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We present the analysis of a single-wavelength fiber-delay-line buffer fed by a batch arrival process, and apply the results to study the influence of (internal) synchronization on performance. We rely on generating functions to develop a discrete-time queueing model that, unlike previously obtained results, is able to cope with concurrent arrivals. Without making any special assumptions on the burst...
This paper proposes a novel architecture, named APOHN, designed for data communications over heterogeneous networks. APOHN enables easy implementation of various existing and upcoming performance optimization solutions with the main objective to keep the standardized TCP/IP reference model untouched. APOHN architecture extends ISO/OSI protocol stack model with an additional layer designed for subnetwork...
This paper proposes a measurement system of QoS parameters for a SIP based Internet telephony service. This system is called QoS agent and will allow telephony user to receive alerts in real time if network conditions are not suitable to make a call. Two complementary types of measurement methods will be used. The first one is called incall method which uses RTCP packets statistics obtained during...
Virtual private networks (VPNs) are overlay networks established on top of a public network backbone with the goal of providing a service comparable to private networks (PNs). The recently proposed VPN hose-model provides customers with flexible and convenient ways to specify their bandwidth requirements. In order to meet specified bandwidth requirements, the network service provider (NSP) must reserve...
The paper deals with the resources availability, recovery time and redundancy of the fibre-based passive optical networks. It also takes into account architectures of the power supply system. The availability models for recovery architectures are presented. The overall quality of recovery calculation is performed. On this basis, different schemes are compared and the rules which of them to use are...
In this paper we define a calculus for communication networks which is suitable for workload loss estimation based on the original definition of stationary loss ratio. Our novel calculus is a probabilistic extension of the deterministic network calculus, and takes an envelope approach to describe arrivals and services for the quantification of resource requirements in the network. We introduce the...
We consider a simplified model for the rate control of TCP sources. In particular, we assume idealized negative feedbacks upon reaching a certain total sending rate, i.e., at the moment when the total sending rate attains a given capacity limit c one of the TCP sources is given a negative feedback and the source reduces its sending rate in a multiplicative manner. Thus, the model takes into account...
DDoS attacks have caused severe damage to servers and are a great intimidation to the development of new services. Recently, a simple but robust detection system was proposed. The referred scheme is based on the monitoring of the source IP addresses of the incoming packets. However, it is possible to show that the proposed scheme is unable to identify correctly the end of an attack and a high variance...
To provide fault-tolerance for multicast connections, different techniques of protection are developed. These techniques can be classed into reactive and pro-active approaches. Reactive approaches can have long recovery latency which is undesirable for many types of applications such as the real time ones. In this paper, we focus on the multicast pro-active fault-tolerance schemes. One of the promising...
The estimation of heavy-tailed probability density function is an important tool for the description of the Web-traffic data and the solution of applied problems such as classification. The paper is devoted to the non-parametric estimation of a heavy-tailed probability density function by a variable bandwidth kernel estimator. Two approaches are used: (1) a preliminary transformation of the data to...
We analyze Internet user traffic flows measured at the access network of a Portuguese ISP. Using singular-value decomposition, the weekly traffic utilization of each user is decomposed in periodic, noise and burst components. The most important component is the periodic, which is responsible for 52% of the total variability of the data set. This component was used to obtain groups of users with similar...
The predictability of Internet traffic is a significant interest in many domains such as adaptive applications, congestion control, admission control, and network management. In this paper, we propose a new traffic prediction model called autoregressive integrated moving average with generalized autoregressive conditional heteroscedasticity (ARIMA/GARCH), which can capture traffic burstiness and exhibit...
With the increasing popularity of mobile wireless communication systems, customers are expecting the same quality of service (QoS), availability and performance from the wireless communication networks as the traditional wire-line networks. Currently the research work on radio channel allocation in cellular mobile systems focuses mainly on two aspects, improving the user admission capability and protecting...
In this paper, we consider adaptive bandwidth allocation (ABA) for capacity tunnels as an effective means for multi-hour network design. Traffic engineering (TE) tunnels established in a network from border-to-border (b2b) can be used not only for route pinning between ingress/egress node pairs but also for efficient implementation of resilient network admission control. If static bandwidth allocation...
The possibility of adding MPLS support to transport networks is considered an important opportunity by telecom carriers that want to add packet services and applications to their networks. However, the question arises whether it is convenient to add MPLS nodes just at the edge of the network to collect packet traffic from users, or it is better to have also MPLS core nodes to exploit packet switching...
Triple Play requires cost-effective implementation of three services that are different in both traffic and QoS requirements. The methods applied for optimization of Ethernet trees must support not only point-to-point pipes but also point-to-multipoint connections for multicast and statistical multiplexing models for better resource allocation. In this paper we present a QoS architecture for Triple...
In this work, we study the minimum cost flow allocation problem with varied survivability. Given a set of demands and a capacitated network, the problem consists of allocating each demand to a set of primary paths that carry the flows realizing the demand volume in the normal operation mode. To ensure survivability, bandwidth is allocated over a disjoint set of backup links protecting the primary...
Railway control systems are largely based on data communication and network technologies. With the adoption of Ethernet-IP as the main technology for building end-to-end real-time networks on railway control systems, the requirement to deliver high availability, quality and secure services over Ethernet has become strategic. Critical real-time traffic is generally penalized and the maximum restoration...
We compare the capacity requirements of two new end-to-end (e2e) protection switching mechanisms: the self-protecting multipath (SPM) and several (multi-)path protection (PP) methods. Their structure consists of disjoint parallel e2e paths and the traffic is distributed over these paths according to a load balancing function. If one of the paths fails, the traffic is redistributed to the working paths...
The existing work on dependability modelling and analysis of networks have main focuses on the, structural properties. However, the communication networks also have dynamic characteristics and behavioral properties, such as changes of topology, routes, and traffic loads, which should necessarily be reflected in the modelling. We regard the dependability modelling and analysis of IP networks with an...
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