waashk/acm huggingface dataset:
real-time support in multihop wireless networks  personal communications and mobile computing will require a wireless network infrastructure which is fast deployable, possibly multihop, and capable of multimedia service support. the first infrastructure of this type was the packet radio network (prnet), developed in the 70's to address the battlefield and disaster recovery communication requirements. prnet was totally asynchronous and was based on a completely distributed architecture. it handled datagram traffic reasonably well, but did not offer efficient multimedia support. recently, under the wamis (wireless adaptive mobile information systems) and glomo arpa programs several mobile, multimedia, multihop (m3) wireless network architectures have been developed, which assume some form of synchronous, time division infrastructure. the synchronous time frame leads to efficient multimedia support implementations. however, it introduces more complexity and is less robust in the face of mobility and channel fading. in this paper, we examine the impact of synchronization on wireless m3 network performance. first, we introduce maca/pr, an asynchronous network based on the collision avoidance mac scheme employed in the ieee 802.11 standard. then, we evaluate and compare several wireless packet networks ranging from the totally asynchronous prnet to the synchronized cluster tdma network. we examine the tradeoffs between time synchronization and performance in various traffic and mobility environments.</par chunhung richard lin mario gerla
instruction issue logic for high-performance, interruptable pipelined processors  the performance of pipelined processors is severely limited by data dependencies. in order to achieve high performance, a mechanism to alleviate the effects of data dependencies must exist. if a pipelined cpu with multiple functional units is to be used in the presence of a virtual memory hierarchy, a mechanism must also exist for determining the state of the machine precisely. in this paper, we combine the issues of dependency-resolution and preciseness of state. we present a design for instruction issue logic that resolves dependencies dynamically and, at the same time, guarantees a precise state of the machine, without a significant hardware overhead. detailed simulation studies for the proposed mechanism, using the lawrence livermore loops as a benchmark, are presented.  g. s. sohi s. vajapeyam
the 'data shunt box' an easy, inexpensive way to transfer text files between computers  a simple, low-cost mechanical switch is used in transfering text files between computers of widely varying size, architecture, manufacturer, and geographic location utilizing standard serial interfaces, typically at 300-1200 baud. no special software is required since the standard utility programs of each computer are used to transmit and receive the text. the only requirement is that the effective rate of character transmission must be slow enough to allow the receiving system to process a character before the next one arrives since no hand-shaking interlock is provided. with the data shunt box, direct 'media- free' data transfer between different systems is within the budget of any user of small systems.  g. s. herman-giddens j. j. shifflette m. s. spach
striping in disk array rm2 enabling the tolerance of double disk failures  there is a growing demand in high reliability beyond what current raid can provide and there are various levels of user demand for data reliability. an efficient data placement scheme called rm2 has been proposed in \cite{park95}, which makes a disk array system tolerable against double disk failures. in this paper, we consider how to choose an optimal striping unit for rm2 particularly when no workload information is available except read/write ratio. a disk array simulator for rm2 has been developed for experimental works. it is shown that rm 2 has an optimal striping unit of two and half tracks in the case of disk read operations, and one third of a single track if any disk write operations are involved.  chan-ik park tae- young choe
loss probability calculations and asymptotic analysis for finite buffer multiplexers in this paper, we propose an approximation for the loss probability, _pl_ (_x_), in a finite buffer system with buffer size _x_. our study is motivated by the case of a high-speed network where a large number of sources are expected to be multiplexed. hence, by appealing to _central limit theorem_ type of arguments, we model the input process as a general gaussian process. our result is obtained by making a simple mapping from the tail probability in an infinite buffer system to the loss probability in a finite buffer system. we also provide a strong asymptotic relationship between our approximation and the actual loss probability for a fairly large class of gaussian input processes. we derive some interesting asymptotic properties of our approximation and illustrate its effectiveness via a detailed numerical investigation. han s. kim ness b. shroff
performance estimation of embedded software with instruction cache modeling  embedded systems generally interact in some way with the outside world. this may involve measuring sensors and controlling actuators, communicating with other systems, or interacting with users. these functions impose real-time constraints on system design. verification of these specifications requires computing an upper bound on the worst-case execution time (wcet) of a hardware/software system. furthermore, it is critical to derive a tight upper bound on wcet in order to make efficient use of system resources.  the problem of bounding wcet is particularly difficult on modern processors. these processors use cache-based memory systems that vary memory access time based on the dynamic memory access pattern of the program. this must be accurately modeled in order to tightly bound wcet. several analysis methods have been proposed to bound wcet on processors with instruction caches. existing approaches either search all possible program paths, an intractable problem, or they use highly pessimistic assumptions to limit the search space. in this paper we present a more effective method for modeling instruction cache activity and computing a tight bound on wcet. the method uses an integer linear programming formulation and does not require explicit enumeration of program paths. the method is implemented in the program cinderella and we present some experimental results of this implementation.  yau-tsun steven li sharad malik andrew wolfe
distributed priority algorithms under one-bit-delay constraint  the paper deals with the issue of station delay in token-ring networks. it explains why one-bit-delay is the minimum possible delay at every station and shows that the station delay depends on the distributed computations performed in the ring. then, the paper introduces the distributed priority mechanism for token-rings, as approved by the ieee-802.5 standard. this mechanism attaches to the token, that circulates around the ring and controls the access to the shared medium, a priority field p and a reservation field r. these two fields work together in an attempt to match the service priority of the ring to the highest priority message that is waiting to be sent.  it is shown that due to the computation restrictions imposed by the one-bit- delay requirements, this priority mechanism has a grave deficiency as follows. when the token priority is higher than the maximum reservation (p > r), the token should make up to p round-trips, where p is the number of priority levels, before p is reduced to r. during this time period, no station may seize the token and send a message. this leads to loss of bandwidth.  the paper presents a new priority mechanism that retains the desired properties of the standard. however, in the new protocol when p > r holds, p is reduced to r in at most 1 round-trip rather than in up to p round-trips.  reuven cohen adrian segall
comparative performance of circuit-switched networks based on blocking probability  a class of dynamic parallel processor interconnection networks, called circuit-switched networks, are composed of layers of small crossbar elements. although such networks provide full connectivity, they are often called blocking networks, since contentions for network links sometimes block message pathways. the results from a study are reported in which the goal was to determine the effect of variations in a network's topology to aid in the selection of more optimal architectures. three approaches were used in the study to determine the relative blocking performance of networks based on topology.  several popular topologies were analyzed by these approaches with respect to availability and probability of blocking. a discussion of the results provides insight into the design of networks containing large numbers of computer nodes by showing why some types of topologies produce more efficient networks than do others.  c. hein
hardware/software tradeoffs for increased performance  most new computer architectures are concerned with maximizing performance by providing suitable instruction sets for compiled code and providing support for systems functions. we argue that the most effective design methodology must make simultaneous tradeoffs across all three areas: hardware, software support, and systems support. recent trends lean towards extensive hardware support for both the compiler and operating systems software. however, consideration of all possible design tradeoffs may often lead to less hardware support. several examples of this approach are presented, including: omission of condition codes, word-addressed machines, and imposing pipeline interlocks in software. the specifics and performance of these approaches are examined with respect to the mips processor.  john hennessy norman jouppi forest baskett thomas gross john gill
impulse: a high performance processing unit for multiprocessors for scientific calculation  in this paper, we propose a high performance processing unit for multiprocessor systems for scientific calculations. this processing unit is called impulse. impulse is equipped with a hardware process control mechanism, and a powerful floating point processor and its controller.  the process control method is based on the concurrent process model called the nc model. in the nc model, the processes and their communicating channels are static, and it is relatively easy to implement the interprocess communication server and process scheduler in hardware according to this model.  to enhance the system performance, impulse is composed of three parts, the task engine, ipc engine, and fpp engine. from the results of simulations, it appears that the ipc engine provides efficient process control even if the granularity of the processes is very fine.  t. boku s. nomura h. amano
providing reliable and fault tolerant broadcast delivery in mobile ad-hoc networks  mobile ad-hoc networks are making a new class of mobile applications feasible. they benefit from the fast deployment and reconfiguration of the networks, are mainly characterized by the need to support many-to-many interaction schema within groups of cooperating mobile hosts and are likely to use replication of data objects to achieve performances and high data availability. this strong group orientation requires specialized solutions that combine adaptation to the fully mobile environment and provide the adequate level of fault tolerance. in this paper, we present the reliable broadcast protocol that has been purposely designed for mobile ad-hoc networks. the reliable broadcast service ensures that all the hosts in the network deliver the same set of messages to the upper layer. it represents the building block to obtain higher broadcast and multicast services with stronger guarantees and is an efficient and reliable alternative to flooding. the protocol is constructed on top of the wireless mac protocol, which in turn sits over the clustering protocol. it provides an exactly once message delivery semantics and tolerates communication failures and host mobility. temporary disconnections and network partitions are also tolerated under the assumption that they are eventually repaired, as specified by a liveness property. the termination of the protocol is proved and complexity and performance analyses are also provided.  elena pagani
scalable qos provision through buffer management in recent years, a number of link scheduling algorithms have been proposed that greatly improve upon traditional fifo scheduling in being able to assure rate and delay bounds for individual sessions. however, they cannot be easily deployed in a backbone environment with thousands of sessions, as their complexity increases with the number of sessions. in this paper, we propose and analyze an approach that uses a simple buffer management scheme to provide rate guarantees to individual flows (or to a set of flows) multiplexed into a common fifo queue. we establish the buffer allocation requirements to achieve these rate guarantees and study the trade-off between the achievable link utilization and the buffer size required with the proposed scheme. the aspect of fair access to excess bandwidth is also addressed, and its mapping onto a buffer allocation rule is investigated. numerical examples are provided that illustrate the performance of the proposed schemes. finally, a scalable architecture for qos provisioning is presented that integrates the proposed buffer management scheme with wfq scheduling that uses a small number of queues. r. guerin s. kamat v. peris r. rajan
architecture and experimental framework for supporting qos in wireless networks using differentiated services  this paper describes the design an implementation of an enhanced differentiated services (diffserv) architectural framework for providing quality of service (qos) in wireless networks. the diffserv architecture has been recently proposed to compliment the integrated services (intserv) model for providing qos in the wired internet. the paper studies whether diffserv framework takes into consideration several factors, including signaling requirements, mobility, losses, lower wireless bandwidth and battery power constraints. it identifies the need for supporting signaling and mobility in wireless networks. the framework and mechanisms have been implemented in the wireless testbed at washington state university. experimental results from this testbed show the validity of the proposed diffserv model and also provide performance analyses. the framework is also designed to be extensible so that other researchers may use our implementation as a foundation for implementing other wireless network algorithms and mechanisms.  indu mahadevan krishna m. sivalingam
tree lans with collision avoidance: protocol, switch architecture, and simulated performance  packet collisions and their resolution create a performance bottleneck in random access lans. a hardware solution to this problem is to use collision avoidance switches. these switches allow the implementation of random access protocols without the penalty of collisions among packets. we describe the designs of some tree lans that use collision avoidance switches. the collision avoidance lans we describe are broadcast star and camb tree (collision avoidance multiple broadcast tree). we next present a possible implementation of a collision avoidance switch using currently available photonic devices. finally, we show the performance of broadcast star and camb tree networks using simulations.  t. suda s. morris t. nguyen
exploiting spatial locality in data caches using spatial footprints modern cache designs exploit spatial locality by fetching large blocks of data called cache lines on a cache miss. subsequent references to words within the same cache line result in cache hits. although this approach benefits from spatial locality, less than half of the data brought into the cache gets used before eviction. the unused portion of the cache line negatively impacts performance by wasting bandwidth and polluting the cache by replacing potentially useful data that would otherwise remain in the cache.this paper describes an alternative approach to exploit spatial locality available in data caches. on a cache miss, our mechanism, called spatial footprint predictor (sfp), predicts which portions of a cache block will get used before getting evicted. the high accuracy of the predictor allows us to exploit spatial locality exhibited in larger blocks of data yielding better miss ratios without significantly impacting the memory access latencies. our evaluation of this mechanism shows that the miss rate of the cache is improved, on average, by 18% in addition to a significant reduction in the bandwidth requirement. sanjeev kumar christopher wilkerson
a microcode-based environment for noninvasive performance analysis  we have developed an environment which allows us to collect data for performance analysis by modifying the microcode of a vax 8600. this use of microprogramming permits data to be collected with minimal system perturbation (i.e. the data is almost as good as that obtained with a hardware monitor) but at the cost and with the ease of use of a software simulator. in this paper we describe the environment that we have developed and present two examples of its use. the first example, procedure call instrumentation, illustrates a technique for gathering data on how certain architectural features are used. the second example, instruction tracing, illustrates a technique for collecting data that can then be used in trace---driven simulation.  s. w. melvin y. n. patt
a comparison of priority-based decentralized load balancing policies  load balancing policies in distributed systems divide jobs into two classes; those processed at their of origination (local jobs) and those processed at some other site in the system after being transfered through a communication network (remote jobs). this paper considers a class of decentralized load balancing policies that use a threshold on the local job queue length at each host in making decisions for remote processing. they differ from each other according to how they assign priorities to each of these job classes, ranging from one providing favorable treatment to local jobs to one providing favorable treatment to remote jobs. under each policy, the optimal load balancing problem is formulated as an optimization problem with respect to the threshold parameter. the optimal threshold is obtained numerically using matrix-geometric formulation and an iteration method. last, we consider the effects that the job arrival process can have on performance. one expects that load balancing for systems operating in an environment of bursty job arrivals should be more beneficial than for an environment with random job arrivals. this fact is observed through numerical examples.  kyoo jeong lee don towsley
m-udp: udp for mobile cellular networks in this paper we present our implementation of a modified udp protocol appropriate for the mobile networking environment. our protocol, like udp, does not guarantee reliable delivery of datagrams. however, unlike udp, it does ensure that the number of lost datagrams is kept small. in this paper we discuss our implementation of m-udp (in netbsd) and compare its performance against that of udp in an experimental mobile network that is currently under development at the university of south carolina. kevin brown suresh singh
signature caching techniques for information filtering in mobile enviroments  this paper discusses signature caching strategies to reduce power consumption for wireless broadcast and filtering services. the two-level signature scheme is used for indexing the information frames. a signature is considered as the basic caching entity in this paper. four caching policies are compared in terms of tune-in time and access time. with reasonable access time delay, all of the caching policies reduce the tune-in time for the two- level signature scheme. moreover, two cache replacement policies are presented and compared by simulation. the result shows that, when the cache size is small, caching only the integrated signatures is recommended. when the size of cache is greater than that of the integrated signatures, caching both of the integrated and simple signatures is better.  wang-chien lee dik lun lee
high-speed local area networks and their performance: a survey  at high data transmission rates, the packet transmission time of a local area network (lan) could become comparable to or less than the medium propagation delay. the performance of many lan schemes degrades rapidly when the packet transmission time becomes small comparative to the medium propagation delay. this paper introduces lans and discusses the performance degradation of lans at high speeds. it surveys recently proposed lan schemes designed to operate at high data rates, including their performance characteristics desirable in lan medium access protocols are identified and discussed. the paper serves as a tutorial for readers less familiar with local computer communication networks. it also serves as a survey of the state-of-the-art lans.  bandula w. abeysundara ahmed e. kamal
a small scale multi-microprocessor network controller (abstract only)  the purpose of this project has been to develop a general purpose network controller for use in a microcomputer laboratory situation. the system uses a cp/m based system as a cross assembler for a variety of microcomputers, i.e. 8085, 8086, 6802, 68000, z80, etc. the developed code is prefaced with a packet of information specifying which microcomputer the code is to be sent to. all of the above mentioned microcomputers are connected to the network controller and the developed code is routed to the specified microcomputer. the system also allows the transmission of code from the microcomputer back to the cp/m system for storage.  kenneth cooper tim kerlin
comparison of raw and internet protocols in a hippi/atm/sonet based gigabit network we compare implementation of raw and internet protocols (tcp, udp) on a programmable hippi host-interface called the network interface unit. the network interface unit connects pixel-planes 5, a message-based graphics multicomputer, to a wide area gigabit network called vistanet. the bisdn network consists of a sonet cross-connect switch and an atm switch. we discuss the tradeoffs between protocols for our target application and present a comparison of end-to-end throughput based on empirical measurements. raj k. singh stephen g. tell shaun j. bharrat
blue: an alternative approach to active queue management  this paper exposes an inherent weakness in current active queue manage ment techniques such asredin that they rely on queue lengths to indicate the severity of congestion. in light of this observation, a fundamentally different active queue management algorithm calledblueis proposed.blueuses packet loss and link utilization to manage congestion. using simulation and controlled experiments,blueis shown to significantly outperformredin providing lower packet loss rates and smaller queuing delays to networked applications such as interactive audio and video.  wu-chang feng dilip kandlur debanjan saha kang g. shin