| 1. |
- Klintskog, Erik, et al.
(författare)
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The DSS, a middleware library for efficient and transparent distribution of language entities
- 2004
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Ingår i: Proc Hawaii Int Conf Syst Sci. ; , s. 4325-4334
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Konferensbidrag (refereegranskat)abstract
- This paper describes a novel language independent model for distribution of language entities, which allows for fine-grained instrumentation of entity consistency protocols on a per-entity basis. The model is implemented as a middleware component, designed to enhance arbitrary high-level programming languages with distribution support on the language entity level. The middleware library is extendable using internal interfaces to add new protocols over three different aspects of distribution.
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| 2. |
- Krishnamurthy, Supriya, et al.
(författare)
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A statistical theory of Chord under churn
- 2005
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. ; 3640, s. 93-103
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Tidskriftsartikel (refereegranskat)abstract
- Most earlier studies of DHTs under churn have either depended on simulations as the primary investigation tool, or on establishing bounds for DHTs to function. In this paper, we present a complete analytical study of churn using a master-equation- based approach, used traditionally in non-equilibrium statistical mechanics to describe steady-state or transient phenomena. Simulations are used to verify all theoretical predictions. We demonstrate the application of our methodology to the Chord system. For any rate of churn and stabilization rates, and any system size, we accurately predict the fraction of failed or incorrect successor and finger pointers and show how we can use these quantities to predict the performance and consistency of lookups under churn. We also discuss briefly how churn may actually be of different 'types' and the implications this will have for the functioning of DHTs in general.
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| 3. |
- Klintskog, Erik, 1972-
(författare)
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Generic distribution support for programming systems
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation provides constructive proof, through the implementation of a middleware, that distribution transparency is practical, generic, and extensible. Fault tolerant distributed services can be developed by using the failure detection abilities of the middleware. By generic we mean that the middleware can be used for many different programming languages and paradigms. Distribution for each kind of language entity is done in terms of consistency protocols, which guarantee that the semantics of the entities are preserved in a distributed setting. The middleware allows new consistency protocols to be added easily. The efficiency of the middleware and the ease of integration are shown by coupling the middleware to a programming system, which encompasses the object oriented, the functional, and the concurrent-declarative programming paradigms. Our measurements show that the distribution middleware is competitive with the most popular distributed programming systems (JavaRMI, .NET, IBM CORBA).
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| 4. |
- Payberah, Amir H.
(författare)
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Distributed Optimization of P2P Media Delivery Overlays
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Media streaming over the Internet is becoming increasingly popular. Currently, most media is delivered using global content-delivery networks, providing a scalable and robust client-server model. However, content delivery infrastructures are expensive. One approach to reduce the cost of media delivery is to use peer-to-peer (P2P) overlay networks, where nodes share responsibility for delivering the media to one another. The main challenges in P2P media streaming using overlay networks include: (i) nodes should receive the stream with respect to certain timing constraints, (ii) the overlay should adapt to the changes in the network, e.g., varying bandwidth capacity and join/failure of nodes, (iii) nodes should be intentivized to contribute and share their resources, and (iv) nodes should be able to establish connectivity to the other nodes behind NATs. In this work, we meet these requirements by presenting P2P solutions for live media streaming, as well as proposing a distributed NAT traversal solution. First of all, we introduce a distributed market model to construct an approximately minimal height multiple-tree streaming overlay for content delivery, in gradienTv. In this system, we assume all the nodes are cooperative and execute the protocol. However, in reality, there may exist some opportunistic nodes, free-riders, that take advantage of the system, without contributing to content distribution. To overcome this problem, we extend our market model in Sepidar to be effective in deterring free-riders. However, gradienTv and Sepidar are tree-based solutions, which are fragile in high churn and failure scenarios. We present a solution to this problem in GLive that provides a more robust overlay by replacing the tree structure with a mesh. We show in simulation, that the mesh-based overlay outperforms the multiple-tree overlay. Moreover, we compare the performance of all our systems with the state-of-the-art NewCoolstreaming, and observe that they provide better playback continuity and lower playback latency than that of NewCoolstreaming under a variety of experimental scenarios. Although our distributed market model can be run against a random sample of nodes, we improve its convergence time by executing it against a sample of nodes taken from the Gradient overlay. The Gradient overlay organizes nodes in a topology using a local utility value at each node, such that nodes are ordered in descending utility values away from a core of the highest utility nodes. The evaluations show that the streaming overlays converge faster when our market model works on top of the Gradient overlay. We use a gossip-based peer sampling service in our streaming systems to provide each node with a small list of live nodes. However, in the Internet, where a high percentage of nodes are behind NATs, existing gossiping protocols break down. To solve this problem, we present Gozar , a NAT-friendly gossip-based peer sampling service that: (i) provides uniform random samples in the presence of NATs, and (ii) enables direct connectivity to sampled nodes using a fully distributed NAT traversal service. We compare Gozar with the state-of-the-art NAT-friendly gossip-based peer sampling service, Nylon, and show that only Gozar supports one-hop NAT traversal, and its overhead is roughly half of Nylon’s.
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| 5. |
- Payberah, Amir H., et al.
(författare)
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GLive : the Gradient overlay as a market maker for mesh-based P2P live streaming
- 2011
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Ingår i: Proceedings - 2011 10th International Symposium on Parallel and Distributed Computing, ISPDC 2011. - 9780769545400 ; , s. 153-162
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Peer-to-Peer (P2P) live video streaming over the Internet is becoming increasingly popular, but it is still plagued by problems of high playback latency and intermittent playback streams. This paper presents GLive, a distributed market-based solution that builds a mesh overlay for P2P live streaming. The mesh overlay is constructed such that (i) nodes with increasing upload bandwidth are located closer to the media source, and (ii) nodes with similar upload bandwidth become neighbours. We introduce a market-based approach that matches nodes willing and able to share the stream with one another. However, market-based approaches converge slowly on random overlay networks, and we improve the rate of convergence by adapting our market-based algorithm to exploit the clustering of nodes with similar upload bandwidths in our mesh overlay. We address the problem of free-riding through nodes preferentially uploading more of the stream to the best up loaders. We compare GLive with our previous tree-based streaming protocol, Sepidar, and New Cools treaming in simulation, and our results show significantly improved playback continuity and playback latency.
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| 6. |
- Payberah, Amir H., et al.
(författare)
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Gozar : NAT-friendly peer sampling with one-hop distributed NAT traversal
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Gossip-based peer sampling protocols have been widely used as a building block for many large-scale distributed applications. However, Network Address Translation gateways (NATs) cause most existing gossiping protocols to break down, as nodes cannot establish direct connections to nodes behind NATs (private nodes). In addition, most of the existing NAT traversal algorithms for establishing connectivity to private nodes rely on third party servers running at a well-known, public IP addresses. In this paper, we present Gozar, a gossip-based peer sampling service that: (i) provides uniform random samples in the presence of NATs, and (ii) enables direct connectivity to sampled nodes using a fully distributed NAT traversal service, where connection messages require only a single hop to connect to private nodes. We show in simulation that Gozar preserves the randomness properties of a gossip-based peer sampling service. We show the robustness of Gozar when a large fraction of nodes reside behind NATs and also in catastrophic failure scenarios. For example, if 80% of nodes are behind NATs, and 80% of the nodes fail, more than 92% of the remaining nodes stay connected. In addition, we compare Gozar with existing NAT-friendly gossip-based peer sampling services, Nylon and ARRG. We show that Gozar is the only system that supports one-hop NAT traversal, and its overhead is roughly half of Nylon's.
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| 7. |
- Payberah, Amir H., et al.
(författare)
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gradienTv : Market-Based P2P Live Media Streaming on the Gradient Overlay
- 2010
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Ingår i: 10th IFIP International Conference on Distributed Applications and Interoperable Systems (DAIS´10), LNCS. - Berlin, Heidelberg : Springer Berlin Heidelberg. ; , s. 212-225
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Konferensbidrag (refereegranskat)abstract
- This paper presents gradienTv, a distributed, market-based approach to live streaming. In gradienTv, multiple streaming trees are constructed using a market-based approach, such that nodes with increasing upload bandwidth are located closer to the media source at the roots of the trees. Market-based approaches, however, exhibit slow convergence properties on random overlay networks, so to facilitate the timely discovery of neighbours with similar upload bandwidth capacities (thus, enabling faster convergence of streaming trees), we use the gossip-generated Gradient overlay network. In the Gradient overlay, nodes are ordered by a gradient of node upload capacities and the media source is the highest point in the gradient. We compare gradienTv with state-of-the-art New-Coolstreaming in simulation, and the results show significantly improved bandwidth utilization, playback latency, playback continuity, and reduction in the average number of hops from the media source to nodes.
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| 8. |
- Payberah, Amir H., et al.
(författare)
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Sepidar : Incentivized market-based P2P live-streaming on the Gradient overlay network
- 2010
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Ingår i: Proceedings - 2010 IEEE International Symposium on Multimedia, ISM 2010. - Taichung. - 9780769542171 ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- Live streaming of video content using overlay networks has gained widespread adoption on the Internet. This paper presents Sepidar, a distributed market-based model, that builds and maintains overlay network trees, which are approximately minimal height, for delivering live media as a number of substreams. A streaming tree is constructed for each substream such that nodes that contribute higher amounts of upload bandwidth are located increasingly closer to the media source at the root of the tree. While our distributed market model can be run against a random sample of nodes, we improve its convergence time to stabilize a tree by executing against a sample of nodes that contribute similar amounts of upload bandwidth. We use the Gradient overlay network to generate samples of such nodes. We address the problem of free-riding through parent nodes auditing the behaviour of their child nodes. We evaluate Sepidar by comparing it in simulation with state-of-the-art NewCoolstreaming. Our results show significantly improved playback latency and playback continuity under churn, flash-crowd, and catastrophic failure experiment scenarios. We also show that using the Gradient improves convergence time of our distributed market model compared to a random overlay network. Finally, we show that Sepidar punishes the performance of free-riders, and that nodes are incentivized to contribute more upload bandwidth by relatively improved performance.
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| 9. |
- Roverso, Roberto, 1982-, et al.
(författare)
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MyP2PWorld : Highly Reproducible Application-level Emulation of P2P Systems
- 2008
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Ingår i: SASOW 2008. - LOS ALAMITOS : IEEE COMPUTER SOC. ; , s. 272-277
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we describe an application-level emulator for P2P systems with a special focus on high reproducibility We achieve reproduciblity by taking control over the scheduling of concurrent events from the operating system. We accomplish that for inter- and intra- peer concurrency The development of the system was driven by the need to enhance the testing process of an already-developed industrial product. Therefore, we were constrained by the architecture of the overlying application. However, we managed to provide highly transparent emulation by wrapping standard/widely-used networking and concurrency APIs. The resulting environment has proven to be useful in a production environment. At this stage, it started to be general enough to be used in the testing process of applications other than the one it was created to test.
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| 10. |
- Roverso, Roberto, 1982-, et al.
(författare)
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On The Feasibility Of Centrally-Coordinated Peer-To-Peer Live Streaming
- 2011
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Ingår i: In Proceedings of IEEE Consumer Communications and Networking Conference 2011. - 9781424487905
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Konferensbidrag (refereegranskat)abstract
- In this paper we present an exploration of central coordination as a way of managing P2P live streaming overlays. The main point is to show the elements needed to construct a system with that approach. A key elementin the feasibility of this approach is a near real-time optimization engine for peer selection. Peer organization in a way that enables high bandwidth utilization plus optimized peer selection based on multiple utility factors make it possible to achieve large source bandwidth savings and provide high quality of user experience. The benefits of our approach are also seen most when NAT constraints come into play.
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