721 research outputs found
Congestion Control for Layered Multicast Transmission
peer reviewedHeterogeneity of receivers makes it hard to control congestion for multicast transmission. Using hierarchical layering of the information is one of the most elegant and efficient approach to tackle this problem. The proposed algorithm is based on this principle and has three objectives: to fulfill intra-session fairness, i.e. between different receivers of the same session; to be fair towards TCP; to fulfill inter-session fairness, i.e. same throughputs (and not number of layers) to concurrent sessions
Control de CongestiĂłn TCP y mecanismos AQM
En los Ășltimos años se ha ido poniendo Ă©nfasis particularmente en la
importancia del retraso sobre la capacidad. Hoy en dĂa, nuestras redes se estĂĄn
volviendo mĂĄs y mĂĄs sensibles a la latencia debido a la proliferaciĂłn de aplicaciones
y servicios como el VoIP, la IPTV o el juego online donde un retardo bajo es esencial
para un desempeño adecuado y una buena experiencia de usuario.
La mayor parte de este retraso innecesario se debe al mal funcionamiento de
algunos bĂșferes que pueblan internet. En vez de desempeñar la tarea para la que
fueron creados, absorber eventuales rĂĄfagas de paquetes con el fin de prevenir su
pérdida, hacen creer al mecanismo de control de congestión que la ruta hacia el
destino actual tiene mĂĄs ancho de banda que el que posee realmente. Cuando la
pérdida de paquetes ocurre, si es que lo hace, es demasiado tarde y el daño en el
enlace, en forma de tiempo de transmisiĂłn adicional, ya se ha producido.
En este trabajo de fĂn de grado intentaremos arrojar luz sobre una soluciĂłn
especĂfica cuyo objetivo es el de reducir el retardo extra producido por esos
hinchados bĂșferes, la GestiĂłn Avanzada de Colas o Active Queue Management
(AQM). Hemos testeado un grupo de estos algoritmos AQM junto con diferentes
modificaciones del control de congestiĂłn de TCP con el fĂn de entender las
interacciones generadas entre esos dos mecanismos, realizando simulaciones en
varios escenarios caracterĂsiticos tales como enlaces transoceĂĄnicos o enlaces de
acceso a red, entre otros.In recent years, the relevance of delay over throughput has been particularly
emphasized. Nowadays our networks are getting more and more sensible to latency
due to the proliferation of applications and services like VoIP, IPTV or online
gaming where a low delay is essential for a proper performance and a good user
experience.
Most of this unnecessary delay is created by the misbehaviour of many bu ers
that populate Internet. Instead of performing the task for what they were
created for, absorbing eventual packet bursts to prevent loss, they deceive the
sender's congestion control mechanisms into believing that the current path to the
destination has more bandwidth than it really has. When the loss event occurs, if it
does, it's too late and the damage on the path, in terms of additional transmission
time, has been done.
On this bachelor thesis we will try to throw light over an speci c solution
that aims to reduce the extra delay produced by these bloated bu ers: Active
Queue Management. We have tested a bunch of AQM algorithms with di erent
TCP modi cations in order to understand the interactions between these two
mechanisms. We performed simulations testing various characteristic scenarios
like Transoceanic links or Access link scenarios, among other.IngenierĂa TelemĂĄtic
Dual-Mode Congestion Control Mechanism for Video Services
Recent studies have shown that video services represent over half of Internet traffic, with a growing trend. Therefore, video traffic plays a major role in network congestion. Currently on the Internet, congestion control is mainly implemented through overprovisioning and TCP congestion control. Although some video services use TCP to implement their transport services in a manner that actually works, TCP is not an ideal protocol for use by all video applications. For example, UDP is often considered to be more suitable for use by real-time video applications. Unfortunately, UDP does not implement congestion control. Therefore, these UDP-based video services operate without any kind of congestion control support unless congestion control is implemented on the application layer. There are also arguments against massive overprovisioning. Due to these factors, there is still a need to equip video services with proper congestion control.Most of the congestion control mechanisms developed for the use of video services can only offer either low priority or TCP-friendly real-time services. There is no single congestion control mechanism currently that is suitable and can be widely used for all kinds of video services. This thesis provides a study in which a new dual-mode congestion control mechanism is proposed. This mechanism can offer congestion control services for both service types. The mechanism includes two modes, a backward-loading mode and a real-time mode. The backward-loading mode works like a low-priority service where the bandwidth is given away to other connections once the load level of a network is high enough. In contrast, the real-time mode always demands its fair share of the bandwidth.The behavior of the new mechanism and its friendliness toward itself, and the TCP protocol, have been investigated by means of simulations and real network tests. It was found that this kind of congestion control approach could be suitable for video services. The new mechanism worked acceptably. In particular, the mechanism behaved toward itself in a very friendly way in most cases. The averaged TCP fairness was at a good level. In the worst cases, the faster connections received about 1.6 times as much bandwidth as the slower connections
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Multimedia delivery in the future internet
The term âNetworked Mediaâ implies that all kinds of media including text, image, 3D graphics, audio
and video are produced, distributed, shared, managed and consumed on-line through various networks,
like the Internet, Fiber, WiFi, WiMAX, GPRS, 3G and so on, in a convergent manner [1]. This white
paper is the contribution of the Media Delivery Platform (MDP) cluster and aims to cover the Networked
challenges of the Networked Media in the transition to the Future of the Internet.
Internet has evolved and changed the way we work and live. End users of the Internet have been confronted
with a bewildering range of media, services and applications and of technological innovations concerning
media formats, wireless networks, terminal types and capabilities. And there is little evidence that the pace
of this innovation is slowing. Today, over one billion of users access the Internet on regular basis, more
than 100 million users have downloaded at least one (multi)media file and over 47 millions of them do so
regularly, searching in more than 160 Exabytes1 of content. In the near future these numbers are expected
to exponentially rise. It is expected that the Internet content will be increased by at least a factor of 6, rising
to more than 990 Exabytes before 2012, fuelled mainly by the users themselves. Moreover, it is envisaged
that in a near- to mid-term future, the Internet will provide the means to share and distribute (new)
multimedia content and services with superior quality and striking flexibility, in a trusted and personalized
way, improving citizensâ quality of life, working conditions, edutainment and safety.
In this evolving environment, new transport protocols, new multimedia encoding schemes, cross-layer inthe
network adaptation, machine-to-machine communication (including RFIDs), rich 3D content as well as
community networks and the use of peer-to-peer (P2P) overlays are expected to generate new models of
interaction and cooperation, and be able to support enhanced perceived quality-of-experience (PQoE) and
innovative applications âon the moveâ, like virtual collaboration environments, personalised services/
media, virtual sport groups, on-line gaming, edutainment. In this context, the interaction with content
combined with interactive/multimedia search capabilities across distributed repositories, opportunistic P2P
networks and the dynamic adaptation to the characteristics of diverse mobile terminals are expected to
contribute towards such a vision.
Based on work that has taken place in a number of EC co-funded projects, in Framework Program 6 (FP6)
and Framework Program 7 (FP7), a group of experts and technology visionaries have voluntarily
contributed in this white paper aiming to describe the status, the state-of-the art, the challenges and the way
ahead in the area of Content Aware media delivery platforms
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