Local Routing Tables Research Articles

Dynamic clustering in Sparse MANETs

In dynamic networks like sparse mobile ad hoc networks used during rescue operations, data and service availability and reachability is crucial. Such dynamic networks can be analysed to identify stable clusters as well as nodes with frequent cluster affiliation changes; these structural and behavioural properties can then be utilised for careful data and service placement and ferry selection. Factors that influence the outcome are the clustering algorithms used and how and when they are applied. In this paper, we identify cluster evolution based on similarities between clusters detected by community detection algorithms on consecutive network snapshots. The community detection algorithms are node agnostic in the sense that they do not elect cluster heads, and are non-intrusive, i.e., they extract topology information from the local routing tables without interfering with the routing algorithm nor creating network traffic. We have performed extensive experiments to evaluate how the choice of clustering algorithm affects the evolution and timeline of clusters and the identification of node-cluster affiliations. Additionally, we compare how well the algorithms perform on selecting nodes for data and service placement and ferrying.

Improve Reliability and Load Balancing of using ACO Mechanism in Ad hoc Network

Ad hoc network consist of autonomous self-organized nodes. Nodes use a wireless medium for communication. Thus two nodes can communicate directly if and only if they are within each other’s transmission radius. In Ad hoc networks, routing not only has to be fast and efficient, but also adaptive to the changes in the network topology; otherwise, the performance may be severely degraded. In a routing task, a message is sent from a source to a destination node in a given network. Two nodes normally communicate via other nodes in a multi-hop fashion. In this paper we analyze an ACO (Ant Colony Optimization) based routing algorithm with AOMDV protocol for load balancing to route packets through shorter and feasible routes. Each ant while moving towards destination collects information about address of each visited node of the followed path means the pheromones values. During backward travel, local network traffic model and routing table is modified by ant based on the goodness of the followed path. The performance of ACO with AOMDV has provides the possibility of light load traffic routes that is not possible to find in normal AOMDV routing protocol and provides the efficient load balancing on the basis of high and low pheromones value. Simulation results shows that the proposed ACO based routing protocol gives performance improvement over other routing protocol by continuously checking for better paths in the network with less overhead. Index Terms Routing, Ad hoc network, AOMDV, ACO, Load balancing

Detecting Communities in Sparse MANETs

In sparse mobile ad hoc networks, placement of services and data is crucial to assure their availability to all nodes because sparse population of nodes can lead to (frequent) network partitions. If these dynamic networks display a fairly stable cluster structure, it is possible to utilize this structure to improve service and data availability. However, clustering in a dynamic network is a very challenging task due to the ever-changing topology and irregular density of such a network. In this paper, we investigate clustering of dynamic networks with the help of community detection mechanisms, using only topology information from the local routing table. The main aim of our approach is to reduce to “zero” the communication overhead needed for cluster management and to dynamically adapt to the size and layout of the network. We have performed extensive experiments to evaluate the consistency, quality, and stability of the clustering returned by our algorithms. The results show that our nonintrusive clustering indeed discovers temporary groups of nodes that form stable clusters in the network. Moreover, even though the local routing tables in general reflect slightly diverging topologies, our results still show only small differences between the communities detected at different nodes.

Modeling, analysis and simulation of ant-based network routing protocols

Using the metaphor of swarm intelligence, ant-based routing protocols deploy control packets that behave like ants to discover and optimize routes between pairs of nodes. These ant-based routing protocols provide an elegant, scalable solution to the routing problem for both wired and mobile ad hoc networks. The routing problem is highly nonlinear because the control packets alter the local routing tables as they are routed through the network. We mathematically map the local rules by which the routing tables are altered to the dynamics of the entire networks. Using dynamical systems theory, we map local protocol rules to full network performance, which helps us understand the impact of protocol parameters on network performance. In this paper, we systematically derive and analyze global models for simple ant-based routing protocols using both pheromone deposition and evaporation. In particular, we develop a stochastic model by modeling the probability density of ants over the network. The model is validated by comparing equilibrium pheromone levels produced by the global analysis to results obtained from simulation studies. We use both a Matlab simulation with ideal communications and a QualNet simulation with realistic communication models. Using these analytic and computational methods, we map out a complete phase diagram of network behavior over a small multipath network. We show the existence of both stable and unstable (inaccessible) routing solutions having varying properties of efficiency and redundancy depending upon the routing parameters. Finally, we apply these techniques to a larger 50-node network and show that the design principles acquired from studying the small model network extend to larger networks.

Roundtrip spanners and roundtrip routing in directed graphs

We introduce the notion of roundtrip-spanners of weighted directed graphs and describe efficient algorithms for their construction. We show that for every integer k ≥ 1 and any ϵ > 0, any directed graph on n vertices with edge weights in the range [1, W ] has a (2 k + ϵ)-roundtrip-spanner with O (min{( k 2 /ϵ) n 1 + 1/ k (log( nW ), ( k /ϵ) 2 n 1 + 1/ k ,(log n ) 2−1/ k }) edges. We then extend these constructions and obtain compact roundtrip routing schemes. For every integer k ≥ 1 and every ϵ > 0, we describe a roundtrip routing scheme that has stretch 4 k + ϵ, and uses at each vertex a routing table of size Õ (( k 2 /ϵ) n 1/ k log( nW )). We also show that any weighted directed graph with arbitrary/ positive edge weights has a 3-roundtrip-spanner with O ( n 3/2 ) edges. This result is optimal. Finally, we present a stretch 3 roundtrip routing scheme that uses local routing tables of size Õ ( n 1/2 ). This routing scheme is essentially optimal. The roundtrip-spanner constructions and the roundtrip routing schemes for directed graphs that we describe are only slightly worse than the best available spanners and routing schemes for undirected graphs. Our roundtrip routing schemes substantially improve previous results of Cowen and Wagner. Our results are obtained by combining ideas of Cohen, Cowen and Wagner, Thorup and Zwick, with some new ideas.

A Comparison of Replication Strategies for Reliable Decentralised Storage

Distributed hash tables (DHTs) can be used as the basis of a resilient lookup service in unstable environments: local routing tables are updated to reflected changes in the network; efficient routing can be maintained in the face of participant node failures. This fault-tolerance is an important aspect of modern, decentralised data storage solutions. In architectures that employ DHTs, the choice of algorithm for data replication and maintenance can have a significant impact upon performance and reliability. This paper presents a comparative analysis of replication algorithms for architectures based upon a specific design of DHT. It presents also a novel maintenance algorithm for dynamic replica placement, and considers the reliability of the resulting designs at the system level. The performance of the algorithms is examined using simulation techniques; significant differences are identified in terms of communication costs and latency.

Compact Routing with Name Independence

This paper is concerned with compact routing schemes for arbitrary undirected networks in the name-independent model first introduced by Awerbuch, Bar-Noy, Linial, and Peleg. A compact routing scheme that uses local routing tables of size $\~{O}(n^{1/2})$, $O(\log^2 n)$-sized packet headers, and stretch bounded by 5 is obtained, where $n$ is the number of nodes in the network. (We use the notation $\~{O}\left(f(n)\right)$ to represent $O(f(n)\log^c{n})$, where $c$ is an arbitrary nonnegative real number, independent of $n$.) Alternative schemes reduce the packet header size to $O(\log n)$ at the cost of either increasing the stretch to 7 or increasing the table size to $\~{O}(n^{2/3})$. For smaller table-size requirements, the ideas in these schemes are generalized to a scheme that uses $O(\log^2 n)$-sized headers and ${O}(k^2n^{2/k})$-sized tables, and achieves a stretch of $\min\{1 + (k-1)(2^{k/2}-2), 16k^2-8k\}$, improving the best previously known name-independent scheme due to Awerbuch and Peleg.

Compact Routing with Minimum Stretch

We present the first universal compact routing algorithm with maximum stretch bounded by 3 that uses sublinear space at every vertex. The algorithm uses local routing tables of size O(n2/3log4/3n) and achieves paths that are most 3 times the length of the shortest path distances for all nodes in an arbitrary weighted undirected network. This answers an open question of Gavoille and Gengler who showed that any universal compact routing algorithm with maximum stretch strictly less than 3 must use Ω(n) local space at some vertex.

At the core of IP networks: link-state routing protocols

As end users and managers of both corporate and Internet service provider (ISP) IP networks, we ask a lot of those devices called routers. They must be reliable and easy to manage, while supporting a variety of LAN and WAN interfaces at a reasonable price. They must forward hundreds of thousands or even millions of packets per second. For each packet, this means the router receives it, extracts the destination address contained in the header, performs a lookup in a local routing table, finds the best match, and then transmits the packet to the next-hop router. The router may even be configured to examine additional fields in the packet and, based on this analysis, decide whether to place the packet in a high-priority transmission queue for expedited service. The author discusses link-state routing protocols.

Group routing without group routing tables: an exercise in protocol design

We present a group routing protocol for a network of processes. The task of the protocol is to route data messages to each member of a process group. To this end, a tree of processes is constructed in the network, ensuring that each group member is included in the tree. To build this tree, the group routing protocol relies upon the local unicast routing tables of each process. Thus, group routing is accomplished by composing two protocols: an underlying unicast routing protocol, whose detailed behavior is unknown but its basic properties are given, and a protocol that builds a group tree based upon the unicast routing tables. The group routing protocol is developed in three steps. First, a simple protocol is obtained, and is proven correct. Then, the protocol is refined twice. Each refined protocol improves upon its predecessor by satisfying all of the predecessor's properties plus some additional stronger properties. The final protocol has the property of adapting the group tree to changes in the unicast routing tables without compromising the integrity of the group tree, even in the presence of unicast routing loops.