Present Internet architecture is facing a number of challenges related to security, scalability, ubiquitous computing, management etc. Many initiatives are being carried out globally on designing new architecture for Future Internet which will address these issues. Large scale testbeds are required to validate new architectural designs. In this regard, two major initiatives being carried out are the European Union's (EU) Future Internet Research and Experimentation (FIRE) and USA's Global Environment for Network Innovations (GENI). Apart from these, other countries like Japan, China and Korea are also working towards their own testbeds. This paper gives an overview of large scale testbed initiatives across the world and discusses the major challenges to the development of the global Future Internet testbed. It also compares two major regional testbed architectures and suggests development of formal architecture for worldwide global testbed which will eliminate improvident investments of time, resources and duplicate efforts.

On-line analysis of output data from discrete event stochastic simulation focuses almost entirely on estimation of means. Most “variance estimation” research in simulation refers to the estimation of the variance of the mean, to construct confidence intervals for mean values. There has been little research on the estimation of variance in simulation. We investigate three methods for point and interval estimates of variance and discuss an implementation of the best technique in an extended version of Akaroa2, a quantitative stochastic simulation controller.

This paper proposes a mobile station (MS)-controlled fast MAC-layer handover (HO) scheme to reduce the HO latency in Mobile WiMAX. Based on the received signal strength (RSS) from any Base Station (BS), the MS can estimate its present distance from that BS. This capability allows the MS, through utilization of the broadcast messages by its Serving BS (SBS) and through few scannings of the Neighbouring BSs (NBS), to self-track its own direction of motion relative to the SBS and the NBSs and thus look ahead to perform an intelligent choice of the Target BS (TBS) for the impending HO. Simulation studies have shown a considerable reduction in the HO latency in the proposed method.

For sequential output data analysis in non-terminating discrete-event simulation, we consider three methods of point and interval estimation of the steady-state variance. We assess their performance in the analysis of the output of queueing simulations by means of experimental cover-age analysis. Over a range of models, estimating variances turns out to involve considerably more observations than estimating means. Thus, selecting estimators with good performance characteristics is even more important.

Summary form only given. Advances of computer technology initiated in the twentieth century have resulted in adoption of computer simulation as the most popular tool of performance evaluation studies of such complex stochastic dynamic systems as e.g. modern multimedia telecommunication networks. Such widespread reliance on simulation studies raises the question of credibility of their results. This question needs to be answered before computer simulation can be objectively accepted as an independent, self-sufficient paradigm of scientific investigations. In this talk, having briefly overviewed the main necessary conditions of any trustworthy simulation study conducted for performance evaluation of stochastic dynamic systems, we will focus on simulation studies with on-line output data analysis. The perils and pitfalls of quantitative discrete- event computer simulation will be considered, together with its fast distributed version, known as Multiple Replications in Parallel.

Normal TCP performs well in wired networks. However, when employed in ad hoc wireless networks, its loss-based congestion window progression causes high network buffer utilization due to large bursts of data, which degrades the network bandwidth utilization. This paper argues that the reactive congestion window progression (based on duplicate ACK and timeouts) should be not used in ad hoc networks and proposes a receiver-oriented rate controller (rater), with a congestion window delimiter for the IEEE 802.11 MAC protocol, instead. In addition, the transient nature of medium availability due to medium contention is addressed by a freezing timer (freezer) at the receiver, which freezes the sender whenever heavy contention is perceived. Finally, ad hoc sender enhancements are proposed for optimizing the performance of the receiver-end, as an optional deployment. The new ad hoc TCP demonstrates outstanding results in terms of goodput, as well as throughput.

The paper is concerned with optimizing end-to-end window controls that achieve proportional fairness in the long run, and then investigating their transient or short-term fairness. An abstracted stochastic model of a bottlenecked connection is employed and the window control is designed to minimize the buffer queue variance while keeping the mean queue level at a target value, taking the round-trip delay into account. A generalized window control aimed at reducing window size fluctuations is also derived. The effects of both the target queue length and a weighting parameter on the short-term fairness, as measured by short-term fairness indices calculated over short time intervals, are investigated using ns-2 simulations.

The route computing overhead caused by on-demand calculation of QoS routes, especially in large networks with heavy traffic, is a concern and can cause scalability problems. This paper introduces a distributed cache architecture to reduce the route computing load, caused by execution of QoS routing algorithms. The distributed nature of the proposed cache architecture facilitates its deployment in large networks. To maximize the performance of the distributed cache architecture, cache snooping has been proposed to alleviate the effects of changes in the network states. In performance evaluation of the proposed distributed cache architecture, we use a broad range of realistic network topologies, network traffic conditions, routing protocols, and aggregation techniques to evaluate different aspects of the proposed cache architecture under different conditions. The results confirm that the distributed cache architecture can significantly reduce the route computing overhead. In addition, our results suggest that the cache snooping can significantly increase the overall routing performance, especially in the presence of highly inaccurate network state information.

One problem with a RED router with fixed parameter settings is that the buffer queue length varies markedly with the traffic level. In this paper, an algorithm is derived analytically for automatically tuning the key RED parameter max/sub p/ to keep the average queue length at the target value despite a varying traffic load. A control-theoretic stability analysis is performed to obtain guidelines for setting the remaining RED parameters and the adaptation frequency. Simulation results show that the new adaptive algorithm is faster acting and more accurate than previously proposed heuristic methods.

The p/sub i/-persistent medium access protocol is an attractive solution for high-speed fiber-optic unidirectional bits networks. Sarkar (1996) investigated the delay versus throughput characteristics and fairness performance of the p/sub i/-persistent protocol, inducting the 1-persistent protocol. The main advantage of 1-persistent protocol over the p/sub i/-persistent protocol is the reduced mean packet delay (network-wide and also for individual stations), but the potential drawback of this protocol is the lack of fairness. In contrast, the p/sub i/-persistent protocol can provide good fairness in the sense that mean delays become almost station position independent, but the main drawback of this protocol is the inevitable increase in packet delay. We propose a new scheme, called p/sub i/-persistent/HH (p/sub i/-persistent protocol with hitch-hiking mechanism for slot pre-use) that can offer the combining advantages of 1-persistent and p/sub i/-persistent protocols (i.e. low mean delay and fairness). The low mean delay as well as fairness is achieved by introducing a special mechanism of slot pre-use, called hitch-hiking (HH). In this paper the p/sub i/-persistent/HH scheme is described and simulation results are presented to verify the projected performance.

In multichannel telecommunication networks, switching systems, and processor-memory interconnects, the need for conflict-free traffic assignment arises whenever packets (or requests) are to be directed from input buffers (processors) to specific outlets (modules). This paper presents an algorithm, based on forward planning, which can be used in the above-mentioned applications for scheduling conflict-free transfers of packets from inputs to outputs. The performance of the algorithm is evaluated in the sense of throughput and delay and is compared with that of system of distinct representatives (SDR), an earlier proposed algorithm featuring 100% assignment efficiency. Then, its worst-case computational complexity is compared with that of SDR and several suboptimal (but low complexity) algorithms reported in literature. The proposed forward planning algorithm is shown to have the lowest order of computational complexity and permits simpler buffer organization and access modes. Moreover, it is shown that forward planning of packet transmissions offers significant performance improvements if the finite capacity of buffers is taken into account.

In multichannel telecommunication networks, switching systems and processor-memory interconnects the need for conflict-free traffic assignment arises whenever packets (or requests) are to be directed from input buffers (processors) to specific outlets (modules). We present an algorithm, based on forward planning, which can be used in the above-mentioned applications for scheduling conflict-free transfers of packets from inputs to outputs. The performance of the algorithm is evaluated in the sense of throughput and delay, and compared with that of the system of distinct representatives (SDR), an earlier proposed algorithm featuring 100% assignment efficiency. Then, its worst case computational complexity is compared with that of SDR and several suboptimal low-complexity algorithms reported in literature. It is shown that forward planning of packet transmissions offers significant performance improvements if the finite capacity of buffers is taken into account. Furthermore, the proposed algorithm has the lowest order of computational complexity and permits simpler buffer organisation and access modes.

article Free Access Share on Message Waiting Time in a Packet Switching System Author: Krzysztof Pawlikowski Telecommunication Institute, Technical University of Gdansk, Majakowskiego Street 11/12, 80-952 Gdansk, Poland Telecommunication Institute, Technical University of Gdansk, Majakowskiego Street 11/12, 80-952 Gdansk, PolandView Profile Authors Info & Claims Journal of the ACMVolume 27Issue 1Jan. 1980 pp 30–41https://doi.org/10.1145/322169.322173Published:01 January 1980Publication History 9citation386DownloadsMetricsTotal Citations9Total Downloads386Last 12 Months8Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF