Routing In Packet-switched Networks Research Articles

ОСОБЕННОСТИ ИЗУЧЕНИЯ ПЕРЕДАЧИ ПАКЕТНОЙ ИНФОРМАЦИИ ПО ТЕХНОЛОГИЯМ КОМПЬЮТЕРНЫХ СЕТЕЙ ОБУЧАЮЩИМИСЯ ЖЕЛЕЗНОДОРОЖНЫХ ВУЗОВ

The article discusses the role of telecommunication systems and networks in the work of railway transport. The authors analyzed the demand for the transfer of information data today, noted the principles of interconnection and building local networks, displayed the revised and supplemented material of the manuals. The introduction of a large number of information equipment in people's lives has led to a global transformation of the digital space. This is especially noticeable in the railway industry, where highquality and timely transmission of information data plays a paramount role in the transportation process. Due to digital transformation, the need for uninterrupted and highquality sending of information over long distances with minimal losses, the need to introduce theoretical and practical material on modern technologies for information data transmission networks. On the basis of this, an urgent need is revealed for training personnel in the study of network technologies in order to improve the efficiency of the functioning of the railway infrastructure. Therefore, it is more important than ever to transform the educational process, to direct resources to introduce as much network equipment as possible into classrooms for visual acquaintance and study of the main points of packet switching by students of the railway university. The work also presents the progress of the laboratory work on the topic "Static Routing in Packet Switching Networks", which is performed in the Cisco Packet Tracer software network emulator. All the necessary commands used to perform laboratory work by students of a railway university are presented. The laboratory work, in turn, is devoted to the user interface, network configuration, one of the types of routing. It is concluded that by developing an educational program for students to study the work of building packet switching networks, it will be possible to produce a qualified specialist who deeply understands the operation of telecommunications equipment. This is what will improve the network component of railway transport.

Directed Steiner trees with diffusion costs

Given a directed arc-weighted graph G with n nodes, a root r and k terminals, the directed steiner tree problem (DST) consists in finding a minimum-weight tree rooted at r and spanning all the terminals. If this problem has several applications in multicast routing in packet switching networks, the modeling is not adapted anymore in networks based upon the circuit switching principle in which some nodes, called non diffusing nodes, are unable to duplicate packets. We define a more general problem, namely the directed steiner tree with a limited number of diffusing nodes (DSTLD), that enables us to model multicast in a network containing at most d diffusing nodes. We show that DSTLD is XP with respect to d, and use this result to build a $$\left\lceil \frac{k-1}{d} \right\rceil $$k-1d-approximation algorithm for DST that is XP in d. We deduce from that result a strong inapproximability property. In particular, we prove that, under the assumption that NP$$\not \subseteq $$źZTIME$$[n^{\log ^{O(1)}n}]$$[nlogO(1)n], there is no polynomial-time approximation algorithm for DSTLD with ratio $$\varOmega \left( \frac{k}{d}\right) $$Ωkd. We finally give an evaluation of performances of an exact algorithm dedicated to the case $$d \le 3$$d≤3.

An FPT algorithm in polynomial space for the Directed Steiner Tree problem with Limited number of Diffusing nodes

Given a directed graph with n nodes, a root r, a set X of k nodes called terminals and non-negative weights ω over the arcs, the Directed Steiner Tree problem (DST) asks for a directed tree T⁎ of minimum cost ω(T⁎) rooted at r and spanning X.If this problem has several applications in multicast routing in packet switching networks, the modeling is no longer adapted in networks based upon the circuit switching principle, in which some nodes, called non-diffusing nodes, are not able to duplicate packets. We study a generalization of DST, called Directed Steiner Tree with Limited number of Diffusing nodes (DSTLD), able to model the multicast routing in a network containing at most d diffusing nodes.We provide an FPT exact algorithm running in time O(td⋅dk⋅n⋅(d+k)) and in polynomial space for DSTLD, where td is the number of unordered rooted trees with d unlabelled nodes. Thereby, we also provide the first exact algorithm running in polynomial space and in FPT time with respect to k which returns an optimal solution for DST instead of the optimal cost only.

All-to-all disjoint multipath routing using cycle embedding

In this paper, we evaluate the performance of disjoint multipath routing approaches for all-to-all routing in packet-switched networks with respect to packet overhead, path length, and routing table size. We develop a novel approach based on cycle embedding to obtain two node-disjoint paths between all source-destination pairs with reduced number of routing table entries maintained at a node (hence the reduced lookup time), small average path length, and less packet overhead. We study the trade-off between the number of routing table entries maintained at a node and the average length of the two disjoint paths by: (a) formulating the cycle-embedding problem as an integer linear program; and (b) developing a heuristic. We show that the number of routing table entries at a node may be reduced to at most two per destination using cycle-embedding approach if the average length of the disjoint paths are allowed to exceed the minimum by 25%.

Real-Time Traffic Scheduling and Routing in Packet-Switched Networks Using a Least-Laxity-First Strategy

In this paper, we address the problem of transmission scheduling and buffer management at a switch in a high-speed packet-switched network. Future computer networks are expected to carry bursty real-time multimedia traffic with specific time-delay requirements. We propose a technique to schedule competing packets at a switch in a packet-switched network with two objectives--(i) maximizing the number of packets that would reach their destination before their deadline has been reached (ii) minimizing the number of packets dropped in transit in the network. The method is broadly based on the popular least-laxity heuristic in real-time process scheduling and is combined with buffer management at the switch.

A neural network method for minimum delay routing in packet-switched networks

In this paper, a neural networks (NNs) based two-phase routing algorithm is proposed. The aim of the first phase is to find a set of alternative routes for each commodity, while the traffic of each commodity is optimally distributed on the alternative routes in the second phase. Our final goal is to route all messages so that the average time delay of a message is minimized. Since the Hopfield neural network (HNN) can only solve problems whose energy functions can be expressed as quadratic forms, the expression of the average time delay of a packet needs first to be simplified and then explicitly included into the energy function. Our algorithm is applied to two network models, both of which have been previously analyzed by other researchers using mathematical methods. Compared with previous results, the proposed algorithm considerably reduces the time delay a packet encounters. A large number of experiments also indicate that the proposed algorithm has very good stability. Our work provides a possible routing policy for future high-speed communication networks due to the fact that a hardware-implemented NN can achieve an extremely high response speed.

Optimizing routing in packet-switched networks with non-Poisson offered traffic

Routing models for packet-switched networks have traditionally been based on the assumption that the offered traffic is Poisson. This is unrealistic since for many applications, real life data streams tend to be extremely "bursty", contradicting the Poisson assumption. This paper introduces a centralized bifurcated routing optimization model for networks with significantly non-Poisson offered traffic. The central purpose of the work is to assess the impact of non-Poisson traffic on routing algorithm developed for Poisson flows. A systematic testing plan for networks with a simple topology and variable levels of capacity, demand and packet length was designed. The results confirmed that Poisson delay formulas together with classical Poisson routing are not appropriate when significant demand is highly variable. The results also show that non-Poisson delay formulas are crucial to the assessment of average delay in these cases.

Distributed routing in packet-switching networks by counterpropagation network

Routing is a problem of considerable importance in a packet-switching network, because it allows both optimization of the transmission speeds available and minimization of the time required to deliver information. In classical centralized routing algorithms, each packet reaches its destination along the shortest path, although some network bandwidth is lost through overheads. By contrast, distributed routing algorithms usually limit the overloading of transmission links, but they cannot guarantee optimization of the paths between source and destination nodes on account of the mainly local vision they have of the problem. The aim of the authors is to reconcile the two advantages of classical routing strategies mentioned above through the use of neural networks. The approach proposed here is one in which the routing strategy guarantees the delivery of information along almost optimal paths, but distributes calculation to the various switching nodes. The article assesses the performance of this approach in terms of both routing paths and efficiency in bandwidth use, through comparison with classical approaches.

Multicast source routing in packet-switched networks

In this paper we present an address coding mechanism for multicast source routing packets in packet-switched networks. A simple algorithm for processing these address codes at intermediate output link adaptors is presented. It involves only the recognition of a particular link label at the front part of the address code and the stripping off of a front segment of the address code and so can easily be implemented in hardware. Recognizing that the recipients of a multicast packet very often need to respond to the source node, we designed the reverse path address code that allows an individual destination node to retrieve the reverse path address without searching the topology database and invoking any route computation program.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation of congestion avoidance and routing in packet switching networks

The development of a flexible computer simulation package for packet switching computer networks that enables the evaluation of different congestion avoidance methods and routing strategies is discussed. The package is presented in terms of the factors involved, the operations required, and the simulation execution considerations. Use of the package for the evaluation of congestion avoidance methods and routing strategies is described. The congestion avoidance methods considered include isarithmic methods with static and dynamic control. In addition, static and dynamic routing strategies are taken into account. The relative differences between the various methods and strategies considered are presented. It has been found that the results obtained agree with previous results, and this confirms the suitability of the package for future investigation. The package would be useful to students and researchers in the field, especially since it uses the widely known computer language Pascal, and is run on an IBM PC(AT).

A distributed adaptive routing algorithm

An algorithm for minimum delay routing in packet-switched networks which is capable of adapting to changes in network input traffic, the addition of new links and nodes, and the failure of existing links and nodes is developed and illustrated. The development is based on theoretical results in Ref.[1] on distributed routing, Newton's method for convex minimization, and the formulation of two separate but cooperating distributed processes which constitute the algorithm itself. The first process, called the normal updating process, provides minimum delay routing given an initial loop-free routing assignment. The second, termed the disturbance adaptive process, generates a new loop-free routing for the first process in response to network changes. The algorithm is applied to a 10 node, 36 link network with 40 commodities, and response characteristics are presented and discussed.

Diffusion Approximations for Time-Dependent Queueing Systems

This paper deals with queueing systems which reveal timedependent behavior. The goal of the paper is to present a set of results which can be applied to the analysis of computer-communication systems. Some new results on the time-dependent analysis of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GI/GI/1</tex> queue and of general queueing networks are given. All these results are based on a transient diffusion model of a single server queue. A parametric-decomposition method of the time-dependent analysis of queueing networks is presented. The method permits the analysis, of the networks where the arrival, service processes and also the routing matrix are time-dependent. It makes possible the analysis of various aspects of computer-communication systems, especially the adaptive routings, the strategies of flow and congestion control, the influence of short overload peaks and other time-varying phenomena in such systems. To illustrate these applications, a simple example of the analysis of the centralized adaptive routing in packet-switching networks is presented.

Delay Analysis of Broadcast Routing in Packet-Switching Networks

Broadcast addressing is the capability to send a packet from a source node to all other nodes in the network. Store-and-forward, packet-switching networks are not inherently designed to carry broadcast packets, and broadcasting has to be implemented by some sort of routing algorithm. In this paper, the source based forwarding algorithm is considered. With this algorithm, a spanning tree is defined for each node, and broadcast packets are sent along the branches of these trees. Approximation methods are presented to obtain a lower bound and estimates of the mean broadcast time. The accuracy of these methods is evaluated by comparison with simulation.