| 1. |
- Almquist, Mathias, et al.
(författare)
-
The Prefetch Aggressiveness Tradeof in 360 degrees Video Streaming
- 2018
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Ingår i: PROCEEDINGS OF THE 9TH ACM MULTIMEDIA SYSTEMS CONFERENCE (MMSYS18). - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450351928 ; , s. 258-269
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Konferensbidrag (refereegranskat)abstract
- With 360 degrees video, only a limited fraction of the full view is displayed at each point in time. This has prompted the design of streaming delivery techniques that allow alternative playback qualities to be delivered for each candidate viewing direction. However, while prefetching based on the users expected viewing direction is best done close to playback deadlines, large buffers are needed to protect against shortfalls in future available bandwidth. This results in conflicting goals and an important prefetch aggressiveness tradeoff problem regarding how far ahead in time from the current playpoint prefetching should be done. This paper presents the first characterization of this tradeoff. The main contributions include an empirical characterization of head movement behavior based on data from viewing sessions of four different categories of 360 degrees video, an optimization-based comparison of the prefetch aggressiveness tradeoffs seen for these video categories, and a data-driven discussion of further optimizations, which include a novel system design that allows both tradeoff objectives to be targeted simultaneously. By qualitatively and quantitatively analyzing the above tradeoffs, we provide insights into how to best design tomorrows delivery systems for 360 degrees videos, allowing content providers to reduce bandwidth costs and improve users playback experiences.
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| 2. |
- Borghol, Youmna, et al.
(författare)
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Characterizing and modelling popularity of user-generated videos
- 2011
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Ingår i: Performance evaluation (Print). - : Elsevier. - 0166-5316 .- 1872-745X. ; 68:11, s. 1037-1055
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Tidskriftsartikel (refereegranskat)abstract
- This paper develops a framework for studying the popularity dynamics of user-generated videos, presents a characterization of the popularity dynamics, and proposes a model that captures the key properties of these dynamics. We illustrate the biases that may be introduced in the analysis for some choices of the sampling technique used for collecting data; however, sampling from recently-uploaded videos provides a dataset that is seemingly unbiased. Using a dataset that tracks the views to a sample of recently-uploaded YouTube videos over the first eight months of their lifetime, we study the popularity dynamics. We find that the relative popularities of the videos within our dataset are highly non-stationary, owing primarily to large differences in the required time since upload until peak popularity is finally achieved, and secondly to popularity oscillation. We propose a model that can accurately capture the popularity dynamics of collections of recently-uploaded videos as they age, including key measures such as hot set churn statistics, and the evolution of the viewing rate and total views distributions over time.
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| 3. |
- Borghol, Youmna, et al.
(författare)
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The Untold Story of the Clones: Content-agnostic Factors that Impact YouTube Video Popularity
- 2012
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Ingår i: Proc. ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD) 2012. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450314626 ; , s. 1186-1194
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Konferensbidrag (refereegranskat)abstract
- Video dissemination through sites such as YouTube can have widespread impacts on opinions, thoughts, and cultures. Not all videos will reach the same popularity and have the same impact. Popularity differences arise not only because of differences in video content, but also because of other "content-agnostic" factors. The latter factors are of considerable interest but it has been difficult to accurately study them. For example, videos uploaded by users with large social networks may tend to be more popular because they tend to have more interesting content, not because social network size has a substantial direct impact on popularity.In this paper, we develop and apply a methodology that is able to accurately assess, both qualitatively and quantitatively, the impacts of various content-agnostic factors on video popularity. When controlling for video content, we observe a strong linear "rich-get-richer" behavior, with the total number of previous views as the most important factor except for very young videos. The second most important factor is found to be video age. We analyze a number of phenomena that may contribute to rich-get-richer, including the first-mover advantage, and search bias towards popular videos. For young videos we find that factors other than the total number of previous views, such as uploader characteristics and number of keywords, become relatively more important. Our findings also confirm that inaccurate conclusions can be reached when not controlling for content.
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| 4. |
- Carlsson, Niklas, et al.
(författare)
-
Caching and optimized request routing in cloud-based content delivery systems
- 2014
-
Ingår i: Performance evaluation (Print). - : Elsevier. - 0166-5316 .- 1872-745X. ; 79, s. 38-55
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Tidskriftsartikel (refereegranskat)abstract
- Geographically distributed cloud platforms enable an attractive approach to large-scale content delivery. Storage at various sites can be dynamically acquired from (and released back to) the cloud provider so as to support content caching, according to the current demands for the content from the different geographic regions. When storage is sufficiently expensive that not all content should be cached at all sites, two issues must be addressed: how should requests for content be routed to the cloud provider sites, and what policy should be used for caching content using the elastic storage resources obtained from the cloud provider. Existing approaches are typically designed for non-elastic storage and little is known about the optimal policies when minimizing the delivery costs for distributed elastic storage.In this paper, we propose an approach in which elastic storage resources are exploited using a simple dynamic caching policy, while request routing is updated periodically according to the solution of an optimization model. Use of pull-based dynamic caching, rather than push-based placement, provides robustness to unpredicted changes in request rates. We show that this robustness is provided at low cost \textendash{} even with fixed request rates, use of the dynamic caching policy typically yields content delivery cost within 10\% of that with the optimal static placement. We compare request routing according to our optimization model to simpler baseline routing policies, and find that the baseline policies can yield greatly increased delivery cost relative to optimized routing. Finally, we present a lower-cost approximate solution algorithm for our routing optimization problem that yields content delivery cost within 2.5\% of the optimal solution.
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| 5. |
- Carlsson, Niklas, et al.
(författare)
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Content Delivery using Replicated Digital Fountains
- 2010
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Ingår i: Proc. IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS ’10). - : IEEE. - 9780769541976 ; , s. 338-348
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Konferensbidrag (refereegranskat)
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| 6. |
- Carlsson, Niklas, 1977-, et al.
(författare)
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Cross-user Similarities in Viewing Behavior for 360°Video and Caching Implications
- 2023
-
Ingår i: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP). - : ASSOC COMPUTING MACHINERY. - 1551-6857 .- 1551-6865. ; 19:5
-
Tidskriftsartikel (refereegranskat)abstract
- The demand and usage of 360°video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360°view into multiple tiles, and adapt the quality of the downloaded tiles based on the user’s expected viewing direction and bandwidth conditions. This paper presents new trace-based analysis methods that incorporate users’ viewports (the area of the full 360°view the user actually sees), a first characterization of the cross-user similarities of the users’ viewports, and a trace-based analysis of the potential bandwidth savings that caching-based techniques may offer under different conditions. Our analysis takes into account differences in the time granularity over which viewport overlaps can be beneficial for resource saving techniques, compares and contrasts differences between video categories, and accounts for uncertainties in the network conditions and the prediction of the future viewing direction when prefetching. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and inform the design of new caching system policies tailored for 360°video.
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| 7. |
- Carlsson, Niklas, et al.
(författare)
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Ephemeral Content Popularity at the Edge and Implications for On-Demand Caching
- 2017
-
Ingår i: IEEE Transactions on Parallel and Distributed Systems. - : IEEE COMPUTER SOC. - 1045-9219 .- 1558-2183. ; 28:6, s. 1621-1634
-
Tidskriftsartikel (refereegranskat)abstract
- The ephemeral content popularity seen with many content delivery applications can make indiscriminate on-demand caching in edge networks highly inefficient, since many of the content items that are added to the cache will not be requested again from that network. In this paper, we address the problem of designing and evaluating more selective edge-network caching policies. The need for such policies is demonstrated through an analysis of a dataset recording YouTube video requests from users on an edge network over a 20-month period. We then develop a novel workload modelling approach for such applications and apply it to study the performance of alternative edge caching policies, including indiscriminate caching and cache on kth request for different k. The latter policies are found able to greatly reduce the fraction of the requested items that are inserted into the cache, at the cost of only modest increases in cache miss rate. Finally, we quantify and explore the potential room for improvement from use of other possible predictors of further requests. We find that although room for substantial improvement exists when comparing performance to that of a perfect "oracle" policy, such improvements are unlikely to be achievable in practice.
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| 8. |
- Carlsson, Niklas, et al.
(författare)
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Had You Looked Where Im Looking? Cross-user Similarities in Viewing Behavior for 360 degrees Video and Caching Implications
- 2020
-
Ingår i: PROCEEDINGS OF THE ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE20). - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450369916 ; , s. 130-137
-
Konferensbidrag (refereegranskat)abstract
- The demand and usage of 360 degrees video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360 degrees view into multiple tiles, and adapt the quality of the downloaded tiles based on the users expected viewing direction and bandwidth conditions. To better understand the potential bandwidth savings that caching-based techniques may offer for this context, this paper presents the first characterization of the similarities in the viewing directions of users watching the same 360 degrees video, the overlap in viewports of these users (the area of the full 360 degrees view they actually see), and the potential cache hit rates for different video categories and network conditions. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and can inform the design of new caching system policies tailored for 360 degrees video.
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| 9. |
- Carlsson, Niklas, et al.
(författare)
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Modeling Priority-based Incentive Policies for Peer-assisted Content Delivery Systems
- 2008
-
Ingår i: NETWORKING 2008 Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 3540795480 - 9783540795483 ; , s. 421-432
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Bokkapitel (refereegranskat)abstract
- Content delivery providers can improve their service scalability and offload their servers by making use of content transfers among their clients. To provide peers with incentive to transfer data to other peers, protocols such as BitTorrent typically employ a tit-for-tat policy in which peers give upload preference to peers that provide the highest upload rate to them. However, the tit-for-tat policy does not provide any incentive for a peer to stay in the system beyond completion of its download.This paper presents a simple fixed-point analytic model of a priority-based incentive mechanism which provides peers with strong incentive to contribute upload bandwidth beyond their own download completion. Priority is obtained based on a peer's prior contribution to the system. Using a two-class model, we show that priority-based policies can significantly improve average download times, and that there exists a significant region of the parameter space in which both high-priority and low-priority peers experience improved performance compared to with the pure tit-for-tat approach. Our results are supported using event-based simulations.
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| 10. |
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| 11. |
- Carlsson, Niklas, et al.
(författare)
-
Multicast Protocols for Scalable On-demand Download
- 2006
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Ingår i: Performance evaluation (Print). - : Elsevier Science Publishers B. V.. - 0166-5316 .- 1872-745X. ; 63:9/10, s. 864-891
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Tidskriftsartikel (refereegranskat)abstract
- Previous scalable protocols for downloading large, popular files from a single server include batching and cyclic multicast. With batching, clients wait to begin receiving a requested file until the beginning of its next multicast transmission, which collectively serves all of the waiting clients that have accumulated up to that point. With cyclic multicast, the file data is cyclically transmitted on a multicast channel. Clients can begin listening to the channel at an arbitrary point in time, and continue listening until all of the file data has been received.This paper first develops lower hounds on the average and maximum client delay for completely downloading a file, as functions of the average server bandwidth used to serve requests for that file, for systems with homogeneous clients. The results show that neither cyclic multicast nor batching consistently yields performance close to optimal. New hybrid download protocols are proposed that achieve within 15% of the optimal maximum delay and 20% of the optimal average delay in homogeneous systems.For heterogeneous systems in which clients have widely varying achievable reception rates, an additional design question concerns the use of high rate transmissions, which can decrease delay for clients that can receive at such rates, in addition to low rate transmissions that can be received by all clients. A new scalable download protocol for such systems is proposed, and its performance is compared to that of alternative protocols as well as to new lower bounds on maximum client delay. The new protocol achieves within 25% of the optimal maximum client delay in all scenarios considered.
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| 12. |
- Carlsson, Niklas, et al.
(författare)
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Non-Euclidian Geographic Routing in Wireless Networks
- 2007
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Ingår i: Ad hoc networks. - : Elsevier Science Publishers B. V.. - 1570-8705 .- 1570-8713. ; 5:7, s. 1173-1193
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Tidskriftsartikel (refereegranskat)abstract
- Greedy geographic routing is attractive for large multi-hop wireless networks because of its simple and distributed operation. However, it may easily result in dead ends or hotspots when routing in a network with obstacles (regions without sufficient connectivity to forward messages). In this paper we propose a distributed routing algorithm that combines greedy geographic routing with two non-Euclidean distance metrics, chosen so as to provide load balanced routing around obstacles and hotspots. The first metric, Local Shortest Path, is used to achieve high probability of progress, while the second metric, Weighted Distance Gain, is used to select a desirable node among those that provide progress. The proposed Load Balanced Local Shortest Path (LBLSP) routing algorithm provides loop freedom, guarantees delivery when a path exists, is able to efficiently route around obstacles, and provides good load balancing.
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| 13. |
- Carlsson, Niklas, et al.
(författare)
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Optimized Adaptive Streaming of Multi-video Stream Bundles
- 2017
-
Ingår i: IEEE transactions on multimedia. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1520-9210 .- 1941-0077. ; 19:7, s. 1637-1653
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to traditional video, multi-view video streaming allows viewers to interactively switch among multiple perspectives provided by different cameras. One approach to achieve such a service is to encode the video from all of the cameras into a single stream, but this has the disadvantage that only a portion of the received video data will be used, namely that required for the selected view at each point in time. In this paper, we introduce the concept of a multi-video stream bundle that consists of multiple parallel video streams that are synchronized in time, each providing the video from a different camera capturing the same event or movie. For delivery we leverage the adaptive features and time-based chunking of HTTP-based adaptive streaming, but now employing adaptation in both content and rate. Users are able to change their viewpoint on-demand and the client player adapts the rate at which data are retrieved from each stream based on the users current view, the probabilities of switching to other views, and the users current bandwidth conditions. A crucial component of such a system is the prefetching policy. For this we present an optimization model as well as a simpler heuristic that can balance the playback quality and the probability of playback interruptions. After analytically and numerically characterizing the optimal solution, we present a prototype implementation and sample results. Our prefetching and buffer management solution is shown to provide close to seamless playback switching when there is sufficient bandwidth to prefetch the parallel streams.
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| 14. |
- Carlsson, Niklas, et al.
(författare)
-
Optimized Dynamic Cache Instantiation
- 2020
-
Ingår i: 2020 IFIP NETWORKING CONFERENCE AND WORKSHOPS (NETWORKING). - : IEEE. - 9783903176287 ; , s. 145-153
-
Konferensbidrag (refereegranskat)abstract
- By caching content at geographically distributed servers, content delivery applications can achieve scalability and reduce wide-area network traffic. However, each deployed cache has an associated cost. As the request rate from a region varies (e.g., according to a daily cycle), there may be periods when the request rate is high enough to justify this cost, and other periods when it is not. Cloud computing offers a solution to problems of this kind, by supporting the dynamic allocation and release of resources. In this paper, we analyze the potential benefits from dynamically instantiating caches using resources from cloud service providers. We develop novel analytic caching models that accommodate time-varying request rates, transient behavior as a cache fills following instantiation, and selective cache insertion policies. Using these models, within the context of a simple cost model, we then develop bounds and compare policies with optimized parameter selections to obtain insights into key cost/performance tradeoffs. We find that dynamic cache instantiation can provide substantial cost reductions, that potential reductions strongly dependent on the object popularity skew, and that selective cache insertion can be even more beneficial in this context than with conventional edge caches.
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| 15. |
- Carlsson, Niklas, 1977-, et al.
(författare)
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Optimized Dynamic Cache Instantiation and Accurate LRU Approximations under Time-varying Request Volume
- 2023
-
Ingår i: IEEE Transactions on Cloud Computing. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2168-7161 .- 2372-0018. ; 11:1, s. 779-797
-
Tidskriftsartikel (refereegranskat)abstract
- Content-delivery applications can achieve scalability and reduce wide-area network traffic using geographically distributed caches. However, each deployed cache has an associated cost, and under time-varying request rates (e.g., a daily cycle) there may be long periods when the request rate from the local region is not high enough to justify this cost. Cloud computing offers a solution to problems of this kind, by supporting dynamic allocation and release of resources. In this paper, we analyze the potential benefits from dynamically instantiating caches using resources from cloud service providers. We develop novel analytic caching models that accommodate time-varying request rates, transient behavior as a cache fills following instantiation, and selective cache insertion policies. Within the context of a simple cost model, we then develop bounds and compare policies with optimized parameter selections to obtain insights into key cost/performance tradeoffs. We find that dynamic cache instantiation can provide substantial cost reductions, that potential reductions strongly dependent on the object popularity skew, and that selective cache insertion can be even more beneficial in this context than with conventional edge caches. Finally, our contributions also include accurate and easy-to-compute approximations that are shown applicable to LRU caches under time-varying workloads.
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| 16. |
- Carlsson, Niklas, et al.
(författare)
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Optimized Periodic Broadcast of Non-linear Media
- 2008
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Ingår i: IEEE transactions on multimedia. - : IEEE. - 1520-9210 .- 1941-0077. ; 10:5, s. 871-884
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Tidskriftsartikel (refereegranskat)abstract
- Conventional video consists of a single sequence of video frames. During a client's playback period, frames are viewed sequentially from some specified starting point. The fixed frame ordering of conventional video enables efficient scheduled broadcast delivery, as well as efficient near on-demand delivery to large numbers of concurrent clients through use of periodic broadcast protocols in which the video file is segmented and transmitted on multiple channels. This paper considers the problem of devising scalable protocols for near on-demand delivery of “nonlinear” media files whose content may have a tree or graph, rather than linear, structure. Such media allows personalization of the media playback according to individual client preferences. We formulate a mathematical model for determination of the optimal periodic broadcast protocol for nonlinear media with piecewise-linear structures. Our objective function allows differing weights to be placed on the startup delays required for differing paths through the media. Studying a number of simple nonlinear structures we provide insight into the characteristics of the optimal solution. For cases in which the cost of solving the optimization model is prohibitive, we propose and evaluate an efficient approximation algorithm.
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| 17. |
- Carlsson, Niklas, et al.
(författare)
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Peer-assisted On-demand Streaming of Stored Media using BitTorrent-like Protocols
- 2007
-
Ingår i: NETWORKING 2007. Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540726050 - 3540726055 ; , s. 570-581
-
Bokkapitel (refereegranskat)abstract
- With BitTorrent-like protocols a client may download a file from a large and changing set of peers, using connections of heterogeneous and time-varying bandwidths. This flexibility is achieved by breaking the file into many small pieces, each of which may be downloaded from different peers. This paper considers an approach to peer-assisted on-demand delivery of stored media that is based on the relatively simple and flexible BitTorrent-like approach, but which is able to achieve a form of “streaming” delivery, in the sense that playback can begin well before the entire media file is received. Achieving this goal requires: (1) a piece selection strategy that effectively mediates the conflict between the goals of high piece diversity, and the in-order requirements of media file playback, and (2) an on-line rule for deciding when playback can safely commence. We present and evaluate using simulation candidate protocols including both of these components.
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| 18. |
- Carlsson, Niklas, et al.
(författare)
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Peer-assisted On-demand Video Streaming with Selfish Peers
- 2009
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Ingår i: NETWORKING 2009. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642013980 - 3642013988 ; , s. 586-599
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Bokkapitel (refereegranskat)abstract
- Systems delivering stored video content using a peer-assisted approach are able to serve large numbers of concurrent requests by utilizing upload bandwidth from their clients to assist in delivery. In systems providing download service, BitTorrent-like protocols may be used in which “tit-for-tat” policies provide incentive for clients to contribute upload bandwidth. For on-demand streaming delivery, however, in which clients begin playback well before download is complete, all prior proposed protocols rely on peers at later video play points uploading data to peers at earlier play points that do not have data to share in return. This paper considers the problem of devising peer-assisted protocols for streaming systems that, similar to download systems, provide effective “tit-for-tat” incentives for clients to contribute upload bandwidth. We propose policies that provide such incentives, while also providing short start-up delays, and delivery of (almost) all video frames by their respective playback deadlines.
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| 19. |
- Carlsson, Niklas, et al.
(författare)
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Server Selection in Large-scale Video-on-Demand Systems
- 2010
-
Ingår i: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP). - : ACM. - 1551-6857 .- 1551-6865. ; 6:1, s. 1:1-1:26
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Tidskriftsartikel (refereegranskat)abstract
- Video on demand, particularly with user-generated content, is emerging as one of the most bandwidth-intensive applications on the Internet. Owing to content control and other issues, some video-on-demand systems attempt to prevent downloading and peer-to-peer content delivery. Instead, such systems rely on server replication, such as via third-party content distribution networks, to support video streaming (or pseudostreaming) to their clients. A major issue with such systems is the cost of the required server resources. By synchronizing the video streams for clients that make closely spaced requests for the same video from the same server, server costs (such as for retrieval of the video data from disk) can be amortized over multiple requests. A fundamental trade-off then arises, however, with respect to server selection. Network delivery cost is minimized by selecting the nearest server, while server cost is minimized by directing closely spaced requests for the same video to a common server. This article compares classes of server selection policies within the context of a simple system model. We conclude that: (i) server selection using dynamic system state information (rather than only proximities and average loads) can yield large improvements in performance, (ii) deferring server selection for a request as late as possible (i.e., until just before streaming is to begin) can yield additional large improvements, and (iii) within the class of policies using dynamic state information and deferred selection, policies using only “local” (rather than global) request information are able to achieve most of the potential performance gains.
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| 20. |
- Carlsson, Niklas, et al.
(författare)
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Tradeoffs in cloud and peer-assisted content delivery systems
- 2012
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Ingår i: 2012 IEEE 12th International Conference on Peer-to-Peer Computing, P2P 2012. - : IEEE. - 9781467328623 ; , s. 249-260, s. 249-260
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Konferensbidrag (refereegranskat)abstract
- With the proliferation of cloud services, cloud-based systems can become a cost-effective means of on-demand content delivery. In order to make best use of the available cloud bandwidth and storage resources, content distributors need to have a good understanding of the tradeoffs between various system design choices. In this work we consider a peer-assisted content delivery system that aims to provide guaranteed average download rate to its customers. We show that bandwidth demand peaks for contents with moderate popularity, and identify these contents as candidates for cloud-based service. We then consider dynamic content bundling (inflation) and cross-swarm seeding, which were recently proposed to improve download performance, and evaluate their impact on the optimal choice of cloud service use. We find that much of the benefits from peer seeding can be achieved with careful torrent inflation, and that hybrid policies that combine bundling and peer seeding often reduce the delivery costs by 20% relative to only using seeding. Furthermore, all these peer-assisted policies reduce the number of files that would need to be pushed to the cloud. Finally, we show that careful system design is needed if locality is an important criterion when choosing cloud-based service provisioning.
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| 21. |
- Carlsson, Niklas, et al.
(författare)
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Using Torrent Inflation to Efficiently Serve the Long Tail in Peer-assisted Content Delivery Systems
- 2010
-
Ingår i: NETWORKING 2010. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642129629 - 3642129625 ; , s. 1-14
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Bokkapitel (refereegranskat)abstract
- A peer-assisted content delivery system uses the upload bandwidth of its clients to assist in delivery of popular content. In peer-assisted systems using a BitTorrent-like protocol, a content delivery server seeds the offered files, and active torrents form when multiple clients make closely-spaced requests for the same content. Scalability is achieved in the sense of being able to accommodate arbitrarily high request rates for individual files. Scalability with respect to the number of files, however, may be much more difficult to achieve, owing to a “long tail” of lukewarm or cold files for which the server may need to assume most or all of the delivery cost. This paper first addresses the question of how best to allocate server resources among multiple active torrents. We then propose new content delivery policies that use some of the available upload bandwidth from currently downloading clients to “inflate” torrents for files that would otherwise require substantial server bandwidth. Our performance results show that use of torrent inflation can substantially reduce download times, by more than 50% in some cases.
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| 22. |
- Carlsson, Niklas, et al.
(författare)
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Worst-case bounds and optimized cache on Mth request cache insertion policies under elastic conditions
- 2018
-
Ingår i: Performance evaluation (Print). - : ELSEVIER SCIENCE BV. - 0166-5316 .- 1872-745X. ; 127, s. 70-92
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Tidskriftsartikel (refereegranskat)abstract
- Cloud services and other shared third-party infrastructures allow individual content providers to easily scale their services based on current resource demands. In this paper, we consider an individual content provider that wants to minimize its delivery costs under the assumptions that the storage and bandwidth resources it requires are elastic, the content provider only pays for the resources that it consumes, and costs are proportional to the resource usage. Within this context, we (i) derive worst-case bounds for the optimal cost and competitive cost ratios of different classes of cache on Mth request cache insertion policies, (ii) derive explicit average cost expressions and bounds under arbitrary inter request distributions, (iii) derive explicit average cost expressions and bounds for short tailed (deterministic, Erlang, and exponential) and heavy-tailed (Pareto) inter-request distributions, and (iv) present numeric and trace-based evaluations that reveal insights into the relative cost performance of the policies. Our results show that a window-based cache on 2nd request policy using a single threshold optimized to minimize worst-case costs provides good average performance across the different distributions and the full parameter ranges of each considered distribution, making it an attractive choice for a wide range of practical conditions where request rates of individual file objects typically are not known and can change quickly. (C) 2018 Elsevier B.V. All rights reserved.
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| 23. |
- Islam, M. Aminul, et al.
(författare)
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Revisiting Popularity Characterization and Modeling for User-generated Videos
- 2013
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Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2013 IEEE 21st International Symposium. - : Institute of Electrical and Electronics Engineers (IEEE). - 9780769551029 - 9781479912094 ; , s. 350-354
-
Konferensbidrag (refereegranskat)abstract
- This paper presents new results on characterization and modeling of user-generated video popularity evolution, based on a recent complementary data collection for videos that were previously the subject of an eight month data collection campaign during 2008/09. In particular, during 2011, we collected two contiguous months of weekly view counts for videos in two separate 2008/09 datasets, namely the ``recently-uploaded'' and the ``keyword-search'' datasets. These datasets contain statistics for videos that were uploaded within 7 days of the start of data collection in 2008 and videos that were discovered using a keyword search algorithm in 2008, respectively. Our analysis shows that the average weekly view count for the recently-uploaded videos had not decreased by the time of the second measurement period, in comparison to the middle and later portions of the first measurement period. The new data is used to evaluate the accuracy of a previously proposed model for synthetic view count generation for time periods that are substantially longer than previously considered. We find that the model yielded distributions of total (lifetime) video view counts that match the empirical distributions, however, significant differences between the model and empirical data were observed with respect to other metrics. These differences appear to arise because of particular popularity characteristics that change over time rather than being week-invariant as assumed in the model.
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| 24. |
- Krishnamoorthi, Vengatanathan, 1987-, et al.
(författare)
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Bandwidth-aware Prefetching for Proactive Multi-video Preloading and Improved HAS Performance
- 2015
-
Ingår i: Proceedings of the ACM International Conference on Multimedia (ACM Multimedia). - New York, USA : Association for Computing Machinery (ACM). - 9781450334594 ; , s. 551-560
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Konferensbidrag (refereegranskat)abstract
- This paper considers the problem of providing users playing one streaming video the option of instantaneous and seamless playback of alternative videos. Recommendation systems can easily provide a list of alternative videos, but there is little research on how to best eliminate the startup time for these alternative videos. The problem is motivated by services that want to retain increasingly impatient users, who frequently watch the beginning of multiple videos, before viewing a video to the end. We present the design, implementation, and evaluation of an HTTP-based Adaptive Streaming (HAS) solution that provides careful prefetching and buffer management. We also present the design and evaluation of three fundamental policy classes that provide different tradeoffs between how aggressively new alternative videos are prefetched versus the importance of ensuring high playback quality. We show that our solution allows us to reduce the startup times of alternative videos by an order of magnitude and effectively adapt the quality such as to ensure the highest possible playback quality of the video being viewed. By improving the channel utilization we also address the discrimination problem that HAS clients often suffer from, allowing us to in some cases simultaneously improve the playback quality of the video being viewed and provide the value-added service of allowing instantaneous playback of the prefetched alternative videos.
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| 25. |
- Krishnamoorthi, Vengatanathan, 1987-, et al.
(författare)
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Empowering the creative user : personalized HTTP-based adaptive streaming of multi-path nonlinear video
- 2013
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Ingår i: FhMN '13 Proceedings of the 2013 ACM SIGCOMM workshop on Future human-centric multimedia networking. - New York, USA : Association for Computing Machinery (ACM). - 9781450321839 ; , s. 53-58
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Konferensbidrag (refereegranskat)abstract
- This paper presents the design, implementation, and validation of a novel system that supports streaming and playout of personalized, multi-path, nonlinear video. In contrast to regular video, in which the file content is played sequentially, our design allows multiple nonlinear video sequences of the underlying (linear) video to be stitched together and played in any personalized order, and clients can be provided multiple path choices. The design combines the ideas of HTTP-based adaptive streaming (HAS) and multi-path nonlinear video. Personalization of the content is achieved with the use of a customized metafile, which is downloaded separately from the underlying media and the manifest file that defines the HAS structure. An extension to the user interface allows path choices to be presented to and made by the user. Novel buffer management and prefetching policies are used to ensure seamless uninterrupted playback regardless of client path choices, even under scenarios in which clients defer their choices until the last possible moment. Our solution allows creative home users to easily create their own multi-path nonlinear video, opening the door to an endless possibility of new opportunities and media forms.
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| 26. |
- Krishnamoorthi, Vengatanathan, 1987-, et al.
(författare)
-
Empowering the Creative User : Personalized HTTP-based Adaptive Streaming of Multi-path Nonlinear Video
- 2013
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Ingår i: Computer communication review. - New York : Association for Computing Machinery (ACM). - 0146-4833 .- 1943-5819. ; 43:4, s. 591-596
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design, implementation, and validation of a novel system that supports streaming and playout of personalized, multi-path, nonlinear video. In contrast to regular video, in which the file content is played sequentially, our design allows multiple nonlinear video sequences of the underlying (linear) video to be stitched together and played in any personalized order, and clients can be provided multiple path choices. The design combines the ideas of HTTP-based adaptive streaming (HAS) and multi-path nonlinear video. Personalization of the content is achieved with the use of a customized metafile, which is downloaded separately from the underlying media and the manifest file that defines the HAS structure. An extension to the user interface allows path choices to be presented to and made by the user. Novel buffer management and prefetching policies are used to ensure seamless uninterrupted playback regardless of client path choices, even under scenarios in which clients defer their choices until the last possible moment. Our solution allows creative home users to easily create their own multi-path nonlinear video, opening the door to an endless possibility of new opportunities and media forms.
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| 27. |
- Krishnamoorthi, Vengatanathan, et al.
(författare)
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Helping Hand or Hidden Hurdle : Proxy-assisted HTTP-based Adaptive Streaming Performance
- 2013
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Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2013 IEEE 21st International Symposium. - : IEEE. - 9780769551029 - 9781479912094 ; , s. 182-191
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Konferensbidrag (refereegranskat)abstract
- HTTP-based Adaptive Streaming (HAS) has become a widely-used video delivery technology. Use of HTTP enables relatively easy firewall/NAT traversal and content caching. While caching is an important aspect of HAS, there is not much public research on the performance impact proxies and their policies have on HAS. In this paper we build an experimental framework using open source Squid proxies and the most recent Open Source Media Framework (OSMF). A range of content-aware policies can be implemented in the proxies and tested, while the player software can be instrumented to measure performance as seen at the client. Using this framework, the paper makes three main contributions. First, we present a scenario-based performance evaluation of the latest version of the OSMF player. Second, we quantify the benefits using different proxy-assisted solutions, including basic best effort policies and more advanced content quality aware prefetching policies. Finally, we present and evaluate a cooperative framework in which clients and proxies share information to improve performance. In general, the bottleneck location and network conditions play central roles in which policy choices are most advantageous, as they significantly impact the relative performance differences between policy classes. We conclude that careful design and policy selection is important when trying to enhance HAS performance using proxy assistance.
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| 28. |
- Mitra, Siddharth, et al.
(författare)
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Characterizing Web-based Video Sharing Workloads
- 2009
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Ingår i: Proc. International World Wide Web Conference (WWW ’09), Madrid, Spain, April 2009. - 9781605584874 ; , s. 1191-1192
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Konferensbidrag (refereegranskat)
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| 29. |
- Mitra, Siddharth, et al.
(författare)
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Characterizing Web-Based Video Sharing Workloads
- 2011
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Ingår i: ACM TRANSACTIONS ON THE WEB. - : ASSOC COMPUTING MACHINERY. - 1559-1131 .- 1559-114X. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Video sharing services that allow ordinary Web users to upload video clips of their choice and watch video clips uploaded by others have recently become very popular. This article identifies invariants in video sharing workloads, through comparison of the workload characteristics of four popular video sharing services. Our traces contain metadata on approximately 1.8 million videos which together have been viewed approximately 6 billion times. Using these traces, we study the similarities and differences in use of several Web 2.0 features such as ratings, comments, favorites, and propensity of uploading content. In general, we find that active contribution, such as video uploading and rating of videos, is much less prevalent than passive use. While uploaders in general are skewed with respect to the number of videos they upload, the fraction of multi-time uploaders is found to differ by a factor of two between two of the sites. The distributions of lifetime measures of video popularity are found to have heavy-tailed forms that are similar across the four sites. Finally, we consider implications for system design of the identified invariants. To gain further insight into caching in video sharing systems, and the relevance to caching of lifetime popularity measures, we gathered an additional dataset tracking views to a set of approximately 1.3 million videos from one of the services, over a twelve-week period. We find that lifetime popularity measures have some relevance for large cache (hot set) sizes (i.e., a hot set defined according to one of these measures is indeed relatively "hot"), but that this relevance substantially decreases as cache size decreases, owing to churn in video popularity.
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| 30. |
- Zhang, Song, et al.
(författare)
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Dynamic File Bundling for Large-scale Content Distribution
- 2012
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Ingår i: <em>IEEE Conference on Local Computer Networks (LCN)</em> 2012. - : IEEE. - 9781467315654 - 9781467315647 - 9781467315630 ; , s. 601-609
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Konferensbidrag (refereegranskat)abstract
- One highly-scalable approach to content delivery is to harness the upload bandwidth of the clients. Peer-assisted content delivery systems have been shown to effectively offload the servers of popular files, as the request rates of popular content enable the formation of self-sustaining torrents, where the entire content of the file is available among the peers themselves. However, for less popular files, these systems are less helpful in offloading servers. With a long tail of mildly popular content, with a high aggregate demand, a large fraction of the file requests must still be handled by servers. In this paper, we present the design, implementation, and evaluation of a dynamic file bundling system, where peers are requested to download content which they may not otherwise download in order to "inflate" the popularity of less popular files. Our system introduces the idea of a super bundle, which consists of a large catalogue of files. From this catalogue, smaller bundles, consisting of a small set of files, can dynamically be assigned to individual users. The system can dynamically adjust the number of downloaders of each file and thus enables the popularity inflation to be optimized according to current file popularities and the desired tradeoff between download times and server resource usage. The system is evaluated on PlanetLab.
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| 31. |
- Zhang, Song, et al.
(författare)
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Towards a Dynamic File Bundling System for Large-scale Content Distribution
- 2011
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Ingår i: <em>Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS 2011)</em>. - 9781457704680 ; , s. 472-474
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Konferensbidrag (refereegranskat)abstract
- Peer-assisted content delivery systems can provide scalable download service for popular files. For mildly popular content, however, these systems are less helpful in offloading servers as the request rate for less popular files may not enable formation of self-sustaining torrents (where the entire content of the file is available among the peers themselves). As there typically is a long tail of mildly popular content, with a high aggregate demand, a large fraction of the file requests must still be handled by servers, and is not off-loadable to peers. Bundling approaches have been proposed where peers are requested to download content which they may not otherwise be interested in order to ``inflate'' the popularity of less popular files. We present the design and implementation of a dynamic bundling system, in which a large number of files may be bundled to form a super bundle. From this super bundle, smaller individual bundles, consisting of a small set of files, can dynamically be assigned to individual users. Our system has the capability to dynamically adjust the number of downloaders of each file, thus allowing popularity inflation to be optimized according to current file popularities.
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