Performance analysis of buffers with train arrivals and correlated output interruptions

In this paper, we study a discrete-time buffer system with a timecorrelated packet arrival process and one unreliable output line. In particular, packets arrive to the buffer in the form of variable-length packet trains at a fixed rate of exactly one packet per slot. The packet trains are assumed to have a geometric length, such that each packet has a fixed probability of being the last of its corresponding train. The output line is governed by a Markovian process, such that the probability that the line is available during a slot depends on the state of the underlying J-state Markov process during that slot. First, we provide a general analysis of the state of the buffer system based on a matrix generating functions approach. This also leads to an expression for the mean buffer content. Additionally, we take a closer look at the distributions of the packet delay and the train delay. In order to make matters more concrete, we next present a detailed and explicit analysis of the buffer system in case the output line is governed by a 2-state Markov process. Some numerical examples help to visualise the influence of the various model parameters

Performance analysis of priority queueing systems in discrete time

The integration of different types of traffic in packet-based networks spawns the need for traffic differentiation. In this tutorial paper, we present some analytical techniques to tackle discrete-time queueing systems with priority scheduling. We investigate both preemptive (resume and repeat) and non-preemptive priority scheduling disciplines. Two classes of traffic are considered, high-priority and low-priority traffic, which both generate variable-length packets. A probability generating functions approach leads to performance measures such as moments of system contents and packet delays of both classes

Session delay in file server output buffers with general session lengths

In this paper, we analyze the delay incurred by session-based traffic in the output buffer of a file server. Users can start and end sessions during which they are active and download information from the file server. Per time slot, each active user downloads a random but strictly positive number of information packets. Each session lasts for a random, yet again, strictly positive number of slots. We model the file server output buffer as a discrete-time infinite-capacity queueing system and we present an analytical technique to study the queueing delay for sessions in case of a general session-length distribution. The analysis method is based on the combination of a generating-functions approach with the use of an infinite-dimensional state description. As a result, a closed-form expression for the mean session delay is obtained. The analysis is illustrated with a numerical example, based on real traces of file server traffic

Multi-path Probabilistic Available Bandwidth Estimation through Bayesian Active Learning

Knowing the largest rate at which data can be sent on an end-to-end path such that the egress rate is equal to the ingress rate with high probability can be very practical when choosing transmission rates in video streaming or selecting peers in peer-to-peer applications. We introduce probabilistic available bandwidth, which is defined in terms of ingress rates and egress rates of traffic on a path, rather than in terms of capacity and utilization of the constituent links of the path like the standard available bandwidth metric. In this paper, we describe a distributed algorithm, based on a probabilistic graphical model and Bayesian active learning, for simultaneously estimating the probabilistic available bandwidth of multiple paths through a network. Our procedure exploits the fact that each packet train provides information not only about the path it traverses, but also about any path that shares a link with the monitored path. Simulations and PlanetLab experiments indicate that this process can dramatically reduce the number of probes required to generate accurate estimates

Discrete-time queues with variable service capacity: a basic model and its analysis

In this paper, we present a basic discrete-time queueing model whereby the service process is decomposed in two (variable) components: the demand of each customer, expressed in a number of work units needed to provide full service of the customer, and the capacity of the server, i.e., the number of work units that the service facility is able to perform per time unit. The model is closely related to multi-server queueing models with server interruptions, in the sense that the service facility is able to deliver more than one unit of work per time unit, and that the number of work units that can be executed per time unit is not constant over time. Although multi-server queueing models with server interruptions-to some extent-allow us to study the concept of variable capacity, these models have a major disadvantage. The models are notoriously hard to analyze and even when explicit expressions are obtained, these contain various unknown probabilities that have to be calculated numerically, which makes the expressions difficult to interpret. For the model in this paper, on the other hand, we are able to obtain explicit closed-form expressions for the main performance measures of interest. Possible applications of this type of queueing model are numerous: the variable service capacity could model variable available bandwidths in communication networks, a varying production capacity in factories, a variable number of workers in an HR-environment, varying capacity in road traffic, etc

Smart Virtualization for Packet Forwarding in 5G and Beyond Communication Networks

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonIn this thesis, novel ideas have been proposed to tackle the delay and connection continuity, which are caused by different factors related to wired and wireless communication system networks. The vast majority, if we do not say all of these systems adopt packet switch schemes to transfer the data amongst network devices. Moreover, all these systems aim to deliver the data from the source to the destination according to particular Identifiers (IDs) of these devices. The most well-known IDs that are used to distinguish devices are IP address, MAC address, and Subscriber National Number. By virtualizing the servers of communication systems, new concepts of communication networks have emerged. For instance, a mobile operator’s core network function servers could be virtualized, installed, and run by Virtual Machines (VMs) to execute these functions. Also, routers, switches, firewalls, and other network devices could be virtualized by using SDN, NFV, and new- generation protocols such as OpenFlow to create a high performance of the virtualized communication network. From this point of view, we proposed novel concepts such as SVeNB which mimicked the functions of the base station and the core network of a mobile operator network. The SVeNB performance exceeded the C-RAN with 68% in user profiles treatment. Also, the SVeNB reduced the End-to-End delay to 62%. Other advantages of the virtualization are ease of separating the functions and control layer of the networks. This approach urged researchers to suggest a new communication network topologies and innovative designing of flexible and programmable routing protocols. As a result of these approaches, emerging the SDN networks to carry packet forwarding schemes on the communication networks. Based on the facts mentioned above, we designed a novel idea to generate a tag as a mobile node’s ID from E.164 standard numbering and MAC address to handle the packets inside the networks. The results showed that the packet loss rate decreased to 4% of that were lost during the handover delay time or while packets re-direction mechanism. At the same time, the MN could receive 96.4% of the data that was lost during the handover process. Mobility management is a vital issue in wireless communication, due to the necessity of changing the ID of the wireless attached Access Points (APs) by a moving target which connects to that APs. The biggest obstacle of mobility is that the addresses resolution should be made in real time. More difficulty is added when the motion of moving targets is very speedy, for example, such as High-Speed Trains. A novel proactive scheme has been presented by chapter 4 for directing the packet flows among the APs, with support of the trigger signal to activate layer 2 handover. By using the triggering signal, the performance of the suggested network surpassed the performance results that were not supported by the triggering signal. The average control delay time was reduced by nearly 45% and the retrieved data were roughly 90% of packet loss when adopting the triggering signal system.Ministry of Higher Education and Scientific Research (MOHESR) / Iraq, Iraqi Cultural Attach

EUROPEAN CONFERENCE ON QUEUEING THEORY 2016

International audienceThis booklet contains the proceedings of the second European Conference in Queueing Theory (ECQT) that was held from the 18th to the 20th of July 2016 at the engineering school ENSEEIHT, Toulouse, France. ECQT is a biannual event where scientists and technicians in queueing theory and related areas get together to promote research, encourage interaction and exchange ideas. The spirit of the conference is to be a queueing event organized from within Europe, but open to participants from all over the world. The technical program of the 2016 edition consisted of 112 presentations organized in 29 sessions covering all trends in queueing theory, including the development of the theory, methodology advances, computational aspects and applications. Another exciting feature of ECQT2016 was the institution of the Takács Award for outstanding PhD thesis on "Queueing Theory and its Applications"