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Future mobile sensing systems are being designed using 802.15.4 low-power short-range radios for a diverse set of devices from embedded mobile motes to sensor-enabled cellphones in support, for example, of people-centric sensing applications. However, there is little known about the use of 802.15.4 in mobile sensor settings nor its impact on the performance of future communication architectures. We present a set of initial results from a simple yet systematic set of benchmark experiments that offer a number of important insights into the radio characteristics of mobile 802.15.4 person-to-person communication. Our results show that the body factor - that is to say, the human body and where sensors are located on the body (e.g., on the chest, foot, in the pocket) - has a significant effect on the performance of the communications system. While this phenomenon has been discussed in the context of other radios (e.g., cellular, WiFi, UWB) its impact on 802.15.4 based mobile sensor networks is not understood. Other findings that also serve to limit the communication performance include the effective contact times between mobile nodes, and, what we term the zero bandwidth crossing, which is a product of mobility and the body factor. This paper presents a set of initial findings and insights on this topic, and importantly, we consider the impact of these findings on the design of future communication architectures for mobile sensing. [ABSTRACT FROM AUTHOR]

The introduction of guard channels in a cellular network is a method for giving priority to on-going calls by having channels exclusively reserved for handover purposes. Herein, an adaptive measurement-based dynamic guard channel scheme is introduced. The proposed scheme uses the number of on-going calls in adjacent cells and measurements of handover probabilities to determine the amount of guard channels to allocate in a cell. To improve the efficiency of the scheme, the calls are divided into groups depending upon mobility and latest visited cell, where separate measurements are performed for every single group. Simulations showed that the proposed scheme seems to be very efficient. [ABSTRACT FROM AUTHOR]

Conventional distribution of real-time multimedia data uses multicasting or a series of relays and tunnels for unicast networks. The former is a capability not popularly enabled by a lot of networks while the static relays cannot readily adapt to changing network conditions and are potential bottlenecks in a heavily accessed system. This paper proposes a dynamic overlay framework for streaming multimedia data over heterogeneous networks. The overlay comprises a self-improving tree which is built from client relays on the fly and a lightweight server to manage the tree. The overlay provides a better QoS than conventional relays as it monitors the network and re-configures the tree to adapt to changing environments. Clients can switch parents for better QoS. The robustness of the tree is improved by using a spiral mechanism and failure of the lightweight server will not impact the data distribution functionality of the existing tree. [ABSTRACT FROM AUTHOR]

This paper presents a performance analysis of a fair sharing mechanism for PC-based software routers, required when the I/O bus and not the CPU is the bottleneck. The mechanism involves changes to the OS kernel and assumes the existence of certain NIC functions, but does not require any changes to the PC hardware architecture. [ABSTRACT FROM AUTHOR]

The Differentiated Services (DiffServ) architecture has been proposed as a scalable solution for providing service differentiation among flows. Towards the enhancement of this architecture, new mechanisms for admission control and a new set of network services are proposed in this paper. Each network service is appropriate for a specific type of traffic and is realized through its own network mechanisms, which are the Traffic Classes. Traffic Classes provide the traffic handling mechanisms for each Network Service and are composed of a set of admission control rules, a set of traffic conditioning rules and a per-hop behavior (PHB). Different traffic-handling mechanisms are proposed for each network service and are implemented with the use of the OPNET simulation tool. A large-scale network is used as a reference topology for studying the performance and effectiveness of the proposed services. [ABSTRACT FROM AUTHOR]

The 3rd Generation Partnership Project (3GPP) uses the IETF Session Initiation Protocol (SIP) as a signalling protocol in the IP Multimedia Subsystem for 3rd generation UMTS networks. Signalling Messages sent using the SIP protocol pass through intermediate SIP nodes in such a way that the message size grows as a result of additional data being added to the message. Modelling of network flows in this case requires careful attention. A simple flow model is presented to get an appreciation for the size of the expected signalling flows. This is particularly important for developing dimensioning models for SIP in 3GPP networks and for the further investigation of Quality of Service (QoS) mechanisms to provide resources needed for signalling. A methodology is presented which defines the minimum requirements for the bit error rate on links used by signalling traffic. [ABSTRACT FROM AUTHOR]

The Virtual Home Environment (VHE) has been introduced as an abstract concept enabling users to access and personalize their subscribed services whatever the terminal they use and whatever the underlying network used. The European IST VESPER project (Virtual Home Environment for Service Personalization and Roaming Users) aims to provide an architectural solution and an implementation of the VHE, providing ubiquitous service availability, personalised user interfaces and session mobility, while users are roaming or changing their equipment. In this paper we present a multimedia delivery service, one of the trial services selected to demonstrate VHE features, showing its interconnection with the so far defined VESPER VHE architecture. [ABSTRACT FROM AUTHOR]

AMnet provides a framework for flexible and rapid service creation. It is based on Programmable Networking technologies and uses active nodes (AMnodes) within the network for the provision of individual, application-specific services. To this end, these AMnodes execute service modules that are loadable on-demand and enhance the functionality of intermediate systems without the need of long global standardization processes. Placing application-dedicated functionality within the network requires a flexible signaling protocol to discover and announce as well as to establish and maintain the corresponding services. AMnet Signaling was developed for this purpose and will be presented in detail within this paper. [ABSTRACT FROM AUTHOR]

Satellite link characteristics cause reduced performance in TCP data transfers. In this paper we present SaTPEP, a TCP Performance Enhancing Proxy which attempts to improve TCP performance by performing connection splitting. SaTPEP monitors the satellite link utilization, and assigns to connections window values that reflect the available bandwidth. Loss recovery is based on Negative Acknowledgements. The performance of SaTPEP is investigated in terms of goodput and fairness, through a series of simulation experiments. Results obtained in these experiments, show significant performance improvement in presence of available bandwidth and at high error rates. [ABSTRACT FROM AUTHOR]

This paper studies and discusses the presence of LRD in network traffic after classifying flows into traffic aggregates. Following DiffServ architecture principles, generic QoS application requirements and the transport protocol in use, a classification criterion of Internet traffic is established. Using fractal theory, the resulting traffic classes are analysed. The Hurst parameter is estimated and used as a measure of traffic burstiness and LRD in each traffic class. The traffic volume per class and per interface is also measured. The study uses real traffic traces collected at a University of Minho major backbone router in different periods of network activity. [ABSTRACT FROM AUTHOR]

This paper provides an overview of development of telecommunications in Slovenia. Major systems, networks and services are briefly considered. The combination of own generic research and critical mass of knowledge had and still has a very positive influence the on development of telecommunications in Slovenia. We propose a two-level network architecture consisting of a simplified data forwarding plane and service control plane. Future technological development and the proposed role of Slovenia as a regional telecommunications hub are presented. [ABSTRACT FROM AUTHOR]

Research of web-servers has recently addressed the problem of content distribution coupled with quality of service (QoS). Due to the explosive growth of services offered over the Internet, novel mechanisms are needed for IP based service delivery to scale in a client-transparent way. This paper addresses the above problem considering also utilization of available processing power of servers. Many developed caching systems dedicate a fixed portion of the processing power for higher QoS services leading to lowered overall throughput of the server system. Here we introduce and simulate a QoS aware caching scheme that offers lower response delay for higher quality services and additionally optimizes utilization of the available processing power. [ABSTRACT FROM AUTHOR]

We consider, in this paper, the call admission control (CAC) problem in a multimedia cellular network that handles several classes of traffic with different resource requirements. The problem is formulated as a Semi-Markov Decision Process (SMDP) problem. It is too complex to allow for an exact solution for this problem, so, we use a real-time neuro-dynamic programming (NDP) [Reinforcement Learning (RL)] algorithm to construct a dynamic call admission control policy. A broad set of experiments shows the robustness of our policies compared to the classical solutions such as Guard Channel [ABSTRACT FROM AUTHOR]

Pervasive computing requires management techniques allowing efficient service handling in volatile contexts. The Java Enhanced Service Architecture (JESA) is a service platform addressing this issue for resource limited devices. A major problem in dynamic service networks is the discovery of desired services. The JESA Service Discovery Protocol (JSDP), one of JESA's core components, is a lightweight, platform independent service discovery protocol for ad-hoc networks. JSDP features transparent operation with or without central service brokers providing scalability from point-to-point connections to larger structured networks. [ABSTRACT FROM AUTHOR]

This paper builds on the assumption that in the future, UMTS, HIPERLAN-2 and DVB-T can be three (co-operating) components of a composite radio infrastructure that offers wideband wireless access to broadband IP-based services. Managing the resources of this powerful, composite-radio infrastructure in an aggregate manner, and multi-operator scenario, is a complex task. This paper presents an approach to the overall UMTS, HIPERLAN-2 and DVB-T network and service management problem, providing the internal operation of a system addressing this problem. Key points addressed are the development of an architecture that can jointly optimise the resources of the technologies in the composite radio environment, and the development of open interfaces with Service Provider mechanisms and the heterogeneous managed infrastructure. [ABSTRACT FROM AUTHOR]

An appealing approach to the admission control problem for traffic with QoS requirements consists in evaluating the resource availability by means of measurement- based techniques. Those techniques allow to provide QoS with minimal changes to the current network devices. In this work, we propose a mechanism to perform active measurement-based admission control for multicast groups with dynamically joining receivers. The proposed mechanism has been implemented in the ns-2 simulation framework, to evaluate its performance. [ABSTRACT FROM AUTHOR]

We present a simple packet level model to show how marking at the DiffServ boundary node and scheduling and discarding inside a DiffServ node affect the division of bandwidth between two delay classes: elastic TCP flows and streaming non-TCP flows. We conclude that only per flow marking together with dependent discarding thresholds across both delay classes is able to divide bandwidth fairly, according to the load of the network, and in a TCP friendly way. [ABSTRACT FROM AUTHOR]

We propose a new application-level clustering algorithm capable of building an overlay spanning tree among participants of large multicast sessions, without any specific help from the network routers. This algorithm is based on a unique definition of zones around nodes and an innovative adaptive cluster size distribution. The proposed method finds application in many context where large-scale overlay trees can be usefull: application-level multicasting, peer-to-peer networks and content distribution networks (among other things). [ABSTRACT FROM AUTHOR]

The UMTS-FDD system, one of the members of the ITU IMT-2000 third generation standard for terrestrial cellular systems, employs pruned Golay sequences to enable initial synchronisation of the mobile terminals to the network. In this paper a low complexity solution for initial synchronisation is proposed, which is able to counteract the performance degradation introduced by large frequency offsets occurring in the mobile station receiver. Simulation results are provided to validate the proposed solution. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of minimizing the routing delay in ad hoc on-demand routing protocols through optimizing the Time-to-Live (TTL) interval for route caching. An analytical framework is introduced to compute the expected routing delay when the source node has a cached route with a given TTL value. Furthermore, a numerical method is proposed to determine the optimal TTL of a newly discovered route cached by the source node. We present simulation results that support the validity of our analysis. [ABSTRACT FROM AUTHOR]

A class of contention-type MAC protocols (e.g., CSMA/CA) relies on random deferment of packet transmission, and subsumes a deferment selection strategy and a scheduling policy that determines the winner of each contention cycle. This paper examines contention-type protocols in a noncooperative an ad-hoc wireless LAN setting, where a number of stations self-optimise their strategies to obtain a more-than-fair bandwidth share. Two scheduling policies, called RT/ECD and RT/ECD-1s, are evaluated via simulation It is concluded that a well-designed scheduling policy should invoke a noncooperative game whose outcome, in terms of the resulting bandwidth distribution, is fair to non-self-optimising stations. [ABSTRACT FROM AUTHOR]

The World-wide Web (WWW) works now as the infrastructure over the Internet for multimedia applications. Internet radio is one of those applications and its growth is explosive. We have started operating an Internet Radio station with streaming music services since April 2000. An Internet radio can broadcast music over the network regardless of such geographic restrictions as the traditional radio systems have. There are some problems and services due to the Internet. This paper reports our operation as well as the issues. We propose our idea on some novel radio services as well. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new MAC protocol for Gigabit Local Area Networks, called the Request Contention Multiple Access (RCMA) protocol. RCMA is proposed to operate in the 10BASE-FP Ethernet network topology at a gigabit data rate. It does not require the sophisticated WDM technology. Unlike the current IEEE 802.3z Gigabit Ethernet MAC protocol, RCMA is efficient and stable for a wide range of user numbers. Furthermore, it can support service differentiation with no additional overhead. Its performance under the saturation condition is analyzed and compared with performance of the current IEEE 802.3z Gigabit Ethernet MAC protocol, and significant performance advantage is demonstrated for RCMA. [ABSTRACT FROM AUTHOR]

In this paper we propose a new router architecture that combines both flexibility and performance. This router architecture aims at combining the best of two worlds: the commercial routers, which have a proven track for stability and performance but lack the flexibility of routers with open source operation system. The latter is particularly flexible because the source code is accessible for analysis and modification purposes as opposed to the traditional commercial routers, whose software can be altered by their manufacturers only. [ABSTRACT FROM AUTHOR]

The current work focuses on the area of group security policy within secure IP multicast and secure group communications. The work explains the background and context, introduces a Group Security Policy Framework, and describes how this fits within the broader Multicast Security Framework developed within the IETF. Finally, the current status of developments within group security policy in the IETF is discussed. [ABSTRACT FROM AUTHOR]

In the 3rd generation multimedia communication world and in the 3GPP standardization consortium, SIP protocol appears to be the preferred signaling protocol. However, the need to communicate with non-SIP based network, e.g. H.323 from ITU-U, is still a reality. The need can be satisfied with the introduction of network gateways (also named Inter-Working Function). One of the open issues about SIP-H.323 interworking is the address resolution, in other words, the automatic forwarding of a SIP call to an H.323 user. The paper proposes a SIP network architecture which can interoperate with H.323 networks, safeguarding the existing software/hardware components, as SIP terminal clients or SIP server proxies or IWF gateways. [ABSTRACT FROM AUTHOR]

In today's Internet, Policy-Based Network Management is gaining more and more proselytes. Its appeal is due to the given opportunity of a standard and consistent way for network configuration, independently of the underlying architecture and Quality of Service (QoS) provisioning model assumptions. The event-driven paradigm, well established in the general-purpose programmers world, through the Policy-Based approach begins to play its role also in the field of network management. In this paper we describe a policy framework suited for dynamic network management in QoS-enabled IP networks. First, we design an object model conceived to represent policies in a network-independent fashion. Then, we describe a management and configuration system based on Common Open Policy Service (COPS). Finally, we show a system prototype pointing out the main features of a Differentiated Services network management and configuration based on Policy System Management. [ABSTRACT FROM AUTHOR]

On-line algorithms are essential for service providers to quickly set up bandwidth-guaranteed paths in their backbone or transport networks. A minimum-interference routing algorithm uses the information regarding the ingress-egress node pairs for selecting a path in the case of on-line connection requests. According to the notion of minimum interference, the path selected should have a minimum interference with paths considered to be critical for satisfying future requests. Here we introduce a new class of minimum-interference routing algorithms, called "simple minimum-interference routing algorithms" (SMIRA), that employ an efficient procedure. These algorithms use static network information comprising the topology and the information about ingress-egress node pairs, as well as the link residual bandwidth. Two typical algorithms belonging to this class are introduced, and their performance is evaluated by means of simulation. The numerical results obtained illustrate their efficiency, expressed in terms of throughput, and fairness. [ABSTRACT FROM AUTHOR]

We present an analytical model for computing call blocking probabilities in a LEO satellite network that carries voice calls. Both satellite-fixed and earth-fixed constellations with inter-orbit links and hand-offs are considered. The model is analyzed approximately by decomposing it into sub-systems. Each sub-system is solved in isolation exactly using a Markov process, and the individual results are combined together through an iterative method. Numerical results demonstrate that our method is accurate for a wide range of traffic patterns. [ABSTRACT FROM AUTHOR]

This paper presents a QoS evaluation in a DiffServ experimental test-bed scenario. We implemented our field trial using prototypal routers running under Linux OS and we arranged them in order to make possible the interconnection with a remote island of a Multi-domain DiffServ network. The performance evaluation of Real-time applications presented in the paper will make clear how it is possible to provide "mission critical" applications with tool-quality level of service when appropriate algorithm and resource sharing are chosen and when these features are associated with a fair degree of aggregation. As a consequence the paper describes the results by means of a Mean Opinion Score (MOS) evaluation campaign to show how Real-Time applications (such as voice and video conferencing) may suffer for the lack of QoS. [ABSTRACT FROM AUTHOR]

A policy based management networking is a new paradigm used to achieve the network management. This paper presents a new policy based Mobile IP users management architecture based on a Common Open Policy Service (COPS) protocol which is currently deployed for QoS management. This paper introduces a new concept of terminal policy enforcement point (TPEP) which allows the terminal to interact with the network enforcing network policies defined by the network manager; it is a key feature of our architecture. The paper presents also the global architecture to support the mobile IP users requirements based mainly on two extensions of COPS protocol; COPS-SLS [1] for QoS negotiation and COPS-MU/MT [2] for policy based user and terminal mobility management. [ABSTRACT FROM AUTHOR]

The paper concerns device discovery in multi-hop networks of Bluetooth devices. We start from the observation that forming a Bluetooth scatternet (i.e., a multi-hop wireless topology) requires each pair of neighboring nodes to have a "symmetric" knowledge of each other, i.e., if node u knows node v then node v knows node u. We investigate the use of the Bluetooth procedures for device discovery (inquiry procedures) in order to guarantee the needed symmetric knowledge for scatternet formation. Through the use of simulations we observed that despite the long time required for each node to become aware of the presence of all its neighbors, the Bluetooth topologies obtained by using the devices discovered after just 6 seconds are connected. The average number of neighbors of each node and the average route length are also consistently close to the values that we would obtain if all the neighbors of a device were discovered. [ABSTRACT FROM AUTHOR]

In this paper we present a protocol for reliable multicast within a group of mobile hosts that communicate with a wired infrastructure by means of wireless technology. The protocol tolerates failures in the wired infrastructure, i.e., crashes of stationary hosts and partitions of wired links. The wireless coverage may be incomplete and message losses could occur even within cells, due to physical obstructions or to the high error rate of the wireless technology, for example. Movements of mobile hosts are accommodated efficiently because they do not trigger any interaction among stationary hosts (i.e., there is no notion of hand-off). We evaluate by simulation the impact of fault-tolerance on the performance of the protocol in normal operating conditions, i.e., in the absence of failures. The results obtained show that the increase in the average latency experienced by messages is limited to few milliseconds. [ABSTRACT FROM AUTHOR]

We present an architecture for a core dWDM network which utilizes the concept of Optical Burst Switching (OBS) coupled with a Just-In-Time (JIT) signaling scheme. It is a reservation based architecture whose distinguishing characteristics are its relative simplicity, its amenability to hardware implementation, support for quality of service and multicast natively. Another important feature is data transparency - the network infrastructure is independent of the format of the data being transmitted on individual wavelengths. In this article we present a brief overview of the architecture and outline the most salient features. [ABSTRACT FROM AUTHOR]

In this paper we propose an architecture for an output queued switch based on the mesh of trees topology. After establishing the equivalence of our proposal with the output queued model, we analyze its features, showing that it merges positive features of the input queued switches (specially their implementability) with all the characteristics typical of output queued ones. Moreover, such an architecture is able to easily and efficiently manage multicast traffic, which is becoming extremely important in networks with traditional communication services integrated in. [ABSTRACT FROM AUTHOR]

Multicast state scalability is among the critical issues which delay the deployment of IP multicast. In our previous work, we proposed a scheme, called aggregated multicast to reduce multicast state. The key idea is that multiple groups are forced to share a single delivery tree. We presented some initial results to show that multicast state can be reduced. In this paper, we develop a more quantitative assessment of the cost/benefit trade-offs. We introduce metrics to measure multicast state and tree management overhead for multicast schemes. We then compare aggregated multicast with conventional multicast schemes, such as source specific tree scheme and shared tree scheme. Our extensive simulations show that aggregated multicast can achieve significant routing state and tree management overhead reduction while containing the expense of extra resources (bandwidth waste and tunnelling overhead, etc.). We conclude that aggregated multicast is a very cost-effective and promising direction for scalable transit domain multicast provisioning. [ABSTRACT FROM AUTHOR]

Multicast routing algorithms such as PIM, CBT, BGMP use shared multicast routing trees and the location of the multicast tree has great impact on the tree cost and the packet delay. In this paper we propose new center location algorithms and a new center relocation algorithm and analyze their performance through simulation studies. The proposed center location algorithms try to find the geographic center of multicast members considering not only multicast group members but also a few non-member nodes which are carefully chosen. Simulation results show that the proposed algorithms find the better center than existing algorithms in terms of tree cost and packet delay. After many members have joined and/or left the group, the previously chosen center may not be a proper place any more and, therefore, we need to find a new center and build a new tree around this new center. We propose a new center relocation algorithm that determines the moment when the new tree should be built around the new center. The algorithm is based on measured packet delays as well as the parameter indicating how much the group has changed. It not only avoids unnecessary center relocation processes but also prevents the cost and worst packet delay of the tree from significantly deviating from the optimal values.... [ABSTRACT FROM AUTHOR]

This paper presents an efficient algorithm for Monte-Carlo simulation of time blocking probabilities for multi-layer multicast streams with the assumption that blocked calls are lost. Users may join and leave the multicast connections freely, thus creating dynamic multicast trees. The earlier published algorithms are applicable to small networks or networks with few users. The present simulation algorithm is based on the inverse convolution method, and is the only effective way to handle large systems, known to the author. [ABSTRACT FROM AUTHOR]

This paper presents an experimental testbed to study the noise effect on the performance of the transport layer over Hybrid Fiber Coaxial (HFC) networks. We have successfully designed and implemented an integrated complex testbed, which is suitable not only for laboratory environments but also reusable for real-world networks. The main purpose of the testbed is modeling the residential broadband data network using hardware simulation under several noise conditions and observing the effects on the performance of popular Internet applications as well as native TCP/UDP performances. A large number of public domain Internet measurement tools have been evaluated, from which several selective software tools have been used. In addition, new software has been developed to combine all software and hardware devices. Based on the testbed, we were able to study several issues of TCP/UDP over HFC networks by making a large number of automatic measurements and analysis. The testbed infrastructure would be very useful for cable operator and end users for monitoring and troubleshooting HFC networks, and can be effectively reused for related studies in similar environments such as wireless and DSL. [ABSTRACT FROM AUTHOR]

IEEE 802.11 specifies a technology for wireless local area networks (LANs) and mobile networking. In this paper, we present an analytical method of estimating the saturation throughput of 802.11 wireless LAN in the presence of noise which distorts transmitted frames. Besides the Basic Access mechanism of the 802.11 MAC protocol, we study such optional tool as the RTS/CTS method, which allows reducing the influence of collisions. In addition to the throughput, our method allows estimating a probability of a packet rejection occurring when the number of packet transmission retries attains its limit. The obtained numerical results of investigating 802.11 LANs by this method are validated by simulation and show high estimation accuracy for any values of protocol parameters and bit error rates. These results also show that the method is an effective tool for tuning the protocol parameters. [ABSTRACT FROM AUTHOR]

A novel analytic framework is devised for the performance modelling and evaluation of a wireless cell using Global System for Mobile telecommunication (GSM) with General Packet Radio Service (GPRS) supporting both voice and multiple class data services, respectively, under a complete partitioning scheme (CPS). In this context, a queueing model is proposed consisting of two independent queueing systems, namely an M/M/c/c loss system with Poissonian GSM traffic and a {GE/GE/1/N1/FCFS → GE/GE/1/N2/PS} system of access and transfer finite capacity queues in tandem having an external Compound Poisson GPRS traffic with geometrically distributed batches and generalised exponential (GE) service times under first-come-first-served (FCFS) and processor sharing (PS) scheduling rules, respectively. Although the analysis of the former loss system is straightforward, the solution of the GE-type queues in tandem is rather complex. This investigation focuses on the analysis of the tandem GE-type queueing system, which is valid for both uplink and downlink connections and provides multiple class data services with different arrival rates, interarrival-time squared co-efficient of variations (SCVs), file (burst) sizes and PS discrimination service levels. The principle of maximum entropy (ME) is used to characterise a product form approximation, subject to appropriate GE-type queueing theoretic constraints per class, and thus, implying a decomposition of the tandem system into GE/GE/1/N1/FCFS and GE/GE/1/N2/PS building block queues, each of which can be analysed in isolation. Subsequently, closed form expressions for state and blocking probabilities are obtained. Typical numerical examples are included to validate the ME solution against simulation and study the effect of external GPRS bursty traffic upon the performance of the cell. [ABSTRACT FROM AUTHOR]

Current quality source-adaptive schemes for multicast multilayered video rely on merging capabilities at special nodes in the network as a means of combining feedback from the whole set of receivers. These strategies reduce network load and avoid feedback implosion at the source. In this paper, we examine how to provide optimal feedback for such schemes. The optimal feedback is achieved when state information from the whole set of receivers is represented in every incoming feedback packet at the source. We show that the choice of a suitable merging time window in the intermediate nodes coupled with a periodical transmission of feedback packets by the receivers leads to near-optimal feedback. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the performance of a lightpath configuration method for optical add/drop multiplexer (OADM) in WDM asymmetric ring network. We consider a multiple queueing system for a node in the ring network and derive loss probability and wavelength utilization factor. Numerical examples show how arrival rate from access network and the threshold specified in the dynamic configuration method affect loss probability and wavelength utilization factor. In addition, comparing the proposed method with static configuration method, the loss probability under the proposed method can be almost the same as that under the static method where lightpaths are pre-established such that all wavelengths in the network are used efficiently. [ABSTRACT FROM AUTHOR]

Optimal control is a possible approach to Internet traffic engineering, which aims to achieve QoS guarantees and efficiency in network resources use. The goal can be better achieved by using the Multi-Protocol Label Switching technique (MPLS), which provides increased scalability, manageability and enhanced QoS functions in IP-based networks. In this context, this paper proposes a method to find the optimal capacity provisioning for a Label Switched Path (LSP) of a MPLS network. The optimal capacity allocation for a given time interval is computed with respect to a quadratic cost function including a switching cost and a management cost for the whole network. The unique optimal solution is analytically computed assuming the knowledge of the offered traffic for the whole control interval. Furthermore, a sub-optimal on line solution is proposed which only requires the knowledge of a narrow sliding window of the offered traffic. Optimal and sub-optimal solutions are compared with respect to a simulated case study, enlightening the simplicity and, at the same time, the effectiveness of the second one. [ABSTRACT FROM AUTHOR]

Over the last few years, a number of mechanisms have been proposed for scheduling different type of traffic over base stations-oriented wireless and mobile systems. The majority of these mechanisms focus on access control in the base stations-to-mobile units part of the wireless and mobile system. Recent proposals for the unlicensed spectrum in the 5GHz band redefine the problem, since base stations operated by different operators and organizations in overlapping geographical areas need access resolution mechanisms to allocate wireless resources. This issue is addressed here, and a multicarrier access control scheme, called QoS based Dynamic Channel Reservation (QDCR), is proposed. QDCR allows base stations to select the least congested available carrier, to compete for carrier reservation based on QoS requirements, and to share the allocated carrier and time with its associated Mobile Terminals (MTs). [ABSTRACT FROM AUTHOR]

The main contribution of this paper is a new online routing algorithm, called Dynamic Online Routing Algorithm (DORA), for dynamic setup of bandwidth guaranteed paths in MPLS networks. The goal of DORA is to accept as many network path setup requests as possible by carefully mapping paths with reserved bandwidth evenly across the network. The key operation behind DORA is to avoid routing over links that: 1) have high potential to be part of any other paths, and 2) have less residual bandwidth available. We compare DORA against other existing constraint-based routing algorithms based on two performance metrics: path setup rejection ratio and percentage of successful reroutes. Our result shows that DORA performs better than the other algorithms in both metrics. [ABSTRACT FROM AUTHOR]

The need for seamless communications in future wireless networks imposes the development of distributed management systems, in which we can distinguish between different business entities, the Service and Network Providers. Such a highly dynamic environment enables the Service Providers to associate with multiple Network Providers and choose the best ones, according to user satisfaction and network's reward criteria. In this direction, this paper presents a Service Management System from the SP's perspective (SP- SMS). The SP-SMS can be separated into two planes, namely the service and network resource plane, and three layers, the Session Configuration Layer, the Local Planning Layer and the Global Planning Layer. Our study focuses on the Local Planning Layer and the role of the related components, which are introduced to describe the functionality of this layer. Through representative results, we demonstrate the superiority of the proposed model, in terms of utilisation and aggregate revenue. [ABSTRACT FROM AUTHOR]

In this article we present a new all-optical broadcast LAN architecture and an accompanying signaling protocol. The distinguishing characteristics of this architecture are its fault-tolerant design and its collision-free nature, which allows it to achieve high throughput in a broadcast environment. The flexibility of the design allows different schedulers to be used, which can introduce new features into the network (e.g. multicast and QoS) as well as optimize its behavior for the specific setting in which it is used. [ABSTRACT FROM AUTHOR]

In this paper, we consider a WDM metro ring architecture with optical burst switching. Several access protocols are proposed and their performance is analyzed by simulation. [ABSTRACT FROM AUTHOR]

In this study the restoration performance of two closely related Sender/Chooser-based distributed path restoration protocols (both extensions of the Self-Healing Network (SHN) to path restoration) is compared. Some pathological situations in which these Sender/Chooser-based restoration algorithms perform suboptimally are identified and, where available, possible solutions are proposed. Built-in mechanisms to resolve contention between Sender/Chooser pairs were found to be very helpful. In addition, the performance of the distributed restoration algorithms studied was found to be close to its theoretical upper bound, suggesting that the pathological situations described may not be that important for real-life networks. Keywords: distributed path restoration, Sender/Chooser based restoration protocols, optical mesh networks, survivable networks E. Gregori et al. (Eds.): NETWORKING 2002, LNCS 2345, pp. 875-886, 2002. [ABSTRACT FROM AUTHOR]