Packet-level traffic control for the Internet: a framework and its experimental validation

This paper presents a theoretical framework, which can be the basis for traffic control and resource management mechanisms, that provide QoS with quantitative guarantees in the Internet. The starting point is a fairly general traffic shaping algorithm for effective rate enforcement which is based on a packet spacing law. Multiplexing several independent shaped streams results in a tight upper bound to the queue-length distribution at the multiplexer. The algorithm effectively works with any kind of input traffic (non-stationary, non-Markovian, heterogeneous, long-range dependent (LRD), etc.). Based on the definition of shaped streams, we devise mechanisms for aggregating, splitting and policing such streams without affecting the queuing performance at subsequent network nodes. Also, a calculus for end-to-end QoS in this framework is presented. The theoretical statements are supported by simulation and experimental results on a network testbed. Since the enforced effective rate features the convenient additivity property , it can be handily used for many traffic control and accounting functions, like policing, admission control, bandwidth allocation and charging.     

A reservation multiple access protocol for microcellularmobile-communication systems

A reservation multiple-access protocol for mobile communications in a microcellular environment is proposed and investigated under high-load conditions, both analytically and by simulation. The reservation scheme proposed uses a reservation channel of the slotted-ALOHA protocol type and an adaptive retransmission probability for stable operation. The capacity of the reservation channel varies with the load above a certain threshold (reservation capacity threshold); in that respect it is a compromise between the R-ALOHA and ALOHA-reservation protocols, both proposed for satellite communications, and the PRMA, an R-ALOHA-type protocol proposed for short-range mobile communication. The access delay is calculated and the optimum reservation capacity threshold is derived to minimize that delay, for specific load conditions     

Clinical experience with fludarabine and its immunosuppressive effects in pretreated chronic lymphocytic leukemias and low-grade lymphomas

Fludarabine monophosphate (FAMP) is a new adenine nucleoside analogue with a promising efficacy in B-cell chronic lymphocytic leukemia (B-CLL) and low-grade non-Hodgkin lymphomas (NHLs). Here, the clinical experience and side effects with FAMP are reported in 77 patients with pretreated CLL (59 B-CLL, 2 T-CLL) and low-grade NHLs (9 immunocytic lymphomas including 5 Waldenstr?m's macroglobulinaemia, 2 centrocytic (cc) and 5 centroblastic-centrocytic (cb-cc) NHLs). 70/77 patients are evaluable for response. All except 8 patients were pretreated with one to four different regimens and had progressive disease. FAMP was administered at a dosage of 25 mg/m2 daily for 5 days as 30 minute infusion every fifth week. Partial (PR) or complete remission (CR) was achieved in 38/56 (68%) and 3/56 (5%) of evaluable patients with CLL, respectively. In 7/8 (1 x CR, 6 x PR) evaluable patients with immunocytic lymphoma and in 3/6 (3 x PR) patients with cc or cb-cc lymphoma remissions were obtained. The probability of progression-free survival was 66% and the event-free survival was 25% and 22% at 12 and 18 months. The median progression-free survival until relapse or death, however, was only 7 months (2-20+). Major toxic effects included infections in 22 patients (grade 3 and 4 WHO), granulocytopenia (mainly grade 3) and nausea in 8 patients (mainly grade 1). 19/22 patients were in PR at the time of occurrence of infectious complications. Meanwhile, 14 patients died due to septicaemia, pneumonia or other infections. Nine patients developed severe septicaemia, 4 patients had pneumocystis carinii or aspergillus pneumonias. The high infection rate may not only be due to hypogammaglobulinaemia and granulocytopenia induced by FAMP but also to a remarkable decrease of CD4+ cells from a median of 2479 to 241 CD4+ cells/microliters after 6 cycles of FAMP. In one case a tumor lysis syndrome was observed. No CNS toxicity was noted. It is concluded that FAMP is effective even in patients with advanced CLL and low-grade NHLs refractory to multiple chemotherapy regimens. However, FAMP has a marked suppressive effect on granulocytes and T-lymphocytes, predominantly CD4+ lymphocytes.     

The “Panopticon” of search engines: the response of the European data protection framework

Nowadays, Internet users are depending on various search engines in order to be able to find requested information on the Web. Although most users feel that they are and remain anonymous when they place their search queries, reality proves otherwise. The increasing importance of search engines for the location of the desired information on the Internet usually leads to considerable inroads into the privacy of users. A heated debate is currently ongoing at European level regarding the question if search engine providers that are established outside the European Union are covered by the European data protection framework and the obligations it imposes on entities that process personal data. The scope of this paper is to examine the applicability of the European data protection legislation to non-EU-based search engine providers and to study the main privacy issues with regard to search engines, such as the character of search logs, their anonymisation and their retention period. Ixquick, a privacy-friendly meta-search engine, will be presented as an alternative to privacy intrusive existing practices of search engines.     

Voice and data integration in the air-interface of a microcellularmobile communication system

A multiple-access protocol and a call acceptance algorithm for voice and data integration in a microcellular mobile communication system are presented. The protocol supports circuit-mode voice, burst-mode voice, and data. A hybrid multiplexing scheme with no boundaries performs statistical multiplexing, the call-level (for circuit-mode voice) and the talkspurt/message-level (for burst-mode voice and data). This scheme achieves high utilization of the available bandwidth compared to pure circuit switching, but with a lower quality in the latter two classes, due to delay during channel access on each talkspurt/message. A two-party transaction model for each class is implemented, giving a realistic load on uplink and downlink. A unified access procedure is presented, and the structure of the required control bursts is described. Performance is analyzed using simulation, and the optimum data-segment size is obtained. The maximum acceptable load is determined for various traffic mixes. A call acceptance algorithm is implemented, and typical simulation results for delay and call blocking are given     

On the optimal,fair and channel-aware cognitive radio network reconfiguration

In this work, we focus on the Joint Channel Assignment and Routing (JCAR) problem in Cognitive Radio Networks (CRNs) and especially on the optimal reconfiguration of secondary networks under the presence of primary users. Secondary CRN users need to adapt their transmission channels promptly, while effectively limit additional or escalating system modifications triggered by the intertweaved primary user activity. Our approach takes into consideration the underlying spectrum switching dynamics and concurrently aims at a fair resource allocation among the active network flows. We take an optimization perspective and formulate the JCAR and network reconfiguration problems as mixed integer linear programs, addressing fairness concerns as well. We propose a heuristic approach which is based on a sequential reduced search space methodology, in order to obtain efficiently solutions of otherwise tough and demanding reconfiguration problems. The operation, effectiveness and performance of the proposed mechanisms are evaluated through analysis and simulations under various working conditions. The obtained numerical results indicate the benefits of the proposed schemes in terms of overhead performance and their scaling properties with respect to more realistic and thus demanding topologies.     

ATM traffic engineering for ABR service provisioning

The Available Bit Rate (ABR) service is being designed as a low-cost transport service over ATM, which will be using the bandwidth left available after servicing connections of another, high-priority class. The implementation of the ABR service requires large buffers at each multiplexing/switching stage to keep cell-loss rates down to a minimum, and a feedback mechanism from the network to the terminals in order for the latter to adjust their traffic profiles according to the prevailing congestion conditions. Thus, an enhanced set of traffic control functions is necessary to support this new service. In this paper the main traffic analysis and control problems related with the ABR service are addressed, modelled and answered on the basis of effective rates defined for the multiplexed connections. Emphasis is given to a simple CAC scheme which consists in allocating peak rates to the high-priority class and effective rates to the ABR class. An adaptive shaping mechanism is then required to enforce the contracted effective rates for the ABR streams. Producing ON/OFF streams facilitates the control functions by allowing the use of approximate closedform calculations.This work has been carried out partly in the framework of the RACE EXPLOIT project.     

Shaping of traffic streams through data spacing

A traffic shaping algorithm, based on suitable spacing of data units, is proposed and validated both theoretically and by simulation. It ensures a “tight” upper bound to the queue-length distribution at subsequent multiplexing stages, being essentially an effective-rate-enforcement mechanism in the asymptotic regime. It does not presume any stationarity, homogeneity or Markovian property of the input streams     

A context-aware middleware for real-time semantic enrichment of distributed multimedia metadata

This paper investigates the problem of the real-time integration and processing of multimedia metadata collected by a distributed sensor network. The discussed practical problem is the efficiency of the technologies used in creating a Knowledge Base in real-time. Specifically, an approach is proposed for the real-time, rule-based semantic enrichment of lower level context features with higher-level semantics. The distinguishing characteristic is the provision of an intelligent middleware-based architecture on which low level components such as sensors, feature extraction algorithms, data sources, and high level components such as application-specific ontologies can be plugged. Throughout the paper, Priamos, a middleware architecture based on Semantic Web technologies is presented, together with a stress-test of the system’s operation under two test case scenarios: A smart security surveillance application and a smart meeting room application. Performance measurements are conducted and corresponding results are exposed.