Cable TV technology for local access
by Jeff Patmore
Co-Authored with: S T Jewell, K D Stalley and R Mudhar
Cable TV networks will pass 17 million homes in the UK by early next century. Reliability has improved dramatically in... more Cable TV networks will pass 17 million homes in the UK by early next century. Reliability has improved dramatically in recent years due to the widespread introduction of fibre into the network. Possibly the biggest attraction of cable is the enormous bandwidth that is available, together with its high degree of flexibility. This flexibility can be utilised to accommodate new services such as digital TV, data and telephony.
Download (.pdf) An Initial Statistical Analysis of the Performance of the UK National JANET Cache
From the The 4th International Web Caching Workshop.
The UK National JANET Cache serves the UK academic & research community, which includes universities, colleges,... more
The UK National JANET Cache serves the UK academic & research community, which includes universities, colleges, research establishments & other organisations, and is funded by the UK Higher Education Funding Council. Its primary objectives are: a) to minimise request response time, (or latency); and b), to minimise the cost of using expensive communications links: in other words to deliver an excellent service whilst ensuring maximum value for money.
In this paper we describe briefly the JANET Cache and the national caching infrastructure in which the JANET Cache plays a pivotal role. We then move on to the main theme, namely the presentation of an initial analysis of JANET Cache usage and performance. Because of the vast amount of logging information available, the bulk of this analysis has been restricted to a four week period in September and October 1998. It is our intention, once additional computing resources come online, to extend this analysis to cover the UK National JANET Cache Service from its inception on 1st August 1997 to the present day. This will be the subject of a future paper.
The initial analysis has yielded many interesting and useful results and conclusions which are summarised and discussed below. In particular it indicates how effective caching is from a user service perspective and the amount of bandwidth actually saved in a real production environment.
Effect of Packet-Size over Network Performance
Keywords: TCP, NS-2, Selective Acknowledgment (SACK), Packet
TCP (Transmission Control Protocol) is the most widely-used protocol on Internet. It divides one large
data into... more
TCP (Transmission Control Protocol) is the most widely-used protocol on Internet. It divides one large
data into small sized packets, called segments. Segmentation is useful for improving network performance. It has
a major problem in that its congestion control algorithm does not allow flows to obtain full available bandwidth
during fast long-distance links. One of the tools for evaluating TCP performance in various network scenarios is
Network Simulator-2 (NS-2). By using this tool one can simulate and evaluate the performance of different TCP
algorithms. In fast network one of the factors that degrade the TCP performance is packet size. Increasing the
packet size decreased the throughput of network, reason being that after crossing dedicated packet size, it will
allocate double the req
CORBA, DCOM E JAVARMI - Uma Análise Comparativa
by Vitor Roque
ROQUE, Vitor Manuel Gomes ; OLIVEIRA, José Luís - CORBA, DCOM E JAVARMI - UMA ANÁLISE COMPARATIVA . Ingenium . , vol. , n.º 46 (Mar. 2000) . p. 87-91. Portuguese text.
Transactional Integrity Issues in Policy Based Network Management Systems
by Vitor Roque
Roque,V., Lopes, R., Oliveira, JL.
Transactional Integrity Issues in Policy Based Network Management Systems
Egitânia Sciencia nº2
Vol. II
Pag. 167-181
IPG
ISBN: 1646-8848
Depósito Legal: 260795/07
http://www.ipg.pt/revistaipg/files/Egitania%20Sciencia_Vol2.pdf | http://www.ipg.pt/revistaipg
As networks increase in size, heterogeneity, complexity and pervasiveness, effective management of such networks... more
As networks increase in size, heterogeneity, complexity and pervasiveness, effective management of such networks becomes more important and increasingly difficult. In this context, PBNM (Policy-Based Network Management) has been gaining popularity in the recent years. New demands on internetworking, services specification, QoS and generically on network management functionality have been driving users to consider this paradigm in their own networks.
As people start exploiting PBNM, another aspect comes to attention: transactional integrity. Transactional control envisages achieving consistent state changes along the network. In other words, state transition in network devices is only authorized if all the related operations are successfully taken.
In this paper we propose a transactional control mechanism for PBNM systems, namely its assurance across different systems and different network domains.
Utilização de Políticas em Gestão de Redes e Sistemas de Informação
by Vitor Roque
Roque, V., Lopes, R.P., Oliveira, J.L.
Utilização de Políticas em Gestão de Redes e Sistemas de Informação
Egitânia Sciencia nº1
Vol. I
Pag. 175-188
IPG
ISBN:1646-8848
Depósito Legal: 260795/07
http://www.ipg.pt/revistaipg/files/Egitania%20Sciencia_Vol1.pdf | http://www.ipg.pt/revistaipg
A gestão das redes tornou-se, nos últimos anos, um tema de máxima importância para as empresas dado que a sua... more
A gestão das redes tornou-se, nos últimos anos, um tema de máxima importância para as empresas dado que a sua organização, os fluxos de informação e métodos de trabalho, quer interna quer externamente, estão cada vez mais dependente do bom funcionamento de redes de comunicação. Esta dependência faz com que a disponibilidade e desempenho destas infra-estruturas e serviços sejam actualmente factores determinantes para o seu sucesso.
Tem-se assistido também a um aumento quer a nível de tamanho, quer a nível de complexidade das redes, o que implica o desenvolvimento rápido de mecanismos de configuração normalizados para que a sua gestão seja feita de uma forma eficaz e rápida.
O conceito de gestão por políticas surgiu nos últimos anos como o paradigma “ideal” para tratar este tipo de necessidades.
Tendo em consideração que a maioria dos actuais sistemas de informação tem uma interdependência quase total com a rede de comunicação que lhe dá suporte, é importante que esta mesma rede esteja a funcionar correctamente, isto é exiba os comportamentos adequados, pois uma sua eventual falha pode levar, em casos extremos, à inoperabilidade total ou parcial do próprio sistema de informação.
A Gestão Baseada em Políticas (PBM – Policy Based Management) apresenta-se como um paradigma adequado quer para gerir estas novas redes de comunicação quer para garantir segurança e, genericamente, definir as politicas de utilização dos sistemas e infra-estrutura de comunicações de uma organização. Este artigo visa expor esta metodologia, o estado de normas e de desenvolvimentos, e discutir a sua utilização nos sistemas de informação actuais de forma a garantir uma administração coordenada e consistente.
Using CIM Extensions to model Managed Entities in Heterogeneous Networks
by Vitor Roque
proc. of the IEEE International Workshop on Management Issues and Challenges in Mobile Computing - MICMC 2005, Nice, France, 15 May 2005.
This paper is devoted to the definition of management information which models specific functionality of the entities... more This paper is devoted to the definition of management information which models specific functionality of the entities that build Daidalos European Project. This management information will be used in policy–based management system (PBNMS) to manage QoS aspects of the network functionality.
Utilização de Políticas em Gestão de Redes e Sistemas de Informação
by Vitor Roque
actas da V Conferência da APSI – CAPSI2004, Lisboa, Portugal, 3-5 Novembro de 2004
A gestão das redes tornou-se, nos últimos anos, um tema de máxima importância para as empresas dado que a sua... more
A gestão das redes tornou-se, nos últimos anos, um tema de máxima importância para as empresas dado que a sua organização, os fluxos de informação e métodos de trabalho, quer interna quer externamente, estão cada vez mais dependente do bom funcionamento de redes de comunicação. Esta dependência faz com que a disponibilidade e desempenho destas infra-estruturas e serviços sejam actualmente factores determinantes para o seu sucesso.
Tem-se assistido também a um aumento quer a nível de tamanho, quer a nível de complexidade das redes, o que implica o desenvolvimento rápido de mecanismos de configuração normalizados para que a sua gestão seja feita de uma forma eficaz e rápida.
O conceito de gestão por políticas surgiu nos últimos anos como o paradigma “ideal” para tratar este tipo de necessidades.
Tendo em consideração que a maioria dos actuais sistemas de informação tem uma interdependência quase total com a rede de comunicação que lhe dá suporte, é importante que esta mesma rede esteja a funcionar correctamente, isto é exiba os comportamentos adequados, pois uma sua eventual falha pode levar, em casos extremos, à inoperabilidade total ou parcial do próprio sistema de informação.
A Gestão Baseada em Políticas (PBM – Policy Based Management) apresenta-se como um paradigma adequado quer para gerir estas novas redes de comunicação quer para garantir segurança e, genericamente, definir as politicas de utilização dos sistemas e infra-estrutura de comunicações de uma organização. Este artigo visa expor esta metodologia, o estado de normas e de desenvolvimentos, e discutir a sua utilização nos sistemas de informação actuais de forma a garantir uma administração coordenada e consistente.
Towards Transactional Integrity Issues in Policy Based Network Management Systems
by Vitor Roque
actas da 7ª Conferência de Redes de Computadores – CRC2004, Leiria, Portugal, 7-8 Outubro de 2004
As networks increase in size, heterogeneity, complexity and pervasiveness, effective management of such networks... more
As networks increase in size, heterogeneity, complexity and pervasiveness, effective management of such networks becomes more important and increasingly difficult. In this context, PBNM (Policy-Based Network Management) has been gaining popularity in the recent years. New demands on internetworking, services specification, QoS and generically on network management functionality have been driving users to consider this paradigm in their own networks.
As people start exploiting PBNM, another aspect comes to attention: transactional integrity. Transactional control envisages achieving consistent state changes along the network. In other words, state transition in network devices is only authorized if all the related operations are successfully taken.
In this paper we propose a transactional control mechanism for PBNM systems, namely its assurance across different systems and different network domains.
Visual Composition of Management Policies
by Vitor Roque
proc. of the 4th Conference on Telecommunications – ConfTele2003, Aveiro, Portugal, 18-20 June 2003.
Policy based management have gained a crescent importance in the last years. New demands on internetworking, on... more Policy based management have gained a crescent importance in the last years. New demands on internetworking, on services specification, on QoS achievement and generically on network management functionality, have driven this paradigm to a very important level. The main idea is to provide services that allow specifying management and operational rules in the same way people do business. Despite the main association of this technology with network management solutions, its generality allows to extend these principles to any business process inside an organization. In this paper we discuss the main proposals in the field, namely the IETF/DMTF model, and we present a proposal that allows the specification of policy rules through a user-friendly and component-oriented graphical interface.
Policy-Based Network Management in an Integrated Mobile Network
by Vitor Roque
Through the seamless integration of different kinds of technologies, services and terminals, and with the expected... more Through the seamless integration of different kinds of technologies, services and terminals, and with the expected offered bandwidth, the next generation networks will put a new set of challenges related to operation and management. In this paper we present a Policy-based Network Management System that is being developed inside the Daidalos IST project.
Executable Graphics for PBNM
by Vitor Roque
http://www.springer.com/computer/communication+networks/book/978-3-540
Policy-Based Network Management (PBNM) is the
application of specific, organisation-level rules in the context... more
Policy-Based Network Management (PBNM) is the
application of specific, organisation-level rules in the context of
networking, in particular for network management operations.
The specification of a policy is performed in a policy language,
usually following a textual representation. However, humans
process images faster than text and they are prepared to process
information presented in two or more dimensions: sometimes it is
easier to explain things using figures and their graphical relations
than writing textual representations.
This paper describes a visual language, in the form of graphics
that are executed in a networking environment, to define a
network management policy. This approach allows to map visual
tokens and corresponding arrangements into other languages to
which a mapping is defined.
Solving Transactional Control in Current Management Frameworks
by Vitor Roque
proc. of the 6th International Conference on Enterprise Information Systems - ICEIS2004, Porto, Portugal, 14-17 April 2004.
Policy Based Network Management has been presented as a paradigm for efficient and customisable management systems.... more Policy Based Network Management has been presented as a paradigm for efficient and customisable management systems. The IETF has provided a framework to describe the concept but some aspects still open like transactional control. In fact transactional control mechanisms are receiving today great attention in the scope of network management. In here, we identify the lacks of current management paradigms concerning transactional control and we propose a policy-based network management system that allows specify operations over aggregations of agents and that provides high-level atomic transactions.
Policies Composition Through Graphical Components
by Vitor Roque
proc. of the 5th International Conference on Enterprise Information Systems - ICEIS2003, Angers, France, 23-26 April 2003.
Policy based management have gained a crescent importance in the two last years. New demands on
internetworking,... more
Policy based management have gained a crescent importance in the two last years. New demands on
internetworking, on services specification, on QoS achievement and generically on network management
functionality, have driven this paradigm to a very important level. The main idea is to provide services that
allow specifying management and operational rules in the same way people do business. Despite the main
focus of this technology has been associated with network management solutions, its generality allows to
extend these principles to any business process inside an organization. In this paper we discuss the main
proposals in the field, namely the IETF/DMTF model, and we present a proposal that allows the
specification of policy rules through a user-friendly and component-oriented graphical interface.
Het Netwerk Imaginaire. Een analyse van de netwerkmaatschappij als metafoor van het moderne verlangen
BA eindscriptie Mediawetenschap (Nieuwe Media & Digitale Cultuur)
De opkomst en ontwikkeling van “nieuwe” technologie gaat altijd vergezeld met verhalen; er ontstaat een discours, een... more
De opkomst en ontwikkeling van “nieuwe” technologie gaat altijd vergezeld met verhalen; er ontstaat een discours, een praktijk van schrijven en spreken, van utopische en dystopische toekomstprojecties. Wat er gezegd, en dientengevolge niet gezegd wordt, en hoe we spreken, bepaalt ons beeld van de wereld . Om het “nieuwe” in te kaderen en te beschrijven vieren associaties en metaforen hoogtij. We proberen nieuwe technologieën in termen van het bekende te beschrijven omdat dit de enige manier is waarop we ze begrijpelijk kunnen maken. Metaforen bepalen zo, omdat deze beeldspraak berust op een vergelijking, de grenzen van hoe we over deze nieuwe technologieën nadenken. De ontwikkeling van de zogenaamde “nieuwe media” hebben er gaandeweg toe geleid dat veel filosofen, theoretici en wetenschappers de samenleving zijn gaan beschrijven en analyseren in termen en metaforen kenmerkend voor de nieuwe media. Een van de belangrijkste hedendaagse termen waarin gesproken wordt is het netwerk (o.a. Van Dijk 1999; Castells 2001; Castells 2010; Barney 2004). Het begrip netwerk wordt veelal gebruikt als een referent naar een fysiek net van verbindingen zoals een wegennet, die we technologische netwerken noemen, of een “onzichtbaar” net van relaties tussen personen, waarbij we spreken over sociale netwerken. Met de opkomst van de technologische netwerken van nieuwe media zoals mobiele telefonie en internet wordt steeds vaker beweerd dat technologische en sociale netwerken meer zijn gaan overlappen.
Ik zal de bewering proberen te staven dat de term “netwerk” een metafoor is; een idee met ideologische en utopische connotaties. Het idee van een netwerk is toepasbaar op allerhande fenomenen, zoals relaties tussen personen, de samenwerking van instituten, bedrijven en landen, communicatie in het algemeen, of de werking van het lichaam. De eenentwintigste eeuw lijkt gedomineerd te gaan worden door dit paradigma van het netwerk. Dit onderzoek zal zich daarom richten op hoe de metafoor van de netwerkmaatschappij gebruikt wordt voor analyse en beschrijving van de mens en de samenleving en wat vooral de technologisch imaginaire implicaties hiervan zijn.
