|
Home
Papers
Program
Committee
Attendees
Copyright
|
Papers
| Title |
Abstract |
GONE: an Infrastructure Overlay for Resilient, DoS-Limiting Networking
Xiaoming Fu (University of Goettingen, DE); Jon Crowcroft (University of Cambridge, UK)
fu.pdf
|
With
today's penetration in volume and variety of information flowing across
the Internet, data and services are experiencing various issues with
the TCP/IP infrastructure, most notably availability, reliability, and
mobility. So far the proposed approaches have focused on applying
application-layer routing and path monitoring for reliability and
enforcing stateful packet filters in hosts or network to protect
against Denial of Service (DoS) attacks. Each of them solves its own
aspect of the problem, trading scalability for availability and
reliability among a relatively small set of nodes, yet there is no
single overall solution addressing these issues in a large scale
available. We propose an alternative overlay network architecture by
introducing a set of generic functions in network edges and end hosts.
We conjecture that the network edge constitutes a major source of DoS,
resilience and mobility issues to the network, and propose a new
solution to this problem, namely the General Internet Signaling
Transport (GIST) Overlay Networking Extension, or GONE. The basic idea
of GONE is to create a half-permanent overlay mesh consisting of
GONE-enabled edge routers, which employs capability-based DoS
prevention and forwards end-to-end user traffic using the GIST
messaging associations. GONE's use of GIST on top of SCTP allows
multi-homing, multi-streaming and partial reliability, while only a
limited overhead for maintaining the messaging association is
introduced. In addition, upon the services provided by GONE overlays,
hosts are identified by their unique host identifiers independent of
their topologies location, and simply require (de-)multiplexing instead
of the traditional connection management and other complex
functionality in the transport layer. As a result, this approach offers
a number of advantages for upper layer end-to-end applications,
including intrinsic provisioning of resilience and DoS prevention in a
dynamic and nomadic environment. |
NSYNC: Network Synchronization for Peer-to-peer Streaming Overlay Construction
Hongbo Jiang (Case Western Reserve University, US); Shudong Jin (Case Western Reserve University, US)
jiang.pdf
|
In
peer-to-peer streaming applications such as IP television and live
shows, a key problem is how to construct an overlay network to provide
high-quality, almost real-time media relay in an efficient and scalable
manner. Much work has focused on the construction of tree and graph
network topology, often based on the inference of network
characteristics (such as delay and bandwidth). Less attention has been
paid to improving the liveness of media delivery, and to exploiting the
flexibility of applications to construct better overlay networks. We
propose the NSYNC, an ongoing work on constructing low-latency overlay
networks for live streaming. It aims at solving the following problems.
In typical applications, peers must buffer a portion of a real-time
event, e.g., for at least a few seconds. Thus, it introduces both (1)
delay, especially long delay for peers that are many hops away from the
origin servers, and (2) partial ordering between the peers. With NSYNC,
the users (such as media players) can slightly increase or decrease the
speed of playing (displaying) media. Thus, the peers in a network can
be synchronized to achieve two effects. First, late peers can catch
early peers (and the origin server) such that the entire peer networks
improve liveness. Second, the client/server roles between a pair of
neighboring peers can be reversed, allowing opportunities for
constructing more efficient overlay networks. NSYNC can be used in
various peer-to-peer streaming systems. Our preliminary results show
NSYNC can be effective. |
Optimistic Load Balancing in a Distributed Virtual Environment
Roman Chertov (Purdue University, US); Sonia Fahmy (Purdue University, US)
chertov.pdf
|
Distributed
virtual environments such as massive multi-player games require support
of multiple servers to balance computational load. This paper
investigates the architecture of a unified environment where the
virtual online world is not partitioned according to rigid boundaries,
but according to an adaptive paradigm. Since it is difficult to develop
an efficient load balancing algorithm for a unified environment, we
propose an optimistic scheme that quickly converges. The cost of
frequent migrations is minimized by using stateless
servers/connections, and following a push/push data model. We analyze
the computational time costs of such a system and give simulation
results to gauge its performance. The simulation results confirm that
our load balancing scheme is efficient and can support large numbers of
clients. |
Harmonic Interleaving: File System Support for Scalable Streaming of Layer Encoded Object
Sooyong Kang (Hanyang University, KR); Youjip Won (Hanyang University, KR); Seunghyun Roh (Hanyang University, KR)
kang.pdf
|
We
propose a novel file system technique to efficiently support scalable
streaming of layer encoded content. From file system's point of view,
scalable streaming introduces another dimension of complexity in disk
scheduling. This is particularly because when a subset of information
is retrieved, the playback does not necessarily coincides with the
sequential access. The current file structure and the file system
organization for real-time multimedia application leaves much to be
desired to efficiently support scalable streaming service. We propose a
new file organization technique called "`Harnominc Interleaving"' whose
basic idea is to cluster the frequently accessed layers together.
Harmonic Interleaving scheme is conceptually very simple but which
layers need to be clustered together is yet to be answered. Further,
proving its effectiveness in practical situation requires rather
serious treatment. We successfully develop elaborate analytical models
for a number of different file organization techniques, which are
Progressive Placement, Interleaving Placement and Harmonic Interleaving
Placement, and perform in depth investigation of various file
organization techniques under varying workload conditions. The models
developed in this work enables us to predict the performance and
efficiency of the storage system in scalable streaming environment. We
find that the Harmonic Interleaving yields the most promising
performance in scalable streaming environment. The result of our work
provides not only the analytical techniques to predict the performance
of a given file organization technique but also the useful guidelines
for ISP or real-time multimedia contents providers on how to organize
their contents in physical system. |
Evaluating Dead Reckoning Variations with a Multi-player Game Simulator
Wladimir Palant (University of Oslo, NO); Carsten Griwodz (University of Oslo, NO); Pål Halvorsen (University of Oslo, NO)
palant.pdf
|
One
of the most difficult tasks when creating an online multi-player game
is to provide the players with a consistent view of the virtual world
despite the network delays. Most current games use prediction
algorithms to achieve this, but usually it does not go beyond applying
the DIS dead reckoning algorithm proposed in the mid-90s. In this paper
we introduce a simulator called GLS that allows us to evaluate
different aspects of DIS and its variations. We examine the impact of
prediction and clock synchronization on game consistency. We also
evaluate the convergence algorithm we introduce here. Furthermore we
look into ways for compensating increasing delays to keep the player's
view of the game state sufficiently consistent with other players. |
A Hybrid Thin-client Protocol for Multimedia Streaming and Interactive Gaming Applications
Davy
De Winter (Hogeschool Gent - Ghent University, BE); Pieter Simoens
(University of Ghent, BE); Lien Deboosere (Ghent University, BE); Filip
De Turck (Ghent University, BE); Joris Moreau (Hogeschool Gent -
Industriële wetenschappen, BE); Bart Dhoedt (Ghent University, BE);
Piet Demeester (Ghent University, BE)
winter.pdf
|
Despite
the growing popularity and advantages of thin-client systems, they
still have some important shortcomings. Current thin-client systems are
ideally suited to be used with classic office-applications but as soon
as multimedia and 3D gaming applications are used they require a large
amount of bandwidth and processing power. Furthermore, most of
multimedia and 3D applications heavily rely on the Graphical Processing
Unit (GPU). Due to the architectural design of thin-client systems,
these applications cannot profit from the GPU resulting in slow
performance and bad image quality. In this paper, we propose a
thin-client system which addresses these problems: we introduce a
realtime desktopstreamer using a H264/AVC-based videocodec to stream
the graphical output of applications after GPU-processing to a
thin-client device, capable of decoding a videostream. We compare this
approach to a number of popular classic thin-client systems in terms of
bandwidth, delay and image-quality. The outcome is an architecture for
a hybrid protocol, which can dynamically switch between a classic
thin-client protocol and realtime desktopstreaming. |
AMTrac: Adaptive Meta-caching for Transcoding
Dongyu Liu (George Mason University, US); Songqing Chen (George Mason University, US); Bo Shen (HP Labs, US)
liu.pdf
|
The
increase of aggregate Internet bandwidth and the rapid development of
3G wireless networks demand efficient delivery of multimedia objects to
all types of wireless devices. To handle requests from wireless devices
at runtime, the transcode-enabled caching proxy has been proposed and a
lot of research has been conducted to study online transcoding. Since
transcoding is a CPU-intensive task, the transcoded versions can be
saved to reduce the CPU load for future requests. However, extensively
caching all transcoded results can quickly exhaust cache space.
Constrained by available CPU and storage, existing transcode-enabled
caching schemes always selectively cache certain transcoded versions,
expecting that many future requests can be served from the cache while
leaving CPU cycles for online transcoding for other requests. But such
schemes treat the transcoder as a black box, leaving no room for
flexible control of joint resource management between CPU and storage.
In this paper, we first introduce the idea of meta-caching by looking
into a transcoding procedure. Instead of caching certain selected
transcoded versions in full, meta-caching identifies intermediate
transcoding steps from which certain intermediate results (called
metadata) can be cached so that a fully transcoded version can be
easily produced from the metadata with a small amount of CPU cycles.
Achieving big saving in caching space with possibly small sacrifice on
CPU load, the proposed meta-caching scheme provides a unique method to
balance the utilization of CPU and storage resources at the proxy. We
further construct a model to analyze the meta-caching scheme and
propose AMTrac, Adaptive Meta-caching for TRAnsCoding, which adaptively
applies meta-caching based on the client request patterns and available
resources. Experimental results show that our proposed AMTrac can
significantly improve the system throughput over existing approaches. |
On the Effects of Multi-hop Buffering and Adaptation for Video-Based Sensor Networking Applications
Jie
Huang (Portland State University, US); Wu-chi Feng (Portland State
University, US); Wu-chang Feng (Portland State University, US); David
Romano (Intel, US)
huang.pdf
|
As video
sensor networks become more widely deployed, mechanisms for buffering
and adaptively transmitting video data within the network are necessary
because of their generally large resource requirements compared to
their scalar counterparts. In video sensor networks, many video sensors
can inject video into the network at the same time as well as store and
forward data for other sensor nodes. The effects of video buffering and
adaptation in such multi-hop networks are not that well understood. In
this paper, we propose a “bucket-brigade-style” multi-hop buffering and
adaptation framework for video-based sensor networking applications. We
explore several approaches in this framework and compare their
performance with traditional IP-based video streaming technologies. Our
experiments show that the proposed framework outperforms traditional
technologies in bandwidth efficiency, video quality, bandwidth sharing
fairness, and energy efficiency. |
The Fun of using TCP for an MMORPG
Carsten Griwodz (University of Oslo, NO); Pål Halvorsen (University of Oslo, NO)
griwodz.pdf
|
Massive
multi-player online games have become a popular, fast growing,
multi-million industry with a very high user mass supporting hundreds
or thousands of concurrent players. In many cases, these games are
centralized and every player communicates with the central server
through a time-critical unicast event stream. Funcom's Anarchy Online
is one of these; it is based on TCP. We find that its kind of traffic
has some interesting properties that inspire changes to protocol or
architecture. In these game streams, using TCP is not TCP-friendly,
using TCP does not have to be slower than using UDP, and only repeated
timeouts ruin game experience. Improving the latter in the sender
implementation does not impose any remarkable penalty on the network.
Alternatively, a proxy architecture for multiplexing could save about
40% resources at the server, allow congestion control to work and also
reduce the lag of the game. |
Assigning Game Server Roles in Mobile Ad-hoc Networks
Oliver Wellnitz (Technische Universitaet Braunschweig, DE); Lars Wolf (TU Braunschweig, IBR, DE)
wellnitz.pdf
|
Over
the last couple of years, multi-player games have become more and more
popular. Additionally, new mobile devices now have sufficient resources
to play these multi-player games in mobile and wireless networks. As
the classic centralized game server design is unsuited for mobile
ad-hoc networks, a group of nodes can take the role of a distributed
game server. This group of nodes can provide the necessary redundancy
which is needed in the dynamic environment of a mobile ad-hoc network.
In this paper we present a modified dominating set algorithm for server
selection which uses local information to determine well-suited nodes
from the group of players. Our algorithm uses three phases (discovery,
determination and marking) to calculate an initial server set and
adjusts to network changes during the game. We implemented our server
selection algorithm in NS-2 and evaluated its behaviour in two
different realistic scenarios for mobile games (schoolyard and train)
as well as in an artificial stress scenario. |
A Platform for Dynamic Microcell Redeployment in Massively Multiplayer Online Games
Bruno
Van Den Bossche (Ghent University, BE); Tom Verdickt (Ghent University,
BE); Bart De Vleeschauwer (Ghent University, BE); Stein De Smet (Ghent
University, BE); Stijn De Mulder (Ghent University, BE); Filip De Turck
(Ghent University, BE); Bart Dhoedt (Ghent University, BE); Piet
Demeester (Ghent University, BE)
bossche.pdf
|
As
Massively Multiplayer Online Games enjoy a huge popularity and are
played by tens of thousands of players simultaneously, an efficient
software architecture is needed to cope with the dynamically changing
loads at the server side. In this paper we discuss a novel way to
support this kind of application by dividing the virtual world into
several parts, called microcells. Every server is assigned a number of
microcells and by dynamically redeploying these microcells when the
load in a region of the world suddenly increases, the platform is able
to adapt to changing load distributions. The software architecture for
this system is described and we also provide some evaluation results
that indicate the performance of our platform. |
Intra-Stream Encoding for Multiple Depth Streams
Sang-Uok Kum (Univ. of North Carolina - Chapel Hill, US); Ketan Mayer-Patel (University of North Carolina, US)
kum.pdf
|
Using
multiple cameras, a dynamic real world scene can be captured,
represented, and streamed for realistic interaction in a 3D immersive
system. One method to represent the dynamic environment is to use
multiple depth streams -- streams with color and depth information.
However the captured data is too large to be streamed uncompressed.
Fortunately, these data exhibit spatial and temporal coherence that can
be used for compression. In this paper, we examine the initial step in
compressing multiple depth streams. To use spatial coherence between
streams to compress multiple depth streams, base reference streams --
intra-streams -- have to be encoded without the use of other depth
streams. We investigate encoding of this base depth stream using only
temporal coherence. The proposed algorithm extends video stream
encoding techniques to encode color and depth. We show that for
encoding a depth stream which require high quality, such as base
reference streams, using separate motion vectors to encode color and
depth performs better than using a single motion vector. |
Design and Evaluation of 3D Video System Based on H.264 View Coding
Kalva
Hari (Florida Atlantic University, US); Liam Mayron (Florida Atlantic
University, US); Lakis Cristodoulou (Florida Atlantic University, US);
Oge Marques (Florida Atlantic University, US); Borko Furht (Florida
Atlantic Univ., US)
hari.pdf
|
Recent
advances in video compression and 3D displays have necessitated a
further understanding and development of 3D video coding algorithms.
The emergence of low cost autostereoscopic displays is expected to
drive the growth of 3DTV services. This paper discusses key issues that
affect the quality of 3D video experience on autostereoscopic displays.
The stereo views can be encoded at different quality without affecting
the perceptual quality of the 3D video. We examine the bounds of this
asymmetric stereo view compression with a user study. The H.264/AVC
video coding algorithm was used to compress each view. This paper also
presents the design and development of a modular video player with
stereoscopic and multi-view capabilities including a discussion of
useful tools for accelerating development and enhancing flexibility.
The player implements the 3D image reconstruction caused by binocular
fusion. A discussion of experimental results and recommendations for
improvements of stereoscopic image quality in terms of 3D video
enhancement, processing and acquisition, deployed video algorithms, as
well as smart encoders and decoders are also presented in this paper. |
FGS-MR: MPEG4 Fine Grained Scalable Multi-Resolution Video Encoding for Adaptive Video Streaming
Siddhartha
Chattopadhyay (University of Georgia, US); Kang Li (University of
Georgia, US); Suchendra Bhandarkar (University of Georgia, US)
chattopadhyay.pdf
|
The
MPEG-4 Fine Grained Scalability (FGS) profile aims at scalable video
encoding, in order to ensure efficient video streaming in networks with
fluctuating bandwidths. In order to allow very low bit rate streaming,
the Base Layer of a FGS video is encoded at a very low bit rate,
consequently, at very low video quality. In this paper, we propose
FGS-MR, which uses content aware multi-resolution video frames to
obtain better video quality for a target bit rate, compared to MPEG-4
FGS Base Layer video encoding. MPEG-4 FGS Base Layer video encoding is
optimized using Adaptive Quantization (FGS-AQ). Given a quantitative
quality of video (e.g. PSNR value) desired, FGS-MR leads to lower bit
rate video encoding compared to FGS-AQ. In addition, FGS-MR is an
integrated approach that requires only encoding side modification, and
is transparent to the decoder, as opposed to FGS-AQ. We have shown
various potential mobile applications which can benefit significantly
by using FGS-MR, such as video conferencing applications. |
Video Authentication for H.264/AVC using Digital Signature Standard and Secure Hash Algorithm
Nandakishore Ramaswamy (Qualcomm Inc, US); K. R. Rao (University of Texas at Arlington, US)
ramaswamy.pdf
|
This
paper proposes a hard video authentication and sender verification
scheme for video sequences compressed using H.264/AVC Main Profile by
using digital signatures and cryptographic hash. Features from the
transform domain are used as the authentication data for a macroblock.
The algorithm can detect the cause of authentication failure and point
out the location of the tampered frames in case of frame tampering.
Results demonstrate that the proposed scheme is highly robust to
temporal and spatial manipulations |
Redundancy-Controllable Adaptive Retransmission Timeout Estimation for Packet Video
Ali Begen (Georgia Institute of Technology, US); Yucel Altunbasak (Georgia Institute of Technology, US)
begen.pdf
|
Time-constrained
error recovery is an integral component of reliable low-delay video
applications. Regardless of the error-control method adopted by the
application, unacknowledged or missing packets must be quickly
identified as lost or delayed, so that necessary timely actions can be
taken by the server/client. Historically, this problem has been
referred to as retransmission timeout (RTO) estimation. Earlier studies
show that existing RTO estimators suffer either from long loss
detection times or large number of pre-mature timeouts. The goal of
this study is to address these problems by developing an adaptive RTO
estimator for high-bitrate low-delay video applications. By exploiting
the temporal dependence between consecutive delay samples, we propose
an adaptive linear delay predictor. This way, our RTO estimator
configures itself based on the video characteristics and varying
network conditions. Our approach also features a controller that
optimally manages the trade-off between the amount of overwaiting and
redundant retransmission rate. The skeleton implementation shows that
the proposed RTO estimator discriminates lost packets from
excessively-delayed packets faster and more accurately than its rivals,
which consequently enables the applications to recover more packets
under stringent delay requirements. |
Understanding Mesh-based Peer-to-Peer Streaming
Nazanin Magharei (University of Oregon, US); Reza Rejaie (University of Oregon, US)
magharei.pdf
|
Existing
peer-to-peer (P2P) streaming mechanisms often use tree-based overlays.
These mechanisms are unable to effectively utilize outgoing bandwidth
of participating peers, and therefore they are not self-scaling. In
contrast, swarm-like content delivery mechanisms such as BitTorrent,
exhibit self-scaling property but incorporating them into P2P streaming
application are challenging due to both in-time requirement of delivery
and the limited availability of future content in P2P streaming
applications. In this paper, we illustrate the fundamental design
issues and tradeoffs in incorporating swarm-like delivery into
mesh-based P2P streaming applications. Leveraging an un-tangled view of
the overlay, we present a global pattern for streaming content over a
mesh-based overlay that can effectively utilize the outgoing bandwidth
of most participating peers. Understanding the proper pattern for
streaming over a mesh sheds an insightful light on design and
evaluation of P2P streaming mechanisms. In particular, we show that for
a given scenario, there is a sweet range for node degree in the overlay
that maximizes delivered quality to individual peers. |
On Combining Temporal Scaling and Quality Scaling for Streaming MPEG
Huahui
Wu (Worcester Polytechnic Institute, US); Mark Claypool (Worcester
Polytechnic Institute, US); Robert Kinicki (Worcester Polytechnic
Institute, US)
wu.pdf
|
Temporal scaling
and quality scaling are both widely-used mechanisms to reduce data
rates of streaming video. However, combinations of temporal and quality
scaling have not been systematically studied. This research extends
previous work to provide a model for combining temporal and quality
scaling, and uses an optimization algorithm to provide a systematic
analysis of their combination over a range of network conditions and
video content. We find: 1) quality scaling typically performs better
than temporal scaling, with performance differences correlated with the
motion characteristics of the video. In fact, when the network capacity
is moderate and the loss rate is low, quality scaling performs nearly
as well as the optimal combination of quality and temporal scaling; 2)
when the network capacity is low and the packet loss rate is high,
quality scaling alone is ineffective, but a combination of quality and
temporal scaling can provide reasonable video quality; 3) adjusting the
amount of forward error correction (FEC) provides significantly better
performance than video streaming without FEC or video streaming with a
fixed amount of FEC. |
AC/DC: an Algorithm for Cheating Detection by Cheating
Stefano Ferretti (University of Bologna, IT); Marco Roccetti (University of Bologna, IT)
ferretti.pdf
|
Time
cheats represent some of the most delicate issues in online gaming.
Since they act on timing properties of generated game events, these
malicious schemes are particularly difficult to thwart when distributed
games are deployed over peer-to-peer architectures. Indeed, the absence
of a global clock shared among peers enables cheaters to see into the
future by waiting for events generated by other peers before generating
its own ones (lookahead cheat). This may give an unfair advantage to
the cheater. In this work, we consider a version of lookahead cheat
generalized in the context of real-time (i.e., not round-based) games.
To face this time cheat, we present an algorithm that enables to detect
cheaters based on monitoring of network latencies. The basic idea is
that of conducting against each suspected peer a sort of cheating
activity, by delaying events before notify them to the (hypothetic)
cheater. This permits to notice whether that peer waits for these
events before generating its own ones. Our claim is that an approach
based on the monitoring of communication patterns among peers, allows
cheat detection without affecting the performances of the game. |
A Multi-stream Adaptation Framework for Bandwidth Management in 3D Tele-immersion
Zhenyu
Yang (University of Illinois at Urbana-Champaign, US); Klara Nahrstedt
(University of Illinois at Urbana-Champaign, US); Bin Yu (University of
Illinois at Urbana-Champaign, US); Ruzena Bajcsy (University of
California, US)
yang.pdf
|
Tele-immersive
environments will improve the state of collaboration among distributed
participants. However, along with the promise a new set of challenges
have emerged including the real-time acquiring, streaming and rendering
of 3D scenes to convey a realistic sense of immersive spaces. Unlike 2D
video conferencing, a 3D tele-immersive environment employs multiple 3D
cameras to cover a much wider field of view, thus generating a very
large volume of data that need to be carefully coordinated, organized,
and synchronized for Internet transmission, rendering and display. This
is a very challenging task and a dynamic bandwidth management must be
in place. To achieve this goal, we propose a multi-stream adaptation
framework for bandwidth management in 3D tele-immersion. The adaptation
framework relies on the hierarchy of mechanisms and services that
exploits the semantic link of multiple 3D video streams in the
tele-immersive environment. We implement a prototype of the adaptation
framework that integrates semantically-linked stream selection, content
adaptation, and 3D data compression with user preference. The
experimental results have demonstrated that the framework shows good
quality of 3D rendering in case of sufficient bandwidth, while it
adapts 3D video streams in a coordinated and user-oriented fashion, and
yields graceful quality degradation in case of low bandwidth
availability. |
Revisiting Multimedia Streaming in Mobile Ad-hoc Networks
Peng Xue (University of Notre Dame, US); Surendar Chandra (University of Notre Dame, US)
kang.pdf
|
Mobile
ad hoc networks have been the subject of active research for a number
of years. In this paper, we investigate the feasibility of using such
networks for transmitting multimedia streams. Our target scenario uses
relatively resource rich laptops. We observed that even modest streams
place inordinate resource demands on the intermediate nodes for a wide
variety of devices and operating systems. Programmed IO operations on
the intermediate node dominates in the amount CPU consumption. This
raises an important design decision for the ad hoc community, should we
a) demand that ad hoc routers support \textit{server-like} hardware
with DMA support, b) force a global resource management scheme that
cooperatively reduces the network flow such that the intermediate nodes
would not see enough traffic to overwhelm them or c) can the local
nodes protect themselves from transit traffic without resorting to
making specific demands out of hardware. In this paper, we explore
mechanisms that can provide some control over the resource consumed
without a major revamp of existing operating systems or requiring
special hardware. We implement our mechanism in the network driver. We
present encouraging preliminary results. |
Optimizing Overlay Topology by Reducing Cut Vertices
Xiaomei
Liu (Michigan State University, US); Li Xiao (Michigan State
University, US); Andrew Kreling (Michigan State University, US); Yunhao
Liu (Hong Kong University of Science and Technolgy, CN)
lui.pdf
|
Most
overlay networks are highly decentralized and self-organized.
Therefore, cut vertices may exist in such systems due to the lack of
centralized management. A cut vertex is defined as a network node whose
removal increases the number of network components. Failure of these
nodes can break an overlay into a large number of disconnected
components and greatly downgrade the network services. In this paper,
we propose a distributed mechanism which efficiently detects the cut
vertices before they fail and neutralizes them into normal overlay
nodes with slight overhead so that the possibility of network
decomposition is minimized after they fail. We prove the correctness of
this algorithm and evaluate the performance of our design through trace
driven simulations. |
Off-line Economies for Digital Media
Darko Kirovski (Microsoft Research, US); Kamal Jain (Microsoft Research, US)
kirkovski.pdf
|
We
propose a novel platform for building off-line markets for digital
content. The key objective is to enable an arbitrary user of specific
digital content to resell it to other users in an off-line peer-to-peer
manner so that part of the proceeds goes to content's copyright holder.
Most importantly, one part of the revenues is retained by the seller as
an incentive for participating in the distributed economy. To address
this objective, a transaction is finalized and incentives distributed
to the seller on-line using a client-server architecture.
Technologically, such systems can be readily created, for example, by
adding a communication tool such as Bluetooth to a portable media
player such as the iPod. In this paper, we present a threat model for
this system and devise a novel protocol that relies on traditional
public-key cryptography to ensure secure and efficient off-line
transactions of arbitrary digital content. As a consequence, in our
system copyright holders can control the pricing and recruit a powerful
marketing and sales force with marginal investment and via various
types of incentives, users are offered the ability to sell or purchase
content they like anywhere, anytime, and to/from anyone. |
|
