An example of dynamic QoS negotiation

The traffic generated by multimedia applications presents a high degree of burstiness that can be hardly described by a static set of traffic parameters. The following paper presents a dynamic QoS negotiation scheme applied to a video streaming application. In applications that uses RSVP, the dynamic and efficient usage of the resources can be reached with the introduction of the renegotiable variable bit rate (RVBR) service, which is based on the renegotiation of the traffic specification. In this paper we describe and discuss the RVBR service and how it applies to resource reservation for Internet traffic with RSVP. For that we propose an architecture design that we evaluate by accomplishing a prototype implementation, whose performance are measured with real MPEG2 video traces. The results we obtained indicate that renegotiation is an efficient mechanism to accommodate traffic fluctuations over the burst time-scale, and that RVBR service can be easily implemented, to this aim, in real applications, using available technology

An example of traffic-accomodating application

The traffic generated by multimedia applications presents a great amount of burstiness, which can hardly be described by a static set of traffic parameters. The dynamic and efficient usage of the resources is one of the fundamental aspects of multimedia networks: the traffic specification should first reflect the real traffic demand, but optimise, at the same time, the resources requested. This paper presents an example of application able to accommodate its traffic to managing QoS dynamically. The paper is focused on the technique used to implement the Dynamic Reallocation Scheme (RVBR) taking into account problems deriving from delay during the reallocation phase

Renegotiable VBR service

In this work we address the problem of supporting the QoS requirements for applications while efficiently allocating the network resources. We analyse this problem at the source node where the traffic profile is negotiated with the network and the traffic is shaped according to the contract. We advocate VBR renegotiation as an efficient mechanism to accommodate traffic fluctuations over the burst time-scale. This is in line with the Integrated Service of the IETF with the Resource reSerVation Protocol (RSVP), where the negotiated contract may be modified periodically. In this thesis, we analyse the fundamental elements needed for solving the VBR renegotiation. A source periodically estimates the needs based on: (1) its future traffic, (2) cost objective, (3) information from the past. The issues of this estimation are twofold: future traffic prediction given a prediction, the optimal change. In the case of a CBR specification the optimisation problem is trivial. But with a VBR specification this problem is complex because of the multidimensionality of the VBR traffic descriptor and the non zero condition of the system at the times where the parameter set is changed. We, therefore, focus on the problem of finding the optimal change for sources with pre-recorded or classified traffic. The prediction of the future traffic is out of the scope of this thesis. Traditional existing models are not suitable for modelling this dynamic situation because they do not take into account the non-zero conditions at the transient moments. To address the shortfalls of the traditional approaches, a new class of shapers, the time varying leaky bucket shaper class, has been introduced and characterised by network calculus. To our knowledge, this is the first model that takes into account non-zero conditions at the transient time. This innovative result forms the basis of Renegotiable VBR Service (RVBR). The application of our RVBR mathematical model to the initial problem of supporting the applications' QoS requirements while efficiently allocating the network resources results in simple, efficient algorithms. Through simulation, we first compare RVBR service versus VBR service and versus renegotiable CBR service. We show that RVBR service provides significant advantages in terms of resource costs and resource utilisation. Then, we illustrate that when the service assumes zero conditions at the transient time, the source could potentially experience losses in the case of policing because of the mismatch between the assumed bucket and buffer level and the policed bucket and buffer level. As an example of RVBR service usage, we describe the simulation of RVBR service in a scenario where a sender transmits a MPEG2 video over a network using RSVP reservation protocol with Controlled-Load service. We also describe the implementation design of a Video on Demand application, which is the first example of an RVBR-enabled application. The simulation and experimentation results lead us to believe that RVBR service provides an adequate service (in terms of QoS guaranteed and of efficient resource allocation) to sources with pre-recorded or classified traffic

A Model for Dynamic QoS Negotiation Applied to an MPEG4 Applications

The traffic generated by multimedia applications presents a great amount of burstiness, which can hardly be described by a static set of traffic parameters. The dynamic and efficient usage of the resources is one of the fundamental aspects of multimedia networks: the traffic specification should first reflect the real traffic demand, but optimise, at the same time, the resources requested. This chapter presents: a model for dynamically renegotiating the traffic specification (RVBR), how this can be integrated with the traffic reservation mechanism RSVP, and an example of application able to accommodate its traffic to managing QoS dynamically. The remaining of this chapter is focused on the technique used to implement RVBR) taking into account problems deriving from delay during the renegotiation phase and on the performance of the application with MPEG4 traffic

Insight in cognitive impairment assessed with the Cognitive Assessment Interview in a large sample of patients with schizophrenia

The Cognitive Assessment Interview (CAI) is an interview-based scale measuring cognitive impairment and its impact on functioning in subjects with schizophrenia (SCZ). The present study aimed at assessing, in a large sample of SCZ (n = 601), the agreement between patients and their informants on CAI ratings, to explore patients' insight in their cognitive deficits and its relationships with clinical and functional indices. Agreement between patient- and informant-based ratings was assessed by the Gwet's agreement coefficient. Predictors of insight in cognitive deficits were explored by stepwise multiple regression analyses. Patients reported lower severity of cognitive impairment vs. informants. A substantial to almost perfect agreement was observed between patients' and informants' ratings. Lower insight in cognitive deficits was associated to greater severity of neurocognitive impairment and positive symptoms, lower severity of depressive symptoms, and older age. Worse real-life functioning was associated to lower insight in cognitive deficit, worse neurocognitive performance, and worse functional capacity. Our findings indicate that the CAI is a valid co-primary measure with the interview to patients providing a reliable assessment of their cognitive deficits. In the absence of informants with good knowledge of the subject, the interview to the patient may represent a valid alternative

IP and ATM Integration

The performance limits of the current Internet make the integration of IP with ATM a hotly debated issue in the networking arena, leading to various competing approaches and products. Legitimate technical and market issues are, however, often intertwined with biased views and hype, with vendors competing in the standards arena as well as on the markets. Together with the speed of technical evolution, this causes confusion for purchasers of networking equipment who, usually preferring a single vendor for their networks, run the risk of remaining locked into solutions that will not scale with the evolving needs and that will not fully inter-operate with other networks, even using the IP protocol. It is important to note that the term 'Internet' refers indeed to a specific network. In the following, we will refer more generally to the TCP/IP family of protocols, in order to encompass all types of IP networks such as intranets, extranets and the Internet. We will cover both IP version 4 (IPv4) and IP version 6 (IPv6). Unless Ipv6 is explicitly stated, IPv4 should be assumed. IP and ATM integration refers here to the support of IP over (or within) ATM. From our point of view, integration is a particular case of coexistence. Another particular case is IP and ATM interworking, which means the interoperation between applications or between complete protocol stacks, based on one side on the IP technology, and on the other side on the ATM technology. For instance, interworking between IETF IP based videoconferencing and ATM based videoconferencing. In this paper, we are not dealing with any interworking scenario. Interworking scenarios do not happen very often and are very difficult to realize. In fact, additional non-trivial aspects like interworking at the user plane, mapping of addresses, and several other issues strictly dependent upon the involved technologies, have to be considered in this case. The scope of this paper will thus be restricted to IP and ATM integration, and three levels of integration have been identified: * Level 1: use of IP over an intermediate layer over ATM (e.g. IP over LAN Emulation over ATM), * Level 2: use of IP directly over ATM (e.g. Classical IP, MARS, NHRP and MPOA), * Level 3: IP merged with ATM (e.g. MPLS). In the integration scenarios considered in this paper, the applications always use a common layer to communicate and, in the specific cases under investigation, this common layer is the IP layer. Therefore we use the term 'applications' to refer to IP applications. The present paper is derived from a so-called 'Guideline', NIG-3, produced by participants of the ACTS 'Chain' NIG: Global Network Interoperability (particularly projects CONVAIR, DIANA, EXPERT, IthACI, MULTICUBE and PETERPAN). ACTS (Advanced Communications Technologies and Services) represents the major telecommunications R&D focus of the European Union's 4th research framework Programme. ACTS uses 'Chains' of related projects as a primary vehicle for concertation, both within ACTS itself, and from ACTS towards groups investigating issues of major importance addressed by the communications sector at large. The Network Inter-operability (NI) Chain Group considers all issues of inter-operability between different types of networks. The current paper focuses on technology, and gives neither commercial, nor time-dependent information. It does not necessarily represent the views of the whole ACTS community or of any single organization participating in the Programme

Mobile Metropolitan Ad hoc Networks MOBILEMAN Architecture, protocols and services

Abstract: The aim of this deliverable is to provide the overview of the architecture, protocols and services designed for the MobileMAN paradigm as emerging at the end of the first year of the project. First, we present the complete architecture with the communication flows among different functions, and then we discuss protocols belonging to the MobileMAN protocols ’ stack. Protocols are presented by following a bottom up approach from wireless technologies up to the application and economic issues. Project funded by the Europea