Matteo D'Ambrosio

Optimal cost/performance design of ATM switches

This paper proposes a methodology for performing an evaluation and optimization of the cost of an ATM switching architecture under performance constraints given in terms of virtual connection blocking probability. An analysis of blocking networks is developed, and combined with known results concerning nonblocking networks, provides a theoretical model which relates traffic characteristics, network topology and blocking probability in a multirate/multiservice broadband environment. An analysis of the characteristics determining the cost of a generic ATM switch implementation follows. The model is oriented to optimize both the topological parameters and the speed advantage, with respect to the main cost factors of VLSI-based switching networks i.e., components count and complexity, interconnection costs. >

Evaluating the limit behavior of the ATM traffic within a network

This paper is concerned with the ATM traffic characterization within the network. Most of the work performed up to now has studied the effects of traffic on the access multiplexer and the first switch of an ATM network. Various source models were assumed to generate the ATM traffic. So, while the performance of a single switch node has been exhaustively examined, the statistical behavior of the traffic modified as it crosses the network has not been thoroughly analyzed yet. This paper, through an analysis of a network of cascaded queues, indicates that limit distributions exist in the statistical behavior of the traffic streams and in the queue performance, although a formal proof is believed to be very hard to obtain. The first modelling step consists of deriving the exact interdeparture time distribution for the cells of a reference-connection arriving to the output queue of a switch node with a general interarrival time distribution and multiplexed with a background traffic stream. The analysis is iterated through a long sequence of cascaded output queues, until the interdeparture time distribution converges. Simulations show that the analytical results are accurate at each stage of the network under the hypothesis of independent queues, and are also good approximations in the case of correlated queues. This study shows that the queue performance at the limit point is always better than the M/D/1 case. The distributions found in this way depend only on the connection bandwidth and on the background traffic behavior. The initial characteristics of a connection (burst length distributions and burst interarrival time distributions) only influence the convergence speed, not the limit distribution.

The A-VPN server: a solution for ATM virtual private networks

The paper presents an architectural element to be included in an ATM cross-connect in order to provide essential features for the deployment of an ATM based virtual private network service (A-VPN service). The A-VPN server aims at a solution of the egress policing problem (bandwidth enforcement function) and incorporates a set of functionalities devoted to the support of an effective statistical multiplexing principle on the different cell streams, by means of suitable buffering, shaping and selective traffic discarding functions. The target solution allows for an improved and possibly optimal utilisation of network resources, compared to peak rate allocation, while ensuring that satisfactory quality of service requirements are matched for bursty traffic. Moreover the A-VPN server is able to grow in a modular way and its approach has no special impact on the functions of the ATM cross-connect; its introduction does not require the support of particular management protocols by the network element. The A-VPN server represents a simple, efficient and cost-effective way for a timely implementation of the A-VPN service.<<ETX>>

Broadening the ATM offer with a full set of service categories

The paper aims at providing a comprehensive picture of the new set of ATM-layer services defined in parallel by the ITU-T and The ATM Forum, outlining the potential benefits that can derive, both to users and network service providers, from the availability of these new functionalities in an ATM-based network. Terminological differences between the ITU-T and ATM Forum documents are compared and clarified and the approaches to the use of quality of service parameters and classes are discussed. The so-called Service Categories (using the ATM Forum nomenclature) are Constant Bit Rate, Variable Bit Rate (VBR), Available Bit Rate (ABR) and Unspecified Bit Rate. The ABR is the newest and the one raising major discussions, as specific congestion control mechanisms, which do represent a real innovation in the ATM framework, have been defined for its support. The paper therefore introduces the ABR service in some details and discusses some still open issues and utilization perspective.

Per-user NFV services with mobility support

This paper presents an architecture to provide endto- end per-user services with support to client mobility, designed according to the SDN and NFV paradigms. Our service platform dynamically configures and launches service requests when the client connects to the network, which are used by a multidomain orchestration system to arrange the required network configuration and computational resources. Service configuration is dynamically updated when a movement of the client is detected, that is, when a client device changes its access point to the network. A prototype implementing the idea has been developed and validated over JOLNET, a real, geographical, OpenFlowbased experimental network connecting several sites in Italy and operated by Telecom Italia.

On the Limit Behaviour of the ATM Traffic within a Network

ABSTRACT The paper is concerned with the ATM traffic characterization within the network. Most of the work performed up to now has studied the effects of the traffic on the access multiplexer and the first switch of an ATM network; various source models were assumed to generate the ATM traffic. So, while the performances of a single switch node have been exhaustively examined, the statistical behaviour of the traffic modified as it crosses the network has not been thoroughly analyzed yet. The paper, through an analysis of a network of cascaded queues, shows that limit distributions exist in the statistical behaviour of the traffic streams and in the queue performances. The first modelling step consists in deriving the exact interdeparture time distribution for the cells of a reference-connection arriving to the output queue of a switch node with a general interarrival (GI) time distribution and multiplexed with a background traffic stream, then the analysis is iterated through a long sequence of cascaded output queues, until the interdeparture time distribution converges to a limit one. Simulations show that the analitycal results are more than accurate at each stage of the network under the hypothesis of independent queues. The study shows that the queue performances at the equilibrium point are always better than the M/D/1 case. The limit distributions depend only on the connection bandwidth and on the background traffic behaviour; the initial characteristics of a connection (burst length distributions and burst interarrival time distributions) do influence only the convergence speed, not the limit distributions.