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Über dieses Buch

Networking 2006 was organized by the University of Coimbra, Portugal, and it was the fifth event in a series of International Conferences on Networking sponsored by the IFIP Technical Committee on Communication Systems (TC 6). Previous events were held in Paris (France) in 2000, Pisa (Italy) in 2002, Athens (Greece) in 2004, and Waterloo (Canada) in 2005. Networking 2006 brought together active and proficient members of the networking community, from both academia and industry, thus contributing to scientific, strategic, and practical advances in the broad and fast-evolving field of communications. The conference comprised highly technical sessions organized thematically, keynote talks, tutorials offered by experts, as well as workshops and panel discussions on topical themes. Plenary sessions with keynote talks opened the daily sessions, which covered Networking Technologies, Services and Protocols, Performance of Computer and Communication Networks, and Mobile and Wireless Communications Systems. The Networking 2006 call for papers attracted 440 submissions from 44 different countries in Asia, Australia, Europe, North America, and South America. These were subject to thorough review work by the Program Committee members and additional reviewers. The selection process was finalized in a Technical Program Committee meeting held in Lisbon on January 23, 2006.



Mobile Ad-Hoc Networks I

A Scheme to Provide Proportionally Differentiated End-to-End Packet Delay in Wireless Multi-hop Ad Hoc Networks

This paper proposes a scheme to provide in a CSMA/CA based multi-hop wireless ad hoc network, a consistent and accurate proportional differentiation in average end-to-end packet delay. The proposed scheme, called PDMED uses a cross-layer approach that requires a distributed scheduler to adapt to the information from a QoS monitor, a route monitor and a channel monitor. Conceptually, the distributed scheduler dynamically adjusts the backoff duration of a flow based on its instantaneous deviation from the maximum average end-to-end packet delay. This is done such that a flow with a larger deviation from the maximum is given a longer backoff duration to give way to transmissions from other flows with smaller deviations. PDMED has been extensively evaluated through random event simulations using OPNET. The results confirm that it is capable of providing a consistent and accurate proportional differentiation, which is otherwise not achievable under various traffic conditions.

Dan Li, Peng-Yong Kong

Service Differentiation Via Adaptive Gateway Discovery in Ad Hoc Networks Connected to Wired Networks

A gateway discovery mechanism is necessary to allow wireless nodes in an ad hoc network to route their packets towards a fixed network. Real-time applications have quality of service parameters and require a gateway discovery mechanism that helps them to maintain their requirements. Therefore we propose in this work a new adaptive gateway discovery scheme that adjusts the frequency of the gateway advertisements dynamically. This protocol is able to differentiate services between applications and it cooperates with real-time flows to maintain the desired quality of service. Simulation results investigate the performance of the proposed adaptive scheme and show its effectiveness in comparison with the hybrid mechanism in the simulated scenarios.

Mari Carmen Domingo

Stability-Throughput Tradeoff and Routing in Multi-hop Wireless Ad-Hoc Networks

We study the throughput of multi-hop routes and stability of forwarding queues in a wireless Ad-Hoc network with random access channel. We focuse on wireless with stationary nodes, such as community wireless networks. Our main result is charactrerization of stability condition and the end-to-end throughput using the balance. We also investigate the impact of routing on end-to-end throughput and stability of intermediate nodes. We find that i) as long as the intermediate queues in the network are stable, the end-to-end throughput of a connection does not depend on the load on the intermediate nodes, ii) we showed that if the weight of a link originating from a node is set to the number of neighbors of this node, then shortest path routing maximizes the minimum probability of end-to-end packet delivery in a network of weighted fair queues with coupled servers. Numerical results are given and support the results of the analysis.

Arzad Alam Kherani, Rachid El Azouzi, Eitan Altman

EASR: An Energy Aware Source Routing with Disjoint Multipath Selection for Energy-Efficient Multihop Wireless Ad Hoc Networks

Wireless ad hoc networks usually consist of mobile battery operated computing devices that communicate over the wireless medium. These devices need to be energy conserving so that the battery life is maximized. The energy for transmission of a packet in the wireless channel remains quite significant and may turn out to be the highest energy consuming component of the device. So, an energy-efficient communication protocol can minimize maintenance and maximize system performance. We propose an Energy Aware Source Routing (EASR) which can be efficient from network long-term connectivity point of view. In this algorithm, multiple routing paths are selected. However, only one path will be used for data transmission at a certain time among multiple paths and each path has probability to be selected. In EASR, the routing paths will be discovered without overlapped. In addition, each path hardly overhears other data transmission. We define an

overhearing ratio

in order to reduce the overhearing energy waste among each selected path. And we show how establish energy efficient multiple paths by making use of

overhearing ratio

. Our simulation results show that our proposed scheme can achieve magnitude improvement of network lifetime and reasonable packet latency time.

Do-Youn Hwang, Eui-Hyeok Kwon, Jae-Sung Lim

Traffic Engineering I

On Improving the Accuracy of OSPF Traffic Engineering

The conventional forwarding rule used by IP networks is to always choose the path with the shortest length – in terms of administrative link weights assigned to the links – to forward traffic. Lately, it has been proposed to use shortest-path-first routing to implement Traffic Engineering in IP networks, promising with a big boost in the profitability of the legacy network infrastructure. The idea is to set the link weights so that the shortest paths, and the traffic thereof, follow the paths designated by the operator. Unfortunately, traditional methods to calculate the link weights usually produce a bunch of superfluous shortest paths, often leading to congestion along the unconsidered paths. In this paper, we introduce and develop novel methods to increase the accuracy of this process and, by means of extensive simulations, we show that our proposed solution produces remarkably high quality link weights.

Gábor Rétvári, József J. Bíró, Tibor Cinkler

Achieving Bursty Traffic Guarantees by Integrating Traffic Engineering and Buffer Management Tools

Traffic engineering tools are applied to design a set of paths, e.g., using MPLS, in the network in order to achieve global network utilization. Usually, paths are guaranteed long-term traffic rates, while the short-term rates of bursty traffic are not guaranteed. The resource allocation scheme, suggested in this paper, handles bursts based on maximal

traffic volume allocation



) instead of a single maximal or sustained rate allocation. This translates to better SLAs to the network customers, namely SLAs with higher traffic peaks, that guarantees burst non-dropping. Given a set of paths and bandwidth allocation along them, the suggested algorithm finds a special collection of bottleneck links, which we term the

first cut

, as the optimal buffering location for bursts. In these locations, the buffers act as an additional resource to improve the network short-term behavior, allowing traffic to take advantage of the under-used resources at the links that precede and follow the bottleneck links. The algorithm was implemented in MATLAB. The resulted provisioning parameters were simulated using NS-2 to demonstrate the effectiveness of the proposed scheme.

Miriam Allalouf, Yuval Shavitt

How Well Do Traffic Engineering Objective Functions Meet TE Requirements?

We compare and evaluate how well-known and novel network-wide objective functions for Traffic Engineering (TE) algorithms fulfil TE requirements. To compare the objective functions we model the TE problem as a linear program and solve it to optimality, thus finding for each objective function the best possible target of any heuristic TE algorithm. We show that all the objective functions are not equivalent and some are far better than others. Considering the preferences a network operator may have, we show which objective functions are adequate or not.

Simon Balon, Fabian Skivée, Guy Leduc

Variable Step Fluid Simulation for Communication Network

We propose a variable step fluid model for communication network in this paper. Our main goal in this research is simulation speedup of a packet-level simulator while maintaining the accuracy. The variable step fluid model not only reduces complexity but also accurately estimates simulation details such as round trip time, queue sizes, TCP windows, and packet drops. In addition, the variable step fluid model reduces event explosions, ripple effects, which have been observed in the traditional fluid models. We validate our model against


simulation with a mixture of TCP and UDP flows under various background traffic scenarios. Our model achieves significant speedup compared to packet-level simulators. For example, the speedup of our fluid model for 20 Mb bottleneck is 40 to 70 against



Hongjoong Kim, Junsoo Lee

Monitoring/Measurements I

Estimating Link Capacity in High Speed Networks

Knowledge of bottleneck capacity of an Internet path is critical for efficient network design, management, and usage. With emerging high speed Internet links, most traditional estimation techniques are limited in providing fast and accurate capacity estimations. In this paper, we propose a new technique, called PBProbe, to estimate high speed links. PBProbe is based on CapProbe; however, instead of solely relying on packet pairs, PBProbe employs a “packet bulk” technique and adapts the bulk length in order to overcome the well known problem with packet pair based approaches, namely the lack of accurate timer resolution. As a result, PBProbe not only preserves the simplicity and speed of CapProbe, but it also correctly estimates link capacities within a much larger range. Using analysis, we evaluate PBProbe with various bulk lengths and network configurations. We then perform emulation and Internet experiments to verify the accuracy and speed of PBProbe on high speed links. The results show that PBProbe is consistently fast and accurate in the great majority of test cases.

Ling-Jyh Chen, Tony Sun, Li Lao, Guang Yang, M. Y. Sanadidi, Mario Gerla

Internet Traffic Mid-term Forecasting: A Pragmatic Approach Using Statistical Analysis Tools

Network planning is usually based on long-term trends and forecasts of Internet traffic. However, between two large updates, telecommunication operators deal with resource allocation in contracts depending on the mid-term evolution of their own traffic. In this paper, we develop a methodology to forecast the fluctuations of Internet traffic in an international IP transit network. We do not work on traffic demands which can not be easily measured in a large network. Instead, we use link counts which are much simpler to obtain. If needed, the origin-destination demands are estimated

a posteriori

through traffic matrix inference techniques. We analyze link counts stemming from France Telecom IP international transit network at the two hours time scale over nineteen weeks and produce forecasts for five weeks (mid-term). Our methodology relies on Principal Component Analysis and time series modeling taking into account the strain of cycles. We show that five components represent 64% of the traffic total variance and that these components are quite stable over time. This stability allows us to develop a method that produce forecasts automatically without any model to fit.

Rachel Babiarz, Jean-Sebastien Bedo

Semantic Compression of TCP Traces

We propose a new methodology,


, for model-based storage and regeneration of TCP traces.


provides significant data compression by exploiting semantics of TCP. Experiments show that


can achieve over 10,000-fold compression ratios for some really large input connections, while still being able to recover several structural and QoS measures.

Gabriel Istrate, Anders Hansson, Sunil Thulasidasan, Madhav Marathe, Chris Barrett

Traffic Anomaly Detection and Characterization in the Tunisian National University Network

Traffic anomalies are characterized by unusual and significant changes in a network traffic behavior. They can be malicious or unintentional. Malicious traffic anomalies can be caused by attacks, abusive network usage and worms or virus propagations. However unintentional ones can be caused by failures, flash crowds or router misconfigurations. In this paper, we present an anomaly detection system derived from the anomaly detection schema presented by Mei-Ling Shyu in [12] and based on periodic SNMP data collection. We have evaluated this system against some common attacks and found that some (Smurf, Sync flood) are better detected than others (Scan). Then we have made use of this system in order to detect traffic anomalies in the Tunisian National University Network (TNUN). For this, we have collected network traffic traces from the Management Information Base MIB of the central firewall of the TNUN network. After that, we calculated the inter-anomaly times distribution and the anomaly durations distribution. We showed that anomalies were prevalent in the TNUN network and that most anomalies lasted less than five minutes.

Khadija Houerbi Ramah, Hichem Ayari, Farouk Kamoun

Wireless Networks I

B-EDCA: A New IEEE 802.11e-Based QoS Protocol for Multimedia Wireless Communications

The IEEE 802.11e draft standard is a proposal defining the mecha-nisms for wireless LANs aiming to provide QoS support to time-sensitive applications. However, recent studies have shown that the IEEE 802.11e (EDCA) performs poorly when the medium is highly loaded due to the high collision rate. Even though several proposals have been proposed to address this problem, they require important changes to the current standard specifications making difficult their actual implementation. In this paper, we propose a simple QoS-aware mechanism and fully compatible with the various operation modes of the EDCA standard as well as the legacy IEEE 802.11 (DCF) scheme. Our design has been based on an in-depth analysis of the several operation modes of both standards. This should ensure full compatibility of operation: an important feature since the transition from the IEEE 802.11 to the IEEE 802.11e will take some time making more likely the existence of hybrid scenarios where both standards will have to coexist. Our simulation results show that our new scheme outperforms the EDCA and other QoS-aware schemes recently reported in the literature.

José Villalón, Pedro Cuenca, Luis Orozco-Barbosa

A Lagrangian Approach for the Optimal Placement of Wireless Relay Nodes in Wireless Local Area Networks

The throughput capacity of WLANs can be improved by a carefully designed relay infrastructure. In this work, we propose an optimization formulation based on Lagrangian relaxation and a subgradient algorithm to compute the best placement of a fixed number of relay nodes (RNs) in a WLAN. We apply this optimization framework to a multi-rate WLAN based on the IEEE 802.11g standard under Rayleigh fading. We then study the expected throughput capacity of a WLAN with relay infrastructure and investigate how the optimal placement of RNs is affected by the number of RNs, path-loss characteristics, and the traffic pattern. Our numerical results show that, in some network scenarios, more than 120% performance gain can be achieved when RNs are strategically installed in the network. Furthermore, we also show that for a wide range of system parameters, optimally placed RNs can significantly increase the network throughput capacity over random placement.

Aaron So, Ben Liang

Correlated Equilibrium in Access Control for Wireless Communications

We study a finite population of mobiles communicating using the slotted ALOHA-type protocol. Our objective is the study of coordination between the mobiles in both cooperative as well as non-cooperative scenarios. Our study is based on the correlated equilibrium concept, a notion introduced by Aumann that broadens the Nash equilibrium. We study ways in which signaling can improve the performance both in the cooperative as well as in the non-cooperative cases, even in the absence of any extra information being conveyed through these signals.

Eitan Altman, Nicolas Bonneau, Mérouane Debbah

Design and Analysis of an Adaptive Backoff Algorithm for IEEE 802.11 DCF Mechanism

This paper presents an adaptive backoff algorithm for the contention-based Distributed Coordination Function (DCF) of the IEEE 802.11 standard. Relying on on-line measurements of the number of sources, the algorithm, called Adaptive BEB, judiciously sets the size of the minimal contention window to adapt to the congestion level in the shared medium. The paper also provides an extension to Adaptive BEB for enhancing its performance over noisy channels. In this extension, a simple EWMA filter is used to derive a Packet Error Rate estimator. The performance evaluation of our proposal is addressed via simulations.

Mouhamad Ibrahim, Sara Alouf

Routing I

A Comparison of Exact and ε -Approximation Algorithms for Constrained Routing

The Constrained Routing Problem is a multi-criteria optimization problem that captures the most important aspects of Quality of Service routing, and appears in many other practical problems. The problem is NP-hard, which causes exact solutions to require an intractable running time in the worst case.


-approximation algorithms provide a guaranteed approximate solution for all inputs while incurring a tractable (i.e., polynomial) computation time. This paper presents a performance evaluation of these two types of algorithms. The main performance criteria are accuracy and speed.

Fernando Kuipers, Ariel Orda, Danny Raz, Piet Van Mieghem

Path Selection Techniques to Establish Constrained Interdomain MPLS LSPs

MultiProtocol Label Switching (MPLS) is used today inside most large Service Provider (SP) networks. In this paper, we analyze the establishment of interdomain MPLS LSPs with QoS constraints. These LSPs cross diverse SP networks that may belong to different companies. We show that using the standard BGP route for the establishment of such LSPs is not sufficient. We propose two path establishment techniques that rely on RSVP-TE and make use of Path Computation Elements (PCEs). Our simulations show that these techniques increase the number of constrained MPLS LSPs that can be established across domain boundaries.

Cristel Pelsser, Olivier Bonaventure

Reliable Routings in Networks with Generalized Link Failure Events

We study routing problems in networks that require guaranteed reliability against multiple correlated link failures. We consider two different routing objectives: The first ensures “local reliability,” i.e., the goal is to route so that each connection in the network is as reliable as possible. The second ensures “global reliability,” i.e., the goal is to route so that as few as possible connections are affected by any possible failure. We exhibit a trade-off between the two objectives and resolve their complexity and approximability for several classes of networks. Furthermore, we propose approximation algorithms and heuristics. We perform experiments to evaluate the heuristics against optimal solutions that are obtained using an integer linear programming solver. We also investigate up to what degree the routing trade-offs occur in randomly generated instances.

Stamatis Stefanakos

Making Outbound Route Selection Robust to Egress Point Failure

Offline inter-domain outbound Traffic Engineering (TE) can be formulated as an optimization problem whose objective is to determine primary egress points for traffic exiting a domain. However, when egress point failures happen, congestion may occur if secondary egress points are not carefully determined. In this paper, we formulate a bi-level outbound TE problem in order to make outbound route selection robust to egress point failures. We propose a tabu search heuristic to solve the problem and compare the performance to three alternative approaches. Simulation results demonstrate that the tabu search heuristic achieves the best performance in terms of our optimization objectives and also keeps traffic disruption to a minimum.

Mina Amin, Kin-Hon Ho, Michael Howarth, George Pavlou

Resource Management and QoS I

An Approach to Off-Line Inter-domain QoS-Aware Resource Optimization

Inter-domain traffic engineering is a key issue when QoS-aware resource optimization is concerned. Mapping inter-domain traffic flows into existing service level agreements is, in general, a complex problem, for which some algorithms have recently been proposed in the literature. In this paper a modified version of a multi-objective genetic algorithm is proposed, in order to optimize the utilization of domain resources from several perspectives: bandwidth, monetary cost, and routing trustworthiness. Results show trade-off solutions and “optimal” solutions for each perspective. The proposal is a useful tool in inter-domain management because it can assist and simplify the decision process.

Manuel Pedro, Edmundo Monteiro, Fernando Boavida

A Distributed QoS Scheduler for Smoothing Output Traffic of Input Buffered Switches

To provide stringent service guarantees such as latency and backlog bounds for input-buffered switches, a set of scheduling algorithm and admission control strategy is proposed. This set of traffic control strategy is primarily based on a single-server scheduling algorithm called Smoothed Round Robin (SRR). SRR possesses a number of advantages which are very attractive to the implementation of input buffered switch. SRR is on order


(1) which requires minimal computational complexity. Secondly, SRR gives good delay bounds and fairness performance for each session. Thirdly, SRR can decompose a sequence into fixed size groups. In this way, by maintaining a SRR scheduler in each output port, scheduling can be performed in a distributed manner which largely reduces the complexity of the algorithm.

Man-Ting Choy, Tony T. Lee

VoD QAM Resource Allocation Algorithms

This paper proposes a new Quadrature Amplitude Modulation (QAM) resource allocation algorithm for Video on Demand (VoD) when there is a mixture of standard definition (SD) and high definition (HD) video streams. We have developed a simulation model to compare this algorithm with two popular algorithms: the least-loaded algorithm and the most-loaded algorithm. We show that our algorithm, which we call the non-mixing algorithm, performs signi-ficantly better than the two existing algorithms by accommodating more streams thereby lowering the blocking probabilities under a range of assum-ptions of peak concurrent usage rate and percentage of HD streams. Using computer simulation we found that the non-mixing algorithm leads to an average of 4.39% higher allowed peak usage rate than the least-loaded and most-loaded algorithms.

Jiong Gong, David Reed, Terry Shaw, Daniel Vivanco, Jim Martin

Performance of Experience-Based Admission Control in the Presence of Traffic Changes

This paper investigates the transient behavior of

experience-based admission control

(EBAC) in case of traffic changes. EBAC is a robust and resource-efficient admission control (AC) mechanism used for reservation overbooking of link capacities in packet-based networks. Recent analyses gave a proof of concept for EBAC and showed its efficiency and robustness through steady state simulation on a single link carrying traffic with constant properties. The contribution of this paper is an examination of the memory from which EBAC gains its experience and which strongly influences the behavior of EBAC in both, stationary and non-stationary state. For the latter, we investigate the transient behavior of the EBAC mechanism through simulation of strong traffic changes which are characterized by either a sudden decrease or increase of the traffic intensity. Our results show that the transient behavior of EBAC partly depends on its tunable memory and that it copes well with even strongly changing traffic characteristics.

Jens Milbrandt, Michael Menth, Jan Junker

Topology and Location Awareness

Topologically-Aware AAA Overlay Network in Mobile IPv6 Environment

In mobile IPv6 network, AAA mechanism is necessary for administration and security because roaming nodes are permitted and become majority. However, disharmonies are exposed when MIPv6 meets AAA. On one hand, AAA procedures increase the latency of MIPv6 handover by inserting several message round trips before mobile registration. Thus the handover performance is reduced. On the other hand, AAA does nothing to help MIPv6 with its security problem. The fact is that MIPv6 has to struggle with those problems by itself. The result is that MIPv6 become complicated and inefficient. The crux of the matter is that AAA and MIPv6 are separately designed from their own viewpoints without mutual reinforcement. In this study, a Topologically-Aware AAA Overlay Network (TA


ON) is used for compatibly combining together resources and capacities from both sides. All connected AAA participators construct an overlay network which is naturally topology-aware. MIPv6 security issues, for example key generating and peer identifying, are handled by AAA. Secret materials and even MIPv6 signals can be delivered through TA


ON. As shown in this paper, at little additional cost all things serve their proper purposes and finally performance and security of MIPv6 are improved.

Jun Li, Xin-ming Ye, Ye Tian

QoS-Aware Multi-tier Location Managements for Integrated WLAN/UMTS Networks

This paper addresses quality of service (QoS)-aware multi-tier location managements for integrated WLAN/UMTS networks. Single registration (SR) and multiple registration (MR) schemes are introduced and improved to support both voice and data services efficiently. The performance of the improved SR and MR schemes is analyzed based on mobility and traffic characteristics of mobile users. The results show that there is tradeoff between improved SR and MR schemes and thus, an appropriate scheme should be selected based on users’ mobility and traffic characteristics. The analytical methodology developed in this paper can be extended to analyze the performance of general heterogeneous networks with multiple wireless access systems, which will be realized in fourth generation (4G) networks.

Yun Won Chung

Leveraging Buffering Delay Estimation for Geolocation of Internet Hosts

Geolocation techniques aim at determining the geographic location of an Internet host based on its IP address. Currently, measurement-based geolocation techniques disregard the buffering delays that may be introduced at each hop along the path taken by probe packets. To fill this gap, we propose the




location using




elay estimation) approach. Although the network delay and the geographic distance between two Internet hosts have been shown to be related to some extent, leveraging buffering delay estimation at each hop for geolocation purposes is challenging for two reasons. First, correctly estimating the buffering delay at intermediate hops along a traceroute path for geolocation purposes depends on the accurate estimation of the geolocation of the intermediate routers. Second, even given an

a priori

knowledge of the location of the routers, estimating the buffering delays is difficult due to the coarse-grained information provided by delay measurements. Relying on traceroute measurements, we show that leveraging buffering delay estimation improves accuracy in the measurement-based geolocation of Internet hosts as well as the confidence that the geolocation service associates to each estimation.

Bamba Gueye, Steve Uhlig, Artur Ziviani, Serge Fdida

Caching and Content Management

A Feedback Control Approach to Mitigating Mistreatment in Distributed Caching Groups

We consider distributed collaborative caching groups where individual members are autonomous and self-aware. Such groups have been emerging in many new overlay and peer-to-peer applications. In a recent work of ours, we considered distributed caching protocols where group members (nodes) cooperate to satisfy requests for information objects either locally or remotely from the group, or otherwise from the origin server. In such setting, we identified the problem of a node being


, i.e., its access cost for fetching information objects becoming worse with cooperation than without. We identified two causes of mistreatment: (1) the use of a

common caching

scheme which controls whether a node should


rely on other nodes in the group by keeping its own local copy of the object once retrieved from the group; and (2) the

state interaction

that can take place when the miss-request streams from other nodes in the group are allowed to affect the state of the local replacement algorithm. We also showed that both these issues can be addressed by introducing two simple additional parameters that affect the caching behavior (the


and the


parameters). In this paper, we argue against a


rule-of-thumb policy of setting these parameters since the performance, in terms of average object access cost, depends on a multitude of system parameters (namely, group size, cache sizes, demand skewness, and distances). We then propose a

feedback control approach

to mitigating mistreatment in distributed caching groups. In our approach, a node independently emulates its performance as if it were acting selfishly and then adapts its reliance and interaction parameters in the direction of reducing its measured access cost below its emulated selfish cost. To ensure good convergence and stability properties, we use a (Proportional-Integral-Differential) PID-style controller. Our simulation results show that our controller adapts to the minimal access cost and outperforms static-parameter schemes.

Georgios Smaragdakis, Nikolaos Laoutaris, Ibrahim Matta, Azer Bestavros, Ioannis Stavrakakis

Locality of Reference in an Hierarchy of Web Caches

This work presents an extensive evaluation of the request filtering in hierarchy of proxy caches. Using the recently proposed ADF (Aggregation, Disaggregation and Filtering) model as well as entropy as metric for Web traffic characterization, we evaluate how locality of reference changes as the streams of requests pass through a hierarchy of caches. Moreover, we propose the use of average entropy for comparing the locality of reference of different streams and present how a proxy server can dynamically calculate the entropy of its incoming request stream.

Fernando Duarte, Fabrício Benevenuto, Virgílio Almeida, Jussara Almeida

DMTP: Controlling Spam Through Message Delivery Differentiation

Unsolicited commercial email, commonly known as spam, has become a pressing problem in today’s Internet. In this paper we re-examine the architectural foundations of the current email delivery system that are responsible for the proliferation of email spam. We argue that the difficulties in controlling spam stem from the fact that the current email system is fundamentally sender-driven and distinctly lacks receiver control over email delivery. Based on these observations we propose a Differentiated Mail Transfer Protocol (DMTP), which grants receivers greater control over how messages from different classes of senders should be delivered on the Internet. In addition, we also develop a formal mathematical model to study the effectiveness of DMTP in controlling spam. Through numerical experiments we demonstrate that DMTP can effectively reduce the maximum revenue that a spammer can gather; moreover, compared to the current SMTP-based email system, the proposed email system can force spammers to stay online for longer periods of time, which may significantly improve the performance of various real-time blacklists of spammers. Furthermore, DMTP provides an incremental deployment path from the current SMTP-based system in today’s Internet.

Zhenhai Duan, Yingfei Dong, Kartik Gopalan

Optical Networks I

Delay Performance Analysis for an Agile All-Photonic Star Network

In this paper, we study the delay performance of a centrally-controlled agile all-photonic star WDM network that provides multiplexing in the time domain over each wavelength. We consider two timeslot allocation strategies, First-Fit (FF) and First-Fit+Random (FFR), as well as network scenarios with different propagation delays. Both theoretical analyses and simulation experiments are conducted to evaluate the delay performance of the network. Through analytical and simulation results, we show that allocating residual free bandwidth can significantly improve queuing delay performance under light traffic load while maintaining good delay performance under heavy traffic load, especially for a network scenario with large propagation delays. The results obtained can be used to guide the design of scheduling algorithms especially for large-scale networks.

Cheng Peng, Peng He, Gregor v. Bochmann, Trevor J. Hall

Designing Scalable WDM Optical Interconnects Using Predefined Wavelength Conversion

This paper investigates the problem of designing scalable and cost-effective wavelength division multiplexing (WDM) optical interconnects. We propose a new design for WDM optical interconnect that has several advantages over existing designs. First, wavelength conversion occurs between two


wavelengths. This not only eliminates the need for expensive wide-range wavelength converters, but also ensures high scalability as the conversion range is independent of the number of the wavelengths in the system. Second, the new design requires a smaller number of switching elements compared to most of the recent best interconnect designs.

Haitham S. Hamza, Jitender S. Deogun

Designing Fast and Bandwidth Efficient Protection Scheme for WDM Optical Networks

In this paper, we introduce the

Pre-cross-connected Segment First

— PXSFirst protection scheme; a new path-based protection schemes for WDM optical networks. The goal of the PXSFirst scheme is to achieve fast recovery, while maximizing bandwidth sharing to improve bandwidth utilization. Similar to pre-cross-connected trails (PXTs) protection scheme, PXSFirst ensures that all backup paths are pre-cross-connected, and hence eliminates the switching configuration delay along backup paths. However, unlike the PXT scheme, where backup paths can only share trails, PXSFirst breaks backup paths into smaller segments by existing end nodes, and hence, increases the possibility of bandwidth sharing. Extensive simulation results for different network topologies and under different traffic patterns show that the proposed scheme has better blocking performance and less bandwidth utilization (an average of 11.0% reduction) compared to existing PXT protection schemes.

Yu Lin, Haitham S. Hamza, Jitender S. Deogun

Mobile Ad-Hoc Networks II

Increasing Fairness and Efficiency Using the MadMac Protocol in Ad Hoc Networks

The IEEE 802.11 MAC layer is known for its unfairness behavior in

ad hoc

networks. Introducing fairness in the 802.11 MAC protocol may lead to a global throughput decrease. It is still a real challenge to design a fair MAC protocol for ad hoc networks that is distributed, topology independent, that relies on no explicit information exchanges and that is efficient,


that achieves a good aggregate throughput. The MadMac protocol deals with fairness and throughput by maximizing aggregate throughput when unfairness is solved. Fairness provided by MadMac is only based on information provided by the 802.11 MAC layer and adds a non-probabilistic modification in 802.11. MadMac has been tested in many configurations that are known to be unfair. In these configurations, MadMac provides a good aggregate throughput while solving the fairness issues.

Tahiry Razafindralambo, Isabelle Guérin-Lassous

Duplicate Address Detection in Wireless Ad Hoc Networks Using Wireless Nature

We consider duplicate address detection in wireless ad hoc networks under the assumption that addresses are unique in two hops neighborhood. Our approaches are based on the concepts of

physical neighborhood views

, that is, the information of physically connected nodes, and

logical neighborhood views

, which are built on neighborhood information propagated in networks. Since neighborhood information is identified by addresses, inconsistency of these two views might occur due to duplicate addresses. It is obvious that consistency of these two views on each node’s neighborhood is necessary for a network to have unique addresses, while the sufficiency depends on the types of information contained in neighborhood views. We investigate different definitions of neighborhood views and show that the traditional neighborhood information, neighboring addresses, is not sufficient for duplication detection, while the wireless nature of ad hoc networks provides useful neighborhood information.

Yu Chen, Eric Fleury

Fault Monitoring in Ad-Hoc Networks Based on Information Theory

Fault detection is a well-known issue in fixed wired networks. Ad-hoc networks provide new challenges towards detecting network failures: the detection task may be hindered by the impossibility to observe a given node. We propose in this paper to monitor the intermittence of network nodes in order to infer network failures. Intermittence can be caused in ad-hoc networks by benign causes due to node mobility and to time-limited out of reachability situations. Abnormal intermittence is however due to faults or malicious network activities. This paper shows how information theoretic measures can identify abnormal intermittence over the routing layer, and proposes a lightweight and distributed intermittence monitoring scheme including several fault detection methods.

Remi Badonnel, Radu State, Olivier Festor

Performance Analysis of Exposed Terminal Effect in IEEE 802.11 Ad Hoc Networks in Finite Load Conditions

The paper evaluates the performance effects of exposed terminals in IEEE 802.11 ad hoc networks in finite load conditions. In this context, employing also models from previous authors’ work, the paper derives analytical models for the estimation of channel utilization and media access delay for IEEE 802.11 ad hoc networks in finite load conditions with and without exposed terminals. The simulation results show that the analytical estimated channel utilization and media access delay metrics are fairly accurate.

Dimitris Vassis, Georgios Kormentzas

Transport Protocols

Modeling and Performance Evaluation of SCTP as Transport Protocol for Firewall Control

Firewalls are a crucial building block for securing IP networks. The usage of out-of-band-signaling protocols (such as SIP) for VoIP and multimedia applications requires a dynamic control of these firewalls, which can be implemented using the Simple Middlebox Configuration Protocol (SIMCO). In this paper, we study the performance of SCTP and TCP as transport protocols for the transaction-based signaling protocol SIMCO, which requires small end-to-end delays. We present an analytical model in order to quantify the impact of head-of-line blocking in SCTP. Both, the model and measurements reveal that SCTP can significantly reduce the SIMCO response times by leveraging transmission over multiple parallel streams. While a few SCTP streams can almost completely avoid head-of-line blocking, our measurements show that TCP may suffer from rather large end-to-end delays.

Sebastian Kiesel, Michael Scharf

Transport Layer Issues in Delay Tolerant Mobile Networks

The tremendous increase in wireless devices and user mobility have ultimately resulted in a new set of networking challenges that previously did not exist. Some of these challenges include large delays, intermittent connectivity and most importantly, the absence of an end-to-end path from sources to destinations. Networks characterized by one or more of these challenges are called

Delay Tolerant Networks (DTNs)

. Researchers have studied DTNs with a major focus on routing issues in such extreme environments. As a result, in this paper, we shift this focus towards addressing and studying transport layer issues in extreme networking environments. We particularly concentrate on investigating and comparing several reliability approaches in a specific category of DTNs known as Delay Tolerant Mobile Networks (DTMNs). We present four different reliability approaches in DTMNs. We also evaluate these approaches under various network conditions via simulation. Our goals from this study are to examine the impact of these reliability approaches, understand the tradeoffs between them, and open the way for further work in transport layer issues in delay tolerant networks.

Khaled A. Harras, Kevin C. Almeroth

Performance of Competing High-Speed TCP Flows

The goal of recent high-speed TCP implementations is to allow scientists who have access to new high-speed networks to efficiently transfer large datasets to their remote colleagues. As of yet, there is no standard high-speed TCP . Because of this, scientists using one high-speed protocol may find themselves sharing a link with scientists using a different high-speed protocol. Previous work has evaluated such inter-protocol performance, but only with both flows starting at the same time – an unlikely situation. We perform an evaluation study using


-2 to investigate the performance of competing high-speed TCP flows where one flow enters a network in which another high-speed flow has already reached its maximum data rate. The fairest result would be for the existing flow to cede half of its bandwidth to the new flow in order to allow both flows to evenly share the link. Our results show that in most cases this does not happen, but rather one high-speed flow dominates the other. Surprisingly, it is not always the existing flow that dominates.

Michele C. Weigle, Pankaj Sharma, Jesse R. Freeman

On the Accuracy of Analytical Models of TCP Throughput

Based on a large set of TCP sessions we first study the accuracy of two well-known analytical models (SQRT and PFTK) of the TCP average rate. This study shows that these models are far from being accurate on average. Actually, our simulations show that 70% of their predictions exceed the boundaries of TCP-Friendliness, thus questioning their use in the design of new TCP-Friendly transport protocols. Our study also shows that the inaccuracy of the PFTK model is largely due to its inability to make the distinction between the two packet loss detection methods used by TCP: triple duplicate acknowledgments or timeout expirations. We then use supervised learning techniques to infer models of the TCP rate. These models show important accuracy improvements when they take into account the two types of losses. This suggests that analytical model of TCP throughput should certainly benefit from the incorporation of the timeout loss rate.

Ibtissam El Khayat, Pierre Geurts, Guy Leduc

Monitoring/Measurements II

High Speed Packet Logging on a Budget

Creating high quality network trace files is a difficult task to accomplish on a limited budget. High network speeds may overburden an individual system running packet logging software such as tcpdump, resulting in trace files with missing information and making analysis difficult or incomplete. High end specialized systems may perform the job well, but may be out of reach due to financial constraints. To the end we developed the

Cheap Logger

(CLog) system which utilizes inexpensive COTS hardware to create a high quality, complete network trace files. A scalable distributed storage system enables the CLog system to expand and continue to create high quality, complete network data trace files even at extremely high data rates.

Chad D. Mano, Jeff Smith, Bill Bordogna, Aaron Striegel

An Efficient Overlay Link Performance Monitoring Technique

Link performance monitoring is a common task required by different overlay networks. Current overlays typically let each node monitor links by itself, which is not scalable for large networks. Earlier improvement proposals either use a centralized approach or sacrifice measurement accuracy. This paper proposes


, a distributed overlay monitoring technique. Based on the proposed


concept, MONET enables peer cooperation so that each node performs a minimum amount of measurement but can deduce the performance of any link. It does not lose accuracy and adapts to IP-layer path dynamics. Theoretical analysis and simulation results, in terms of monitoring cost and querying overhead, are also discussed in this paper.

Zhi Li, Lihua Yuan, Prasant Mohapatra

Measurement of Radio Propagation Path Loss over the Sea for Wireless Multimedia

In order to estimate the signal parameters accurately for wireless multimedia services, it is necessary to estimate a system’s propagation characteristics through a medium. Propagation analysis provides a good initial estimate of the signal characteristics. The ability to accurately predict radio propagation behavior for wireless multimedia services is becoming crucial to system design. Since site measurements are costly, propagation models have been developed as a suitable, low cost, and convenient alternative [1]. A number of studies have been conducted to quantitatively predict the characteristics of propagation in inhabited areas on land having many wireless multimedia service users, resulting in a number propagation prediction models being proposed. However, since very few such studies have been conducted for the sea, which has a different physical layer structure from land, the propagation prediction model for free space has been commonly used. Thus, in this study, I measured the propagation path loss of a 1950 MHz band signal over the sea surface, and analyzed the results by comparing them with the path loss data of a propagation prediction model in free space, which is frequently used to predict the propagation path loss over the sea surface.

Dong You Choi

Workload Loss Examinations with a Novel Probabilistic Extension of Network Calculus

The estimation of the expected traffic loss ratio (workload loss ratio, WLR) is a key issue in provisioning Quality of Service in packet based communication networks. Despite of its importance, the stationary (long run) loss ratio in queueing analysis is usually estimated through other assessable quantities, typically based on the approximates of the buffer overflow probability. In this paper we define a calculus for communication networks which is suitable for workload loss estimation based on the original definition of stationary loss ratio. Our novel calculus is a probabilistic extension of the deterministic network calculus, and takes an envelope approach to describe arrivals and services for the quantification of resource requirements in the network. We introduce the effective w-arrival curve and the effective w-service curve for describing the inputs and the service and we show that the per-node results can be extended to a network of nodes with the definition of the effective network w-service curve.

András Gulyás, József Bíró


Optimized Handoff Decision Mechanisms for Scalable Network Mobility Support

Network Mobility (NEMO) is concerned with managing the mobility of an entire network and included one or more Mobile Routers (MRs) which are connected as gateways to the Internet. This paper proposes the optimal handoff decision mechanisms, not only avoiding the ‘ping-pong effect’ and frequent handoffs, but also reducing handoff latency under multi-hop network mobility. The simulation results demonstrate that the proposed method is well adapted for supporting network mobility over traditional handoff decision algorithms.

Sangwook Kang, Yunkuk Kim, Woojin Park, Jaejoon Jo, Sunshin An

Fast Re-authentication for Handovers in Wireless Communication Networks

The evolution of wireless access technologies and the capabilities of today’s mobile devices lead to an increasing demand of communication bandwidth. More and more packet-switched wireless access networks like Wireless Local Area Networks (WLANs) and networks based on Worldwide Interoperability for Microwave Access (WiMAX) are publicly available and operated by different providers. In order to achieve a high network coverage isolated access network providers are supposed to co-operate and to support handovers for users from access networks belonging to the same core network. Efficient authentication mechanisms are required that on the one hand exclude unauthorized users from the network and on the other hand support seamless handovers across access network boundaries. We propose a ticket-based fast re-authentication scheme that is independent from the actual authentication method and that only slightly modifies well-established standards like the Extensible Authentication Protocol (EAP) and the Remote Authentication Dial In User Service (RADIUS). As it is network technology independent, it in principle also allows fast handovers across different access network technologies.

Ralf Wienzek, Rajendra Persaud

Handover Operation in Mobile IP-over-MPLS Networks

This paper examines mobility operations, and particularly handovers in an environment, where Hierarchical Mobile IP is operating over MPLS. The work in this paper improves on existing methods of MIP-MPLS interworking first by defining a simple framework based on Hierarchical Mobile IPv6 (HMIPv6) and second by outlining the relevant protocol design assumptions. In addition, the combined protocol is examined in detail under two scenarios and a comprehensive explanation of the operation of intra- and inter-cell handovers is presented.

Vasos Vassiliou

The Design and Implementation of a Quality-Based Handover Trigger

Wireless connectivity is needed to bring IP-based telephony into serious competition with the existing cellular infrastructure. However it is well known that voice quality problems can occur when used with unlicensed spectrum technologies such as the popular IEEE 802.11 standards. The cellular infrastructure could provide alternative network access should users roam out of 802.11 coverage or if heavy traffic loads are encountered in the 802.11 cell. Therefore, our goal is to design a handover mechanism to switch ongoing calls to the cellular network when the 802.11 network cannot sustain sufficient call quality. We have investigated load and coverage scenarios and designed, implemented and evaluated the performance of an 802.11 quality-based trigger for the handover of voice calls to the cellular network. We show that our predictive solution addresses the coverage problem and evaluate it within a real setting.

Ian Marsh, Björn Grönvall, Florian Hammer


An Efficient Algorithm for Resource Sharing in Peer-to-Peer Networks

The performance of peer-to-peer systems depends on the level of cooperation of the system’s participants. While most existing peer-to-peer architectures have assumed that users are generally cooperative, there is great evidence from widely deployed systems suggesting the opposite. To date, many schemes have been proposed to alleviate this problem. However, the majority of these schemes are either too complex to use in practice, or do not provide strong enough incentives for cooperation.

In this work we propose a scheme based on the general idea that offering uploads brings revenue to a node, and performing downloads has a cost. We also introduce a theoretical model that predicts the performance of the system and computes the values of the scheme’s parameters that achieve a desired performance. Our scheme is quite simple and very easy to implement. At the same time, it provides very strong incentives for cooperation and improves the performance of P2P networks significantly. In particular, theory and realistic simulations show that it reduces the query response times and file download delays by one order of magnitude, and doubles the system’s throughput.

Wei-Cherng Liao, Fragkiskos Papadopoulos, Konstantinos Psounis

On the Identification and Analysis of P2P Traffic Aggregation

The main purpose of this paper is twofold. First, we propose a novel identification method to reveal P2P traffic from traffic aggregation. Our method is based on a set of heuristics derived from the robust properties of P2P traffic. We show the high accuracy of the proposed algorithm based on a validation study. Second, several results of a comprehensive traffic analysis, focusing on the differences between P2P and non-P2P traffic, are reported in the paper. Our results show that the unique properties of P2P application traffic seem to fade away during aggregation and characteristics of the traffic will be similar to that of other non-P2P traffic aggregation.

Trang Dinh Dang, Marcell Perényi, András Gefferth, Sándor Molnár

A Decentralized Recommendation System Based on Self-organizing Partnerships

Small World patterns have been found in many social and natural networks, and even in Peer-to-Peer topologies. In this paper, we analyze File Sharing applications that aggregate virtual communities of users exchanging data. In these domains, it is possible to define overlaying structures that we call “Preference Networks” that show self organized interest-based clusters. The relevance of this finding is augmented with the introduction of a proactive recommendation scheme that exploits this natural feature. The intuition behind this scheme is that a user would trust her network of “elective affinities” more than anonymous and generic suggestions made by impersonal entities.

Giancarlo Ruffo, Rossano Schifanella, Enrico Ghiringhello

Enhancing the P2P Protocols to Support Advanced Multi-keyword Queries

Recently, Peer-to-Peer has become a popular paradigm for building distributed systems, aiming to provide resource localization and sharing in large-scale networks. However, advanced searching for resources remains an open issue. The flooding technique used by some Peer-to-Peer systems is expensive in bandwidth usage, and it shows a serious lack in scalability. Also, more efficient systems based on distributed hash tables (DHT) lack in query expressiveness and flexibility. This paper addresses this issue by discussing existing solutions, and proposing a novel approach to support advanced multi-keyword queries in the context of Peer-to-Peer systems. It extends the existing, and widely established, DHT-based localization frameworks. This new approach can substantially reduce the bandwidth consumption and improve the load balancing over the network.

Samir Ghamri-Doudane, Nazim Agoulmine


Chasing: An Efficient Streaming Mechanism for Scalable and Resilient Video-on-Demand Service over Peer-to-Peer Networks

Provisioning scalable and resilient Video-on-Demand (VoD) service is both challenging and interesting. Recently, peer-to-peer (P2P) networks are introduced to address the scalability of VoD service over Internet. Most of existing work follows the line of cache-and-relay (CR) scheme to accommodate the asynchronous characteristic of requests from a community of end users. Aiming to take full advantages of bandwidth capacities at each node and pre-recorded feature of requested video files at streaming server, we improve traditional CR approach by efficiently exploiting surplus bandwidth and proactively prefetching media contents from either the server or other peers. Our proposed basic chasing and advanced chasing mechanism not only achieve significant reduction of workload on streaming server, which could translate into better scalability, but also help the streaming session to adapt to volatile network fluctuation. Our extensive experiments have demonstrated encouraging results with respect to increased system performance.

Jian-Guang Luo, Yun Tang, Shi-Qiang Yang

A Practical Approach to SIP, QoS and AAA Integration

In this paper, we present an overall architecture to integrate SIP-based session management with scalable QoS features and AAA functionality. The QoS features include a bandwidth reservation in the access network based on the Next Steps in Signaling (NSIS) architecture. Furthermore, we employ the DiffServ compliant Priority Promotion Scheme (PPS) which is a packet probing scheme to verify end-to-end premium bandwidth availability. To avoid misuse of the QoS features AAA functionality is added that binds the QoS usage with the specific SIP sessions. The AAA functionality is achieved by applying a combination of the widespread RADIUS protocol with the Common Open Policy Service (COPS). As a proof of concept our architecture has been implemented and performance tested. The strength of our approach is that it keeps away complexity from the carrier networks while providing QoS with access control in a scalable fashion.

Michael Stier, Emanuel Eick, Eckhart Koerner

Efficient Overlay Audio Conferencing

In this paper, we present a thorough and realistic analysis of audio conferencing over application-level multicast (ALM).

Through flexibility and ease-of-deployment, ALM is a compelling alternative group-communication technique to IP Multicast — which has yet to see wide-scale deployment in the Internet. However, proposed ALM techniques suffer from inherent latency inefficiencies, which we show, through realistic simulation and exploration of perceived quality in multi-party conversation, to be greatly problematic for the realisation of truly-scalable audio-conferencing systems over ALM.

In this work, we propose to adapt dynamically the application-level distribution structure to the conversational pattern of the audio conference. The contribution of this paper is threefold: we develop a novel perceptual quality model for multi-party audio conversations; we provide dynamic adaptation via a simple next-speaker prediction technique and we validate the proposed approach by using a large and detailed corpus of real multi-party conversations.

Norbert Egi, Nick Blundell, Laurent Mathy

On the Stability of End-Point-Based Multimedia Streaming

In this paper we propose an analytical model of a resilient, tree-based end-node multicast streaming architecture that employs path diversity and forward error correction for improved resilience to node churns and packet losses. Using the model and via simulations we study the performance of this architecture in the presence of packet losses and dynamic node behavior. We show that the overlay can distribute data to nodes arbitrarily far away from the root of the trees as long as the loss probability is lower than a certain threshold, but the probability of packet reception suddenly drops to zero once this threshold is exceeded. The value of the threshold depends on the ratio of redundancy and on the number of the distribution trees. Using the model and simulations we show that correlated and inhomogeneous losses slightly worsen the overlay’s performance. We apply the model to study the effects of dynamic node behavior and compare its results to simulations.

György Dán, Viktória Fodor, Gunnar Karlsson


Multicast Tree Aggregation in Large Domains

Tree aggregation is an efficient proposition that can solve the problem of multicast forwarding state scalability. The main idea of tree aggregation is to force several groups to share the same delivery tree: in this way, the number of multicast forwarding states per router is reduced. Unfortunately, when achieving tree aggregation in large domains, few groups share the same tree and the aggregation ratio is small. In this paper, we propose a new algorithm called


(Tree Aggregation in Large Domains) that achieves tree aggregation in domains with a large number of nodes. The principle of


is to divide the domain into several sub-domains and to achieve the aggregation in each of the sub-domain separately. In this way, there is possible aggregation in each of the sub-domain and the number of forwarding states is significantly reduced. We show the performance of our algorithm by simulations on a Rocketfuel network of 200 routers.

Joanna Moulierac, Alexandre Guitton, Miklós Molnár

Analysis and Performance Evaluation of a Multicast File Transfer Solution for Congested Asymmetric Networks

In this paper, we propose and analyze a multicast application called SOMA (SynchrOnous Multicast Application) which offers multicast file transfer service in an asymmetric intra-campus environment. For efficient bandwidth utilization, SOMA uses IP multicasting. We also propose a complete multicast transport protocol involving both, the flow and error correction algorithms. The protocol adapts the window size and the overall application transfer bitrate to the minimum network capacity, allowing synchronism and reacting quickly when congestion arises at any network router. The application behavior has been intensively tested by simulation and experimentally in a lab, using a mixture of wired and wireless intra-campus networks. In addition, we develop a mathematical model to validate analytically some of the most important protocol parameters. The methodology employed to define, analyze and evaluate this multicast protocol is, indeed, another contribution of the work and can be easily extended to other multicast protocols.

Pilar Manzanares-Lopez, Juan Carlos Sanchez-Aarnoutse, Josemaria Malgosa-Sanahuja, Joan Garcia-Haro

Traffic Engineering II

Multi-Layer Traffic Engineering Through Adaptive λ-Path Fragmentation and De-fragmentation

In Multi-Layer networks, where more than one layer is dynamic, i.e., connections are set up using not only the upper, e.g., IP layer but the underlying wavelength layer as well leads often to suboptimal performance due to long wavelength paths, that do not allow routing the traffic along the shortest path. The role of MLTE (Multi-Layer Traffic Engineering) is to cut these long wavelength paths into parts (fragments) that allow better routing at the upper layer (fragmentation), or to concatenate two or more fragments into longer paths (defragmentation) when the network load is low and therefore less hops are preferred.

In this paper we present a new model (GG: Grooming Graph) and an algorithm for this model that supports Fragmentation and De-Fragmentation of wavelength paths making the network always instantly adapt to changing traffic conditions. We introduce the notion of

shadow capacities

to model “lightpath tailoring”. We implicitly assume that the wavelength paths carry such, e.g., IP traffic that can be interrupted for a few microseconds and that even allows minor packet reordering.

To show the superior performance of our approach in various network and traffic conditions we have carried out an intensive simulation study.

Tibor Cinkler, Péter Hegyi, Márk Asztalos, Géza Geleji, János Szigeti, András Kern

Managing Traffic Demand Uncertainty in Replica Server Placement with Robust Optimization

The replica server placement problem determines the optimal location where replicated servers should be placed in content distribution networks, in order to optimize network performance. The estimated traffic demand is fundamental input to this problem and its accuracy is essential for the target performance to be achieved. However, deriving accurate traffic demands is far from trivial and uncertainty makes the target performance hard to predict. We argue that it is often inappropriate to optimize the performance for only a particular set of traffic demands that is assumed accurate. In this paper, we propose a scenario-based robust optimization approach to address the replica server placement problem under traffic demand uncertainty. The objective is to minimize the total distribution cost across a variety of traffic demand scenarios while minimizing the performance deviation from the optimal solution. Empirical results demonstrate that robust optimization for replica server placement can achieve good performance under all the traffic demand scenarios while non-robust approaches perform significantly worse. This approach allows content distribution providers to provision better and predictable quality of service for their customers by reducing the impact of inaccuracy in traffic demand estimation on the replica server placement optimization.

Kin-Hon Ho, Stylianos Georgoulas, Mina Amin, George Pavlou

An Information Theoretic Approach for Systems with Parallel Distributions: Case Studying Internet Traffic

The principle of Minimum Relative Entropy (MRE) is applied to characterize a ‘proportionality’ relationship between the state probabilities of infinite and finite capacity queues at equilibrium and thus, establish an information theoretic interpretation for the exact global balance solution of some finite capacity queues with or without correlated arrival processes. This result serves to establish the utility of the MRE inference technique and encourage its applicability to the analysis of more complex, and thus more realistic, queuing systems. The principles of Maximum Entropy (ME) and MRE are then employed, as least-biased methods of inference, towards the analysis of a Internet link carrying realistic TCP traffic, that exhibit this ‘proportionality’ relationship between a finite and infinite buffer system, as produced by a large number of connections. The analytic approximations are validated against exhaustive simulation experiments. Despite its simplicity, the methodology captures the behavior of the system under study both in the cases of finite and infinite buffers and finally and can easily be utilized for network management and design, capacity planning, and congestion control.

Charalabos Skianis, Lambros Sarakis

Optical Networks II

Characterization of the Burst Aggregation Process in Optical Burst Switching

We describe an analytic approach for the calculation of the departure process from a burst ggregation algorithm that uses both a timer and maximum/minimum burst size. The arrival process of packets is assumed to be Poisson or bursty modelled by an Interrupted Poisson Process (IPP). The analytic results are approximate and validation against simulation data showed that they have good accuracy.

Xenia Mountrouidou, Harry G. Perros

Improving Bandwidth Efficiency in a Multi-service Slotted Dual Bus Optical Ring Network

The paper proposes two IP packet aggregation techniques, called DAT (Deterministic Aggregation Technique) and WATT (Work-conserving Aggregation Technique with Timer), to adapt IP traffic to a multi-service optical slotted network. To perform aggregation, IP packets belonging to different classes of service (CoS) are polled according to the strict priority (SP) or to an hybrid version of the probabilistic priority (PP) scheduling discipline originally proposed in [1, 2]. An approximate analytical model is given in the case of DAT under the SP discipline. In addition, extensive simulations are used to study the impact of self-similar traffic on the aggregation processes. Finally, performance comparisons between the aggregation techniques and the standard approach (where no aggregation is performed) are carried out in the context of a slotted dual bus optical ring network (SDBORN) which is a candidate viable solution for metropolitan area networks (MAN).

Mohamad Chaitou, Gérard Hébuterne, Hind Castel

Issues on Performance Assessment of Optical Burst Switched Networks: Burst Loss Versus Packet Loss Metrics

With the increasing interest in optical burst switching (OBS) networks, the performance assessment of this kind of networks became of particular concern. Recently, some authors suggested that burst loss was not a reliable performance assessment metric for OBS networks. Refuting this claim, this paper presents simulation results obtained for a ring network, using real tributary IPv4 packets as source for the burst assembly. It is shown that burst loss, packet loss and byte loss lead to similar results over a wide range of burst assembly scenarios and network loads, using different resource reservation schemes. Therefore, burst loss is a reliable metric and can be used for evaluation of performance of optical burst switched networks, when realistic burst assembly algorithms are considered over real traffic.

Nuno M. Garcia, Przemyslaw Lenkiewicz, Paulo P. Monteiro, Mário M. Freire

Mobile Ad-Hoc Networks III

A Multi-hop MAC Forwarding Protocol for Inter-vehicular Communication

Conventional topology-based routing protocols such as AODV, DSR and ZRP are not suitable for inter-vehicular communication, where the duration of communication lasts extremely shortly. This paper presents a new inter-vehicular communication protocol called the Multi-hop MAC Forwarding Protocol (MMFP). The MMFP avoids explicit path setup in order to reduce the control overhead associated with it, but instead uses the reachability information towards the destination at each hop. Next-hop nodes are determined on-the-fly by contention based on a priority value. The basic operations of the MMFP are conceptually similar to that of MAC bridges and position-based ad-hoc routing protocols. The MMFP is designed to be integrated with the IEEE 802.11 MAC protocol in order to achieve higher efficiency and accuracy in its time-critical operations. It is shown through simulations that the MMFP outperforms the AODV in a realistic inter-vehicular communication scenario in terms of both the end-to-end delay and packet delivery ratio.

Woosin Lee, Hyukjoon Lee, Hyun Lee, ChangSub Shin

Route Lifetime Based Optimal Hop Selection in VANETs on Highway: An Analytical Viewpoint

We consider the problem of optimal next-hop selection in a route between two vehicles, for a simple scenario of Vehicular ad hoc networks (VANETs) on a highway. For a given approximation of the optimal number of hops, we seek the optimal choice of next-hop based on its speed and inter-node distances, so as to maximize the expected route lifetime. Under a Markovian assumption on the process of speed of nodes, we show that the optimal choice of speeds attempts to equalize the lifetimes of adjacent links. A monotone variation property of the speed of relay nodes under the optimal policy is proved. These properties have been confirmed with simulations. The optimal policies and their structures can assist in enhancing the performance of existing VANET routing protocols.

Dinesh Kumar, Arzad A. Kherani, Eitan Altman

On the Performances of the Routing Protocols in MANET: Classical Versus Self-organized Approaches

Mobile Ad Hoc Networks (MANET) are spontaneous wireless networks of mobile nodes without any fixed infrastructure. MANET are promised to a large spectrum of military or civilian utilizations. Routing is a key topic in such networks: overhead must be minimized, optimizing the delay and reducing the packet losses. Several routing protocols were proposed in the literature but, recently, new routing protocols based on a self-organization like Virtual Structure Routing (VSR) were proposed. VSR is based on a self-organized structure with an important stability and persistence. In this paper, we aim to quantify the contribution of the self-organization on the routing behavior and performances. We oppose VSR as a self-organized protocol to the classical one: reactive (AODV), proactive (OLSR) and clustered (CBRP). The impact of the mobility and the density, the horizontal and the vertical scalabilities are studied.

Fabrice Theoleyre, Fabrice Valois

Performance Modeling of Epidemic Routing

In this paper, we develop a rigorous, unified framework based on Ordinary Differential Equations (ODEs) to study epidemic routing and its variations. These ODEs can be derived as limits of Markovian models under a natural scaling as the number of nodes increases. While an analytical study of Markovian models is quite complex and numerical solution impractical for large networks, the corresponding ODE models yield closed-form expressions for several performance metrics of interest, and a numerical solution complexity that does not increase with the number of nodes. Using this ODE approach, we investigate how resources such as buffer space and power can be traded for faster delivery, illustrating the differences among the various epidemic schemes considered. Finally we consider the effect of buffer management by complementing the forwarding models with Markovian and fluid buffer models.

Xiaolan Zhang, Giovanni Neglia, Jim Kurose, Don Towsley

Wireless Sensor Networks

Maximum Lifetime Routing and Data Aggregation for Wireless Sensor Networks

In this paper we solve the maximum lifetime routing (MLR) problem for a sensor network by joint optimizing routing and data aggregation. We present a smoothing method to overcome the nondifferentiability of the objective function. By exploiting the special structure of the network, we derive the necessary and sufficient conditions to achieve the optimality. Based on these conditions, a gradient descent algorithm is designed for its solution. The proposed algorithm is shown to converge to the optimal value efficiently under all network configurations. The incorporation of optimal routing and data aggregation is shown via many examples to provide significant improvement of the network lifetime.

Cunqing Hua, Tak-Shing Peter Yum

Managing Random Sensor Networks by means of Grid Emulation

A common assumption in sensor networks is that the sensors are located according to a uniform random distribution. In this paper we show that uniform random points on the two dimensional unit square are almost a “grid”. In particular, for a synchronous geographic sensor network we show how to emulate any grid protocol on random sensor networks, with high probability.

This suggests the following framework. In order to solve a problem on a random sensor network we solve the same problem on the grid. Then we use our emulation to make the obtained solution suitable for random sensor network. We analyze the cost of the emulation in terms of consumed energy and time. Finally we provide three examples that illustrate our method.

Zvi Lotker, Alfredo Navarra

Distributed Data Gathering in Multi-sink Sensor Networks with Correlated Sources

In this paper, we propose an effective distributed algorithm to solve the minimum energy data gathering (MEDG) problem in sensor networks with multiple sinks. The problem objective is to find a rate allocation on the sensor nodes and a transmission structure on the network graph, such that the data collected by the sink nodes can reproduce the field of observation, and the total energy consumed by the sensor nodes is minimized. We formulate the problem as a linear optimization problem. The formulation exploits data correlation among the sensor nodes and considers the effect of wireless channel interference. We apply Lagrangian dualization technique on this formulation to obtain a subgradient algorithm for computing the optimal solution. The subgradient algorithm is asynchronous and amenable to fully distributed implementations, which corresponds to the decentralized nature of sensor networks.

Kevin Yuen, Baochun Li, Ben Liang

Abstract Frames for Reducing Overhearing in Wireless Sensor Networks

We present a novel idea for energy saving by avoiding the reception of redundant broadcast frames. It is based on sending an abstract frame just before a data frame: the former contains a digest of the latter. We evaluate the energy savings of this scheme analytically and by means of simulation in ns-2. Although we have applied our approach to SMAC, the key idea is generic and can be used to reduce energy consumed by broadcast frames in a large variety of MAC protocols.

Abdelmalik Bachir, Dominique Barthel, Martin Heusse, Andrzej Duda

Resource Management and QoS II

Dynamic Resource Allocation in Communication Networks

Efficient dynamic resource provisioning algorithms are necessary to the development and automation of Quality of Service (QoS) networks. The main goal of these algorithms is to offer services that satisfy the QoS requirements of individual users while guaranteeing at the same time an efficient utilization of network resources. In this paper we introduce a new service model that provides quantitative per-flow bandwidth guarantees, where users subscribe for a guaranteed rate; moreover, the network periodically individuates unused bandwidth and proposes short-term contracts where extra-bandwidth is allocated and guaranteed exclusively to users who can exploit it to transmit at a rate higher than their subscribed rate. To implement this service model we propose a dynamic provisioning architecture for intra-domain Quality of Service networks. We develop an efficient bandwidth allocation algorithm that takes explicitly into account traffic statistics to increase the users’ benefit and the network revenue simultaneously. We demonstrate through simulation in realistic network scenarios that the proposed dynamic provisioning model is superior to static provisioning in providing resource allocation both in terms of total accepted load and network revenue.

Antonio Capone, Jocelyne Elias, Fabio Martignon, Guy Pujolle

Fair Assured Services Without Any Special Support at the Core

Many users require IP networks with the capacity to guarantee a minimum throughput even during periods of congestion. Furthermore, it is also desirable to share the excess unsubscribed bandwidth among active users if aggregate demand does not exceed network capacity. This kind of service, named assured service, can be provided through the

Assured Forwarding


Per Hop Behavior

(PHB) defined in the DiffServ architecture. DiffServ mechanisms require special networking support at both the edge and the core nodes to guarantee the differentiated service. In this paper we propose the

Ping Trunking

scheme as a suitable mechanism to provide assured services to network users without the need for modifying core nodes.

Ping Trunking

is an edge-to-edge management technique that completely addresses the regulation of aggregate traffic streams at the edge of the network. In addition, it also overcomes some unfairness issues found in AF when sharing the available bandwidth among heterogeneous aggregates. Simulation results have validated the effectiveness of our proposal.

Sergio Herrería-Alonso, Manuel Fernández-Veiga, Andrés Suárez-González, Miguel Rodríguez-Pérez, Cándido López-García

Max-Min Fair Distribution of Modular Network Flows on Fixed Paths

In this paper a new aspect of the classical max-min fairness fixed-path problem is investigated. The considered (multi-criteria) optimization problem is almost identical to the continuous-flow problem, with the additional complicating assumption that flows must be integral. We show that such an extension makes the problem substantially more difficult (in fact

${\mathcal NP}$

-hard). Through comparison with the closely related continuous-flow problem, a number of properties for the solution of the extended problem are derived. An algorithm, based on sequential resolution of linear programs, that shows to be useful (produce optimal solutions) for many instances of the considered problem, is given. It follows that this algorithm can be made exact, through substituting the involved linear programs by mixed-integer programs.

Pål Nilsson, Michał Pióro

Anticipatory Distributed Packet Filter Configuration for Carrier-Grade IP-Networks

Packet filters have traditionally been used to shield IP networks from known attack flows, ususally within firewall systems connecting trusted and non-trusted network segments. As IP networks grow and tend to connect to more and more neighbor networks with unknown trust status, carrier-grade operators in particular are beginning to experience raising costs due to increasingly complex filter configurations that have to be applied to their networks, in order to maintain a desired security level. In this paper, we present a discussion on the general properties of distributed packet filter configurations and an algorithm for a simplified compilation of anticipatory static packet filter configurations in heterogenous IP networks.

Birger Toedtmann, Erwin P. Rathgeb

Wireless Networks II

Fast Handoff Scheme for Seamless Multimedia Service in Wireless LAN

In this paper, we propose a fast handoff method for seamless multimedia service in IEEE 802.11 WLAN. The proposed method uses an improved access point (AP) with additional radio frequency (RF) module, SNIFFER, monitoring the movement of the station (STA). By using the SNIFFER, the proposed method can completely remove the probe delay. Furthermore, we also propose an effective handoff decision method taking into account the quality of service (QoS) in the application layer. The proposed method uses packet loss information and the received signal strength indication (RSSI) for the handoff decision. Experimental results show that the proposed method can improve the performance of the seamless multimedia service by drastically reducing the handoff delay and packet loss.

Hye-Soo Kim, Sang-Hee Park, Chun-Su Park, Jae-Won Kim, Sung-Jea Ko

On the Tradeoff Between Blocking and Dropping Probabilities in CDMA Networks Supporting Elastic Services

This paper is a sequel of previous work, in which we proposed a model and computational technique to calculate the Erlang capacity of a single CDMA cell that supports elastic services. The present paper extends that base model by taking into account two important features of CDMA. First, we capture the impact of

soft blocking

by modeling the neighbor cell interference as a lognormally distributed random variable. Secondly, we model the impact of the outage by taking into account that in-progress sessions can be


with a probability that depends on the current load in the system. We then consider a system with elastic and rigid service classes and analyze the trade-off between the total (soft and hard) blocking probabilities on the one hand and the throughput and the session drop probabilities on the other.

Gábor Fodor, Miklós Telek, Leonardo Badia

A Point-to-Point Protocol Improvement to Reduce Data Call Setup Latency in Cdma2000 System

The wireless cellular networks have evolved from IS-95A/B to cdma2000 1X, EV-DO, and WCDMA to improve data service quality. A carries also preserve in their efforts to rev up wireless data service. Despite this efforts, call setup latency has occurred on cdma2000 1X and EV-DO systems. It is an impediment to data service activation. In measuring the real delay time during call establishment from MS to BSC, PCF and PDSN, it is found out that point-to-point protocol between MS and PDSN is major source of delay. Therefore, a simplified PPP is proposed, considering the difference in transmission speed of links among nodes. Then the inter-working scenarios between MS and PDSN is presented with simplified PPP and/or legacy PPP, and the proposed scheme is verified with superior performance over legacy PPP, through comparing the number of packets required for data call setup.

Eun-sook Lee, Kyu-seob Cho, Sung Kim

Performance and Analysis of CDM-FH-OFDMA for Broadband Wireless Systems

Frequency-hopping (FH) methods in the Orthogonal frequency division multiplexing access(OFDMA) system,which are to assign user-specific subcarrier to the active users, have been paid much attention to in the broadband wireless communication system. In this paper, we present a novel multiple access scheme, referred to as CDM-FH-OFDMA, which is the extension of FH-OFDMA with code division multiplexing (CDM). This scheme can exploit the frequency diversity gain without the aid of channel coding. And it also can be employed in the multi-cell environment with one frequency reuse factor. Computer simulation demonstrates effectiveness of CDM-FH-OFDMA and the conclusion is followed.

Kan Zheng, Lu Han, Jianfeng Wang, Wenbo Wang

Routing II

Multi-service Routing: A Routing Proposal for the Next Generation Internet

Quality of Service support plays a major role in the Next Generation Internet. QoS routing protocols must cope with service differentiation to enhance this support. This paper proposes a service aware QoS routing protocol, the Multi-Service routing, which is an extension to traditional intra-domain routing protocols. It proposes a new path selection policy that guides higher priority traffic through the shortest path and diverts lower priority traffic through longer paths when service performance degradation is foreseen. Simulations results shows that the proposed routing performs better than existing QoS routing and link-state protocols.

António Varela, Teresa Vazão, Guilherme Arroz

Quantifying the BGP Routes Diversity Inside a Tier-1 Network

Many large ISP networks today rely on route-reflection [1] to allow their iBGP to scale. Route-reflection was officially introduced to limit the number of iBGP sessions, compared to the


sessions required by an iBGP full-mesh. Besides its impact on the number of iBGP sessions, route-reflection has consequences on the diversity of the routes known to the routers inside an AS. In this paper, we quantify the diversity of the BGP routes inside a tier-1 network.

Our analysis shows that the use of route-reflection leads to a very poor route diversity compared to an iBGP full-mesh. Most routers inside a tier-1 network know only a single external route in eBGP origin. We identify two causes for this lack of diversity. First, some routes are never selected as best by any router inside the network, but are known only to some border routers. Second, among the routes that are selected as best by at least one other router, a few are selected as best by a majority of the routers, preventing the propagation of many routes inside the AS. We show that the main reason for this diversity loss is how BGP chooses the best routes among those available inside the AS.

Steve Uhlig, Sébastien Tandel

Distributed QoS Routing for Backbone Overlay Networks

In recent years, overlay networks have emerged as an attractive alternative for supporting value-added services. Due to the difficulty of supporting end-to-end QoS purely in end-user overlays, backbone overlays for QoS support have been proposed. In this paper, we describe a backbone QoS overlay network architecture for scalable, efficient and practical QoS support. In this architecture, we advocate the notion of QoS overlay network (referred to as QSON) as the backbone service domain. The design of QSON relies on well-defined business relationships between the QSON provider, network service providers and end users. A key challenge in making QSON a reality consists of efficiently determining routes for end user QoS flows based on the service level agreements between the QSON provider and network service providers. In this paper, we propose and present a scalable and distributed QoS routing scheme that can be used to efficiently route end user QoS flows through QSON. We demonstrate the effectiveness of our solution through simulations.

Li Lao, Swapna S. Gokhale, Jun-Hong Cui

Distributed Linear Time Construction of Colored Trees for Disjoint Multipath Routing

Disjoint multipath routing (DMPR) is an effective strategy to achieve robustness in networks, where data is forwarded along multiple link- or node-disjoint paths. DMPR poses significant challenges in terms of obtaining loop-free multiple (disjoint) paths and effectively forwarding the data over the multiple paths, the latter being particularly significant in datagram networks. One approach to reduce the number of routing table entries for multipath forwarding is to construct two trees, namely red and blue, rooted at a destination node such that the paths from a source to the destination on the two trees are link/node-disjoint. This paper develops the first distributed algorithm for constructing the colored trees whose running time is linear in the number of links in the network. The paper also demonstrates the effectiveness of employing generalized low-point concept rather than traditional low-point concept in the DFS-tree to reduce the average path lengths on the colored trees.

Srinivasan Ramasubramanian, Mithun Harkara, Marwan Krunz

Optical Networks III

Cross-Virtual Concatenation for Ethernet-over-SONET/SDH Networks

Ethernet-over-SONET/SDH (EoS) with virtual concatenation is a popular approach for interconnecting geographically distant Ethernet segments using the SDH transport infrastructure. In this paper, we introduce a new concatenation technique, referred to as

cross-virtual concatenation

(CVC), which involves the concatenation of

virtual channels

(VCs) of hetrogenous capacities and can be implemented by a simple upgrade at SDH end nodes, thus utilizing the existing legacy SDH infrastructure. By employing CVC for EoS systems, we show that the SDH bandwidth can be harvested more efficiently than in conventional virtual concatenation. We later consider the routing problems associated with CVC connections, namely the connection establishment problem and the connection upgrade problem. We propose ILP and heuristic solutions to solve such problems. Simulations are conducted to evaluate the performance of the proposed heuristic and to demonstrate the advantages of employing CVC.

Satyajeet S. Ahuja, Marwan Krunz

Optimal Wavelength Converter Placement with Guaranteed Wavelength Usage

In this paper, we study the following problem. Given the network topology and traffic demand, determine how a minimum set of wavelength converters should be placed to ensure that the number of wavelengths needed will not exceed a given bound




, where


is the maximum link load in the network and u is a parameter defined by the network designer to reflect the overall availability of wavelength resources. This problem, however, is proved to be NP-hard. Hence we develop an efficient heuristic algorithm and extensive theoretical and experimental studies are carried out to verify the effectiveness and performance of the algorithm.

Can Fang, Chor ping Low

Estimating Network Offered Load for Optical Burst Switching Networks

The Optical Burst Switching (OBS) technology itself is still in the early stage of development and various studies are often performed independently, resulting in difficult comparison between individual data sets (including such controversial studies as burst/packet loss evaluation). To facilitate the future research and evaluation of OBS networks, in this paper we examine relations between standard network parameters and the resulting network offered load, creating a common ground for comparing various simulation results. Means of estimating the resulting network offered load based on parameters describing the network topology and type of traffic are developed and examined for various simulation scenarios (topologies, loads, etc.). It is argued that, given the target offered load value for a given topology, it is always possible to estimate the required idle time which had to be applied in the network nodes, in order to keep the offered network load at the pre-defined level.

Przemyslaw Lenkiewicz, Marek Hajduczenia, Mário M. Freire, Henrique J. A. da Silva, Paulo P. Monteiro

Poster Session

An Adaptive Parameter Deflection Routing to Resolve Contentions in OBS Networks

Currently, the contention resolution is one of research focuses for optical burst switching (OBS). The paper presents a new contention resolution scheme, named as

adaptive parameter-based deflection routing

, which can control the deflection according to the time-varying traffic load and the QoS requirements. Compared with other schemes, the simulation results show that it can improve the overall


and the individual


of each class burst, and alleviate the offset-time deficit on QoS guarantee.

Keping Long, Xiaolong Yang, Sheng Huang, Qianbin Chen, Ruyan Wang

Bandwidth Utilization in Sorted-Priority Schedulers

This paper first introduces bandwidth utilization metric and then analyzes sorted-priority schedulers in the terms of the metric. The results show that the utilization is directly proportional to both the number of delay bound classes and the dependency of delay bound on rate but inversely proportional to packet size.

Tae Joon Kim

A Multicast Approach for UMTS: A Performance Study

In this paper, a multicast scheme for UMTS which only requires insignificant modifications in the current UMTS network infrastructure is analyzed. We analytically present the multicast routing mechanism behind our scheme as well as the multicast group management functionality of it. Furthermore, we present an evaluation of our scheme in terms of its performance. The critical parameters for the evaluation of the scheme are the number of multicast users within the multicast group, the amount of data sent to the multicast users, the density of the multicast users within the cells and the type of transport channel used for the transmission of the multicast data over the air.

Antonios Alexiou, Dimitrios Antonellis, Christos Bouras

Echidna: Efficient Clustering of Hierarchical Data for Network Traffic Analysis

There is significant interest in the network management community about the need to improve existing techniques for clustering multi-variate network traffic flow records so that we can quickly infer underlying traffic patterns. In this paper we investigate the use of clustering techniques to identify interesting traffic patterns in an efficient manner. We develop a framework to deal with mixed type attributes including numerical, categorical and hierarchical attributes for a one-pass hierarchical clustering algorithm. We demonstrate the improved accuracy and efficiency of our approach in comparison to previous work on clustering network traffic.

Abdun Naser Mahmood, Christopher Leckie, Parampalli Udaya

Cross-Layer Performance of a Distributed Real-Time MAC Protocol Supporting Variable Bit Rate Multiclass Services in WPANs

A cross-layer optimization problem to maximize utilization for a distributed real-time medium access control (MAC) protocol supporting variable bit rate (VBR) multiclass services is formulated. A complete sharing (CS) scheme is used as the admission control policy at the connection level to relate the maximum number of devices that can be admitted in the wireless personal area network (WPAN) to the grade of service (GoS) of blocking probability at the connection level, the quality of service (QoS) of packet loss probability at the packet level and the effective data transmission slots efficiency at the MAC layer. With this cross-layer analytical framework, the maximum number of devices that can be admitted into the system to achieve maximum utilization while maintaining prescribed GoS/QoS requirements under different total device mean connection arrival rate can be determined. Numerical results are presented to demonstrate the effectiveness of the proposed cross-layer coupling strategy.

David Tung Chong Wong, Jon W. Mark, Kee Chaing Chua

Performance Analysis of IEEE802.16e Random Access Protocol with Mobility

In this paper, the performance of IEEE802.16e random access protocol with handover procedure is examined in terms of access throughput and mean access delay, by using equilibrium point analysis(EPA). In the analysis, retransmission probability, which is a typical input parameter in the literature so far, is iteratively obtained from equilibrium number of backlogs in the system in conjunction with a binary exponential backoff algorithm. In numerical examples, the effects of SSs’ mobility on access throughput and mean access delay are examined.

Sang-Sik Ahn, Hyong-Woo Lee, Jun-Bae Seo, Choong-Ho Cho

Cost-Benefit Analysis of Web Prefetching Algorithms from the User’s Point of View

Since web prefetching techniques were proposed in the second half of the 90s as mechanisms to reduce final users’ perceived latency, few attempts to evaluate their performance have been done in the research literature. Even more, to the knowledge of the authors this is the first study that evaluates different proposals from the user’s point of view, i.e., considering the latency perceived by the user as the key metric. This gap between the proposals and their correct performance comparison is due to the difficulty to use a homogeneous framework and workload. This paper is aimed at reducing this gap by proposing a cost-benefit analysis methodology to fairly compare prefetching algorithms from the user’s point of view. The proposed methodology has been used to compare three of the most used algorithms in the bibliography, considering current workloads.

Josep Domènech, Ana Pont, Julio Sahuquillo, José A. Gil

An MPLS-Based Micro-mobility Solution

IEEE-802.21-Based Control Plane

Core network micro-mobility solutions resolve L3 handovers and may be based on the Internet Protocol (IP) or on Multi-Protocol Label Switching (MPLS). When a micro-mobility solution triggers the L3 handover before the L2 handover, it is called predictive, otherwise reactive. The outage period due to the handover is smaller for predictive solutions. However, in order to be predictive, a L3 mobility solution needs support from the underlying link-layer. This support may be provided with the help of IEEE 802.21 that is exploited for intra-technology handovers in WLANs in this paper.

Rajendra Persaud, Ralf Wienzek, Gerald Berghoff, Ralf Schanko

A Comparative Performance Study of IPv6 Transitioning Mechanisms – NAT-PT vs. TRT vs. DSTM

One of the major challenges faced by the IPv6 community in recent years has been to define the scenarios in which transitioning mechanisms should be used and which ones should be selected given a specific scenario. This paper aims to supplement this by presenting the results of a comparative evaluation carried out on three major IPv6 interoperation mechanisms; NAT-PT, TRT and DSTM. This work attempts not only to determine the outright performance of each mechanism against the other but also against a theoretical evaluation of the specification. Our results show that while DSTM performs well both NAT-PT and TRT place significant overheads on the network.

Michael Mackay, Christopher Edwards

CAC: Context Adaptive Clustering for Efficient Data Aggregation in Wireless Sensor Networks

Wireless sensor networks are characterized by the widely distributed sensor nodes which transmit sensed data to the base station cooperatively. However, due to the spatial correlation between sensor observations, it is not necessary for every node to transmit its data. There are already some papers on how to do clustering and data aggregation in-network, however, no one considers about the data distribution with respect to the environment. In this paper a context adaptive clustering mechanism is proposed, which tries to form clusters of sensors with similar output data within the bound of a given tolerance parameter. With similar data inside a cluster, it is possible for the cluster header to use a simple technique for data aggregation without introducing large errors, thus can reduce energy consumption and prolong the sensor lifetime. The algorithm proposed is very simple, transparent, localized and does not need any central authority to monitor or supervise it.

Guang-yao Jin, Myong-Soon Park

On the Performance of Cooperative Diversity in Infrastructure-Based Networks with Two Relays

In this paper, the performance of four cooperative relaying schemes, which are classified by requiring a quantity of feedback information, is evaluated in the high SNR region and is compared with that of MIMO relaying schemes with two antennas. For amplify-and-forward (AF) relay, all schemes except the second hop selection scheme provide the second order diversity gain in high SNR region. For decode-and-forward (DF) relay, despite using more channel information, the coherent BF scheme does not offer the second order diversity. A system level simulation is evaluated to analyze the effects of user distribution in terms of the average capacity. For AF relay, the capacity of the cooperative relaying model is higher than that of the MIMO relaying model as about 0.2 bps/Hz. For DF relay, the MIMO relaying model provides capacity gain about larger than 0.3 bps/Hz for the coherent beamforming and the Alamouti-based scheme since the effect of array gain at relay for these schemes is more dominant factor to increase the capacity compared with the effect of reducing path loss.

Jun Yeop Jung

IP Mobility Support with a Multihomed Mobile Router

This paper proposes a multihoming-based seamless handover scheme using a mobile router with dual egress interfaces for wireless train networks. The proposed scheme deploys dual antennas which are individually located at each end of the train for space diversity and connected to each egress interface of a mobile router. Since one of the two egress interfaces of the mobile router can continuously receive packets through its antenna while the other is undergoing a handover, the proposed scheme can support a seamless handover providing no service disruption or packet loss.

Hee-Dong Park, Dong-Won Kum, Yong-Ha Kwon, Kang-Won Lee, You-Ze Cho

Performance Analysis and Design: Power Saving Backoff Algorithm for IEEE 802.11 DCF

In this paper, we propose an approach to saving power by more aggressively using sleep mode. The sleep duration is estimated by measuring the on-line traffic information, i.e. slot utilization. A considerable amount of power can be saved by using the approach. Our approach does not use any additional signaling channel, nor does it need any overhead in the involved protocol. The algorithm is readily implementable, requiring minimum processing and memory resources.

Feng Zheng, Barry Gleeson, John Nelson

A Fast Pattern-Matching Algorithm for Network Intrusion Detection System

We present a multi-gigabit rate multiple pattern-matching algorithm with TCAM that enables protecting against malicious attacks in a high-speed network. The proposed algorithm significantly reduces the number of TCAM lookups per payload with



jumping window

scheme. Due to the reduced number of TCAM lookups, we can easily achieve multi-gigabit rate for scanning the packet payload in order to inspect the content. Furthermore, multi-packet inspection is achieved easily by the extended state transition diagram with the

shifting distance

. With experimental results, we have clearly justified the proposed algorithm works well for a multi-gigabit network intrusion detection system.

Jung-Sik Sung, Seok-Min Kang, Taeck-Geun Kwon

Multicast OLSP Establishment Scheme in OVPN over IP/GMPLS over DWDM

OVPN (Optical Virtual Private Network) over IP (Internet Protocol)/GMPLS (Generalized Multi-Protocol Label Switching) over DWDM (Dense Wavelength Division Multiplexing) technology with QoS assurances is considered as a promising approach for the next generation OVPN. In this paper, we suggest a multicast OLSP (Optical Label Switched Path) establishment mechanism for supporting high bandwidth multicast services. For the establishment of the multicast OLSP, we propose a new multicast tree generation algorithm VS-MIMR (Virtual Source-based Minimum Interference Multicast Routing) that finds the minimum interference path between virtual source nodes. We also suggest an entire OVPN control mechanism to adapt the operation of the routing and signaling protocols of GMPLS.

Jeong-Mi Kim, Oh-Han Kang, Jae-Il Jung, Sung-Un Kim

Directional Reception vs. Directional Transmission for Maximum Lifetime Multicast Delivery in Ad-Hoc Networks

In this paper, we present a mixed-integer linear program (MILP) designed to optimize max-min path lifetime for multicasts in directional antenna equipped networks in the presence of interference. We then employ the MILP to perform a head-to-head comparison between directional transmission and directional reception. We also propose and analyze a new directional reception heuristic. Our results indicate that directional reception can match directional transmission when extending path lifetime, with lower complexity and employing routes that use much less cumulative power.

Kerry Wood, Luiz A. DaSilva

Micro- and Macroscopic Analysis of RTT Variability in GPRS and UMTS Networks

We study the data from a passive TCP/IP traffic measurement from a Finnish operator’s GPRS/UMTS network. Of specific interest is the variability of Round Trip Times (RTTs) of TCP flows. The RTTs are analysed at micro- and macroscopic level. The microscopic level involves detailed analysis of the RTTs of individual flows, and we are able to detect, e.g., periodic behavior (via Lomb periodogram) and rate changes in the radio channel. At the macroscopic level we focus on the impact of so called self-congestion caused by bandwidth sharing at the mobile device itself, and it is shown how this seriously affects the RTTs observed by a given flow, both in GPRS and in UMTS.

Jorma Kilpi, Pasi Lassila

Control Plane Protection Using Link Management Protocol (LMP) in the ASON/GMPLS CARISMA Network

In the ITU-T ASON architecture, the control plane is responsible for providing intelligence to the network. The GMPLS paradigm pleads for a separation between the control plane and the forwarding plane. If the control plane is deployed disjoint from the forwarding plane, recovery mechanisms to ensure its proper operation are required. In this paper, on one hand, a quasi-associated mode backup control channel proposal is compared with a traditional associated 1:1 protection. On the other hand, extensions to LMP defined by the IETF are presented and evaluated to address both control channel and nodal failure recovery. The merits of the proposals are assessed by experimental results.

Jordi Perelló, Eduard Escalona, Salvatore Spadaro, Fernando Agraz, Jaume Comellas, Gabriel Junyent

A Novel Resource Allocation Scheme for Reducing MAP Overhead and Maximizing Throughput in MIMO-OFDM Systems

We propose a novel resource allocation scheme, which can reduce MAP overhead and maximize the throughput in the MIMO-OFDM systems. In the message based broadband access system, we need to minimize the MAP overhead since the excessive MAP overhead causes degradation of system throughput. Increasing the size of resource allocation unit can reduce MAP overhead. However, multiuser diversity gain becomes smaller as the size of re-source allocation unit increases. Therefore, we investigate joint optimization between multiuser diversity gain and MAP overhead size. Using the proposed scheme, we can reduce MAP overhead size as well as achieve high throughput.

Chung Ha Koh, Kyung Ho Sohn, Ji Wan Song, Young Yong Kim

Secure Routing Using Factual Correctness

The routing protocols in use today operate on implicit trust among the different routers. Specifically, the distance vector routing (DVR) protocols compute routing tables in a distributed manner, based on this implicit trust. This trust model however fails to ensure the factual correctness of the routing updates, which is very critical for secure routing. We propose a neighbor update propagation model to ensure factual correctness and detect malicious activity by any subverted router. We also propose a secure DVR protocol based on this model using simple cryptographic primitives, and with minimal operational overhead.

Muthusrinivasan Muthuprasanna, Govindarasu Manimaran

Entropy Based Flow Aggregation

Flow measurement evolved into the primary method for measuring the composition of Internet traffic. Cisco’s NetFlow is a widely deployed flow measurement solution that uses a configurable static sampling rate to control processor and memory usage on the router and the amount of reporting flow records generated. But during flooding attacks the memory and network bandwidth consumed by flow records can increase beyond what is available. In this paper, we propose an entropy based flow aggregation algorithm, which not only alleviates the problem in memory and export bandwidth, but also maximizes the accuracy of legitimate flows. Relying on information-theoretic techniques, the algorithm efficiently identifies the clusters of attack flows in real time and aggregates those large number of short attack flows to a few metaflows. Finally, we evaluate our system using real trace files from the Internet.

Yan Hu, Dah-Ming Chiu, John C. S. Lui

Monitoring Wireless Sensor Networks Using a Model-Aided Approach

A wireless sensor network may consist of a large number of small, battery-powered, wireless sensor nodes and works in an unattended way. In order to manage the sensor network and collect data from the network efficiently, we need to know the state of the WSN. In this paper, we propose a model-aided approach to support the monitoring of the state of WSNs. In this approach, models are created on base station to support the monitoring of the network, and mobile agents are injected into the network to collect state information. Experimental results show the effectiveness of our approach.

Chongqing Zhang, Minglu Li, Min-You Wu, Wenzhe Zhang

VBF: Vector-Based Forwarding Protocol for Underwater Sensor Networks

In this paper, we tackle one fundamental problem in Underwater Sensor Networks (UWSNs): robust, scalable and energy efficient routing. UWSNs are significantly different from terrestrial sensor networks in the following aspects: low bandwidth, high latency, node float mobility (resulting in high network dynamics), high error probability, and 3-dimensional space. These new features bring many challenges to the network protocol design of UWSNs. In this paper, we propose a novel routing protocol, called vector-based forwarding (VBF), to provide robust, scalable and energy efficient routing. VBF is essentially a position-based routing approach: nodes close to the “vector” from the source to the destination will forward the message. In this way, only a small fraction of the nodes are involved in routing. VBF also adopts a localized and distributed self-adaptation algorithm which allows nodes to weigh the benefit of forwarding packets and thus reduce energy consumption by discarding the low benefit packets. Through simulation experiments, we show the promising performance of VBF.

Peng Xie, Jun-Hong Cui, Li Lao

Hybrid ARQ Scheme with Antenna Permutation for MIMO Systems in Slow Fading Channels

In this paper, an equivalent model for the hybrid automatic retransmission request (HARQ) multi-input multi-output (MIMO) systems with a proper combining scheme is first introduced. Based on this effective model, we present a simple technique, termed antenna permutation scheme (APS), which permutates the transmit antennas at each retransmission to improve the diversity gain from retransmissions in the slow fading environment. The theory analysis and simulation results demonstrate that the system with APS can achieve much better bit error performance.

Jianfeng Wang, Meizhen Tu, Kan Zheng, Wenbo Wang

Scalable Quantitative Delay Guarantee Support in DiffServ Networks Through NSIS

This paper investigates the issue of enabling scalable quantitative delay guarantee support in DiffServ networks through NSIS. A NSIS QoS Model is utilized to add the admission control framework to the DiffServ architecture and reservation-based admission control algorithms are designed for ingress and interior nodes respectively for enabling quantitative delay guarantees in a DiffServ domain. Due to the NSIS protocol suite can support aggregate reservations effectively and the admission control algorithms are distributed at the ingress and interior nodes, our approach can enable the quantitative end-to-end delay guarantees in a DiffServ domain while still maintaining its simplicity and scalability.

Jian Zhang, Maxweel Carmo, Marilia Curado, Jorge Sá Silva, Fernando Boavida

SDC: A Distributed Clustering Protocol for Peer-to-Peer Networks

Network clustering can facilitate data discovery and peer-lookup in peer-to-peer systems. In this paper, we design a distributed network clustering protocol, called SCM-based Distributed Clustering (SDC), for peer-to-peer networks. In this protocol, clustering is dynamically adjusted based on Scaled Coverage Measure (SCM), a practical clustering accuracy measure. By exchanging messages with neighbors, peers can dynamically join or leave a cluster so that the clustering accuracy of the whole network is improved. SDC is a fully distributed protocol which requires only neighbor information, and it can handle node dynamics locally with very small message overhead while keeping good quality of clustering. Through extensive simulations, we demonstrate that SDC can discover good quality clusters very efficiently.

Yan Li, Li Lao, Jun-Hong Cui

A New Burst Scheduling Algorithm for Edge/Core Node Combined Optical Burst Switched Networks

The burst contention problem in Optical Burst Switching network is an intrinsically serious problem. Many researches have tried to solve this problem, however it have been known that avoiding the burst loss is very difficult issues in the current OBS network. To improve burst blocking rate, we consider the edge/core combined OBS network where the core node performs the edge node function as well. Through this architecture, available amount of data burst that the node generates can be expected with respect to offset-time of transit data bursts. Any researches for this area has not been performed, thus we propose a new data scheduling algorithm for the edge/core combined OBS network where data bursts that the node generates do not interrupt transit data bursts from previous nodes. We analyzed the data burst loss rate and the throughput in relation with the offset-time of transit data bursts. Results show that the loss rate of the data bursts is drastically reduced and the throughput improves when the offset-time of transit data bursts increases.

SeoungYoung Lee, InYong Hwang, HongShik Park

Distributed Real-Time Monitoring with Accuracy Objectives

We introduce A-GAP, a protocol for continuous monitoring of network state variables with configurable accuracy. Network state variables are computed from device counters using aggregation functions, such as SUM, AVERAGE and MAX. In A-GAP, the accuracy is expressed in terms of the average error and is controlled by dynamically configuring filters in the management nodes. The protocol follows the push approach to monitoring and uses the concept of incremental aggregation on a self-stabilizing spanning tree. A-GAP is decentralized and asynchronous to achieve robustness and scalability. We provide some results from evaluating the protocol for an ISP topology (Abovenet) in several scenarios through simulation. The results show that we can effectively control the fundamental trade-off between accuracy and overhead. The protocol overhead can be reduced significantly by allowing only small error objectives.

Alberto Gonzalez Prieto, Rolf Stadler

Improving Load Balance of Ethernet Carrier Networks Using IEEE 802.1S MSTP with Multiple Regions

With IEEE 802.1S Multiple Spanning Tree Protocol, an Ethernet operator can define different network regions. A Common Spanning Tree (CST) is defined in such a way that a link failure inside a region does not affect the CST outside the region and additional Spanning Trees inside each region can be configured to achieve better load balance. We propose a procedure to determine the MSTP parameters configuration with multiple regions that optimize load balance and show its efficiency through computational results. We compare multiple region solutions with single region solutions, using a previous work on the single region case, and show that the multiple regions approach is better when traffic is mainly between switches belonging to the same region.

Amaro de Sousa, Gil Soares

A Simple Sink Mobility Support Algorithm for Routing Protocols in Wireless Sensor Networks

In order to support the sink mobility of conventional routing protocols, we propose a simple route maintaining algorithm which does not use the flooding method. In the proposed method, when the sink loses the connection with the source, it does not rebuild an entire route but simply repairs the existing route based on local information. Experimental results show that the proposed algorithm drastically improves the conventional routing protocols in terms of both energy and delay in case of mobile sink.

Chun-Su Park, You-Sun Kim, Kwang-Wook Lee, Seung-Kyun Kim, Sung-Jea Ko

Concurrent Diagnosis of Clustered Sensor Networks

In this paper, we present an energy-efficient on-line diagnosis algorithm for cluster-based wireless sensor networks. It employs local comparisons of sensed data and dissemination of the decision made by the comparison results. Cluster-heads act as checkers for their associated cluster members. Redundant sensor nodes, as far as sensing coverage is concerned, are partially utilized to tolerate misbehavior of cluster-heads. Final decision on the fault status of sensor nodes is made at the base station. Computer simulation shows that high fault coverage can be achieved for a wide range of fault rates.

Chin-Woo Cho, Yoon-Hwa Choi


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