6975415
Distributing Layered Encoded Video through Caches
The efficient distribution of stored information has become a major concern in the Internet which has increasingly become a vehicle for the transport of stored video. Because of the highly heterogeneous access to the Internet, researchers and engineers have argued for layered encoded video. We investigate delivering layered encoded video using caches. Based on the stochastic knapsack theory, we develop a model for the layered video caching problem. We propose heuristics to determine which videos and which layers in the videos should be cached in order to maximize the revenue from the streaming service. We evaluate the performance of our heuristics through extensive numerical experiments. We find that, for typical scenarios, the revenue increases nearly logarithmically with the cache size and linearly with the link bandwidth that connects the cache to the origin servers. We also consider service models with request queuing and negotiations about the delivered stream quality and find that both extensions provide only small revenue increases.
45021908
Video-on-Demand Over ATM: Constant-Rate Transmission and Transport
We introduce a specific transport and transmission scheme for video-on-demand (VoD) called constant-rate transmission and transport (CRTT). CRTT establishes a constant bit-rate (CBR) virtual channel between the video provider and the viewer's set-top box (STB) and then transmits cells from the provider into this channel at a constant rate. Since we assume that the number of cells in a frame is variable, CRTT requires that some number of cells be built up in an STB buffer before the commencement of playback. The build up, cell transmission rate, and the set-top memory size must be chosen so that there is no starvation or overflow at the STB. We develop fundamental relationships between these parameters for viable CRTT. We then apply the theory to an MPEG encoding of Star Wars and find that the minimal STB memory far CRTT is 23 Mbytes. We also consider varying the constant rate over a small number of intervals. We find, for example, that for Star Wars approximately 2 Mbytes of set-top memory suffices with 32 constant-rate intervals.
22940589
Asynchronous voice: a personal account
Asynchronous voice is the interactive communication process of people leaving voice messages for other people and the other people responding with their voice messages. A primitive form of asynchronous voice is a kind of telephone tag in which people use voice mail to have an interactive conversation. The author gives a personal account of his work with asynchronous voice and asynchronous learning.
1908016
Optimal peer selection for P2P downloading and streaming
In a P2P system, a client peer may select one or more server peers to download a specific file. In a P2P resource economy, the server peers charge the client for the downloading. A server peer's price would naturally depend on the specific object being downloaded, the duration of the download, and the rate at which the download is to occur. The optimal peer selection problem is to select, from the set of peers that have the desired object, the subset of peers and download rates that minimizes cost. In this paper we examine a number of natural peer selection problems for both P2P downloading and P2P streaming. For downloading, we obtain the optimal solution for minimizing the download delay subject to a budget constraint, as well as the corresponding Nash equilibrium. For the streaming problem, we obtain a solution that minimizes cost subject to continuous playback while allowing for one or more server peers to fail during the streaming process. The methodologies developed in this paper are applicable to a variety of P2P resource economy problems.
18166886
On Routing in ATM Networks
Alternative routing of calls has long been acknowledged as a means of increasing call throughput and robustness in the telephone network. Given these performance gains, it is natural to consider dynamic routing of Virtual Circuits (VCs) in Asynchronous Transfer Mode (ATM) networks. Unlike telephone networks, VCs have heterogeneous bandwidth characteristics and Quality of Service requirements that the routing algorithm must take into account in order to optimize performance. In this paper we attempt to classify ATM networks according to the network characteristics that have the greatest bearing on the performance of dynamic routing algorithms; we also discuss appropriate routing algorithms for diierent classes of ATM network. The classiication is based on the degree of heterogeneity of the sources and the degree of statistical multiplexing.
27961905
Performance evaluation of redirection schemes in content distribution networks
Content distribution on the Web is moving from an architecture where objects are placed on a single, designated server to an architecture where objects are replicated on geographically distributed servers and clients transparently access a nearby copy of an object. In this paper we study how the different redirection schemes used in modern content distribution networks affect the user-perceived performance in normal Web page viewing. Using both simulations and experiments with real Web servers we show that redirection schemes that require clients to retrieve different parts of a Web page from different servers yield sub-optional performance compared to schemes where a client accesses only one server for all the parts of a Web page. This implies that when replicating Web pages, we should treat the whole page (HTML and images) as a single entity.
9861347
Conjunctive selection conditions in main memory
We consider the fundamental operation of applying a conjunction of selection conditions to a set of records. With large main memories available cheaply, systems may choose to keep the data entirely in main memory, in order to improve query and/or update performance.The design of a data-intensive algorithm in main memory needs to take into account the architectural characteristics of modern processors, just as a disk-based method needs to consider the physical characteristics of disk devices. An important architectural feature that influences the performance of main memory algorithms is the branch misprediction penalty. We demonstrate that branch misprediction has a substantial impact on the performance of an algorithm for applying selection conditions.We describe a space of "query plans" that are logically equivalent, but differ in terms of performance due to variations in their branch prediction behavior. We propose a cost model that takes branch prediction into account, and develop a query optimization algorithm that chooses a plan with optimal estimated cost. We also develop an efficient heuristic optimization algorithm.We provide experimental results for a case study based on an event notification system. Our results show the effectiveness of the proposed optimization techniques. Our results also demonstrate that significant improvements in performance can be obtained by applying a methodology that takes branch misprediction latency into account.
9519416
Selection conditions in main memory
We consider the fundamental operation of applying a compound filtering condition to a set of records. With large main memories available cheaply, systems may choose to keep the data entirely in main memory, in order to improve query and/or update performance.The design of a data-intensive algorithm in main memory needs to take into account the architectural characteristics of modern processors, just as a disk-based method needs to consider the physical characteristics of disk devices. An important architectural feature that influences the performance of main memory algorithms is the branch misprediction penalty. We demonstrate that branch misprediction has a substantial impact on the performance of an algorithm for applying selection conditions.We describe a space of "query plans" that are logically equivalent, but differ in terms of performance due to variations in their branch prediction behavior. We propose a cost model that takes branch prediction into account, and develop a query optimization algorithm that chooses a plan with optimal estimated cost for conjunctive conditions. We also develop an efficient heuristic optimization algorithm. We also show how records can be ordered to further reduce branch misprediction effects.We provide experimental results for a case study based on an event notification system. Our results show the effectiveness of the proposed optimization techniques. Our results also demonstrate that significant improvements in performance can be obtained by applying a methodology that takes branch misprediction latency into account.
2682993
Monotonic aggregation in deductive databases
We propose a semantics for aggregates in deductive databases based on a notion of minimality. Unlike some previous approaches, we form a minimal model of a program component including aggregate operators, rather than insisting that the aggregate apply to atoms that have been fully determined, or that aggregate functions are rewritten in terms of negation. In order to guarantee the existence of such a minimal model we need to insist that the domains over which we are aggregating are complete lattices, and that the program is in a sense monotonic. Our approach generalizes previous approaches based on the well-founded semantics and various forms of stratification. We are also able to handle a large variety of monotonic (or pseudo-monotonic) aggregate functions.
2792911
The New Jersey Data Reduction Report
An arrangement is shown for controlling transmission of blocks of information to and from a plurality of major components of a digital computer system interconnected by common buses. The disclosed arrangement operates so that any component of the system may normally seize, on a nonpriority basis, one of the buses at the beginning of any time slot defined by two successive clock pulses generated by a single source and applied to all components simultaneously; however, if a special instruction is encountered during execution of a program, any component may retain a bus for more than one time slot. The disclosed arrangement also permits error checking of transmitted information from a given major component without interfering with transmission from any other major component and automatically causes retransmission of any block of information found to be improperly transmitted originally. Still further, the disclosed arrangement permits buses to be dedicated during execution of a program or, if desired, any complete major component to be replaced without affecting any other major component.
16955834
Querying Multiple Features of Groups in Relational Databases
Some aggregate and grouping queries are conceptually simple, but difficult to express in SQL. This difficulty causes both conceptual and implementation problems for the SQLbased database system. Complicated queries and views are hard to understand and maintain. Further, the code produced is sometimes unnecessarily inefficient, as we demonstrate experimentally using a commercial database system. In this paper, we examine a class of queries involving (potentially repeated) selection, grouping and aggregation over the same groups, and propose an extension of SQL syntax that allows the succinct representation of these queries. We propose a new relational algebra operation that represents several levels of aggregation over the same groups in an operand relation. We demonstrate that the extended relational operator can be evaluated using efficient algorithms. We describe a translation from the extended SQL language into our algebraic language. We have implemented a preprocessor that evaluates our extended language on top of a commercial l This research was supported by a grant from the AT&T Foundation, by a David and Lucile Packard Foundation Fellowship in Science and Engineering, by a Sloan Foundation Fellowship, by NSF grants IRI-9209029, CDA-90-24735, and by an NSF Young Investigator award. Permission to copy without fee all or part of this material is gmnted provided that the wpier are not made or distributed for direct commercial advantage, the VLDB wpyrinht notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, or to republish, requires a fee and/or special permission from the Endowment. Proceedings of the 22nd VLDB Conference Mumbai(Bombay), India, 1996 database system. We demonstrate that on a variety of examples, our implementation improves performance over standard SQL representations of the same examples by orders of magnitude.