bluuebunny/crossref_metadata_2025 huggingface dataset:
Connection caching of traffic adaptive dynamic virtual circuits
Authors: Jomer P.
Published: October 2004

Local Area Networks may be interconnected using X.25 networks. If only the OSI connectionless network protocol (CLNP) is supported on the LANs, then this same protocol must operate above X.25, using the X.25 service as a virtual data link layer. The intermediate systems in this case must support CLNP packet delivery over X.25 virtual circuits, implementing the ISO 8473/DAD1 subnetwork dependent convergence function to resolve the differences which exist between the OSI connectionless network service and the connection-oriented service offered by the X.25 subnetwork. This means that the main functionality of this subnetwork dependent convergence function is to open virtual circuits on packet demand and to close them when no traffic has occurred for a period of time. This paper describes an algorithm, which calculates such a time period by taking into account the current traffic load, the connection cost and the maintenance cost.
Descriptive names in X.500
Authors: Neufeld G. W.
Published: October 2004

This paper presents a new name form for the OSI X.500 directory system. The primary function of the directory is to provide a name-to-object look-up facility for OSI objects. The directory consists of a set of agents and a database which is distributed among the agents. The directory database is structured as a tree where each node, or entry, corresponds to an object. An entry consists of a set of attributes where one or more attributes are designated as the object name relative to the entry's immediate superior. X.500 defines a name as an ordered sequence of entry names starting from the root and terminating at the object. Therefore, a user must know the names of all the superiors of an object. In contrast, the descriptive name form is an unordered set of attributes. Only enough attributes need be given to distinguish the object from other objects. As a result, users do not have to know or understand the underlying hierarchy of the directory in order to do name look-up.
REXDC—a remote execution mechanism
Authors: Chang C.-C.
Published: October 2004

A new concept, Remote EXecution with During Construct (REXDC), is introduced. In addition to the Remote Procedure Call (RPC) functionality, it allows the client to execute cooperatively with the server during the call period. The During Construct (DC) is a unit where effective cooperation between the client and the server is provided. A mechanism is proposed to integrate the REXDC into a many-client and many-server environment. The mechanism provides a way to program different types of process to process communication and synchronization.
A top down unification of minimum cost spanning tree algorithms
Authors: Merritt S. M.
Published: October 2004

The problem of the design of communications networks has spawned the development of many of the algorithms currently used to solve the minimum cost spanning tree problem. We show that three minimum cost spanning tree algorithms, those by Kruskal, Prim, and Esau and Williams, can be derived from a single problem specification using “specification and transformation by parts,” a methodology for deriving families of algorithms. This approach is an alternative to the Kershenbaum and Chou unification of spanning tree algorithms. Whereas the Kershenbaum & Chou approach might be called bottom up, this is a top down approach which shows the original unity of the algorithms which emerges from the statement of the problem and also the essential differences. Besides pedagogical and aesthetic value, we maintain that an understanding of the algorithms from this perspective may be helpful in network design and modification.
New results on deriving protocol specifications from service specifications
Authors: Khendek F. , von Bochmann G. , Kant C.
Published: October 2004

Previous papers describe an algorithm for deriving a specification of protocol entities from a given service specification. A service specification defines a particular ordering for the execution of service primitives at the different service access points using operators for sequential, parallel and alternative executions. The derived protocol entities ensure the correct ordering by exchanging appropriate synchronization messages, between one another through the underlying communication medium.

This paper presents several new results which represent important improvements to the above protocol derivation approach. First the language restriction to finite behaviors is removed by allowing for the definition of procedures which can be called recursively. Secondly, a new derivation algorithm has been developed which is much simpler than the previous one. Third, the resulting protocol specifications are much more optimized than those obtained previously.
Group communication in multichannel networks with staircase interconnection topologies
Authors: McKinley P. K. , Liu J. W. S.
Published: October 2004

Recently, multichannel networks composed of several parallel, medium-speed channels multiplexed on a single high-speed medium have been proposed as a practical way to harness the high bandwidths of optical fibers. In order to limit the cost of network interfaces, a partially-connected multichannel network allows each node access to only a proper subset of the channels, its channel set. Staircase interconnection topologies constitute a family of partially-connected multichannel networks in which every node can still send messages directly to every other node.

Group-based computer applications composed of cooperative processing entities are proliferating. The communication among processes in group-based applications typically involves multiple destinations and is often symmetric and temporally local. In this paper, we investigate the problem of supporting group communication in staircase multichannel networks. We analyze those properties of staircase topologies that benefit temporally local multicast communication. We then develop an adaptive protocol that permits nodes to dynamically change their channel sets. These changes are based on recent network traffic history, thus enabling the topology to conform to network traffic patterns and, specifically, group locality. Analytical and simulation results are presented.
A testbed for wide area ATM research
Authors: Tnnenhouse D. L. , Leslie I. M.
Published: October 2004

Asynchronous Transfer Mode (ATM) has been advocated as the basis of multiservice telecommunications in the next century. However, the public telecommunication technology of the 1990's will be ISDN, which presents a circuit switched subscriber interface. An obvious approach to building a wide area ATM network is to build it on top of primary rate ISDN. In this paper we describe the lessons learned through the design and deployment of such a network.
An improved protocol test generation procedure based on UIOS
Authors: Chan W. Y. L. , Vuong C. T. , Otp M. R.
Published: October 2004

This paper shows the Unique Input/Output, UIO, approach and the Distinguishing Sequence, DS, approach for the conformance testing of protocol implementations do not always produce identical fault converges, contrary to a previous claim. In the UIO approach, when UIO sequences and signatures are not unique in an implementation, they may not be able to detect erroneous states in the implementation. The UIO approach is revised here with the addition of a verification procedure to ensure that the UIO sequences are all unique in an implementation. Since signatures are generally not unique, this revision requires substituting the use of a signature for a state, S, with a set of input/output sequences, IO(S,K)s, unique to S, each of which distinguishes S from at least one other state, K. Verification is then applied to the IO(S,K)s. Fault coverage in the revised UIO, UIOv, approach is better than that in the original approach. A uniqueness criterion is discussed here to capture a desirable fault coverage for finite-state machine, FSM, test sequences. This criterion ensures the detection of any faulty FSM implementation provided that its set of states does not exceed that in the specified FSM. It is shown that test sequences generated by the UIOv approach and the DS approach always satisfy the uniqueness criterion. In fact, the DS approach is a special case of the UIOv approach; however, the UIOv approach has wider applicability and is generally applicable to k-distinguishable FSMs.
Security enhancement for Optimal Strong-Password Authentication protocol
Authors: Lin Chih-Wei , Shen Jau-Ji , Hwang Min-Shiang
Published: October 2004

In 2001, Lin et al. proposed an optimal strong-password authentication protocol called the OSAP protocol. However, Chen and Ku pointed out that it is vulnerable to the stolen-verifier attack. In this paper, we shall propose an improved version of the OSAP protocol to enhance the security.
Parallizable simple authenticated key agreement protocol
Authors: Lee Sung-Woon , Kim Woo-Hun , Kim Hyun-Sung , Yoo Kee-Young
Published: October 2004

Recently, Yeh and Sun proposed a simple authenticated key agreement protocol resistant to password guessing attacks called SAKA that is simple and cost-effective. And they provided a formal proof of security to show its strength against both passive and active adversaries. Compared with the previous well-known protocols, SAKA has less number of steps and less computation cost. However, considering the total execution time, SAKA is not the most efficient method, since it does not provide parties with parallel computation. In this paper, we present parallelizable simple authenticated key agreement protocol for improving the efficiency of the SAKA while maintaining provable security.
DFTS
Authors: Wei Qingsong , Lu Xianliang , Zhou Xu
Published: October 2004

Computerized data is becoming critical to the survival of an enterprise. RAID is a popular mechanism to offer fault-tolerance storage. But RAID can not work when two more disks fail and the distance it can reach is very limited. This paper presents a novel distributed high fault-tolerance storage mechanism called DFTS. DFTS makes use of disk space of the node in distributed network to build a public storage space which users can access like local disk. File is stored in form of original file fragments and their mutual XOR verification fragments among the nodes of the network. File is available even when a part of nodes fail. DFTS realizes long-distance fault-tolerance storage. In addition, performance of the DFTS is more than an order of magnitude higher than that of single computer. The experiments in this paper show that DFTS can offer high fault-tolerance and advanced performance.
HCCM
Authors: Guangchun Luo , Jun Zhang , Xianliang Lu , Jun Lu
Published: October 2004

This paper presents a novel Hierarchical Cache Consistence Mechanism -- HCMM. HCMM is specially designed for the large scale distributed file system in WAN and can well adapt to work in WAN. HCMM uses hierarchical method to manage the consistence of caches, and can minimize the overhead of network communication and cache management. This paper also sets up a theory model to analyze the performance of HCMM. The results of theoretical analysis prove that the performance of HCMM is better than conventional cache consistence mechanism.
Towards efficient resource on-demand in Grid Computing
Authors: Yang Kun , Guo Xin , Galis Alex , Yang Bo , Liu Dayou
Published: October 2004

The essence of Grid Computing is to provide efficient Resource on Demand (RoD). This paper addresses this challenge from the perspective of network, the living platform of Grid, by providing effective Quality of Service (QoS) mechanisms (both IntServ and DiffServ) inside the Grid networking environment. Specifically, the efficiency of this QoS mechanism is maximized by policy-based management taking care of the flexible control of QoS parameters/components and active networks technology looking after the fast delivery of various QoS configurations. The first experiment exemplified the current implementation status.
An asymmetric stream communication system
Authors: Black Andrew P.
Published: October 2004

Input and output are often viewed as complementary operations, and it is certainly true that the direction of data flow during input is the reverse of that during output. However, in a conventional operating system, the direction of
control
flow is the same for both input and output: the program plays the active role, while the operating system transput primitives are always passive. Thus there are
four
primitive transput operations, not two: the corresponding pairs are passive input and active output, and active input and passive output. This paper explores the implications of this idea in the context of an object oriented operating system.

This work is supported in part by the National Science Foundation under Grant No. MCS-8004111. Computing equipment and technical support are provided in part under a cooperative research agreement with Digital Equipment Corporation.
Resource management in a decentralized system
Authors: Craft Daniel H.
Published: October 2004

The heterogeneous collection of machines constituting the Processor Bank at Cambridge represents an important set of resources which must be managed. The Resource Manager incorporates these machines into a wider view of resources in a network. It will accept existing resources and specifications for constructing others from existing ones. It will then allocate these to clients on demand, combining existing resources as necessary. Resource management in a decentralized system presents interesting problems: the resources are varied and of a multi-level nature; they are available at different locations from where they are required; the stock of available resources varies dynamically; and the underlying system is in constant flux
.
Hints for computer system design
Authors: Lampson Butler W.
Published: October 2004

Experience with the design and implementation of a number of computer systems, and study of many other systems, has led to some general hints for system design which are described here. They are illustrated by a number of examples, ranging from hardware such as the Alto and the Dorado to applications programs such as Bravo and Star.
A message system supporting fault tolerance
Authors: Borg Anita , Baumbach Jim , Glazer Sam
Published: October 2004

A simple and general design uses message-based communication to provide software tolerance of single-point hardware failures. By delivering all interprocess messages to inactive backups for both the sender and the destination, both backups are kept in a state in which they can take over for their primaries.

An implementation for the Auragen 4000 series of M68000-based systems is described. The operating system, Auros
TM
, is a distributed version of UNIX*. Major goals have been transparency of fault tolerance and efficient execution in the absence of failure.
A perspective on how ATM lost control
Authors: Crosby Simon , Rooney Sean , Isaacs Rebecca , Bos Herbert
Published: October 2004

Contrary to the initial high expectations, ATM failed to become the universal network technology covering all services and running from the desktop to the backbone. This paper tries to identify the technological problems that contributed to this failure.
The influence of ATM on operating systems
Authors: Smith Jonathan M.
Published: October 2004

The features of ATM offered many attractions to the application community, such as fine-grained multiplexing and high-throughput links. These created considerable challenges for the O.S. designer, since a small protocol data unit size (the 48 byte "cell") and link bandwidths within a (binary) order of magnitude of memory bandwidths demanded considerable rethinking of operating system structure.Using an historical and personal perspective, this paper describes two aspects of that rethinking which I participated in directly, namely, those of new event signalling and memory buffering schemes. Ideas and techniques stemming from ATM network research influenced first research operating systems and then commercial operating systems. The positive results of ATM networking, although indirect, have benefitted applications and systems far beyond the original design goals.
A taxonomy and design considerations for Internet accounting
Authors: Kouadio Michel , Pooch Udo
Published: October 2004

Economic principles are increasingly being suggested for addressing some complex issues related to distributed resource allocation for QoS (Quality of Service) enhancement. Many proposals have been put forth, including various strategies from Pricing Theory and market-based insights for security in the Internet. A central need of these endeavors lies in the design of efficient accounting architecture for collecting, storing, processing and communicating relevant technical information to parties involved in transactions. This paper proceeds to a systematic classification of the major characteristics of accounting models with the aim of highlighting important features to optimize for building effective architectures.
Efficient micro-mobility using intra-domain multicast-based mechanisms (M&M)
Authors: Helmy Ahmed , Jaseemuddin Muhammad , Bhaskara Ganesha
Published: October 2004

One very important metric in evaluation of IP mobility protocols is handover performance. Handover occurs when a mobile node changes its network point-of-attachment. If not performed efficiently, handover delays, jitters and packet loss directly impact applications and services. With the Internet growth and heterogeneity, it becomes crucial to design efficient handover protocols that are scalable, robust and incrementally deployable. Mobile IP (MIP) has been shown to exhibit poor handover performance during micro-mobility. We propose a new architecture for providing efficient and smooth handover, while being able to coexist and inter-operate with other technologies. Specifically, we propose an intra-domain multicast-based mobility architecture, where a visiting mobile is assigned a multicast address to use while moving within a domain. Efficient handover is achieved using standard multicast join/prune mechanisms.Two approaches are proposed and contrasted. The first introduces the concept of proxy-based mobility, while the other uses algorithmic mapping to obtain the multicast address of visiting mobiles. We show that the algorithmic mapping approach has several advantages over the proxy approach, and provide mechanisms to support it.Simulations used to evaluate our scheme and compare it to other micro-mobility schemes - CIP and HAWAII. The proactive handover results show that both M&M and CIP show low handoff delay and packet reordering depth as compared to HAWAII. The reason for M&M's comparable performance with CIP is that both use bi-cast in proactive handover. M&M, however, handles multiple border routers in a domain, where CIP fails. Also using a proactive path setup mechanism, we show that M&M clearly outperforms CIP in case of reactive handover.
Crossover scaling effects in aggregated TCP traffic with congestion losses
Authors: Liljenstam Michael , Ogielski Andy T.
Published: October 2004

We critically examine the claims that TCP congestion control contributes to the observed self-similar traffic rate correlations. A simulation model is designed to analyze aggregated traffic of many TCP file transfers, with network topologies large enough so that each transfer has independent packet losses due to competition with other TCP traffic. To separate the effects of session-level variability from network-level variability we examine traffic consisting of small fixed-size files, and of heavy-tailed distribution of file sizes, with small variance of inter-session periods.We find that, with increasing packet loss rate, traffic rate scaling crosses over from the regime dominated by file size distribution to another scaling regime that is independent of file sizes. That loss-dominated scaling stretches over the timescales from RTT to the longest consecutive TCP time-outs (hundreds of seconds), and is not asymptotic. Analysis at the flow level exposes the mechanism of the crossover, from scaling dominated by variability of the flow ON-periods to that dominated by variability of the OFF-periods.However, it is unlikely that TCP timeouts contribute much to observed Internet traffic correlation structure, as they would matter only if widespread congestion losses exceeding 10% dominated the typical behavior of the Internet.
Performance of multihop wireless networks
Authors: De Couto Douglas S. J. , Aguayo Daniel , Chambers Benjamin A. , Morris Robert
Published: October 2004

Existing wireless ad hoc routing protocols typically find routes with the minimum hop-count. This paper presents experimental evidence from two wireless test-beds which shows that there are usually multiple minimum hop-count paths, many of which have poor throughput. As a result, minimum-hop-count routing often chooses routes that have significantly less capacity than the best paths that exist in the network. Much of the reason for this is that many of the radio links between nodes have loss rates low enough that the routing protocol is willing to use them, but high enough that much of the capacity is consumed by retransmissions. These observations suggest that more attention be paid to link quality when choosing ad hoc routes; the paper presents measured link characteristics likely to be useful in devising a better path quality metric.
Is IP going to take over the world (of communications)?
Authors: Molinero-Fernández Pablo , McKeown Nick , Zhang Hui
Published: October 2004

While it is technically pleasing to believe that IP will dominate all forms of communication, our delight in its elegance is making us overlook its shortcomings. IP is an excellent means to exchange data, which explains its success. It remains ill suited as a means to provide many other types of service; and is too crude to form the transport infrastructure in its own right. To allow the continued success of IP, we must be open-minded to it living alongside, and co-operating with other techniques (such as circuit switching) and protocols that are optimized to different needs. In this position paper, we question some of the folklore surrounding IP and packet switching. We conclude that while packet-switched IP will continue to dominate best-effort data services at the edge of the network, the core of the network will use optical circuit switching as a platform for multiple services.
The power of epidemics
Authors: Vogels Werner , van Renesse Robbert , Birman Ken
Published: October 2004

Building very large computing systems is extremely challenging, given the lack of robust scalable communication technologies. This threatens a new generation of mission-critical but very large computing systems. Fortunately, a new generation of "gossip-based" or epidemic communication primitives can overcome a number of these scalability problems, offering robustness and reliability even in the most demanding settings. Epidemic protocols emulate the spread of an infection in a crowded population, and are both reliable and stable under forms of stress that will disable most traditional protocols. This paper describes some of the common problems that arise in scalable group communication systems and how epidemic techniques have been used to successfully address these problems.
Dimensions
Authors: Ganesan Deepak , Estrin Deborah , Heidemann John
Published: October 2004

An important class of networked systems is emerging that involve very large numbers of small, low-power, wireless devices. These systems offer the ability to sense the environment densely, offering unprecedented opportunities for many scientific disciplines to observe the physical world. In this paper, we argue that a data handling architecture for these devices should incorporate their extreme resource constraints - energy, storage and processing - and spatio-temporal interpretation of the physical world in the design, cost model, and metrics of evaluation. We describe DIMENSIONS, a system that provides a unified view of data handling in sensor networks, incorporating long-term storage, multi-resolution data access and spatio-temporal pattern mining.
Wireless sensor networks
Authors: Elson Jeremy , Römer Kay
Published: October 2004

Wireless sensor networks (WSNs) consist of large populations of wirelessly connected nodes, capable of computation, communication, and sensing. Sensor nodes cooperate in order to merge individual sensor readings into a high-level sensing result, such as integrating a time series of position measurements into a velocity estimate. The physical time of sensor readings is a key element in this process called data fusion. Hence, time synchronization is a crucial component of WSNs. We argue that time synchronization schemes developed for traditional networks such as NTP [23] are ill-suited for WSNs and suggest more appropriate approaches.
Protection
Authors: Lampson Butler W.
Published: October 2004

Abstract models are given which reflect the properties of most existing mechanisms for enforcing protection or access control, together with some possible implementations. The properties of existing systems are explicated in terms of the model and implementations.
Survey of design goals for operating systems
Authors: Abernathy David H. , Mancino John S. , Pearson Charls R. , Swiger Dona C.
Published: October 2004

The paper reports the results of a literature search on the subject "design goals for operating systems." In addition, design goals of specific operating systems are reviewed and a general set of operating system design goals is developed. Special-purpose design goals and conflicts among design goals are also discussed.
The TYPESET-10 Message Exchange Facility
Authors: Spier Michael J. , Hill Richard L. , Stein Timothy J. , Bricklin Daniel
Published: October 2004

This paper describes the design considerations which led to the successful implementation of an interprocess communication mechanism, named the Message Exchange Facility (MX). The software implemented Message Exchange Facility provides services analogous to those of the hardware bus. It is the central link that binds a collection of synergistic asynchronous processes into a single systemic entity, the Digital Equipment Corporation's TYPESET-10 computerized newspaper production system. The peculiar functional constraints and requirements -dictated by TYPESET-10's specialized runtime environment- confronted us with a very difficult, and at the same time highly challenging, design problem. In this paper, the emphasis is placed on the decision making process leading from the statement of the problem to a specific technical solution.
The GM multiple console time sharing system
Authors: Brown R. R. , Elshoff J. L. , Ward M. R.
Published: October 2004

General Motors Research Laboratories found in 1968 that no operating system, in existence or anticipated, was capable of supporting the demands of a large number of graphic terminals at a reasonable cost. Since a clear need for such a system was at hand, the Computer Science Department embarked on a project of hardware selection and software design and implementation. The total operating system is described here in five papers. They emphasize respectively l) the project background and major design principles, 2) the execution environment made available to application programs, 3) the implementation and status of privileged portions of the system, 4) the mechanism which handles interrupts and other system messages, and 5) the stand alone which performed the system initialization procedures.The resulting system had many desirable attributes, and thus convinced the designers, implementors, and users that the design as implemented was a useful and valuable one, even though rather unorthodox. The concepts embedded in the system and its components appear to be exportable to many other machine architectures, since they reflect the architecture of the host computer only in details, not in fundamental ways.One of the most important aspects of the design philosophy was that all portions of the system were designed together as mutually supportive components. This even extended to the programming language, whose execution environment was made the standard throughout the system, and was initialized for application programmers. This philosophy worked well and deserves wider attention.
Some new transitions in hierarchical level structures
Authors: Ekanadham K. , Bernstein A. J.
Published: October 2004

In the context of hierarchical level structured designs, two new level transistions are discussed. A downward transfer to a lower level of the system is introduced which involves a modified return mechanism. An upward return for exception handling using trap registers is generalized to many levels. This results in a level switch which is more flexible without much additional overhead.
Business models and market mechanisms
Authors: Palmer Jonathan , Lindemann Markus
Published: October 2004

The paper examines business models utilizing three different market mechanisms on the Internet: direct search, broker, and dealer. Utilizing capital markets and information theory to compare the business models, the research looks at specific market mechanisms instantiated in PriceScan, NetMarket, and Bottom Dollar. The web sites supporting the market structures were also evaluated on trust mechanisms, reputational ratings, information quality, availability, speed, and liquidity. Twenty standard, consumer products offered through these markets were evaluated over a three-month period examining pricing, availability, and speed of response.There were significant differences across the three models. Direct search and broker models had the highest availability and quickest response. Brokers made the greatest use of trust mechanisms. Direct search and dealers offered the greatest liquidity. Information quality was the highest in the dealer, with strong market, price movement, and product information. Lowest overall prices were consistently evident in the direct search. Allocational efficiency was difficult to determine, but an evaluation of the earlier efficiencies suggests that in situations where consistent market availability is not required, overall the direct search model is the most allocationally efficient. In situations requiring immediate market availability, the broker model appears to be the most allocationally efficient with quick response, competitive prices, and good information quality.The paper extends earlier work in business models and market efficiencies by comparing specific instantiations of the models and developing definitions for and a typology of efficiencies based on capital markets theory. In addition, the paper includes technical and qualitative analysis of Web sites supporting the business models.
E-commerce value creation and destruction
Authors: Craighead Christopher W. , Shaw Neal G.
Published: October 2004

Although researchers have proposed a number of business models for organizations to use in managing electronic commerce applications, very few of these models have been able to produce value consistently for the adopting organizations. We argue that the failure of these business models is largely due to the fact that (1) they do not consider the effects of both direct and indirect value to the firm, (2) they do not view the supply chain as a macro level entity that must be managed just as organizations are managed, and (3) they do not consider the effects of interdependencies among firms in a given supply chain.As a first step in addressing the shortcomings of existing electronic commerce business models, we propose an integrated model of electronic commerce in the supply chain based upon a resource-based view of a firm. The new business model demonstrates that information technology can be used to add value to the final consumer by adding both direct and indirect value at multiple points in a supply chain. The model is used to derive static and dynamic business rules for the management of electronic commerce in the supply chain among multiple business partners. Finally, implications of the business model for researchers and practitioners are discussed.
Farsite
Authors: Adya Atul , Bolosky William J. , Castro Miguel , Cermak Gerald , Chaiken Ronnie , Douceur John R. , Howell Jon , Lorch Jacob R. , Theimer Marvin , Wattenhofer Roger P.
Published: October 2004

Farsite is a secure, scalable file system that logically functions as a centralized file server but is physically distributed among a set of untrusted computers. Farsite provides file availability and reliability through randomized replicated storage; it ensures the secrecy of file contents with cryptographic techniques; it maintains the integrity of file and directory data with a Byzantine-fault-tolerant protocol; it is designed to be scalable by using a distributed hint mechanism and delegation certificates for pathname translations; and it achieves good performance by locally caching file data, lazily propagating file updates, and varying the duration and granularity of content leases. We report on the design of Farsite and the lessons we have learned by implementing much of that design.
Taming aggressive replication in the Pangaea wide-area file system
Authors: Saito Yasushi , Karamanolis Christos , Karlsson Magnus , Mahalingam Mallik
Published: October 2004

Pangaea is a wide-area file system that supports data sharing among a community of widely distributed users. It is built on a symmetrically decentralized infrastructure that consists of commodity computers provided by the end users. Computers act autonomously to serve data to their local users. When possible, they exchange data with nearby peers to improve the system's overall performance, availability, and network economy. This approach is realized by aggressively creating a replica of a file whenever and wherever it is accessed.This paper presents the design, implementation, and evaluation of the Pangaea file system. Pangaea offers efficient, randomized algorithms to manage highly dynamic and potentially large groups of file replicas. It applies optimistic consistency semantics to replica contents, but it also offers stronger guarantees when required by the users. The evaluation demonstrates that Pangaea outperforms existing distributed file systems in large heterogeneous environments, typical of the Internet and of large corporate intranets.
Ivy
Authors: Muthitacharoen Athicha , Morris Robert , Gil Thomer M. , Chen Benjie
Published: October 2004

Ivy is a multi-user read/write peer-to-peer file system. Ivy has no centralized or dedicated components, and it provides useful integrity properties without requiring users to fully trust either the underlying peer-to-peer storage system or the other users of the file system.An Ivy file system consists solely of a set of logs, one log per participant. Ivy stores its logs in the DHash distributed hash table. Each participant finds data by consuiting all logs, but performs modifications by appending only to its own log. This arrangement allows Ivy to maintain meta-data consistency without locking. Ivy users can choose which other logs to trust, an appropriate arrangement in a semi-open peer-to-peer system.Ivy presents applications with a conventional file system interface. When the underlying network is fully connected, Ivy provides NFS-like semantics, such as close-to-open consistency. Ivy detects conflicting modifications made during a partition, and provides relevant version information to application-specific conflict resolvers. Performance measurements on a wide-area network show that Ivy is two to three times slower than NFS.
Vertigo
Authors: Flautner Krisztián , Mudge Trevor
Published: October 2004

Combining high performance with low power consumption is becoming one of the primary objectives of processor designs. Instead of relying just on sleep mode for conserving power, an increasing number of processors take advantage of the fact that reducing the clock frequency and corresponding operating voltage of the CPU can yield quadratic decrease in energy use. However, performance reduction can only be beneficial if it is done transparently, without causing the software to miss its deadlines. In this paper, we describe the implementation and performance-setting algorithms used in Vertigo, our power management extensions for Linux. Vertigo makes its decisions automatically, without any application-specific involvement. We describe how a hierarchy of performance-setting algorithms, each specialized for different workload characteristics, can be used for controlling the processor's performance. The algorithms operate independently from one another and can be dynamically configured. As a basis for comparison with conventional algorithms, we contrast measurements made on a Transmeta Crusoe-based computer using its built-in LongRun power manager with Vertigo running on the same system. We show that unlike conventional interval-based algorithms like LongRun, Vertigo is successful at focusing in on a small range of performance levels that are sufficient to meet an application's deadlines. When playing MPEG movies, this behavior translates into a 11%--35% reduction of mean performance level over LongRun, without any negative impact on the framerate. The performance reduction can in turn yield significant power savings.
Memory resource management in VMware ESX server
Authors: Waldspurger Carl A.
Published: October 2004

VMware ESX Server is a thin software layer designed to multiplex hardware resources efficiently among virtual machines running unmodified commodity operating systems. This paper introduces several novel ESX Server mechanisms and policies for managing memory. A
ballooning
technique reclaims the pages considered least valuable by the operating system running in a virtual machine. An
idle memory tax
achieves efficient memory utilization while maintaining performance isolation guarantees.
Content-based page sharing
and
hot I/O page remapping
exploit transparent page remapping to eliminate redundancy and reduce copying overheads. These techniques are combined to efficiently support virtual machine workloads that overcommit memory.
ReVirt
Authors: Dunlap George W. , King Samuel T. , Cinar Sukru , Basrai Murtaza A. , Chen Peter M.
Published: October 2004

Current system loggers have two problems: they depend on the integrity of the operating system being logged, and they do not save sufficient information to replay and analyze attacks that include any non-deterministic events. ReVirt removes the dependency on the target operating system by moving it into a virtual machine and logging below the virtual machine. This allows ReVirt to replay the system's execution before, during, and after an intruder compromises the system, even if the intruder replaces the target operating system. ReVirt logs enough information to replay a long-term execution of the virtual machine instruction-by-instruction. This enables it to provide arbitrarily detailed observations about what transpired on the system, even in the presence of non-deterministic attacks and executions. ReVirt adds reasonable time and space overhead. Overheads due to virtualization are imperceptible for interactive use and CPU-bound workloads, and 13--58% for kernel-intensive workloads. Logging adds 0--8% overhead, and logging traffic for our workloads can be stored on a single disk for several months.
Resource overbooking and application profiling in shared hosting platforms
Authors: Urgaonkar Bhuvan , Shenoy Prashant , Roscoe Timothy
Published: October 2004

In this paper, we present techniques for provisioning CPU and network resources in shared hosting platforms running potentially antagonistic third-party applications. The primary contribution of our work is to demonstrate the feasibility and benefits of overbooking resources in shared platforms, to maximize the platform yield: the revenue generated by the available resources. We do this by first deriving an accurate estimate of application resource needs by profiling applications on dedicated nodes, and then using these profiles to guide the placement of application components onto shared nodes. By overbooking cluster resources in a controlled fashion, our platform can provide performance guarantees to applications even when overbooked, and combine these techniques with commonly used QoS resource allocation mechanisms to provide application isolation and performance guarantees at run-time. When compared to provisioning based on the worst-case, the efficiency (and consequently revenue) benefits from controlled overbooking of resources can be dramatic. Specifically, experiments on our Linux cluster implementation indicate that overbooking resources by as little as 1% can increase the utilization of the cluster by a factor of two, and a 5% overbooking yields a 300--500% improvement, while still providing useful resource guarantees to applications.
Pastiche
Authors: Cox Landon P. , Murray Christopher D. , Noble Brian D.
Published: October 2004

Backup is cumbersome and expensive. Individual users almost never back up their data, and backup is a significant cost in large organizations. This paper presents
Pastiche
, a simple and inexpensive backup system. Pastiche exploits excess disk capacity to perform peer-to-peer backup with no administrative costs. Each node minimizes storage overhead by selecting peers that share a significant amount of data. It is easy for common installations to find suitable peers, and peers with high overlap can be identified with only hundreds of bytes. Pastiche provides mechanisms for confidentiality, integrity, and detection of failed or malicious peers. A Pastiche prototype suffers only 7.4% overhead for a modified Andrew Benchmark, and restore performance is comparable to cross-machine copy.
Secure routing for structured peer-to-peer overlay networks
Authors: Castro Miguel , Druschel Peter , Ganesh Ayalvadi , Rowstron Antony , Wallach Dan S.
Published: October 2004

Structured peer-to-peer overlay networks provide a substrate for the construction of large-scale, decentralized applications, including distributed storage, group communication, and content distribution. These overlays are highly resilient; they can route messages correctly even when a large fraction of the nodes crash or the network partitions. But current overlays are not secure; even a small fraction of malicious nodes can prevent correct message delivery throughout the overlay. This problem is particularly serious in open peer-to-peer systems, where many diverse, autonomous parties without preexisting trust relationships wish to pool their resources. This paper studies attacks aimed at preventing correct message delivery in structured peer-to-peer overlays and presents defenses to these attacks. We describe and evaluate techniques that allow nodes to join the overlay, to maintain routing state, and to forward messages securely in the presence of malicious nodes.
An analysis of Internet content delivery systems
Authors: Saroiu Stefan , Gummadi Krishna P. , Dunn Richard J. , Gribble Steven D. , Levy Henry M.
Published: October 2004

In the span of only a few years, the Internet has experienced an astronomical increase in the use of specialized content delivery systems, such as content delivery networks and peer-to-peer file sharing systems. Therefore, an understanding of content delivery on the lnternet now requires a detailed understanding of how these systems are used in practice.This paper examines content delivery from the point of view of four content delivery systems: HTTP web traffic, the Akamai content delivery network, and Kazaa and Gnutella peer-to-peer file sharing traffic. We collected a trace of all incoming and outgoing network traffic at the University of Washington, a large university with over 60,000 students, faculty, and staff. From this trace, we isolated and characterized traffic belonging to each of these four delivery classes. Our results (1) quantify, the rapidly increasing importance of new content delivery systems, particularly peer-to-peer networks, (2) characterize the behavior of these systems from the perspectives of clients, objects, and servers, and (3) derive implications for caching in these systems.
The effectiveness of request redirection on CDN robustness
Authors: Wang Limin , Pai Vivek , Peterson Larry
Published: October 2004

It is becoming increasingly common to construct network services using redundant resources geographically distributed across the Internet. Content Distribution Networks are a prime example. Such systems distribute client requests to an appropriate server based on a variety of factors---e.g., server load, network proximity, cache locality--in an effort to reduce response time and increase the system capacity under load. This paper explores the design space of strategies employed to redirect requests, and defines a class of new algorithms that carefully balance load, locality, and proximity. We use large-scale detailed simulations to evaluate the various strategies. These simulations clearly demonstrate the effectiveness of our new algorithms, which yield a 60--91% improvement in system capacity when compared with the best published CDN technology, yet user-perceived response latency remains low and the system scales well with the number of servers.
The design and implementation of Zap
Authors: Osman Steven , Subhraveti Dinesh , Su Gong , Nieh Jason
Published: October 2004

We have created Zap, a novel system for transparent migration of legacy and networked applications. Zap provides a thin virtualization layer on top of the operating system that introduces pods, which are groups of processes that are provided a consistent, virtualized view of the system. This decouples processes in pods from dependencies to the host operating system and other processes on the system. By integrating Zap virtualization with a checkpoint-restart mechanism, Zap can migrate a pod of processes as a unit among machines running independent operating systems without leaving behind any residual state after migration. We have implemented a Zap prototype in Linux that supports transparent migration of unmodified applications without any kernel modifications. We demonstrate that our Linux Zap prototype can provide general-purpose process migration functionality with low overhead. Our experimental results for migrating pods used for running a standard user's X windows desktop computing environment and for running an Apache web server show that these kinds of pods can be migrated with subsecond checkpoint and restart latencies.
Security issues for wireless ATM networks
Authors: Patiyoot Danai
Published: October 2004

To be able to fulfil the need of user in wireless ATM, the system has to acquire features. One of the system features for the wireless ATM is functionality especially the security aspect. There is so far tittle, if not none, security consideration in the developing of wireless ATM standard. Therefore a wide range of features in security functions is in consideration. This paper tried to define the features of security in wireless ATM networks considering it features from existing fixed ATM network and wireless network security provided. It does not attempt to define the cryptographic system, but rather provide a template in making cryptographic systems for those required features.
The design of QoS guarantee network subsystem
Authors: Wen Jun , Lu Xianliang
Published: October 2004

The current Internet service model treats all requests equivalently, there are great need of Quality of Service guarantee for real-time traffic. The paper covers two QoS guarantee methods: Integrated Service and Differentiated Service, and discusses its interoperation problems. To estimate the efficient bandwidth of traffic flow requirement, we use Fractional Brownian Motion model to simulate the self-similar traffic. The algorithm can plenty utilize bandwidth. When combining with the user-level network processing and interoperation of Intserv and Diffserv, the new network architecture can have better QoS guarantees. The experiments prove this result.