Papers by Edmundo Monteiro
Proceedings of SPIE International …, Dec 16, 1998
Several approaches have been proposed to empower communication systems with quality of service (Q... more Several approaches have been proposed to empower communication systems with quality of service (QoS) capabilities. In general, their main goal is to coherently support the end-to-end performance needs of applications, based on the establishment of, and agreement on, a set of concepts, policies and mechanisms. Regardless of the used approach, an important challenge associated with quality of service provision is the development of an efficient and flexible way to monitor QoS. The existence of an effective ...
CoNEXT 2005 - Proceedings of the 2005 ACM Conference on Emerging Network Experiment and Technology, 2005
It is common practice to evaluate the performance of Measurement Based Admission Control under tr... more It is common practice to evaluate the performance of Measurement Based Admission Control under traffic, which exhibits Long-Range-Dependency (LRD) and Self-Similarity (SS) effects. These phenomena are generated by multiplexing Markov ON/OFF sources with Pareto distributed ON and OFF times. Due to dependencies on a myriad of parameters, however, it can be questioned if resulting traffic actually exhibits SS and LRD effects. Further fostered by the lack of evaluation tools, the proof for is commonly missing. For that reason, in this paper we evaluate the robustness of SS and LRD effects in artificially generated traffic to parameter settings. Using a typical simulation for performance evaluation, we measure the degree of SS and LRD.
Journal of Communications Software and Systems, 2008
IEEE 802.16 is yet a very recent technology and released hardware does frequently only support st... more IEEE 802.16 is yet a very recent technology and released hardware does frequently only support standards partially. The same applies to public available simulation tools, in particular for NS-2. As the latter is the de-facto standard in science and as we use it for our research in the context of the WEIRD project, we evaluate the IEEE 802.16 support for NS-2. We present several general but also specific issues, which areimportant in order to carry out reliable research based on thesetools. In particular, we show in much detail where modulesdeviate significantly and even fail totally.
Resumo Neste artigo é descrita a implementação da estratégia de encaminhamento com Qualidade de S... more Resumo Neste artigo é descrita a implementação da estratégia de encaminhamento com Qualidade de Serviço desenvolvida no LCT-UC 1. São apresentadas a arquitectura do sistema e as extensões realizadas ao protocolo OSPF incluído no ambiente de desenvolvimento de protocolos de encaminhamento GateD, sobre o sistema operativo FreeBSD. São discutidos resultados preliminares de avaliação da estratégia proposta.
Dsom, 1994
This paper presents the basic ideas behind a project that addresses the development of a high lev... more This paper presents the basic ideas behind a project that addresses the development of a high level notation for the specification of network management applications. The notation is being successfully used at the University of Coimbra as a common language for the development of network management tools and prototype applications. The proposed notation has the intent to bridge the gap between the basic mechanisms offered by the common network management protocols and the high-level functionality required by network management applications. The paper highlights the simple but powerful syntax rules of the notation, that enable an application developer to easily write complex expressions and object relations, and to define new objects from numerical and logical expressions, freeing him/her of the low-level details of network management services and protocols. In addition, the capability to use specialised syntax modules is illustrated with the presentation of a specification for a fault-management application.
Ieee Globecom 2006, Nov 1, 2006
Abstract Next generation IP networks are envisioned to be heterogeneous, to provide a wide variet... more Abstract Next generation IP networks are envisioned to be heterogeneous, to provide a wide variety of services, and to support mobility of users with distinct requirements. Moreover, mobile communications are expected to expand from telephony to publish-subscribe services, such as real-time multimedia. With this goal, the University of Coimbra is working with DoCoMo Euro-Labs on a unifying control architecture for multimedia publish-subscribe services over an IP-based mobile system, where our proposal aims to control the quality of ...
Critical infrastructure (CI) services are consumed by the society constantly and we expect them t... more Critical infrastructure (CI) services are consumed by the society constantly and we expect them to be available 24 hours a day. A common definition is that CIs are so vital to our society that a disruption or destruction would have a severe impact on the social well-being and the economy on a national and an international level. CIs can be mutually dependent on each other and a failure in one infrastructure can cascade to another interdependent infrastructure to cause service disruptions. Methods to better assess and monitor CIs and their interdependencies in order to predict possible risks have to be developed. This work addresses the problem of the quality of information exchanged among interconnected CI, the quality of the relationship in terms of trust and security and the use of Trust and Reputation management along with the Policy Based Management paradigm is the proposed solution to be applied at the CI interconnection points for information exchange.
ABSTRACT Resumo -a ausência de mecanismos de suporte à qualidade de serviço na camada MAC das red... more ABSTRACT Resumo -a ausência de mecanismos de suporte à qualidade de serviço na camada MAC das redes Ethernet foi superada com o desenvolvimento das normas IEEE 802.1D e IEEE 802.1Q. Este artigo descreve o desenvolvimento de novos módulos para o simulador NS-2 que suportam a simulação de qualidade de serviço em redes Ethernet. Os módulos respeitam as normas IEEE 802.1Q/D e implementam as recomendações referentes à priorização de tráfego. A implementação é avaliada através de simulações de redes locais comutadas em full-duplex, e são parte da contribuição do Laboratório de Comunicações e Telemática da Universidade de Coimbra para o projecto EuQoS [1]. I. INTRODUÇÃO Network Simulation 2 (NS-2) [2] é uma ferramenta de simulação de eventos discretos amplamente utilizada na área das rede de computadores. O NS-2 é uma ferramenta open source e suporta a simulação de uma grande variedade de protocolos de rede. Implementado nas linguagens C++ e Otcl, o NS-2 é bastante flexível, permitindo que novas extensões sejam desenvolvidas e adicionadas. Os resultados de qualquer simulação efectuada no NS-2 podem ser analisados por diferentes ferramentas como o Network Animator (NAM), o Xgraph [3] ou o gnuplot [4]. O desenvolvimento de redes Ethernet a 1 e 10 Gbps possibilitou a expansão das tecnologias Ethernet para cenários de grande dimensão. Actualmente, as redes Ethernet abrangem desde simples redes domésticas – Small Office Home Office (SOHO), até às redes de grande área (WAN). Neste contexto, é importante encontrar novos mecanismos para o suporte à Qualidade de Serviço (QoS) nas redes Ethernet. As normas IEEE 802.1Q [5] e IEEE 802.1D [6] vêm de encontro a esta necessidade, especificando meios para a priorização de pacotes na camada MAC. A norma IEEE 802.1Q define a operação de LANs virtuais (VLAN) em bridges LAN. A norma modifica o cabeçalho do frame MAC, adicionando um campo de 4 bytes (Figura 1), que é usado tanto para o controle de operação de uma VLAN quanto para a implementação de QoS através da priorização dos pacotes. Os primeiros 2 bytes (TPID) do campo são utilizados para identificar um frame 802.1Q (todos os frames 802.1Q têm este campo atribuído com o valor 0x8100). Os outros 2 bytes são constituídos por 3 sub-campos: um indicador de formato canónico (CFI), o campo VLAN (usado para armazenar o identificador da rede virtual) e um campo de 3 bits usado para marcar o pacote com uma certa prioridade. Fig. 1. Frame Ethernet.
Functional standardization activities in ISO and in regional workshops are currently addressing e... more Functional standardization activities in ISO and in regional workshops are currently addressing end-system profiles and network layer relay profiles for the interconnection of several types of subnetworks. In order to achieve end-system interconnectivity, connection-mode network layer relays appear as one of the key pieces of the Open Systems Interconnection puzzle. In this paper the authors present a proposal for a connection-mode relay profile that is being input to the European Workshop for Open Systems, discuss the relevant profile options, and identify some issues-concerning the proposed as well as other relay profiles-that will require future attention and discussion.
Because the world wide range of the Internet and infrastructure advance, customers can access any... more Because the world wide range of the Internet and infrastructure advance, customers can access any service over the entire world despite their location. However, the vending strategy current used in the Internet is no longer desirable to most of the providers. They no more wish to offer infrastructure facilities and charge based on how much traffic clients generate. Providers want to offer services and charge for them, thus providing types of services for clients according to their needs. In this paper we propose an architecture for service management in inter-domain environments, which supports the service life cycle. Despite it deals with several service management aspects, we plan to focus in the service composition and service negotiation functionalities. This architecture is able to offer a common infrastructure to provide different types of service and allows dynamic configuration and provisioning of services based on an end-to-end connection. It was built based on NGN principles and is composed of three layers: business layer for negotiation and service orchestration between providers; policy layer used for resource management and; infrastructure layer for network configuration. To validate the architecture we implemented a scenario comprising the service life cycle of an inter-domain VPN establishment, using RFC 4364 mechanisms for configuration.
Computer Communications, May 1, 2011
Despite efforts to improve the current IEEE 802.11 standard to fully optimize the physical layer,... more Despite efforts to improve the current IEEE 802.11 standard to fully optimize the physical layer, the performance of wireless mesh networks still depends on the routing process for a correct selection of routes. With regard to this question, several cross-layer routing metrics have been developed to improve wireless multi-hop mesh routing. This paper sets out a new taxonomy that can be used to help understand, classify and compare the state-of-the-art situation with regard to cross-layer routing metrics for wireless mesh networks. A ...
Proceedings Ieee Infocom 2006 25th Ieee International Conference on Computer Communications, Apr 23, 2006
In this paper we present a methodology for detecting traffic anomalies. To accomplish that, and a... more In this paper we present a methodology for detecting traffic anomalies. To accomplish that, and as a demarcation from similar works, we combine multi-scale and multi-criteria analysis with a tomography process analysis. With a complete knowledge of traffic anomalies, we intend to define anomalies signatures that could be used in a large range of scopes as traffic engineering, routing and intrusion detection systems, and much more. Traffic anomalies, anomaly profile, overlay network routing I.
Security concerns in computer networks resulted in a remarkable proliferation of network firewall... more Security concerns in computer networks resulted in a remarkable proliferation of network firewalls. However, the mere presence of more firewalls in the network is not a guarantee of more secure networks. The average expertise of today's firewall administrator is probably lower than it was a few years ago, resulting in an increased possibility of faulty installations, poor configuration and ineffective monitoring. This scenario calls for safer and more cost-efficient procedures for firewall deployment and maintenance. This paper presents a framework we have developed for integrated management of firewall appliances. The advantages of such a framework are manifold: it reduces installation and maintenance costs (several firewalls become remotely installable and manageable from a single remote location); it simplifies firewall configuration (firewall policies are definable using an easyto-use graphical interface, rather than the error-prone mechanisms required by most firewall implementations); it simplifies the resolution of hardware failures (since firewall configuration if kept in a remote database, it is sufficient to replace the faulty hardware and automatically upload the saved configuration into the new hardware); it enables the administration of geographically distributed firewall environments; and it provides an integrated monitoring facility that concentrates logs and health reports from several firewalls in a single database.
Page 1. March 15th, 2005 IPS-MoMe 2005 Comparative Study of Inter- Domain Traffic Optimization Al... more Page 1. March 15th, 2005 IPS-MoMe 2005 Comparative Study of Inter- Domain Traffic Optimization Algorithms Manuel Pedro Department of Informatics Engineering University of Coimbra Portugal Page 2. March 15th, 2005 IPS-MoMe 2005 Outline ��� Objective ��� Inter-domain model ��� Problem definition ��� The algorithms ��� Test scenarios ��� Results ��� Conclusion Page 3. March 15th, 2005 IPS-MoMe 2005 Objective ��� Select the optimum mapping between the incoming inter-domain traffic flows into the network inter-domain resources ...
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Papers by Edmundo Monteiro