Source-destination Node Pairs Research Articles

Modified Gamma Network: Design and Reliability Evaluation

Background: VLSI technology advancements have resulted the requirements of high computational power, which can be achieved by implementing multiple processors in parallel. These multiple processors have to communicate with their memory modules by using Interconnection Networks (IN). Multistage Interconnection Networks (MIN) are used as IN, as they provide efficient computing with low cost. Objective: The objective of the study is to introduce new reliable Gamma MIN named as a Modified Gamma Interconnection Network (MGIN), which provide reliability and fault-tolerance with less number of stages of Switching element only. Methods: Switching Element (SE) of bigger size i.e. 2×3/3×2 has been employed at input/output stages inspite of 1×3/3×1 sized SE at input/output stages with reduction in one intermidiate stage. Fault tolerance has been introduced in the form of disjoint paths formed between each sourcedestnation node pair. Hence reliability has been improved. Results: Terminal, Broadcast and Network Reliability has been evaluated by using Reliability Block Diagrams for each source-destination node pair. The results have been shown, which depicts the higher reliability values for newly proposed network. The cost analysis shows that new MGIN is a cheaper network than other Gamma variants. Conclusion: MGIN has better reliability and Fault-tolerance than priviously proposed Gamma MIN.

Squeezed Protection in Elastic Optical Networks Subject to Multiple Link Failures

Elastic optical network (EON) is fast becoming a key solution for designing optical network with better usage of spectrum resources or other objectives of interest to tenant and/or operators. A primary concern of EONs is to protect the network against failures of its elements, because this kind of event can provoke the loss of substantial amount of traffic. In this paper, we propose a new mixed integer linear programming (MILP) formulation for protecting the network traffic against multiple link failures. The key idea is to use bandwidth squeezing together with grooming capability to provide few extra traffic for protection and guarantee a minimum bandwidth for each source-destination node pair under multiple failure events. The proposed formulation solves the virtual topology design problem jointly with the grooming, routing, modulation and spectrum allocation (RMSA) tasks. Due to the non-deterministic polynomial time (NP-hard) nature of the proposed MILP formulation, a heuristic strategy (referred to as two-step MILP) for large networks is also proposed. The solutions and performance of the proposed MILP formulation and two-step MILP analyzed through case studies in a small network. In addition, the performance of three large networks is assessed for cases scenarios where connections are under different service-level agreement (SLA). In view of proposed formulation and two-step MILP, it is possible to identify the configurations that ensure better usage of spectrum resources with different kinds of protection against single or multiple link failures.

SEGIN-Minus: A New Approach to Design Reliable and Fault-Tolerant MIN

Background:VLSI technology advancements have resulted the requirements of high computational power, which can be achieved by implementing multiple processors in parallel. These multiple processors have to communicate with their memory modules by using Interconnection Networks (IN). Multistage Interconnection Networks (MIN) are used as IN, as they provide efficient computing with low cost.Objective:the objective of the study is to introduce new reliable MIN named as a (Shuffle Exchange Gamma Interconnection Network Minus) SEGIN-Minus, which provide reliability and faulttolerance with less number of stages.Methods:MUX at input terminal and DEMUX at output terminal of SEGIN has been employed with reduction in one intermidiate stage. Fault tolerance has been introduced in the form of disjoint paths formed between each source-destnation node pair. Hence reliability has been improved.Results:Terminal, Broadcast and Network Reliability has been evaluated by using Reliability Block Diagrams for each source-destination node pair. The results have been shown, which depicts the hiher reliability values for newly proposed network. The cost analysis shows that new SEGINMinus is a cheaper network than SEGIN.Conclusion:SEGIN-Minus has better reliability and Fault-tolerance than priviously proposed SEGIN.

High Performance Dynamic Resource Allocation for Guaranteed Service in Network-on-Chips

This paper proposes a dedicated connection allocation unit—the NoCManager—implementing the connection allocation functionality in circuit-switched network-on-chip (NoC) based on time-division-multiplexing (TDM). The NoCManager employs a novel trellis-search-algorithm (TESSA) that solves the allocation optimization problem by making use of dynamic programming approach. This enables to explore all possible paths between source-destination node pairs in order to determine the shortest available path. Three different trellis structures are proposed and analyzed for the purpose of different application scenarios. In contrast to previous TDM allocation approaches, the proposed method offers the following advantages: (1) hardware supported fast and high-throughput allocation mechanism; (2) improved success rate due to parallel multi-slot multi-path search mechanism; (3) selection of the contention-free shortest path with a guaranteed low latency; (4) general mathematical formulation allowing a variety of optimization ideas. The proposed method is compared to the state of the art centralized and distributed techniques under uniformly distributed random traffic as well as real-application traffic. The experimental results demonstrate two orders of magnitude improvement in allocation speed and tens of times higher success rate against the centralized software solutions, and 5 to 10 percent higher success rate against the centralized hardware solution. Moreover, it achieves up to 8x higher allocation speed and up to 29 percent higher success rate against recently proposed distributed solution.

Non-SPF routing algorithm based on ordered semi-group preference algebra

Layer 2 network technology is extending beyond its traditional local area implementation and finding wider acceptance in provider's metropolitan area networks and large-scale cloud data center networks. This is mainly due to its plug-and-play capability and native mobility support. Many efforts have been put to increase the bisection bandwidth in layer 2 network, which has been constrained by the spanning tree protocol (STP) that layer 2 network uses for preventing looping. The recent trend is to incorporate layer 3's routing approach into layer 2 network so that multiple paths can be used for forwarding traffic between any source-destination (S-D) node pair. Equal cost multipath (ECMP) is one such example. However, ECMP may still be limited in generating multiple paths due to its shortest path (lowest cost) requirement. In this paper, we consider a non-shortest-path routing approach, called equal preference multipath (EPMP) based on ordered semi group theory, which can generate more paths than ECMP. In EPMP routing, all the paths with different traditionally-defined costs, such as hops, bandwidth, etc., can be determined equally now and thus they become equal candidate paths. By the comparative tests with ECMP, EPMP routing not only generates more paths, provides 15% higher bisection bandwidth, but also identifies bottleneck links in a hierarchical network when different traffic patterns are applied. EPMP is more flexible in controlling the number and length of multipath generation. Simulation results indicate the effectiveness of the proposed algorithm. It is a good reference for non-blocking running of big datacenter networks.

Reliability evaluation of time evolving Delay Tolerant Networks based on Sum-of-Disjoint products

Network reliability evaluation of Delay Tolerant Networks (DTNs) is a challenging task due to their inherent features like node mobility, dynamically changing network topology and existence of highly disruptive environmental conditions etc. The research so far on such time-evolving dynamic networks mainly focusses on topology control, routing and information propagation with a little attention paid towards computing their overall network reliability. In this paper, we model DTNs by using Time Aggregated Graph and propose the notion of time-stamped-minimal path sets between a given source-destination pair of nodes, besides, providing a simple yet novel method to enumerate them. Further, by employing Multiple Variable Inversion-Sum of Disjoint Products algorithm, we obtain disjointed time-stamped-minimal path sets, which have a one-to-one mapping with the overall reliability expression of such time evolving networks. For obtaining instances of a DTN during an operational period, we resort to Monte Carlo Simulation to simulate the dynamically changing topology and other probabilistically varying network aspects. The simulation results demonstrate the efficacy of our proposal. At the end, we also present some initial investigation and insight on the time-stamped-minimal cut sets and problem in enumerating them, and infer that the usual notion of cut sets seems inapplicable for dynamic networks.

The Global Packing Number of a Fat-Tree Network

Data centers play an important role in today’s Internet development. Research to find scalable architecture and efficient routing algorithms for data center networks has gained popularity. The fat-tree architecture, which is essentially a folded version of a Clos network, has proved to be readily implementable and is scalable. In this paper, we investigate routing on a fat-tree network by deriving its global packing number and by presenting explicit algorithms for the construction of optimal, load-balanced routing solutions. Consider an optical network that employs wavelength division multiplexing in which every user node sets up a connection with every other user node. The global packing number is basically the number of wavelengths required by the network to support such a traffic load, under the restriction that each source-to-destination connection is assigned a wavelength that remains constant in the network. In mathematical terms, consider a bidirectional, simple graph, $G$ and let $N\subseteq V(G)$ be a set of nodes. A path system $\mathcal {P}$ of $G$ with respect to $N$ consists of $|N|(|N|-1)$ directed paths, one path to connect each of the source-destination node pairs in $N$ . The global packing number of a path system $\mathcal {P}$ , denoted by $\Phi (G,N,\mathcal {P})$ , is the minimum integer $k$ to guarantee the existence of a mapping $\phi :\mathcal {P}\to \{1,2,\ldots, k\}$ , such that $\phi (P)\neq \phi (\widehat {P})$ if $P$ and $\widehat {P}$ have common arc(s). The global packing number of $(G,N)$ , denoted by $\Phi (G,N)$ , is defined to be the minimum $\Phi (G,N,\mathcal {P})$ among all possible path systems $\mathcal {P}$ . In additional to wavelength division optical networks, this number also carries significance for networks employing time division multiple access. In this paper, we compute by explicit route construction the global packing number of $(\text {T}_{n},N)$ , where T n denotes the topology of the $n$ -ary fat-tree network, and $N$ is considered to be the set of all edge switches or the set of all supported hosts. We show that the constructed routes are load-balanced and require minimal link capacity at all network links.

Spectrum allocation and protocol based on cognitive acoustic technique in underwater networks

In this paper, a strategy is developed for spectrum sharing among multiple cognitive users in underwater environment. This strategy requires all nodes to negotiate and reallocate the channels before sending data, and Hungarian method is used to maximize the sharing rewards. Simulation results show that the proposed strategy can avoid collisions between source-destination node pairs, and guarantee that the communication system gets maximum sharing rewards. Both the parameters of POMDP model and the number of available channels have influence on the system sharing rewards, and the rewards will increase when the channels have larger transition probabilities or more channels are available for communication. However, the channels with larger bandwidths can attract more nodes to access, and thus will lead to more collisions.

Cooperative Dual-Hop Wireless Communication Systems With Beamforming Over <inline-formula> <tex-math notation="LaTeX">$\eta-\mu$</tex-math></inline-formula> Fading Channels

The end-to-end performance of cooperative beamforming in dual-hop relaying systems operating over η - μ fading channels is investigated. In the analysis, the source-destination node pair is equipped with multiple antennas, whereas the fixedgain relay has a single antenna. The η - μ fading channel has Nakagami-m, Rayleigh, one-sided Gaussian, and Nakagami-q (Hoyt) channels as special cases. In this paper, novel statistical expressions for the generalized moments of the end-to-end signal- to-noise ratio (SNR), cumulative density function (cdf), probability density function (pdf), and moment-generating function (mgf) are derived and evaluated. Furthermore, the obtained results are used to derive new and simple expressions for the pdf, the outage probability, and the mgf of the end-to-end SNR over Nakagami-m fading channels. In addition, we show that the derived expression for parameter C over the Nakagami-m fading channel is incorrect, and hence, it leads to inaccurate results. Also, we study the impact of the fading parameters η and μ on the end-to-end system performance. Simulation results show that, in contrast to the fading parameter η, μ has a significant impact on the system performance.

Equal Preference Multi-Path Routing for L2 Hierarchical Networks

The layer 2 network technology is extending beyond its traditional local area implementation and finding wider acceptance in provider’s metropolitan area networks and large-scale cloud data center networks. This is mainly due to its plug-and-play capability and native mobility support. Many efforts have been put to increase the bisection bandwidth in a layer 2 network, which has been constrained by the spanning tree protocol that a layer 2 network uses for preventing looping. The recent trend is to incorporate layer 3’s routing approach into a layer 2 network so that multiple paths can be used for forwarding traffic between any source-destination (S-D) node pair. ECMP (equal cost multipath) is one such example. However, ECMP may still be limited in generating multiple paths due to its shortest path (lowest cost) requirement. In this paper, we consider a non-shortest-path routing approach, called EPMP (Equal Preference Multi-Path) that can generate more paths than ECMP. The EPMP is based on the ordered semi-group algebra. In the EPMP routing, paths that differ in traditionally-defined costs, such as hops, bandwidth, etc., can be made equally preferred and thus become candidate paths. We found that, in comparison with ECMP, EPMP routing not only generates more paths, provides higher bisection bandwidth, but also allows bottleneck links in a hierarchical network to be identified when different traffic patterns are applied. EPMP is also versatile in that it can use various ways of path preference calculations to control the number and the length of paths, making it flexible (like policy-based routing) but also objective (like shortest path first routing) in calculating preferred paths.

Reliable multistage interconnection network design

High-performance supercomputers generally comprise millions of CPUs in which interconnection networks play an important role to achieve high performance. New design paradigms of dynamic on-chip interconnection network involve a) topology b) synthesis, modeling and evaluation c) quality of service, fault tolerance and reliability d) routing procedures. To construct a dynamic highly fault tolerant interconnection networks requires more disjoint paths from each source-destination node pair at each stage and dynamic rerouting capability to use the various available paths effectively. Fast routing and rerouting strategy is needed to provide reliable performance on switch/link failures. This paper proposes two new architecture designs of fault tolerant interconnection networks named as reliable interconnection networks (RIN-1 and RIN-2). The proposed layouts are multipath multi-stage interconnection networks providing four disjoint paths for all the source-destination node pairs with dynamic rerouting capability. The designs can withstand switch failures in all the stages (including input and output stages) and provide more reliability. Reliability analysis of various MIN architectures is evaluated. On comparing the results with some existing MINs it is evident that the proposed designs provides higher reliability values and fault tolerance.

Understanding Multi-Task Schedulabilityin Duty-Cycling Sensor Networks

In many sensor network applications, multiple data forwarding tasks usually exist with different source-destination node pairs. Due to limitations of the duty-cycling operation and interference, however, not all tasks can be guaranteed to be scheduled within their required delay constraints. We investigate a fundamental scheduling problem of both theoretical and practical importance, called multi-task schedulability problem, i.e., given multiple data forwarding tasks, to determine the maximum number of tasks that can be scheduled within their deadlines and work out such a schedule. We formulate the multi-task schedulability problem, prove its NP-Hardness, and propose an approximate algorithm with analysis on the performance bound and complicity. We further extend the proposed algorithm by explicitly altering duty cycles of certain sensor nodes so as to fully support applications with stringent delay requirements to accomplish all tasks. We then design a practical scheduling protocol based on proposed algorithms. We conduct extensive trace-driven simulations to validate the effectiveness and efficiency of our approach with various settings.

Joint Optimal Routing and Power Allocation for Spectral Efficiency in Multihop Wireless Networks

Given a multihop wireless network and a source-destination pair of nodes, this paper addresses the problem of jointly selecting a communication route and allocating transmit power levels, so that the end-to-end spectral efficiency of the route exceeds a desired threshold. Spectral-efficient routing has been subject to interest in the recent literature. The transmit power level, however, has been assumed to be known, and route selection was considered in isolation. This paper presents the first rigourously proven optimal, polynomial-time algorithms for two versions of the joint spectral-efficient routing and power allocation problem: sum-power minimization and maximum power minimization. The proposed algorithms rely on the divide-and-conquer principle and the Bellman-Ford algorithm for shortest (or widest) path computation. Our computational results further illustrate the efficiency of the proposed approach.

Stability vs. optimality in selfish ring routing

We study asymmetric atomic selfish routing in ring networks, which has diverse practical applications in network design and analysis. We are concerned with minimizing the maximum latency of source-destination node-pairs over links with linear latencies. We show that there exists an optimal solution that is a 9-approximate Nash equilibrium, significantly improving the existing upper bound of 54 on the instability factor. We present fast implementation of the best response dynamics for computing a Nash equilibrium. Furthermore, we perform empirical study on the price of stability, narrowing the gap between the lower and upper bounds to 0.7436.

Secure Routing and Data Transmission in Mobile Ad Hoc Networks

In this paper, we present an identity (ID) based protocol that secures AODV and TCP so that it can be used in dynamic and attack prone environments of mobile ad hoc networks. The proposed protocol protects AODV using Sequential Aggregate Signatures (SAS) based on RSA. It also generates a session key for each pair of source-destination nodes of a MANET for securing the end-to-end transmitted data. Here each node has an ID which is evaluated from its public key and the messages that are sent are authenticated with a signature/ MAC. The proposed scheme does not allow a node to change its ID throughout the network lifetime. Thus it makes the network secure against attacks that target AODV and TCP in MANET. We present performance analysis to validate our claim.

Performance Evaluation of Fault Tolerance Protocols in MANET

A mobile ad hoc network (MANET) is a collection of wireless mobile nodes communicating with each other using multi-hop wireless Links without any existing network infrastructure or centralized administration. It has been shown that using multiple paths to route messages between any sourcedestination pair of nodes (instead of using a single path) balances the load more evenly throughout the network. The common belief is that the same is true for ad hoc networks, i.e., multi-path routing balances the load significantly better than single-path routing. Our Protocol, called MPOLSR & MDART is a multipath routing protocol for MANET. In addition route recovery & loop detection are implemented in MPOLSR in order to improve quality of service regarding OLSR.MP-OLSR is suitable for mobile, large & dense network with large traffic & could satisfy critical multimedia applications with high on time constraints. While MDART is an efficient protocol which gives improved performance in large networks. MDART is an enhancement of shortest path routing protocol known as Dynamic Address Routing (DART).MDART discovers and stores multiple paths to the destination in the routing table. In this paper, we have compare and analysis the performance of proactive multipath routing protocols for MANET under different scenarios & metrices using NS-2.

A Research Paper on Comparison between Energy Efficient Routing Protocol with Energy and Location in MANET

Energy is an important issue in MANET (Mobile Ad hoc Network). Nodes in network are working in presence of limited energy. So, energy efficient routing is needed for reducing energy consumption. Energy efficient routing schemes can greatly reduce energy consumption and extends the lifetime of the networks. Multipath routing protocol (AOMDV) having more than one path, if the first one is break then second provides the proper packet delivery, this causes reduced node energy consumption and the topology of MANETs always changes, due to the high mobility of nodes. This makes it more difficult to find the routes that message packets use when they are routed. The location based routing provides the location information of the destination to route a packet toward. This paper provides comparison and study on reduced energy consumption by using multipath protocol and performance which is evaluated by performance metrics in case of AOMDV and energy based AOMDV. Now here DREAM protocol is used with AOMDV to finding location of mobile nodes but not with energy but here measures their performance with both multipath protocols. I. INTRODUCTION A mobile ad hoc network (MANET) is a dynamic distributed system of mobile formed by means of multi-hop wireless communication without the use of any existing network infrastructure. MANET routing protocols can be classified into two classes. Proactive protocols, they requires the nodes to periodically exchange the table information to update the pre-determine routes between any pair of source destination nodes. Reactive protocols can establish routes only when they require. MANET routing protocols can be classified on the bases of the methods of delivery of data packets from source to destination. Single Path routing protocols learn routes and select a single best route to each destination. These protocols are incapable of load balancing traffic. Multi-path routing protocols learn routes and can select more than one path to a destination. These protocols are better for performing load balancing. This paper provides the comparison between results about Multipath routing in AOMDV (13), AOMDV with location and Energy with AOMDV.

Traffic Grooming in WDM Mesh Networks: A Light-Trail Implementation

In this work, we study the problem of efficient traffic grooming using light-trail. In case of lightpath a complete wavelength is dedicated between source and destination node. Once a lightpath is set up, the entire wavelength is used exclusively by the source-destination node pair. Data cannot be transmitted or received by nodes along the lightpath except the starting and ending node. However, it is often observed that the bandwidth requirement in today’s network is often varying and does not justify the need for allocating an entire wavelength for a single data transmission. Therefore, the wavelength capacity may be underutilized. Then the term light-trail came into existence, it was proposed to avoid the inability of intermediate nodes to use a connection wavelength. In this work, we have proposed a traffic grooming algorithm to maximize the network throughput for wavelength-routed mesh networks using static light-trail. The efficiency of our approach has been established through extensive simulation on different sets of traffic demands with different bandwidth granularities for different network topologies and compared the approach with existing algorithm.

Weighted Sum Rate Maximization in OFDM Based Cooperative Cognitive Radios: A Joint Optimization Approach

Improving utilization of the radio spectrum is the main goal of Cognitive Radio Networks (CRN). Recent studies made use of cooperative relay technology in cognitive networks, to increase transmission diversity gain. In this paper we consider an OFDM based cooperative cognitive network with a pair of Source-Destination nodes as the primary user (PU), and a pair of Source-Destination nodes—which is assisted with a relay—as the secondary (cognitive) user (SU). Both primary and secondary users share a same spectrum. In a two hop transmission, the source transmits in the first hop, and the half-duplex relay decodes the message, re-encodes and forwards it to the destination in the second hop on a different subcarrier. The cognitive network obeys an underlay paradigm where the SU is allowed to transmit simultaneously with PU, while its power is limited such that the interference caused for PU does not exceed a defined temperature. Under this constraint, a joint subcarrier pairing and power allocation is proposed for SU to maximize its weighted sum rate. The problem is transformed to a convex optimization problem and solved in the dual domain. Then an algorithm to achieve feasible solutions is used based on the optimization results. Through extensive simulations, we compare the spectrum utilization of the proposed approach with the existing ones, and show that interestingly the proposed method improves the weighted sum rate of SU.

A cross-layer framework for optimal delay-margin, network lifetime and utility tradeoff in wireless visual sensor networks

For wireless multimedia sensor networks a distributed cross-layer framework is proposed, which not only achieves an optimal tradeoff between network lifetime and its utility but also provides end-to-end delay-margin. The delay-margin, defined as the gap between maximum end-to-end delay threshold and the actual end-to-end delay incurred by the network, is exploited by the application layer to achieve any desired level of delay quality-of-service. For optimal performance tradeoff an appropriate objective function for delay-margin is required, which is obtained by employing sensitivity analysis. Sensitivity analysis is performed by incorporating delay-margin in the end-to-end delay constraints while penalizing its price in the objective function. For distributed realization of proposed cross-layer framework, the optimal tradeoff problem is decomposed into network lifetime, utility and delay-margin subproblems coupled through dual variables. The numerical results for performance evaluation show that compromising network utility does not guarantee both lifetime and delay-margin improvement, simultaneously, for the set of operating points. Performance evaluation results also reveal that the fairness among different delay-margins, corresponding to different source–destination node pairs, can be improved by relaxing the end-to-end delay threshold.