Characterizing user‐perceived impairment events using end‐to‐end measurements

Measures of quality of service (QoS) must correlate to end‐user experience. For multimedia services, these metrics should focus on the phenomena that are observable by the end‐user. Metrics such as delay and loss may have little direct meaning to the end‐user because knowledge of specific coding and/or adaptive techniques is required to translate delay and loss to the user‐perceived performance. Impairment events, as defined in this paper, are observable by the end‐users independent of coding, adaptive playout or packet loss concealment techniques employed by their multimedia applications. Time between impairments and duration of impairments are metrics that are easily understandable by a network user. Methods to detect these impairment events using end‐to‐end measurements are developed here. In addition, techniques to identify Layer 2 route changes and congestion events using end‐to‐end measurements are also developed. These are useful in determining what caused the impairments. End‐to‐end measurements were conducted for about 26 days on 9 different node pairs to evaluate the developed techniques. Impairments occurred at a high rate on the two paths on which congestion events were detected. On these two paths, congestion occurred for 6–8 hours during the day on weekdays. Impairments caused by route changes were rare but lasted for several minutes. Copyright © 2005 John Wiley & Sons, Ltd.     

Link repair in managed multi‐domain connections with end‐to‐end quality guarantees

The Internet is a platform providing connection channels for various services. Whereas for services like email the best‐effort nature of the Internet can be considered sufficient, other services strongly depend on service‐specific connection quality parameters. This quality dependence has led to dedicated content distribution networks as a workaround solution for services like YouTube. Such workarounds are applicable to a small number of services only. With the global application of the Internet, the impact of quality of service varies from annoyance due to jitter in VoIP communication to endangering human lives in telemedicine applications. Thus network connections with end‐to‐end quality guarantees are indispensable for various existing and evolving services. In this paper we consider point‐to‐point multi‐domain network connections for which the end‐to‐end quality has to be assured. Our contribution includes the classification of fault cases in general and countermeasures against end‐to‐end performance degradation. By correlating events and reasonable countermeasures, this work provides the foundation for quality assurance during the operation phase of end‐to‐end connections. We put our contribution in the context of a vision of global‐goal‐aware self‐adaptation in computer networks and outline further research areas that require a similar classification to the work provided here. Copyright © 2012 John Wiley & Sons, Ltd.     

A Subthreshold CMOS RF Front‐End Design for Low‐Power Band‐III T‐DMB/DAB Receivers

This letter presents a CMOS RF front‐end operating in a subthreshold region for low‐power Band‐III mobile TV applications. The performance and feasibility of the RF front‐end are verified by integrating with a low‐IF RF tuner fabricated in a 0.13‐μm CMOS technology. The RF front‐end achieves the measured noise figure of 4.4 dB and a wide gain control range of 68.7 dB with a maximum gain of 54.7 dB. The power consumption of the RF front‐end is 13.8 mW from a 1.2 V supply.     

End‐to‐end performance of transmit antenna selection and generalized selection combining in dual‐hop amplify‐and‐forward relay network in the presence of feedback errors

In this paper, end‐to‐end performance of transmit antenna selection (TAS) and generalized selection combining (GSC) is studied in a dual‐hop amplify‐and‐forward relay network over flat Rayleigh fading channels. In the system, source and destination equipped with multiple antennas, communicate by the help of single relay equipped with single antenna. Source‐destination link is not available. TAS is used for transmission at the source, and GSC is used for reception at the destination. By considering the relay location and the presence of error in feedback channel from the relay to the source, we derive closed‐form outage probability, moment generating function and moments of end‐to‐end signal‐to‐noise ratio, and closed‐form symbol error probability (SEP) expressions for channel state information (CSI)‐based and fixed relay gains. The diversity order and array gain of the network are obtained for both CSI‐based and fixed relay gains by deriving asymptotical outage probability and SEP expressions. The analytical results are validated by the Monte Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Time‐varying network link loss rate tracking from unicast end‐to‐end measurements

Time‐varying network link loss rate is a useful information for network managers to discover and locate the network link failures. This paper proposes a method to track time‐varying network link loss rates from unicast end‐to‐end measurements. The method first trains a state transition matrix to capture the spatio‐temporal characters of packet link transmission probabilities by sending end‐to‐end probe packets and then estimates the time‐varying link loss rates using the state transition matrix and the end‐to‐end measurements obtained from background traffic (the existed packets in network). We also introduce a validation step to check and retrain the state transition matrix in order to ensure the accuracy of the state transition matrix. Our method is capable of tracking the variation of link loss rates without incessantly sending probe packets, which is very feasible for many practical applications. The ns‐2 simulation results show the good performance of our method.     

Customer‐managed end‐to‐end lightpath provisioning

Customer‐owned and managed optical networks bring new cost‐saving benefits. Two types of such networks are becoming widely used: metro dark fiber networks and long‐haul leased wavelength networks. Customers may invoke a special QoS mechanism where end‐to‐end (E2E) lightpaths are dynamically established across multiple independently managed customer domains. The cost of bandwidth is substantially reduced since it largely becomes a capital cost rather than an ongoing service charge. Customers can optimize the overall resource consumption by utilizing resources from different suppliers. Remote peering and transit reduce the Internet connectivity cost. Bandwidth and quality of service are guaranteed because customers directly peer with each other using transport networks. An architecture for a customer‐managed E2E lightpath provisioning system is presented. Integration with Grid applications is discussed and a prototype demonstration is described. Copyright © 2005 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

Performance analysis of two‐way wireless‐powered Amplify‐and‐Forward relaying in the presence of co‐channel interference

In this paper, we investigate the performance assessment of a bidirectional relaying system using energy harvesting techniques. We assume independent and nonidentically distributed (i.n.i.d.) Nakagami‐m fading channels where the amplify‐and‐forward relay is subject to co‐channel interference (CCI) due to transmissions of other transmitters. Two different scenarios, namely, scenario I and scenario II are evaluated. In scenario I, both end‐sources provide the required energy for the relay, whereas the relay also harvests energy from the co‐channel interferes. Then, in the first phase of cooperation, both end‐sources send the information to the relay, and after amplifying the received signal, relay transfers information to the appropriate destination in the second time‐slot. In the scenario II, both end‐sources harvest energy from the relay. After that, the information cooperative transmission is done similar to the first scenario. For both considered scenarios, tight closed‐form expressions of outage probability, symbol error probability, ergodic capacity, and throughput are obtained at arbitrary signal‐to‐noise‐ratios (SNRs). To get more insights, simplified high SNR results for both scenarios are also deduced where the diversity orders are obtained. Monte Carlo simulation results are presented to validate the correctness of our proposed analysis. Our results explicitly demonstrate that the first scenario has a better performance than the second one in the medium and high SNR region, whereas the second scenario outperforms the first one in the low SNR regime.     

An altruism‐based trust‐dependent message forwarding protocol for opportunistic networks

In opportunistic networks (OppNets), which are characterized by intermittent end‐to‐end connections, the messages are routed in a store‐carry‐and‐forward fashion using the locally inferred knowledge about the behavior of nodes. As such, most OppNets routing protocols use social metrics that are dependent on the nodes' past information. But the participation of nodes in the message forwarding process is not guaranteed without incentivizing them because most nodes are reluctant in sharing their private resources for public uses. In this paper, some socially derived psychological attributes of a node are introduced to ensure their trustworthy participation in the message forwarding process, leading to the design of an altruism‐dependent trust‐based data forwarding mechanism for OppNets (called ATDTN). In this protocol, each node is associated with a dynamically changing altruism value representing its trust in the network, which is used to determine its status with regard to its participation in message forwarding. Through trace‐driven simulations using the ONE simulator, it is shown that ATDTN outperforms IronMan and SimBet protocols for routing in OppNets (respectively, 18% and 48% improvement), in terms of delivery ratio, end‐to‐end delay, overhead count, and average number of hops, under varying buffer size and time‐to‐live.     

A new privacy and authentication protocol for end‐to‐end mobile users

In this papecr, we propose a new privacy and authentication scheme for end‐to‐end mobile users. There are three goals in our scheme. The first allows two end‐to‐end mobile users to communicate privately each other. The second allows two end‐to‐end mobile users to distribute a session key simply. The third allows two end‐to‐end mobile users to mutually authenticate. Copyright © 2003 John Wiley & Sons, Ltd.     

Fair end‐to‐end window‐based congestion control in time‐varying data communication networks

Communication networks are time varying and, hence, fair sharing of network resources among the users in such a dynamic environment is a challenging task. In this context, a time‐varying network model is designed, and the shortest user's route is found. In the designed network model, an end‐to‐end window‐based congestion control scheme is developed with the help of internal nodes or router, and the end user can get implicit feedback (throughput). This scheme is considered as fair if the allocation of resources among users minimizes overall congestion or backlog in the networks. Window update approach is based on a multi‐class fluid model and is updated dynamically by considering delays (communication, propagation, and queuing) and the backlog of packets in the user's routes. Convergence and stability of the window size are obtained using a Lyapunov function. A comparative study with other window‐based methods is also provided.     

Performance comparison of end‐to‐end and on‐the‐spot traffic‐aware techniques

Traffic‐aware routing protocols have recently received considerable attention. This has been motivated by the role that it could play in extending the network's lifetime (or operational time) as it target the reservation of node's power and better utilisation of channel bandwidth, which could lead to performance improvement in terms of important performance metrics including throughput and end‐to‐end delay. Traffic‐aware techniques can be classified into two categories, namely end‐to‐end and on‐the‐spot, based on the way of establishing and maintaining routes between any source and destination. Although there has been much work on both categories, there has been no comparative performance study of the two approaches. To the best of our knowledge, this is the first work that carries out such a performance comparison. To this end, we have adapted our traffic‐aware technique namely load density to suggest a new ‘on‐the‐spot’ traffic‐aware technique. The main reason for doing this adaptation is to ensure that the comparison between the two approaches is fair and realistic. The study will reveal the main performance characteristics of the two approaches under various traffic and network conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Secure Connectivity Probability of Multi‐hop Clustered Randomize‐and‐Forward Networks

This work investigates secure cluster‐aided multi‐hop randomize‐and‐forward networks. We present a hop‐by‐hop multi‐hop transmission scheme with relay selection, which evaluates for each cluster the relays that can securely receive the message. We propose an analytical model to derive the secure connectivity probability (SCP) of the hop‐by‐hop transmission scheme. For comparison, we also analyze SCPs of traditional end‐to‐end transmission schemes with two relay‐selection policies. We perform simulations, and our analytical results verify that the proposed hop‐by‐hop scheme is superior to end‐to‐end schemes, especially with a large number of hops or high eavesdropper channel quality. Numerical results also show that the proposed hop‐by‐hop scheme achieves near‐optimal performance in terms of the SCP.     

Tailorable Thermal Properties Through Reactive Blending Using Orthogonal Chemistries and Layer‐by‐Layer Deposition of Poly(1,3,5‐hexahydro‐1,3,5‐triazine) Networks

The ability to tune both the thermal and mechanical properties of poly(1,3,5‐hexahydro‐1,3,5‐triazine)s (PHTs) is critical to meet the increasingly stringent demands of structural materials. To this end, PHTs are modified during the process of vitrification using a reactive blending technique. Two strategies are employed: (i) the incorporation of a monomer or oligomer that contains amino end groups that are integrated into the network via hemiaminal chemistry and (ii) the incorporation of functional monomers bearing reactive end groups capable of self‐polymerization, as well as insertion by copolymerization with the PHT‐forming reagents to form mixed networks. Both strategies produce homogeneous materials, mitigating any adverse thermal properties of the parent PHT material. Here, a deposition method bringing the PHT technology platform to more diverse, economical and large‐scale applications is also introduced. A unique layer‐by‐layer spray‐coating approach of solutions containing 4,4′‐oxydianiline (ODA) and multifunctional amines obtained by conjugate addition to acrylates is developed, allowing for the preparation of large‐scale PHT‐polymer blend films. The ODA–PHT enables high strength and modulus of the final material, while incorporation of acrylates provide an economical approach to polymer blends with tremendous functional group diversity and will allow for recyclability under mild conditions.     

Performance analysis of a variable‐gain amplify‐and‐forward relayed mixed RF‐FSO system

In this work, an amplify‐and‐forward variable‐gain relayed mixed RF‐FSO system is studied. The considered dual‐hop system consists of a radio frequency (RF) link followed by a free space optical (FSO) channel. The RF link is affected by short‐term multipath fading and long‐term shadowing effects and is assumed to follow the generalized‐K fading distribution that approximates accurately several important distributions often used to model communication channels. The FSO channel experiences fading caused by atmospheric turbulence that is modeled by the gamma‐gamma distribution characterizing moderate and strong turbulence conditions. The FSO channel also suffers path loss and pointing error induced misalignment fading. The performance of the considered system is analyzed under the collective influence of distribution shaping parameters, pointing errors that result in misalignment fading, atmospheric turbulence, and path loss. The moment‐generating function of the Signal power to noise power ratio measured end‐to‐end for this system is derived. The cumulative distribution function for the Signal power to noise power ratio present between the source and destination receiver is also evaluated. Further, we investigate the error and outage performance and the average channel capacity for this system. The analytical expressions in closed form for the outage probability, symbol and bit error rate considering different modulation schemes and channel capacity are also derived. The mathematical expressions obtained are also demonstrated by numerical plots.     

In‐service QoS monitoring of real‐time applications using SM MIB

Current network management needs an end‐to‐end overview of various flows rather than the information that is purely local to the individual devices. The typical manager‐centric polling approach, however, is not suitable to understand network‐wide behavior of a large‐scale Internet. In this paper, we propose a new management information base (MIB) approach called Service Monitoring MIB (SM MIB). The MIB provides a network manager with dynamic end‐to‐end management information by utilizing special packets. The special packet is an Internet control message protocol (ICMP) application that is sent to a remote network element to monitor Internet services. The SM MIB makes an end‐to‐end management feasible while it reduces management‐related traffic and manager‐to‐manager interactions. Real examples show that the proposed SM MIB is useful for end‐to‐end QoS monitoring. We discuss the accuracy of the obtained data as well as the monitoring overhead. Copyright © 2004 John Wiley & Sons, Ltd.     

End‐to‐end delay and packet drop rate performance for a wireless sensor network with a cluster‐tree topology

In this paper, we study the delay performance in a wireless sensor network (WSN) with a cluster‐tree topology. The end‐to‐end delay in such a network can be strongly dependent on the relative location between the sensors and the sink and the resource allocations of the cluster heads (CHs). For real‐time traffic, packets transmitted with excessive delay are dropped. Given the timeline allocations of each CH for local and inter‐cluster traffic transmissions, an analytical model is developed to find the distribution of the end‐to‐end transmission delay for packets originated from different clusters. Based on this result, the packet drop rate is derived. A heuristic scheme is then proposed to jointly find the timeline allocations of all the CHs in a WSN in order to achieve the minimum and balanced packet drop rate for traffic originated from different levels of the cluster tree. Simulation results are shown to verify the analysis and to demonstrate the effectiveness of the proposed CH timeline allocation scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

SDN‐based fault‐tolerant on‐demand and in‐advance bandwidth reservation in data center interconnects

Geographically distributed data centers are interconnected through provisioned dedicated WAN links, realized by circuit/wavelength–switching that support large‐scale data transfer between data centers. These dedicated WAN links are typically shared by multiple services through on‐demand and in‐advance resource reservations, resulting in varying bandwidth availability in future time periods. Such an inter‐data center network provides a dynamic and virtualized environment when augmented with cloud infrastructure supporting end‐host migration. In such an environment, dynamically provisioned network resources are recognized as extremely useful capabilities for many types of network services. However, the existing approaches to in‐advance reservation services provide limited reservation capabilities, eg, limited connections over links returned by the traceroute over traditional IP‐based networks. Moreover, most existing approaches do not address fault tolerance in the event of node or link failures and do not handle end‐host migrations; thus, they do not provide a reliability guarantee for in‐advance reservation frameworks. In this paper, we propose using multiple paths to increase bandwidth usage in the WAN links between data centers when a single path does not provide the requested bandwidth. Emulation‐based evaluations of the proposed path computation show a higher reservation acceptance rate compared to state‐of‐art reservation frameworks, and such computed paths can be configured with a limited number of static forwarding rules on switches. Our prototype provides the RESTful Web service interface for link‐fail and end‐host migration event management and reroutes paths for all the affected reservations.     

An end‐to‐end alternative to TCP PEPs: Initial Spreading,a TCP fast start‐up mechanism

While Transmission Control Protocol (TCP) Performance Enhancing Proxy (PEP) solutions have long been undisputed to solve the inherent satellite problems, the improvement of the regular end‐to‐end TCP congestion avoidance algorithms and the recent emphasis on the PEPs drawbacks have opened the question of the PEPs sustainability. Nevertheless, with a vast majority of Internet connections shorter than ten segments, TCP PEPs continue to be required to counter the poor efficiency of the end‐to‐end TCP start‐up mechanisms. To reduce the PEPs dependency, designing a new fast start‐up TCP mechanism is therefore a major concern. But, while enlarging the Initial Window (IW) up to ten segments is, without any doubt, the fastest solution to deal with a short‐lived connection in an uncongested network, numerous researchers are concerned about the impact of the large initial burst on an already congested network. Based on traffic observations and real experiments, Initial Spreading has been designed to remove those concerns whatever the load and type of networks. It offers performance similar to a large IW in uncongested network and outperforms existing end‐to‐end solutions in congested networks. In this paper, we show that Initial Spreading, taking care of the satellite specificities, is an efficient end‐to‐end alternative to the TCP PEPs. Copyright © 2015 John Wiley & Sons, Ltd.     

Mitigating file‐sharing misbehavior with movement synchronization to increase end‐to‐end availability for delay sensitive streams in vehicular P2P devices

When dealing with wireless connectivity in a mobile peer‐to‐peer (MP2P) environment, there are many concerns about the offered efficiency and availability of the requested resources and concerns about practicality considerations. These considerations deal with the movement and deployment of continuous connectivity. The intermittent connectivity is a major factor for object sharing misbehavior because it aggravates the connectivity and reliability. MP2P environments are in need of specialized placement algorithms where structured index‐centric solutions will be able to provide efficiency and object location determination over intermittent connectivity and communication. Replication of any requested object and redundancy face the requests' failures because they create severe duplications, and aggravate the capacity of the end‐to‐end path. This work proposes a framework that enables mitigation between the file sharing misbehavior in contrast to the movement synchronization, and it quantifies the parameters that affect the end‐to‐end efficient transmission by taking into consideration the synchronization between moving peers to assign the requested resources in the end‐to‐end path. Resilience metrics are introduced to enable reliability in cooperative file sharing procedure. The proposed scheme considers synchronization and assignment of the moving mobile Infostation peer with certain object indices to a certain vehicle via a synchronized cooperative scheme where the file sharing process is performed through the message ferry mobile peer. In addition, a resource assignment cooperation engine is developed taking into consideration the social cooperation model and the end‐to‐end capacity of the relay path. The proposed resource exchange apparatus for file chunks' migration is performed to enable delay sensitive streaming. The proposed model is evaluated through experimental simulation taking measures for the throughput and the reliability offered and for the robustness for sharing resources of any capacity in dynamically changing MP2P wireless environments under synchronized movements. Copyright © 2012 John Wiley & Sons, Ltd.     

End‐to‐end response time with fixed priority scheduling: trajectory approach versus holistic approach

In this paper, we are interested in providing deterministic end‐to‐end guarantees to real‐time flows in a distributed system. We focus on the end‐to‐end response time, quality of service (QoS) parameter of the utmost importance for such flows. We assume that each node uses a Fixed Priority scheduling. We determine a bound on the end‐to‐end response time of any real‐time flow with a worst case analysis using the trajectory approach. We establish new results that we compare with those provided by the classical holistic approach for flows visiting the same sequence of nodes. These results show that the trajectory approach is less pessimistic than the holistic one. Moreover, the bound provided by our worst‐case analysis is reached in various configurations, as shown in the examples presented. Copyright © 2004 John Wiley & Sons, Ltd.