1973175
The AURORA Gigabit Testbed
Abstract AURORA is one of five U.S. networking testbeds charged with exploring applications of, and technologies necessary for, networks operating at gigabit per second or higher bandwidths. The emphasis of the AURORA testbed, distinct from the other four testbeds, BLANCA, CASA, NECTAR and VISTANET, is research into the supporting technologies for gigabit networking. Like the other testbeds, AURORA itself is an experiment in collaboration, where government initiative (in the form of the Corporation for National Research Initiatives, which is funded by DARPA and the National Science Foundation) has spurred interaction among pre-existing centers of excellence in industry, academia, and government. AURORA has been charged with research into networking technologies that will underpin future high-speed networks. This paper provides an overview of the goals and methodologies employed in AURORA, and points to some preliminary results from our first year of research, ranging from analytic results to experimental prototype hardware. This paper enunciates our targets, which include new software architectures, network abstractions, and hardware technologies, as well as applications for our work.
18179112
Balancing performance and flexibility with hardware support for network architectures
The goals of performance and flexibility are often at odds in the design of network systems. The tension is common enough to justify an architectural solution, rather than a set of context-specific solutions. The Programmable Protocol Processing Pipeline (P4) design uses programmable hardware to selectively accelerate protocol processing functions. A set of field-programmable gate arrays (FPGAs) and an associated library of network processing modules implemented in hardware are augmented with software support for function selection and composition, and applied to processing-intensive portions of a user-programmable protocol stack. The system is sufficiently flexible to support protocol stacks that are dynamically altered in reaction to changing network conditions or user needs.The P4 can be transparently inserted into a conventional protocol architecture, such as that of TCP/IP. This experimental demonstration shows that the P4's programmability can be used to significantly improve the performance of TCP/IP under operating conditions where the protocol would perform poorly without augmentation. Generalizing from these experiments, the P4 is shown to have many applications as an open platform for implementing adaptive and programmable networks, and has illustrated new security issues that arise in FPGA-based architectures.The P4 and closely-related systems, such as network processors, are attractive architectural solutions to balancing performance and flexibility.
11110729
Active bridging
Active networks accelerate network evolution by permitting the network infrastructure to be programmable, on a per-user, per-packet, or other basis. This programmability must be balanced against the safety and security needs inherent in shared resources.This paper describes the design, implementation, and performance of a new type of network element, an Active Bridge. The active bridge can be reprogrammed "on the fly", with loadable modules called switchlets. To demonstrate the use of the active property, we incrementally extend what is initially a programmable buffered repeater with switchlets into a self-learning bridge, and then a bridge supporting spanning tree algorithms. To demonstrate the agility that active networking gives, we show how it is possible to upgrade a network from an "old" protocol to a "new" protocol on-the-fly. Moreover, we are able to take advantage of information unavailable to the implementors of either protocol to validate the new protocol and fall back to the old protocol if an error is detected. This shows that the Active Bridge can protect itself from some algorithmic failures in loadable modules.Our approach to safety and security favors static checking and prevention over dynamic checks when possible. We rely on strong type checking in the Caml language for the loadable module infrastructure, and achieve respectable performance. The prototype implementation on a Pentium-based HP Netserver LS running Linux with 100 Mbps Ethernet LANS achieves ttcp throughput of 16 Mbps between two PCs running Linux, compared with 76 Mbps unbridged. Measured frame rates are in the neighborhood of 1800 frames per second.
17924974
Towards effective practitioner evaluation: an exploration of issues relating to skills, motivation and evidence
Although academics are increasingly expected to undertake studies of their practice, particularly where this involves the use of learning technology, experience to date suggests that meeting this expectation has proved difficult. This paper attempts to explain this difficulty. After reviewing literature that provides a rationale for practitioner evaluation, the experiences of three projects (EFFECTS, ASTER and SoURCE) which attempted to draw on this process are described. Three main areas of difficulty are discussed: the skills and motivations of the academics involved, and the kinds of evidence (and its analysis) that ‘count’ for a given evaluation. This discussion leads to the identification of a number of problems that inhibit practitioner evaluation, including ambiguity in the nature and purpose of evaluation, and a general feeling that the function of evaluation has already been served through existing quality mechanisms. Finally, the possible implications are considered of some or all of the steps in the evaluation process being undertaken by an evaluator working alongside the academic.
15945659
Distributed Query Processing on the Grid
Distributed query processing (DQP) has been widely used in data intensive applications where data of relevance to users is stored in multiple locations. This paper argues: (i) that DQP can be important in the Grid, as a means of providing high-level, declarative languages for integrating data access and analysis; and (ii) that the Grid provides resource management facilities that are useful to developers of DQP systems. As well as discussing and illustrating how DQP technologies can be deployed within the Grid, the paper describes a prototype implementation of a DQP system running over Globus.
932967
Modulation and Information Hiding in Images
We use concepts from communication theory to characterize information hiding schemes: the amount of information that can be hidden, its perceptibility, and its robustness to removal can be modeled using the quantities channel capacity, signal-to-noise ratio, and jamming margin. We then introduce new information hiding schemes whose parameters can easily be adjusted to trade off capacity, imperceptibility, and robustness as required in the application. The theory indicates the most aggressive feasible parameter settings. We also introduce a technique called predistortion for increasing resistance to JPEG compression. Analogous tactics are presumably possible whenever a model of anticipated distortion is available.
16226748
Polar: an architecture for a parallel ODMG compliant object database
Object database management systems (ODBMS) are now established as the database management technology of choice for a range of challenging data intensiv e applications. Furthermore, the applications associated with object databases typically have stringen t performance requirements, and some are associated with very large data sets. Ho w ever, despite the demands made on object databases by applications, there has been surprisingly little work on parallel object databases. This paper presents the arc hitecture and some preliminary performance results for the Polar ODMG compliant parallel object database. The architecture described has been implemented in a shared-nothing environment on a network of PCs. The paper describes how OQL queries are compiled, parallelized and executed in this environment, and includes some preliminary performance results for OQL queries using the 007 benchmark.
5328327
Fault-tolerant parallel applications using queues and actions
There are many techniques supporting execution of large computations over a network of workstations (NOW) but data intensive computations are usually run on high performance parallel machines. A NOW comprising individual user's machines typically has a low performance interconnect and suffers arbitrary changes of availability. Exploiting such resources to execute data intensive computations is difficult but even in a more constrained environment there is an unfulfilled need for fault-tolerance. The structuring approach presented fulfills this need. Performance exceeding 100 Mflop/s is demonstrated for large fault-tolerant out of core examples of matrix multiplication and Cholesky factorisation using five 133 MHz Pentium compute machines.