2,380 research outputs found
IP-Level Satellite Link Emulation with KauNet
Distributed applications and transport protocols communicating over a satellite link may react very strongly to conditions specific to that kind of link. Providing a evaluation framework to allow tests of real implementations of such software in that context is quite a challenging task. In this paper we demonstrate how the use of the general-purpose KauNet IP-level emulator combined with satellite-specific packet loss patterns can help by reproducing losses and delays experienced on a satellite link with a simple Ethernet LAN setup. Such a platform is an essential tool for developers performing continuous testing as they provide new features for e.g. video codecs or transport-level software like DCCP and its congestion control components
A Framework for Quality-Driven Delivery in Distributed Multimedia Systems
In this paper, we propose a framework for Quality-Driven Delivery (QDD) in distributed multimedia environments. Quality-driven delivery refers to the capacity of a system to deliver documents, or more generally objects, while considering the users expectations in terms of non-functional requirements. For this QDD framework, we propose a model-driven approach where we focus on QoS information modeling and transformation. QoS information models and meta-models are used during different QoS activities for mapping requirements to system constraints, for exchanging QoS information, for checking compatibility between QoS information and more generally for making QoS decisions. We also investigate which model transformation operators have to be implemented in order to support some QoS activities such as QoS mapping
Performance evaluation of an open distributed platform for realistic traffic generation
Network researchers have dedicated a notable part of their efforts
to the area of modeling traffic and to the implementation of efficient traffic
generators. We feel that there is a strong demand for traffic generators
capable to reproduce realistic traffic patterns according to theoretical
models and at the same time with high performance. This work presents an open
distributed platform for traffic generation that we called distributed
internet traffic generator (D-ITG), capable of producing traffic (network,
transport and application layer) at packet level and of accurately replicating
appropriate stochastic processes for both inter departure time (IDT) and
packet size (PS) random variables. We implemented two different versions of
our distributed generator. In the first one, a log server is in charge of
recording the information transmitted by senders and receivers and these
communications are based either on TCP or UDP. In the other one, senders and
receivers make use of the MPI library. In this work a complete performance
comparison among the centralized version and the two distributed versions of
D-ITG is presented
Multimedia resources: An information model and its application to an MPEG2 video codec
Still today, diagnosing a problem with multimedia resources, such as video and sound cards, is insufficiently automated. These resources therefore cannot be accurately managed. One reason for this is the lack of their thorough modeling. In this paper, we fulfill this need, by proposing a generic information model, which we further apply to an MPEG2 video codec. We highlight the main characteristics of this kind of codec, identify parameters that influence these characteristics, and reveal some of the trade-offs that the application developer can consider in order to design efficient software for MPEG2 codecs. In addition to the benefits of this modeling for the user and the application developer, we also show how useful it could be for the providers of distribution services, such as live video transmission. These providers can use our model to achieve resource management on an end-to-end basis
VXA: A Virtual Architecture for Durable Compressed Archives
Data compression algorithms change frequently, and obsolete decoders do not
always run on new hardware and operating systems, threatening the long-term
usability of content archived using those algorithms. Re-encoding content into
new formats is cumbersome, and highly undesirable when lossy compression is
involved. Processor architectures, in contrast, have remained comparatively
stable over recent decades. VXA, an archival storage system designed around
this observation, archives executable decoders along with the encoded content
it stores. VXA decoders run in a specialized virtual machine that implements an
OS-independent execution environment based on the standard x86 architecture.
The VXA virtual machine strictly limits access to host system services, making
decoders safe to run even if an archive contains malicious code. VXA's adoption
of a "native" processor architecture instead of type-safe language technology
allows reuse of existing "hand-optimized" decoders in C and assembly language,
and permits decoders access to performance-enhancing architecture features such
as vector processing instructions. The performance cost of VXA's virtualization
is typically less than 15% compared with the same decoders running natively.
The storage cost of archived decoders, typically 30-130KB each, can be
amortized across many archived files sharing the same compression method.Comment: 14 pages, 7 figures, 2 table
Framework For Efficient Cosimulation And Fast Prototyping on Multi-Components With AAA Methodology: LAR Codec Study Case
pp 1667 - 1671Real-time signal and image applications have significant time constraints involving the use of several powerful calculation units. Programmable multi-component architectures have proven to be a suitable solution combining flexibility and computation power. This paper presents a methodology for the fast design of signal and image processing applications. In a unified framework, application modeling, cosimulation and fast implementation onto parallel heterogeneous architectures are enabled and help to reduce time-to-market. Moreover, automatic code generation provides a high abstraction level for users. Finally, the worthwhile nature of Matlab/C language cosimulation is illustrated on a still image codec named LAR
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