Download or read book The Design Analysis and Performance Evaluation of a Slotted time Mac protocol for Ad hoc Wireless Networks written by Nikhil Singh and published by . This book was released on 2004 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book MAC Protocols Design and a Cross layered QoS Framework for Next Generation Wireless Networks written by Essaïd Sabir and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present dissertation deals with the problem of under-utilization of collision channels and other related problems in wireless networks. It deals with the design of random access protocols for wireless systems and provides a mathematical framework for performance evaluation of multihop based heterogeneous wireless networks. This thesis is divided into three parts. In the first part, we propose new versions of slotted aloha incorporating power control, priority and hierarchy. Our simulations were important to understand the behaviour of such a system and the real impact of involved parameters (transmit power, transmit rate, arrival rate, hierarchy order). Both team problem (common objective function is maximized) and game problem (each user maximizes its own objective) were discussed. Introducing hierarchy seems to provide many promising improvement without/or with a low amount of external information. We also proposed two distributed algorithms to learn the desired throughput. Next, we developed in the second part an analytical Framework to evaluate performances of multihop based heterogeneous Wireless networks. We built a cross-layer model and derived expression of stability, end-to-end throughput and end-to-end delay. Furthermore, we provided an accurate approximation for the distribution of end-to-end delay in multihop ad hoc networks (operating with slotted aloha protocol). As a direct application, we highlighted how streaming and conversational flows could be supported in this class of ubiquitous networks. The third part of this thesis is devoted to understanding and modelling of IEEE 802.11e DCF/EDCF-operated multihop ad hoc networks. We indeed built a complete and simple APPLICATION/NETWORK/MAC/PHY cross-layered model with finite retries per packet per flow. We analyzed the stability of forwarding queues and derived expression of end-to-end throughput. We finally proposed a Fountain code-based MAC layer to improve the throughput/fairness over the network.

Download or read book MAC Protocols for Cyber Physical Systems written by Feng Xia and published by Springer. This book was released on 2015-06-04 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a literature review of various wireless MAC protocols and techniques for achieving real-time and reliable communications in the context of cyber-physical systems (CPS). The evaluation analysis of IEEE 802.15.4 for CPS therein will give insights into configuration and optimization of critical design parameters of MAC protocols. In addition, this book also presents the design and evaluation of an adaptive MAC protocol for medical CPS, which exemplifies how to facilitate real-time and reliable communications in CPS by exploiting IEEE 802.15.4 based MAC protocols. This book will be of interest to researchers, practitioners, and students to better understand the QoS requirements of CPS, especially for healthcare applications.

Download or read book Protocol Design and Performance Evaluation for Wireless Ad Hoc Networks written by Fei Tong and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Benefiting from the constant and significant advancement of wireless communication technologies and networking protocols, Wireless Ad hoc NETwork (WANET) has played a more and more important role in modern communication networks without relying much on existing infrastructures. The past decades have seen numerous applications adopting ad hoc networks for service provisioning. For example, Wireless Sensor Network (WSN) can be widely deployed for environment monitoring and object tracking by utilizing low-cost, low-power and multi-function sensor nodes. To realize such applications, the design and evaluation of communication protocols are of significant importance. Meanwhile, the network performance analysis based on mathematical models is also in great need of development and improvement.This dissertation investigates the above topics from three important and fundamental aspects, including data collection protocol design, protocol modeling and analysis, and physical interference modeling and analysis. The contributions of this dissertation are four-fold.First, this dissertation investigates the synchronization issue in the duty-cycled, pipelined-scheduling data collection of a WSN, based on which a pipelined data collection protocol, called PDC, is proposed. PDC takes into account both the pipelined data collection and the underlying schedule synchronization over duty-cycled radios practically and comprehensively. It integrates all its components in a natural and seamless way to simplify the protocol implementation and to achieve a high energy efficiency and low packet delivery latency. Based on PDC, an Adaptive Data Collection (ADC) protocol is further proposed to achieve dynamic duty-cycling and free addressing, which can improve network heterogeneity, load adaptivity, and energy efficiency. Both PDC and ADC have been implemented in a pioneer open-source operating system for the Internet of Things, and evaluated through a testbed built based on two hardware platforms, as well as through emulations.Second, Linear Sensor Network (LSN) has attracted increasing attention due to the vast requirements on the monitoring and surveillance of a structure or area with a linear topology. Being aware that, for LSN, there is few work on the network modeling and analysis based on a duty-cycled MAC protocol, this dissertation proposes a framework for modeling and analyzing a class of duty-cycled, multi-hop data collection protocols for LSNs. With the model, the dissertation thoroughly investigates the PDC performance in an LSN, considering both saturated and unsaturated scenarios, with and without retransmission. Extensive OPNET simulations have been carried out to validate the accuracy of the model.Third, in the design and modeling of PDC above, the transmission and interference ranges are defined for successful communications between a pair of nodes. It does not consider the cumulative interference from the transmitters which are out of the contention range of a receiver. Since most performance metrics in wireless networks, such as outage probability, link capacity, etc., are nonlinear functions of the distances among communicating, relaying, and interfering nodes, a physical interference model based on distance is definitely needed in quantifying these metrics. Such quantifications eventually involve the Nodal Distance Distribution (NDD) intrinsically depending on network coverage and nodal spatial distribution. By extending a tool in integral geometry and using decomposition and recursion, this dissertation proposes a systematic and algorithmic approach to obtaining the NDD between two nodes which are uniformly distributed at random in an arbitrarily-shaped network.Fourth, with the proposed approach to NDDs, the dissertation presents a physical interference model framework to analyze the cumulative interference and link outage probability for an LSN running the PDC protocol. The framework is further applied to analyze 2D networks, i.e., ad hoc Device-to-Device (D2D) communications underlaying cellular networks, where the cumulative interference and link outage probabilities for both cellular and D2D communications are thoroughly investigated.

Download or read book Advanced Information Networking and Applications written by Leonard Barolli and published by Springer Nature. This book was released on 2021-04-23 with total page 801 pages. Available in PDF, EPUB and Kindle. Book excerpt: ​This book covers the theory, design and applications of computer networks, distributed computing and information systems. Networks of today are going through a rapid evolution, and there are many emerging areas of information networking and their applications. Heterogeneous networking supported by recent technological advances in low-power wireless communications along with silicon integration of various functionalities such as sensing, communications, intelligence and actuations is emerging as a critically important disruptive computer class based on a new platform, networking structure and interface that enable novel, low-cost and high-volume applications. Several of such applications have been difficult to realize because of many interconnections problems. To fulfill their large range of applications, different kinds of networks need to collaborate, and wired and next-generation wireless systems should be integrated in order to develop high-performance computing solutions to problems arising from the complexities of these networks. The aim of the book “Advanced Information Networking and Applications” is to provide latest research findings, innovative research results, methods and development techniques from both theoretical and practical perspectives related to the emerging areas of information networking and applications.

Download or read book Medium Access Protocol MAC Design for Wireless Multi hop Ad Hoc and Sensor Networks written by Afef Sayadi and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless multi-hop ad hoc and sensor networks provide a promising solution to ensure ubiquitous connectivity for the Future Internet. Good network connectivity requires designing a reliable Medium Access Control (MAC) protocol, which is a challenging task in the ad hoc and sensor environments. The broadcast and shared nature of the wireless channel renders the bandwidth resources limited and expose the transmissions to relatively high collisions and loss rates. The necessity to provide guaranteed Quality of Service (QoS) to the upper layers triggered the design of conflict-free MAC protocols. The TDMA synchronization constraint is basically behind the rush of MAC protocol design based on a fixed frame size. This design shows inflexibility towards network variations and creates a network dimensioning issue that leads to a famine risk in case the network is under-dimensioned, and to a waste of resources, otherwise. Moreover, the alternative dynamic protocols provide more adaptive solutions to network topology variations at the expense of a fair access to the channel. Alongside with the efficient channel usage and the fair medium access, reducing the energy consumption represents another challenge for ad hoc and sensor networks. Solutions like node activity scheduling tend to increase the network lifetime while fulfilling the application requirements in terms of throughput and delay, for instance. Our contributions, named OSTR and S-OSTR, address the shortcomings of the medium access control protocol design in the challenging environment of wireless multi-hop ad hoc and sensor networks, respectively. For OSTR the idea consists in adopting a dynamic TDMA frame size that increases slot-by-slot according to the nodes arrival/departure to/from the network, and aiming to achieve a minimum frame size. For this end, OSTR couples three major attributes: (1) performing slot-by-slot frame size increase, (2) providing a spatial reuse scheme that favors the reuse of the same slot if possible, (3) and ensuring an on-demand frame size increase only according to the node requirements in terms of throughput. To tackle different frame sizes co-existence in the network, OSTR brings a cooperative solution that consists in fixing an appointment, a date when the frame size in the network is increased. Concerning S-OSTR, it is an amendment of OSTR for wireless sensor networks. It brings the idea of a dynamic active period, since it deploys a dynamic frame size that is built slot-by-slot according to nodes arrival to the network. S-OSTR enforces the slot-by-slot frame size increase by a node activity scheduling to prolong the inactivity period in the network, and hence prolong the overall network lifetime for wireless sensor networks. Our contributions are both based on the new dynamic TDMA frame size increase that consists in increasing the frame size slot-by-slot aiming to achieve a shorter frame size, and hence improve the channel utilization, and reduce the energy consumption. The performance analysis of OSTR and S-OSTR shows that they present good potentials to support QoS requirements, to provide energy-efficiency, to ensure fair medium access, to accommodate network topology changes and finally, to enhance robustness against scalability. The impact of this new TDMA frame size increase technique on the medium access control protocol performance is highlighted through multiple simulations of OSTR and S-OSTR. Multiple comparative studies are also handled to point out the effectiveness of this new technique and the soundness of our contributions.

Download or read book MAC Protocol Design in Full Duplex Enabled Wireless Networks written by Liqun Fu and published by Springer Nature. This book was released on with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Topics on Ad Hoc Wireless Network Design written by Hazer Inaltekin and published by . This book was released on 2006 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Position Location Techniques and Applications written by David Munoz and published by Academic Press. This book was released on 2009-05-15 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the definitive guide to the techniques and applications of position location, covering both terrestrial and satellite systems. It gives all the techniques, theoretical models, and algorithms that engineers need to improve their current location schemes and to develop future location algorithms and systems. Comprehensive coverage is given to system design trade-offs, complexity issues, and the design of efficient positioning algorithms to enable the creation of high-performance location positioning systems. Traditional methods are also reexamined in the context of the challenges posed by reconfigurable and multihop networks. Applications discussed include wireless networks (WiFi, ZigBee, UMTS, and DVB networks), cognitive radio, sensor networks and multihop networks. Features Contains a complete guide to models, techniques, and applications of position location Includes applications to wireless networks, demonstrating the relevance of location positioning to these "hot" areas in research and development Covers system design trade-offs and the design of efficient positioning algorithms, enabling the creation of future location positioning systems Provides a theoretical underpinning for understanding current position location algorithms, giving researchers a foundation to develop future algorithms David Muñoz is Director and César Vargas is a member of the Center for Electronics and Telecommunications, Tecnológico de Monterrey, Mexico. Frantz Bouchereau is a senior communications software developer at The MathWorks Inc. in Natick, MA. Rogerio Enríquez-Caldera is at Instituto Nacional de Atrofisica, Optica y Electronica (INAOE), Puebla, Mexico. Contains a complete guide to models, techniques and applications of position location Includes applications to wireless networks (WiFi, ZigBee, DVB networks), cognitive radio, sensor networks and reconfigurable and multi-hop networks, demonstrating the relevance of location positioning to these ‘hot’ areas in research and development Covers system design trade-offs, and the design of efficient positioning algorithms enables the creation of future location positioning systems Provides a theoretical underpinning for understanding current position location algorithms, giving researchers a foundation to develop future algorithms

Download or read book Protocol Design and Analysis for Cooperative Wireless Networks written by Wei Song and published by Springer. This book was released on 2016-11-03 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the design and analysis of protocols for cooperative wireless networks, especially at the medium access control (MAC) layer and for crosslayer design between the MAC layer and the physical layer. It highlights two main points that are often neglected in other books: energy-efficiency and spatial random distribution of wireless devices. Effective methods in stochastic geometry for the design and analysis of wireless networks are also explored. After providing a comprehensive review of existing studies in the literature, the authors point out the challenges that are worth further investigation. Then, they introduce several novel solutions for cooperative wireless network protocols that reduce energy consumption and address spatial random distribution of wireless nodes. For each solution, the book offers a clear system model and problem formulation, details of the proposed cooperative schemes, comprehensive performance analysis, and extensive numerical and simulation results that validate the analysis and examine the performance under various conditions. The last section of this book reveals several potential directions for the research on cooperative wireless networks that deserve future exploration. Researchers, professionals, engineers, and consultants in wireless communication and mobile networks will find this book valuable. It is also helpful for technical staff in mobile network operations, wireless equipment manufacturers, wireless communication standardization bodies, and governmental regulation agencies.

Download or read book Wireless Personal Area Networks written by Jelena Misic and published by John Wiley & Sons. This book was released on 2008-02-28 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless Personal Area Networks provides an in-depth analysis of the recent IEEE 802.15.4 standard for low data rate wireless personal area networks (LR-WPANs), including suggestions to improve performance and comparisons with the related 802.15.1 (Bluetooth) standard. It assesses the suitability of the standard for the development and deployment of wireless sensor networks as well as providing guidance and insight into the relative advantages and disadvantages of various performance solutions. Wireless Personal Area Networks: Provides a comprehensive, in-depth look at the issues surrounding WPAN network operation and performance. Investigates multi-cluster networks and compares how they can be implemented. Analyzes the performance of a single cluster under different traffic and power management regimes including uplink vs. downlink traffic, acknowledged vs. unacknowledged traffic, saturation vs. non-saturation, and the like. Discusses security issues in WPANs such as different security threats, their impact on performance, standard security mechanisms, and security policies. Compares the IEEE 802.15.4 standard with the related Bluetooth IEEE 802.15.1 standard in terms of suitability for implementing wireless sensor networks. This reference is a valuable tool for developers and researchers getting acquainted with various aspects of IEEE 802.15.4 technology. Graduate students studying courses such as Performance Evaluation, Wireless Sensor Networks and Queuing Theory will also find this book very insightful.

Download or read book Smart Grid and Internet of Things written by Yi-Bing Lin and published by Springer Nature. This book was released on 2021-03-05 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume, SGIoT 2020, constitutes the refereed proceedings of the 4th EAI International Conference on Smart Grid and Internet of Things, SGIoT 2020, held in TaiChung, Taiwan, in December 2020. The IoT-driven smart grid is currently a hot area of research boosted by the global need to improve electricity access, economic growth of emerging countries, and the worldwide power plant capacity additions. The 40 papers presented were reviewed and selected from 159 submissions and present broad range of topics in wireless sensor, vehicular ad hoc networks, security, blockchain, and deep learning.

Download or read book Wireless Networks Model and Optimization Based Approaches to Clock Synchronization Random Access MAC and Video Streaming written by Nikolaos M. Freris and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We, via a model and optimization-based approach, address three issues related to wireless networks: clock synchronization, medium access control (MAC) and scalable video streaming. In Chapter 2 we develop, study and simulate a new model-based distributed network clock synchronization protocol. In a network of clocks, a given node is taken as reference and is associated with the time evolution t. We introduce and analyze a stochastic model for clocks, in which the relative speedup of a clock with respect to the reference node, called the skew, is characterized by an exponential transformation of an Orstein-Uhlenbeck process. We study the properties of our model, namely moment and sample path properties of the stochastic processes, and calculate its Allan variance. We show how our model can be used to translate the time of a clock to another clock's units. We study the problem of synchronizing clocks in a network, which amounts to estimating the instantaneous relative skews and relative offsets, i.e., the differences in the clock readouts, by exchange of time-stamped packets between pairs of nodes in the network. Based on a stochastic model for delays, we derive a scheme for obtaining relative skew measurements in a communication link by sending two time-stamped packets from node i to node j in order to obtain a noisy measurement of their relative skew. We develop an algorithm for filtering relative skew measurements across a link (i,j) in order to estimate the logarithm of the relative skew. We study the properties of the algorithms and provide theoretical guarantees on their performance. We also develop an online, centralized, model-based, asynchronous skew estimation algorithm for optimal filtering of the time-stamps in the entire network, as well as an efficient distributed suboptimal scheme which demonstrates near-optimal performance in simulations. Furthermore, we study some implementation issues, and present a scheme for pairwise relative offset estimation given skew estimates. We use the distributed asynchronous algorithm to obtain nodal offset estimates from relative offset estimates. We combine our findings into developing a new protocol for clock synchronization, namely the Model-Based Clock Synchronization Protocol (MBCSP). We present a comparative simulation study of its performance versus the leading scheme by Solis et al. (2006); the results show that MBCSP performs better in terms of skew, offset and delay estimation. Finally, we have performed trace-driven simulation based on time-stamps obtained from Berkeley motes. Our scheme outperforms that of Solis et al. by 45%, where we used the accuracy in predicting the receipt time-stamp at the sender as the clock synchronization metric. In Chapter 3, we study random access based MAC in the framework of network utility maximization (NUM). There has been much recent interest in protocol design for wireless networks based on maximizing a network utility function. A significant advance is the observation that a decomposition of the Lagrangian suggests an approach where transmissions are scheduled to minimize back-pressure. However, a satisfactory MAC protocol that can realize such a scheduling algorithm is notably missing, and we develop one potential scheme. We present a candidate random access MAC protocol that extends an existing algorithm by Gupta and Stolyar (2006) in calculating the access probabilities. We also consider the online adaptation of access probabilities using local information about queue lengths and active links. We provide OPNET simulation results to compare the performance of our scheme with the leading schemes. We estimate the capacity region of our scheme by simulation for various topologies and multiple flows. Our simulation studies indicate that our extension in conjunction with an implementation of back-pressure significantly outperforms the slotted-time algorithm of Gupta and Stolyar (2006). In Chapter 4, we present performance bounds for random access based MAC using carrier-sense multiple access (CSMA). In recent work, it was shown that a distributed CSMA-based MAC protocol is throughput-optimal which, in turn, implies that the class of controlled distributed random access MAC protocols can support the entire capacity region. It is challenging to study the performance of such schemes in terms of mean delays and compare it with some known results on the performance of centralized scheduling. We modify the model of Jiang and Walrand (2008) to obtain Markov chain models that incorporate the queue lengths as well as the information about the independent set, for single-hop networks. We show that the delay of the new models yields an upper bound on the delay of the original models. We derive upper and lower bounds on the mean total delay at the steady-state, and show that these bounds coincide with those for max-weight scheduling. Finally, we develop a method of deriving upper and lower bounds for random-access schemes by using linear programs (LPs). We present an optimization program for minimizing the upper bounds. In Chapter 5, we consider multihomed scalable video streaming systems where each video is concurrently transmitted over several access networks to a client. The problem is to determine which video packets of a video stream to transmit, and associate each video packet with an access network, so that the video quality at the client is maximized under measured network conditions. We present a network model and a video distortion model to capture the network conditions and video distortion characteristics, respectively. We develop a mathematical formulation to find the streaming strategy for maximizing the average video quality at the client. While the formulation can be optimally solved using exhaustive search or dynamic programming, doing so takes a prohibitively long time, and is not practical for real-time video streaming servers. In order to efficiently solve the problem in real time, we propose several suboptimal convex problems along with two heuristic algorithms. We conduct extensive trace-driven simulations to evaluate the algorithms using real network conditions and actual scalable video streams. We compare our algorithms against the rate control algorithms defined in the Datagram Congestion Control Protocol (DCCP) standard. The simulation results show that our algorithms significantly outperform current systems while being TCP-friendly. For example, compared to DCCP, our algorithms achieve at least 10 dB quality improvement and result in up to 83% packet delivery delay reduction. Finally, we study the trade-off between efficiency and optimality: One of the heuristic algorithms runs faster and is suitable for large-scale streaming systems, while the other one achieves better video quality and is more appropriate for smaller streaming servers. The convex programming approach demonstrates a good trade-off between running time and performance.

Download or read book Performance Evaluation of a Mac Protocol for Hybrid Wireless Networks written by Rajesh Verma and published by LAP Lambert Academic Publishing. This book was released on 2014-12-22 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, due to basic features of MANETs and bandwidth constraint at MAC layer the throughput, delay and maintaining connectivity has been a major focus for research. Here, different issues of MAC protocols and TCP connectivity have been surveyed in detail. Further, channel utilization can be maximized by employing spatial reuse of the wireless channel at the MAC layer. A high throughput MAC protocol called Multiple-Beam Antenna Array MAC (MBAA-MAC) is proposed and analyzed for MANETs. Proposed MBAA-MAC protocol has been simulated to evaluate its performance in terms of throughput and delay under different network topology scenarios. Again, using this protocol, multiple concurrent transmissions are scheduled to improve the aggregate throughput of the network. The conventional MANETs provide communication in a limited geographical area. This was one of the major limitations of MANETs. A hybrid model is also proposed which is a combination of static & mobile nodes. The MBAA-MAC operates on static nodes. A grid topology consisting of chain of nodes has been simulated for different concurrent transmissions

Download or read book Broadband Powerline Communications written by Halid Hrasnica and published by John Wiley & Sons. This book was released on 2005-01-14 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Broadband Powerline Communications: Network Design covers the applications of broadband PLC systems in low-voltage supply networks, a promising candidate for the realization of cost effective solutions for “last mile” communications networks. There are many activities surrounding the development and application of PLC technology in the access area, particularly because of strong interest of new network providers after the deregulation of telecommunications market. Nowadays, there are no existing standards for broadband PLC networks, which use a frequency range up to 30 MHz. This book includes relevant and timely information regarding broadband PLC systems and especially PLC access networks and contributions to the design aspects of broadband PLC access systems and their network components. This book: Offers explanations on how broadband PLC networks are realized, what the important characteristics for the transmission on electrical power grids are, and which implementation solutions have been recently considered for the realization of broadband PLC systems. Considers various system realizations, disturbance scenarios and their impact the transmission in PLC networks, electro-magnetic compatibility, applied modulation schemes, coding, and error handling methods. Pays particular attention to the specifics of the PLC MAC layer and its protocols, as well as the modelling and performance evaluation of broadband PLC networks.

Download or read book Performance Analysis of Distributed MAC Protocols for Wireless Networks written by Xinhua Ling and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book MAC Layer and Routing Protocols for Wireless Ad Hoc Networks with Asymmetric Links and Performance Evaluation Studies written by Guoqiang Wang and published by . This book was released on 2007 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a heterogeneous mobile ad hoc network (MANET), assorted devices with different computation and communication capabilities co-exist. In this thesis, we consider the case when the nodes of a MANET have various degrees of mobility and range, and the communication links are asymmetric. Many routing protocols for ad hoc networks routinely assume that all communication links are symmetric, if node A can hear node B and node B can also hear node A. Most current MAC layer protocols are unable to exploit the asymmetric links present in a network, thus leading to an inefficient overall bandwidth utilization, or, in the worst case, to lack of connectivity. To exploit the asymmetric links, the protocols must deal with the asymmetry of the path from a source node to a destination node which affects either the delivery of the original packets, or the paths taken by acknowledgments, or both. Furthermore, the problem of hidden nodes requires a more careful analysis in the case of asymmetric links. MAC layer and routing protocols for ad hoc networks with asymmetric links require a rigorous performance analysis. Analytical models are usually unable to provide even approximate solutions to questions such as end-to-end delay, packet loss ratio, throughput, etc.