An error-controlled approximate analysis of a stochastic fluid flowmodel applied to an ATM multiplexer with heterogeneous on-off sources

The stochastic fluid flow approach is applied to the analysis of the cell loss performance of an ATM multiplexer. The input traffic stream offered to the multiplexer is the superposition of heterogeneous on-off sources with independent and exponentially distributed on and off times. The focus is on the numerical investigation of the steady-state behavior of models involving very large state spaces. To this end, an efficient algorithm for the evaluation of tight upper and lower bounds of the cell loss probability is developed. The algorithm allows a significant reduction of the computational burden, while yielding a guaranteed overestimate of the error implied by the proposed approximation of the cell loss probability. Numerical results are presented both to assess the tightness of the proposed bounds and to gain insight into the behavior of heterogeneous traffic mixes. The main conclusion, from the multiplexer performance evaluation point of view, is that it is not convenient to mix very different traffic streams in a completely shared FIFO buffer, without some kind of control     

Definition and performance analysis of a simple, ABR-likecongestion control scheme for satellite ATM networks with guaranteedloss performance

We describe an ATM system architecture for satellite communications. The proposed architecture includes on-board switching, and supports the ATM traffic categories defined in previous specifications. In this framework, a critical issue is the control of congestion phenomena. In particular, the application of feedback-based control strategies to a satellite network is critical due to the peculiarities of such an environment: very large propagation delay, expensive transfer capacity, and limited on-board processing capability. The available bit rate (ABR) is the ATM service category handled according to a reactive congestion control (RCC). The focus of this paper is the definition of an RCC that is fully compatible with the standard ABR protocols, and that takes into account the constraints of the satellite environment. We also derive an analytical model that allows us to evaluate the performance of the proposed scheme and to dimension the system. The analytical model is validated with simulations     

A Comparison of the Utilization Efficiency between a Stateful and a Stateless Admission Control in IP Networks in a Heterogeneous Traffic Case

The IETF developed two main approaches to provide QoS aware services in the Internet: Integrated Services (IntServ) and Differentiated Services (DiffServ). Both have well known pros and cons (e.g., [Huston, 24; Bernet et al., 2]). The stateful IntServ has a greater level of accuracy and a finer level of granularity. The stateless DiffServ possesses excellent scaling properties, but lacks a standardized admission control scheme and, upon overload in a given service class, degradation of service can occur. To provide QoS in DiffServ, three possible strategies are: (i) plain and heavy over-dimensioning; (ii) admission control at the borders of the DiffServ region, coupled with suitable assumptions on the distribution of the traffic within the region, which can lead to over-dimensioning, even if less severe than the previous one; (iii) per-node admission control within the region. Following RFC2990, we recently proposed an “admission control function which can determine whether to admit a service differentiated flow along the nominated network path” [Huston, 24], i.e., the third of the above strategies. This function, named GRIP (Gauge and Gate Reservation with Independent Probing), can provide strict QoS guarantees by means of stateless DiffServ-compliant procedures. This feature is paid with a potential loss of efficiency, with respect to an ideal, stateful admission control. The goal of this paper is to evaluate analytically such loss of efficiency, in a specific heterogeneous scenario. In other words, we want to estimate how much resources we can waste if we go stateless and avoid state maintenance functions. The comparison between stateless and stateful approaches is performed under the constraint of strictly offering the same performance levels, in terms of, e.g., loss probability and delay.     

Steady-state analysis of the MMPP/G/1/K queue

An exact analysis of the MMPP/G/1/K queuing model is carried out, yielding the whole buffer occupancy probability distribution and in particular the loss probability. The solution is obtained by an algorithmic procedure and requires only algebraic manipulations. An expression for the Laplace-Stieltjes transform of the virtual waiting time distribution is derived     

A Layer 3 Movement Detection Algorithm Driving Handovers in Mobile IP

The evolution and the spreading of wireless access technology and the consequent increase of user mobility will make handover procedures critical for the provision of Quality of Service in the next generation wireless Internet. Often, layer 3 handovers are supposed to be driven by access layer procedures. In this way, the movement detection delay can be reduced, but at the expenses of making the Mobile IP protocol dependent of lower layer implementations. Furthermore, this approach may not be effective when users roam among heterogeneous networks. Nevertheless, movement detection algorithms, which operate at the Mobile IP layer, imply appreciable delays, usually intolerable for real time services.In this paper, we propose a Mobile IP handover scheme based on a novel movement detection algorithm at layer 3, able to timely manage migrations by exploiting advertisements losses, combined with a two-timers mechanism.We analyze the performance of our algorithm in terms of handover delay and throughput, and we show that our solution is able to decrease the movement detection delay as much as 47% with respect to other literature solutions that pursue similar approaches. In addition, this feature implies also higher values of the throughput seen by the TCP layer.This work has been carried out in the framework of the FIRB Project PRIMO, co-financed by the Italian Ministry for Education, Higher Education and Research (MIUR).Nicola Blefari Melazzi received his Laurea degree in Electrical Engineering in 1989, magna cum laude with publication of his thesis, and earned the Dottore di Ricerca (Ph.D.) in Information and Communication Engineering in 1994, both at the University of Roma La Sapienza, Italy. In 1993 he joined the University of Roma Tor Vergata, as an Assistant Professor. From 1998 to 2002 he has been an Associate Professor at the University of Perugia. In 2002 he came back to the University of Roma Tor Vergata as a Full Professor of Telecommunications.Dr. Blefari-Melazzi has been involved in consulting activities and research projects, including standardization and performance evaluation work. His research projects have been funded by the Italian Ministry of Education, University and Research, by the Italian National Research Council, by industries, by the European Union and by the European Space Agency. He also reviewed research proposals and research projects.Dr. Blefari-Melazzi served as reviewer, TPC member, session chair and guest-editor to IEEE conferences and journals.His research interests include the performance evaluation, design and control of broadband integrated networks, wireless LANs and satellite networks. He is also conducting research on multimedia traffic modeling, mobile and personal communications, quality of service guarantees and real time services support in the Internet.Mauro Femminella received his Laurea degree in Electronic Engineering in 1999, magna cum laude with publication of his thesis, and earned the Ph.D. degree in Electronic Engineering in 2003, both at the University of Perugia, Italy. He was Consulting Engineer for the University of Perugia, and for the consortia CoRiTel and RadioLabs. Actually he holds a position as contract researcher at the Department of Information and Electronic Engineering at the University of Perugia.He was involved in a number of research projects co-funded by the European Union (programs ACTS and IST), by the Italian Ministry for Education, Higher Education and Research (MIUR), and by the European Space Agency (ESA).He is co-author of a number of papers in international conferences and journals.His research interests focus on design and performance evaluation of satellite networks, content delivery networks, IP quality of service and IP mobility.Fabio Pugini received his laurea degree (M.S.) in Electronic Engineering (magna cum laude) in 2000 from University of Rome La Sapienza. He was with the INFOCOM Dept. of the same University during 2001 and 2002 as Ph.D. student in Computer Science. His main research interests regarded Mobility issues and QoS provision in IP networks. He was consulting engineer for the DIEI Department of the University of Perugia and was involved in the following European Projects: SUITED, WHYLESS.COM, FIFTH. In 2002 he received his M.B.A. degree from University of Rome Tor Vergata. He worked as a system analyst in MBDA Missile Defense Systems and currently he is with McKinsey & Company as a Junior Associate.     

Improving the efficiency of circuit-switched satellite networks bymeans of dynamic bandwidth allocation capabilities

Current satellite systems operate according to circuit switching transfer modes. To improve flexibility and efficiency, several kinds of packet switching systems have been proposed. However, it appears that full packet switches are still too complex and expensive to be implemented on board the satellites in the near future. For the time being, dynamic bandwidth allocation capabilities (DBAC) provide a compromise solution when satellite systems are based on classical circuit switches, since the DBAC payload allows changing dynamically the capacity of each connection, without teardown and setup. We consider a DBAC satellite system, and define algorithms to allocate the bandwidth so as to provide deterministic and statistical QoS guarantees. Standard dual leaky buckets (DLBs) regulate the traffic sources. We define bandwidth-handling policies, design connection admission control rules, and evaluate the system performance analytically. Results show a significant increase in bandwidth utilization of our system, when compared to a plain circuit switching solution     

A resource management scheme for satellite networks

Satellite networks with dynamic bandwidth allocation capabilities (DBAC) are based on classical circuit switches. The DBAC payload allows changing the capacity of each connection dynamically, without tearing down and setting up the connection. An analysis of our DBAC satellite system performance shows a significant increase in the overall utilization factor of our system compared to a plain circuit switching solution     

On the buffer occupancy of an IEEE 802.11 station in a hot-spot

In this paper we evaluate analytically the average occupancy of the transmission buffer of a 802.11 station (STA). The station belongs to a Wi-Fi Hot-Spot and exchanges data with a fixed host. The data exchange is regulated by the Transmission Control Protocol (TCP). The research interest is motivated by the fact that several papers assume that in these conditions the STA buffer is nearly empty. On the contrary, we prove that this assumption may be wrong and discuss the consequences of this fact. We test the proposed model by means of ns2 simulation, ascertain its accuracy, and highlight its limits.