coordinates. In dynamic multihop packet-switching communication networks, routing elements can join or leave during network operation or exhibit intermittent failures. We present an algorithm for online greedy graph embedding in the hyperbolic plane that enables incremental embedding of network nodes as they join the network, without disturbing the global embedding. Even a single link or node removal may invalidate the greedy routing success guarantees in network embeddings based on an embedded spanning tree subgraph. As an alternative to frequent reembedding of temporally dynamic network graphs in order to retain the greedy embedding property, we propose a simple but robust generalization of greedy distance routing called Gravity-Pressure (GP) routing. Our routing method always succeeds in finding a route to the destination provided that a path exists, even if a significant fraction of links or nodes is removed subsequent to the embedding. GP routing does not require precomputation or maintenance of special spanning subgraphs and, as demonstrated by our numerical evaluation, is particularly suitable for operation in tandem with our proposed algorithm for online graph embedding.

Internet route deaggregation and route selection preferencing

Abstract: A method and system for managing the routing of traffic within a network develops a topological address space map of the network to enable a “best route” selection process. The network is comprised of a backbone connected to a plurality of peering partners. Points on the network monitor traffic flows. A central facility analyzes the traffic flows and routes within the network and performs intelligent routing management. Intelligent routing management ensures that traffic is properly routed through preferred routes on the network, and avoids inefficient routing. Intelligent routing management also selects new routes to be injected into the network in order to further improve the accuracy of the address space map of the network. Intelligent routing management ensures that bandwidth is requested and delivered topologically closely to peering partner networks, and that traffic is carried by the backbone for long haul data distribution in both directions.

Routing strategies in multihop cooperative networks

Abstract: The fading characteristics and broadcast nature of wireless channels are usually not fully considered in the design of routing protocols for wireless networks. In this paper, we combine routing and cooperative diversity, with the consideration of a realistic channel model. We focus on a multihop network with multiple relays at each hop, and three routing strategies are designed to achieve the full diversity gain provided by cooperation among the relays. In particular, an optimal routing strategy is proposed to minimize the end-to-end outage, which requires the channel information of all the links and serves as a performance bound. An ad-hoc routing strategy is then proposed based on a hop-by-hop relay selection, which can be easily implemented in a distributed way. As expected, ad-hoc routing performs worse than optimal routing, especially with a large number of hops. To achieve a good complexity-performance tradeoff, an N-hop routing strategy is further proposed, where a joint optimization is performed every N hops. Simulation results are provided which verify the outage analyses of the proposed routing strategies.

Indirect adaptive routing on large scale interconnection networks

Abstract: Recently proposed high-radix interconnection networks [10] require global adaptive routing to achieve optimum performance. Existing direct adaptive routing methods are slow to sense congestion remote from the source router and hence misroute many packets before such congestion is detected. This paper introduces indirect global adaptive routing (IAR) in which the adaptive routing decision uses information that is not directly available at the source router. We describe four IAR routing methods: credit round trip (CRT) [10], progressive adaptive routing (PAR), piggyback routing (PB), and reservation routing (RES). We evaluate each of these methods on the dragonfly topology under both steady-state and transient loads. Our results show that PB, PAR, and CRT all achieve good performance. PB provides the best absolute performance, with 2-7% lower latency on steady-state uniform random traffic at 70% load, while PAR provides the fastest response on transient loads. We also evaluate the implementation costs of the indirect adaptive routing methods and show that PB has the lowest implementation cost requiring

Multirate Anypath Routing in Wireless Mesh Networks

Abstract: In this paper, we present a new routing paradigm that generalizes opportunistic routing in wireless mesh networks. In multirate anypath routing, each node uses both a set of next hops and a selected transmission rate to reach a destination. Using this rate, a packet is broadcast to the nodes in the set and one of them forwards the packet on to the destination. To date, there is no theory capable of jointly optimizing both the set of next hops and the transmission rate used by each node. We bridge this gap by introducing a polynomial-time algorithm to this problem and provide the proof of its optimality. The proposed algorithm runs in the same running time as regular shortest-path algorithms and is therefore suitable for deployment in link-state routing protocols. We conducted experiments in a 802.11b testbed network, and our results show that multirate anypath routing performs on average 80% and up to 6.4 times better than anypath routing with a fixed rate of 11 Mbps. If the rate is fixed at 1 Mbps instead, performance improves by up to one order of magnitude. I. INTRODUCTION The high loss rate and dynamic quality of links make routing in wireless mesh networks extremely challenging (1). Anypath routing 1 has been recently proposed as a way to circumvent these shortcomings by using multiple next hops for each destination (3)-(6). Each packet is broadcast to a forwarding set composed of several neighbors, and the packet must be retransmitted only if none of the neighbors in the set receive it. Therefore, while the link to a given neighbor is down or performing poorly, another nearby neighbor may receive the packet and forward it on. This is in contrast to single-path routing where only one neighbor is assigned as the next hop for each destination. In this case, if the link to this neighbor is not performing well, a packet may be lost even though other neighbors may have overheard it. Existing work on anypath routing has focused on wireless networks that use a single transmission rate. This approach, albeit straightforward, presents two major drawbacks. First, using a single rate over the entire network underutilizes available bandwidth resources. Some links may perform well at a higher rate, while others may only work at a lower rate. Secondly and most importantly, the network may become disconnected at a higher bit rate. We provide experimental measurements from a 802.11b testbed which show that this phenomenon is not uncommon in practice. The key problem is that higher transmission rates have a shorter radio range, which reduces network density and connectivity. As the bit rate in- creases, links becomes lossier and the network eventually gets disconnected. Therefore, in order to guarantee connectivity, single-rate anypath routing must be limited to low rates. In multirate anypath routing, these problems do not exist; however, we face different challenges. First, we must find 1 We use the term anypath rather than opportunistic routing, since oppor- tunistic routing is an overloaded term also used for opportunistic contacts (2).

Beacon-less geographic routing made practical: challenges, design guidelines, and protocols

Abstract: Geographic routing has emerged as one of the most efficient and scalable routing solutions for wireless sensor networks. In traditional geographic routing protocols, each node exchanges periodic one-hop beacons to determine the position of its neighbors. Recent studies proved that these beacons can create severe problems in real deployments due to the highly dynamic and error-prone nature of wireless links. To avoid these problems, new variants of geographic routing protocols that do not require beacons are being proposed. In this article we review some of the latest proposals in the field of beacon-less geographic routing and introduce the main design challenges and alternatives. In addition, we perform an empirical study to assess the performance of beacon-based and beacon-less routing protocols using a real WSN deployment.

BUFFALO: bloom filter forwarding architecture for large organizations

Abstract: In enterprise and data center networks, the scalability of the data plane becomes increasingly challenging as forwarding tables and link speeds grow. Simply building switches with larger amounts of faster memory is not appealing, since high-speed memory is both expensive and power hungry. Implementing hash tables in SRAM is not appealing either because it requires significant overprovisioning to ensure that all forwarding table entries fit. Instead, we propose the BUFFALO architecture, which uses a small SRAM to store one Bloom filter of the addresses associated with each outgoing link. We provide a practical switch design leveraging flat addresses and shortest-path routing. BUFFALO gracefully handles false positives without reducing the packet-forwarding rate, while guaranteeing that packets reach their destinations with bounded stretch with high probability. We tune the sizes of Bloom filters to minimize false positives for a given memory size. We also handle routing changes and dynamically adjust Bloom filter sizes using counting Bloom filters in slow memory. Our extensive analysis, simulation, and prototype implementation in kernel-level Click show that BUFFALO significantly reduces memory cost, increases the scalability of the data plane, and improves packet-forwarding performance.

Comparison Research between XY and Odd-Even Routing Algorithm of a 2-Dimension 3X3 Mesh Topology Network-on-Chip

Abstract: The Network-on-Chip (NoC) has been recognized as a paradigm to solve System-on-Chip (SoC) design challenges. The routing algorithm is one of key researches of a NoC design. XY routing algorithm, which is a kind of distributed deterministic routing algorithms, is simple to be implemented. Odd-Even (OE) routing algorithm, whose implementation is complex, is a sort of distributed adaptive routing algorithms with deadlock-free ability. We demonstrate the two routing algorithms in details at first. XY routing algorithm and OE routing algorithm are then simulated and compared based on a 3X3 mesh topology NoC with NIRGAM simulator. The simulation results show that OE routing algorithm, whose P parameter equals to 1.09, increases P parameter greatly as compared to XY routing algorithm, whose P parameter equals to 0.86, in a 2-dimension 3X3 mesh topology NoC, with Constant Bit Rate (CBR) traffic condition of each tail.

Enabling large-scale storage in sensor networks with the Coffee file system

Abstract: Persistent storage offers multiple advantages for sensor networks, yet the available storage systems have been unwieldy because of their complexity and device-specific designs. We present the Coffee file system for flash-based sensor devices. Coffee provides a programming interface for building efficient and portable storage abstractions. Unlike previous flash file systems, Coffee uses a small and constant RAM footprint per file, making it scale elegantly with workloads consisting of large files or many files. In addition, the performance overhead of Coffee is low: the throughput is at least 92% of the achievable direct flash driver throughput. We show that network layer components such as routing tables and packet queues can be implemented on top of Coffee, leading to increased performance and reduced memory requirements for routing and transport protocols.

Enhanced tree routing for wireless sensor networks

Abstract: Tree routing (TR) is a low-overhead routing protocol designated for simple, low-cost and low-power wireless sensor networks. It avoids flooding the network with path search and update messages in order to conserve bandwidth and energy by using only parent-child links for packet forwarding. The major drawback of TR is the increased hop-counts as compared with more sophisticated path search protocols. We propose an enhanced tree routing (ETR) strategy for sensor networks which have structured node address assignment schemes. In addition to the parent-child links, ETR also uses links to other one-hop neighbours if it is decided that this will lead to a shorter path. It is shown that such a decision can be made with minimum storage and computing cost by utilizing the address structure. Detailed algorithms for applying ETR to ZigBee networks are also presented. Simulation results reveal that ETR not only outperforms TR in terms of hop-counts, but also is more energy-efficient than TR.

Decentralized Coding Algorithms for Distributed Storage in Wireless Sensor Networks

Abstract: We consider large-scale wireless sensor networks with $n$ nodes, out of which k are in possession, (e.g., have sensed or collected in some other way) k information packets. In the scenarios in which network nodes are vulnerable because of, for example, limited energy or a hostile environment, it is desirable to disseminate the acquired information throughout the network so that each of the n nodes stores one (possibly coded) packet so that the original k source packets can be recovered, locally and in a computationally simple way from any k(1 + \epsilon) nodes for some small \epsilon > 0. We develop decentralized Fountain codes based algorithms to solve this problem. Unlike all previously developed schemes, our algorithms are truly distributed, that is, nodes do not know n, k or connectivity in the network, except in their own neighborhoods, and they do not maintain any routing tables.

Optimal forwarder list selection in opportunistic routing

Abstract: Unlike traditional wireless routing protocols which use a single fixed path, opportunistic routing explicitly takes advantage of the broadcast nature of wireless communications by using a set of forwarders to opportunistically perform packet forwarding. A key issue in the design of opportunistic routing protocols is the forwarder list selection problem. In this paper we establish a general theory for analyzing the forwarder list selection problem, and develop an optimal solution, the minimum transmission selection (MTS) algorithm, which minimizes the expected number of transmissions and it can be incorporated into existing opportunistic routing protocols to select optimal forwarder lists. Our theory and algorithm can also be generalized to optimize other routing objectives such as minimizing the expected transmission time or energy consumption in opportunistic routing. Through extensive simulations, we demonstrate that in more than 90% cases the MTS algorithm outperforms the ETX forwarder selection scheme used in existing opportunistic routing protocols such as ExOR and MORE.

REER: Robust and Energy Efficient Multipath Routing Protocol for Wireless Sensor Networks

Abstract: Wireless Sensor Networks (WSNs) are subject to node failures because of energy constraints, as well nodes can be added to or removed from the network upon application demands, resulting in unpredictable topology changes. Furthermore, due to limited transmission range of wireless sensor nodes, multiple hops are usually needed for a node to exchange information with other nodes or sink node(s). This makes the design of routing protocols in such networks a challenging task. In all proposed single path routing schemes a periodic low-rate flooding of data is required to recover from path failures, which causes consumption of scarce resources of the sensor node. Thus multipath routing schemes is an optimal alternative to maximize the network lifetime. Multipath routing schemes distribute the traffic across multiple paths instead of routing all the traffic along a single path, which spreads consumed energy evenly across the nodes within the network, potentially resulting in longer lifetimes. In this paper, we propose a robust and energy efficient multipath routing protocol (shortly abbreviated as REER). REER uses the residual energy, node available buffer size, and Signal-to-Noise Ratio (SNR) to predict the best next hop through the paths construction phase. REER examines two methods of traffic allocation; the first method uses a single path among the discovered paths to transfer the data message, when this path cost falls bellow a certain threshold, it then switches to the next alternative path. The second method is to split up the transmitted message into number of segments of equal size, add XOR-based error correction codes, and then transmit it across multiple paths simultaneously to increase the probability that an essential portion of the packet is received at the destination without incurring excessive delay. Through computer simulation, we evaluate and study the performance of our routing protocol and compare it with other protocols. Simulation results show that our protocol achieves more energy savings, lower average delay and higher packet delivery ratio than other protocols.

TO-GO: TOpology-assist geo-opportunistic routing in urban vehicular grids

Abstract: Road topology information has recently been used to assist geo-routing, thereby improving the overall performance. However, the unreliable wireless channel nature in urban vehicular grids (due to motion, obstructions, etc) still creates problems with the basic greedy forwarding. In this paper, we propose TO-GO (TOpology-assisted Geo-Opportunistic Routing), a geo-routing protocol that exploits topology knowledge acquired via 2-hop beaconing to select the best target forwarder and incorporates opportunistic forwarding with the best chance to reach it. The forwarder selection takes into account of wireless channel quality, thus significantly improving performance in error and interference situations. Extensive simulations confirm TO-GO superior robustness to errors/losses as compared to conventional topology-assisted geographic routing.

Route-over vs mesh-under routing in 6LoWPAN

Abstract: Transmission of IPv6 packets over Low-power Wireless Personal Area Networks (6LoWPAN) was considered nearly impractical once. The size of IPv6 packets is much larger than the packet size of the IEEE 802.15.4 data link layer. 6LoWPAN implements an adaptation layer between network and data link layers. Main purpose of the adaptation layer is to fragment and reassemble IPv6 packets. Implementation of the adaptation layer enhances the routing/forwarding decision of packets both network and adaptation layers. We can divide the routing scheme in 6LoWPAN into two categories: the mesh-under and the route-over, based on the routing decision taken on adaptation layer or network layer respectively. In this paper we perform an analytical comparison between these two schemes in terms of the packet/fragment arrival probability, the total number of transmissions and the total delay between source and destination. We also compare the selective fragment retransmission mechanism between mesh-under and route-over schemes.

Efficient implementation of distributed routing algorithms for NoCs

Abstract: Chip multiprocessors (CMPs) are gaining momentum in the high-performance computing domain. Networks-on-chip (NoCs) are key components of CMP architectures, in that they have to deal with the communication scalability challenge while meeting tight power, area and latency constraints. 2D mesh topologies are usually preferred by designers of general purpose NoCs. However, manufacturing faults may break their regularity. Moreover, resource management frameworks may require the segmentation of the network into irregular regions. Under these conditions, efficient routing becomes a challenge. Although the use of routing tables at switches is flexible, it does not scale in terms of latency and area due to its memory requirements. Logic-based distributed routing (LBDR) is proposed as a new routing method that removes the need for routing tables at all. LBDR enables the implementation of many routing algorithms on most of the practical topologies we may find in the near future in a multi-core system. From an initial topology and routing algorithm, a set of three bits per switch/output port is computed. Evaluation results show that, by using a small logic, LBDR mimics the performance of routing algorithms when implemented with routing tables, both in regular and irregular topologies. LBDR implementation in a real NoC switch is also explored, proving its smooth integration in the architecture and its negligible hardware and performance overhead.

Small-Scale and Large-Scale Routing in Vehicular Ad Hoc Networks

Abstract: A vehicular ad hoc network (VANET) is a highly mobile wireless ad hoc network that is targeted to support vehicular safety, traffic monitoring, and other applications. Mobility models used in traditional mobile ad hoc networks cannot directly be applied to VANETs since real-world factors such as road layouts and traffic regulations are not considered. In this paper, we propose a vehicular mobility model that reflects real-world vehicle movement and study the performance of packet-routing protocols. First, we study the routing in small-scale VANETs and propose two routing schemes: (1) connection-based restricted forwarding (CBRF) and (2) connectionless geographic forwarding (CLGF). With the insights obtained, we consider routing in large-scale VANETs. Since road complexity and traffic variety may cause many potential problems that existing routing protocols cannot address, we introduce a two-phase routing protocol (TOPO) that incorporates road map information. The proposed protocol defines an overlay graph with roads of high vehicular density and access graphs that are connected to the overlay. While in the overlay, packets are forwarded along a precalculated path. As far as access routing is concerned, we employ the aforementioned CBRF and CLGF schemes and send packets to the overlay or handle packets delivered from the overlay. We argue that the TOPO can serve as a framework that integrates existing VANET routing protocols. We also consider data diversity in VANETs and design the TOPO as an intelligent transportation system (ITS)-friendly protocol. To validate our design philosophy and the routing protocol, we use different areas in the city of Orlando, FL, and generate vehicular mobility traces, following our mobility models. We feed the traces to network simulators and study the routing behavior. Simulation results demonstrate the performance and effectiveness of the proposed routing protocols for large-scale VANET scenarios.

Scalable Routing in Cyclic Mobile Networks

Abstract: The nonexistence of an end-to-end path poses a challenge in adapting traditional routing algorithms to delay-tolerant networks (DTNs). Previous works have covered centralized routing approaches based on deterministic mobility, ferry-based routing with deterministic or semideterministic mobility, flooding-based approaches for networks with general mobility, and probability-based routing for semideterministic mobility models. Unfortunately, none of these methods can guarantee both scalability and delivery. In this paper, we extend the investigation of scalable deterministic routing in DTNs with repetitive mobility based on our previous works. Instead of routing with global contact knowledge, we propose a routing algorithm that routes on contact information compressed by three combined methods. We address the challenge of efficient information aggregation and compression in the time-space domain while maintaining critical information for efficient routing. Then, we extend it to handle a moderate level of uncertainty in contact prediction. Analytical studies and simulation results show that the performance of our proposed routing algorithm, DTN hierarchical routing (DHR), is comparable to that of the optimal time-space Dijkstra algorithm in terms of delay and hop count. At the same time, the per-node storage overhead is substantially reduced and becomes scalable.

Region-Based Routing: A Mechanism to Support Efficient Routing Algorithms in NoCs

Abstract: An efficient routing algorithm is important for large on-chip networks [network-on-chip (NoC)] to provide the required communication performance to applications. Implementing NoC using table-based switches provide many advantages, including possibility of changing routing algorithms and fault tolerance, due to the option of table reconfigurations. However, table-based switches have been considered unsuitable for NoCs due to their perceived high area and power consumption. In this paper, we describe the region-based routing (RBR) mechanism which groups destinations into network regions allowing an efficient implementation with logic blocks. RBR can also be viewed as a mechanism to reduce the number of entries in routing tables. RBR is general and can be used in conjunction with any adaptive routing algorithm. In particular, we have evaluated the proposed scheme in conjunction with a general routing algorithm, namely segment-based routing (SR) and an application specific routing algorithm (APSRA) using regular and irregular mesh topologies. Our study shows that the number of entries in the table is significantly reduced, especially for large networks. Evaluation results show that RBR requires only four regions to support several routing algorithms in a 2-D mesh with no performance degradation. Considering link failures, our results indicate that RBR combined with SR is able to tolerate up to 7 link failures in an 8times8 mesh. RBR also reduces area and power dissipation of an equivalent table-based implementation by factors of 8 and 10, respectively. Moreover, the degradation in performance of the network is insignificant when using APSRA combined with RBR.

SGF: A state-free gradient-based forwarding protocol for wireless sensor networks

Abstract: Limitation on available resources is a major challenge in wireless sensor networks. Due to high rates of unexpected node/link failures, robust data delivery through multiple hops also becomes a critical issue. In this article we present a state-free gradient-based forwarding (SGF) protocol to address these challenges. Nodes running SGF do not maintain states of neighbors or network topology and thus can scale to very large networks. Without using routing tables, SGF builds a cost field called gradient that provides each node the direction to forward data. The maintenance of gradient is purely driven by data transmissions and hence incurs little overhead. To adapt to transient channel variations and topology changes, the forwarder of a routing node is selected opportunistically among multiple candidate nodes through a distributed contention process. Simulation results show that SGF achieves significant energy savings and outperforms several existing data forwarding protocols in terms of packet delivery ratio and end-to-end delay.

Privacy-Preserving Content-Based Publish/Subscribe Networks

Abstract: Privacy and confidentiality are crucial issues in content-based publish/subscribe (CBPS) networks. We tackle the problem of end-user privacy in CBPS. This problem raises a challenging requirement for handling encrypted data for the purpose of routing based on protected content and encrypted subscription information. We suggest a solution based on a commutative multiple encryption scheme in order to allow brokers to operate in-network matching and content based routing without having access to the content of the packets. This is the first solution that avoids key sharing among end-users and targets an enhanced CBPS model where brokers can also be subscribers at the same time.

Load-balancing in MANET shortest-path routing protocols

Abstract: Mobile ad hoc networks (MANET) are infrastructure-less networks, dynamically formed by an independent system of mobile nodes that are connected via wireless links. Because routing is performed by nodes with limited resources, load should be efficiently distributed through the network. Otherwise, heavily-loaded nodes may make up a bottleneck that lowers the network performances by congestion and larger delays. Regrettably, load-balancing is a critical deficiency in MANET shortest-path routing protocols, as nodes at the center of the network are much heavily-loaded than the others. Thus, we propose, in this paper, load-balancing mechanisms that push the traffic further from the center of the network. Basically, we provide novel routing metrics that take into account nodes degree of centrality, for both proactive and reactive routing protocols. Simulations show that the proposed mechanisms improve the load distribution and significantly enhance the network performances in terms of average delay and reliability.