131720
Dynamic reconfiguration of an optical interconnect
The advent of optical technology that can feasibly support extremely high bandwidth chip-to-chip communication raises a host of architectural questions in the design of digital systems. Terabit per second (and higher) bandwidths have not previously been available at the chip level. In this paper we examine the use of this optical technology in the design of a network router, a system for which previous designs have been I/O-limited at the chip level. Specifically, we examine the benefits of bandwidth reconfigurability, a capability of the proposed switch fabric, and illustrate the performance impact associated with different reconfiguration rates.
34325813
Timing Control of VLSI Based NlogN and Crossbar Networks
Two basic data flow control methods for circuit switched, pipelined networks of the general nlogn and crossbar (cb) topologies are modelled and their effects on overall data rates achievable are determined. The synchronous method uses a global clock and as network modules grow, clock skew and clock tree charge/discharge times grow resulting in lower data rates. The asynchronous method relies on local request/acknowledge signals to control data movement and hence its performance is less affected by system growth. 12 references.
5272318
On Designing Interconnection Networks for Multiprocessors
This paper considers various physical constraints which influence the design of interconnection networks used in multiprocessor systems. Design expressions are presented for implementing an N log N packet passing interconnection network composed for circuit switched crossbar chip modules. Expressions reflecting chip level and board level pin and area constraints are derived and used to determine the network delay expected at a given clock frequency. Logic and memory delay, signal path delay, clock skew and clock tree delay parameters are defined and used to determine the maximum frequency which can be obtained with a given design. An example 2048x2048 network... Read complete abstract on page 2.
18137632
Collecting Data About Logic Simulation
Design of high-performance hardware and software-based gate-switch-level logic simulators requires knowledge about the logic simulation process itself. Unfortunately, little data is publicly available concerning key aspects of this process. An example of this is the lack of published empirical measurements relating to the time distribution of events generated by such simulators. This paper presents a gate-switch-level logic simulator lsim which is oriented towards the collection of data about the simulation process. The basic components of lsim are reviewed, and its relevant data gathering facilities are discussed. An example is presented which illustrates the use of lsim in gathering data on event distributions and on communications requirements under alternative logic circuit partitionings.
206622431
Pin Limitations and Partitioning of VLSI Interconnection Networks
Multiple processor interconnection networks can be characterized as having N' inputs and N' outputs, each being B' bits wide. A major implementation constraint of large networks in the VLSI environment is the number of pins available on a chip, Np. Construction of large networks requires partitioning of the N' * N' * B' network into a collection of N * N switch modules with each input and output port being B (B ≤ B') bits wide. If each module corresponds to a single chip, then a large network can be implemented by interconnecting the chips in a particular manner. This correspondence presents a methodology for selecting the optimum values of N and B given values of N', B', Np, and the number of control lines per port. Models for both banyan and crossbar networks are developed and arrangements yielding minimum: 1) number of chips, 2) average delay through the network, and 3) product of number of chips and delay, are presented.
27473158
Interconnection Networks: Physical Design and Performance Analysis
This paper considers various physical constraints which influence the design of interconnection networks used in multiprocessor systems. Design expressions are presented for implementing an N log N packet passing interconnection network composed of circuit switched crossbar chip modules. Expressions reflecting chip level and board level pin and area constraints are derived and used to determine the network delay expected at a given clock frequency. Logic and memory delay, signal path delay, clock skew, and clock distribution delay parameters are defined and used to determine the maximum frequency which can be obtained with a given design. An example 2048 × 2048 network design is considered. This example indicates that using aggressive packaging and MOS technology, a clock frequency of about 40 Mhz is achievable. However, even at this frequency, this network would result in a one-way delay (ignoring blocking and hot spot delays) of about 1 μsec. A read operation from memory requiring a round trip would thus require about 2 μsec. This represents considerable slowdown when compared with accessing strictly local memory and appears to be a major problem in the design of network centered multiprocessor architectures.
59766135
Improving Responsiveness for Wide-Area Data Access
Improving Resp onsiveness for WideArea Data AccessLaurent AmsalegPhilipp e BonnetMichael J FranklinINRIABullUniversity of MarylandAnthonyTomasicTolga UrhanINRIAUniversity of MarylandAbstractIn a widearea environment the time rquird to obtain data from remote sources can varyunpredictably due to network congestion link failure or other problems Traditional techniquesfor query optimization and query execution do not cope wel l with such unpredictabilityThestatic nature of those techniques prevents them from adapting to remote access delays that ariseat runtime In this paper we describe two separate but relatedtechniques aimed at tackling thisproblem The rst technique cal led Query Scrambling hides relatively short intermittent delaysby dynamical ly adjusting query execution plans onthey The second technique addresses thelongerterm unavailability of data sources by al lowing the return of partial query answers whensome of the data needed to ful ly answer a query are missingIntro ductionThe continued dramatic growth in global interconnectivity via the Internet has made aroundtheclo ckondemand access to widelydistribu ted data a common exp ectation for many computer users Advances in resource discoery heterogeneous data management and semistructured data managementare providingsemanticto ols to enable the access and correlation of data from diverse widelydistributedsources A limiting factor of suchwork however is the diculty of providing resp onsive data access tousers due to the highly varying resp onsetime and availabilitycharacteristics of remote data sources ina widearea environment Data access over widearea networks inolves a large numb er of data sourcesintermediate sites and communications links all of which are vulnerable to congestion and failuresSuch problems can intro duce signicant and unpredictabledelaysin the access of information fromremote sourcesCurrent distributed query pro cessing approaches p erform p o orly in the widearea environmentThey p ermit unexp ected delays to directly increase the query resp onse time allowing query executionCopyright IEEE Personal use of this material is permitted However permission to reprintrepublish this material for advertising or promotional purposes or for creating new col lective works for resale or rdistribution to serversor lists or to reuse any copyrightedcomponent of this work in other works must be obtainedfrom the IEEEBulletin of the IEEE Computer So cietyTechnical Committee on Data EngineeringThis work was partially supp orted by the NSF under Grant IRI by Bellcore and by an IBM SharedUniversity Researchaward Laurent Amsaleg did this work while he was at the Univy of Maryland and was supp ortedin part by an INRIA Fellowship Philipp e Bonnet and AnthonyTomasic p erformed this work in the context of Dyadean RD jointventure b etween Bull and INRIA
9056980
Prefetching from a broadcast disk
Broadcast disks have been proposed as a means to efficiently deliver data to clients in "asymmetric" environments where the available bandwidth from the server to the clients greatly exceeds the bandwidth in the opposite direction. A previous study investigated the use of cost based caching to improve performance when clients access the broadcast in a demand driven manner (S. Acharya et al., 1995). Such demand driven access however, does not fully exploit the dissemination based nature of the broadcast, which is particularly conducive to client prefetching. With a broadcast disk, pages continually flow past the clients so that in contrast to traditional environments, prefetching can be performed without placing additional load on shared resources. We argue for the use of a simple prefetch heuristic called PT and show that PT balances the cache residency time of a data item with its bandwidth allocation. Because of this tradeoff, PT is very tolerant of variations in the broadcast program. We describe an implementable approximation for PT and examine its sensitivity to access probability estimation errors. The results show that the technique is effective even when the probability estimation is substantially different from the actual values.
2815522
Efficient Filtering of XML Documents for Selective Dissemination of Information
Information Dissemination applications are gaining increasing popularity due to dramatic improvements in communications bandwidth and ubiquity. The sheer volume of data available necessitates the use of selective approaches to dissemination in order to avoid overwhelming users with unnecessaryinformation. Existing mechanisms for selective dissemination typically rely on simple keyword matching or “bag of words” information retrieval techniques. The advent of XML as a standard for information exchangeand the development of query languages for XML data enables the development of more sophisticated filtering mechanisms that take structure information into account. We have developed several index organizations and search algorithms for performing efficient filtering of XML documents for large-scale information dissemination systems. In this paper we describe these techniques and examine their performance across a range of document, workload, and scale scenarios.
16056367
Performance tradeoffs for client-server query processing
The construction of high-performance database systems that combine the best aspects of the relational and object-oriented approaches requires the design of client-server architectures that can fully exploit client and server resources in a flexible manner. The two predominant paradigms for client-server query execution are data-shipping and query-shipping We first define these policies in terms of the restrictions they place on operator site selection during query optimization. We then investigate the performance tradeoffs between them for bulk query processing. While each strategy has advantages, neither one on its own is efficient across a wide range of circumstances. We describe and evaluate a more flexible policy called hybrid-shipping, which can execute queries at clients, servers, or any combination of the two. Hybrid-shipping is shown to at least match the best of the two "pure" policies, and in some situations, to perform better than both. The implementation of hybrid-shipping raises a number of difficult problems for query optimization. We describe an initial investigation into the use of a 2-step query optimization strategy as a way of addressing these issues.
1844352
Supporting aggregate queries over ad-hoc wireless sensor networks
We show how the database community's notion of a generic query interface for data aggregation can be applied to ad-hoc networks of sensor devices. As has been noted in the sensor network literature, aggregation is important as a data reduction tool; networking approaches, however, have focused on application specific solutions, whereas our in-network aggregation approach is driven by a general purpose, SQL-style interface that can execute queries over any type of sensor data while providing opportunities for significant optimization. We present a variety of techniques to improve the reliability and performance of our solution. We also show how grouped aggregates can be efficiently computed and offer a comparison to related systems and database projects.