Buffer Management

In this paper, we present an approach to construct a built-in block-based hierarchical index structures, like Rtree, to organize data sets in one, two, or higher dimensional space and improve the query performance towards the common query types (e.g., point query, range query) on Hadoop distributed file system (HDFS). The query response time for data sets that are stored in HDFS can be significantly reduced by avoiding exhaustive search on the corresponding data sets in the presence of index structures. The basic idea is to adopt the conventional hierarchical structure to HDFS, and several issues, including index organization, index node size, buffer management, and data transfer protocol, are considered to reduce the query response time and data transfer overhead through network. Experimental evaluation demonstrates that the built-in index structure can efficiently improve query performance, and serve as cornerstones for structured or semistructured data management.

The lack of proper project planning is often cited as one of the main reasons why projects fail to be completed in time and within budget. In this paper we identify and illuminate several possible misconceptions that go round in project management periodicals and in the mindset of practicing project managers and that may hamper successful project planning. The misconceptions relate to the role of the critical path, the critical sequence (critical chain), active schedules, and the insertion of buffers in the baseline schedule as a protective mechanism against schedule distortions during project execution. The possible fallacies are illustrated using example schedules developed for an illustrative project.

The commercial deployment of LTE Release 8 is gaining significant momentum all over the globe, and LTE is evolving to LTE-Advanced which offers various new features to meet or exceed IMT-Advanced requirements. Since LTE-Advanced targets ambitious spectral efficiency and peak throughput, it poses tremendous system design challenges to operators and manufacturers, especially for mobile terminals. This article discusses modem design issues related to carrier aggregation, enhanced ICIC for HetNet, detection of eight layer transmission, reference signals for enhanced multi-antenna support, and HARQ buffer management. We provide an overview of technical challenges and sketch the perspectives for tackling them to exploit the full benefits of LTE-Advanced system.

H.264/MPEG-4 AVC standard appears highly competitive due to its high efficiency, flexibility and error resilience. In order to maintain universal multimedia access, statistical multiplexing, or adaptive video content delivery, etc., it induces an immense demand for converting a large volume of existing multimedia content from other formats into the H.264/AVC format and vice versa. In this work, we study the remultiplexing and resynchronization issue within system coding after transcoding, aiming to sustain the management and time information destroyed in transcoding and enable synchronized decoding of decoder buffers over a wide range of retrieval or receipt conditions. Given the common intention of multiplexing and synchronization mechanism in system coding of different standards, this paper takes the most widely used MPEG-2 transport stream (TS) as an example, and presents a software system and the key technologies to solve the time stamp mapping and relevant buffer management. The solution reuses previous information contained in the input streams to remultiplex and resynchronize the output information with the regulatory coding and composition structure. Experimental results showed that our solutions efficiently preserve the performance in multimedia presentation.

Delay Tolerant Networks (DTNs) uses the store-carry-forward scheme for the delivery of the messages, with this way data transmission can be successfully done despite of the absence of continuous end-to-end paths. The opportunities of message forwarding in such types of networks usually are limited due to the absence of contemporaneous paths. In such networks, the "store-carryforward" methodology is used for the transmission of the messages to be delivered to their intend destinations in a hop by hop manner. It arises many problems like how to schedule the messages, how to drop the messages in the buffer due to the impulsive nature of the nodes. It also arises many challengeable situations like short contact durations between the two nodes, limited storage capacity of nodes and so on. This paper evaluates the performance of MOFO buffer management technique with three routing protocols i.e. Epidemic, Prophet and MaxProp under variable message buffer sizes (5MB to 40MB). Such evaluation can improve the performance of the opportunistic networks by reducing the overhead ratio, enhancing the delivery rate, minimizing latency average and hop count average in a certain degree. So four performance evaluation metrics namely delivery probability, latency average, overhead ratio and hop count average are used in this study. This study uses ONE (Opportunistic Network Environment) simulator for the performance evaluation of the MOFO buffer management technique and routing protocols. The evaluation results shows that the performance of different protocols can benefit to optimizing the performance of delay tolerant networks in terms of delivery probability, Latency average, Overhead ratio and Hop count average of messages with the increase in message buffer size. Finally, this study suggested that which routing protocol is most suitable with MOFO buffer management technique.

To appear in Information Systems real-time database system is a database system in which transactions have explicit timing constraints such as deadlines. Apart from satisfying the database consistency constraints, transaction executions must also satisfy these timing constraints. The goal of transaction and query processing in real-time databases is to maximise the number of successful transactions in the system. This paper reports on the design, development and performance evaluation of RT-Genesis, a real-time database management system resulting from modifying an existing commercial DBMS, Genesis. RT-Genesis is a relational database management system that accommodates SQL queries and transactions having time constraints. It features time-cognizant algorithms for scheduling, concurrency control and bu er management. The system has been tested and the performance of the di erent algorithms compared in isolation as well as in combination with di erent classes of SQL workloads. In addition, a two-phased approach to transaction execution has also been implemented with the goal of exploiting access invariance to improve predictability.

In this paper, we present a survey on management mechanisms used for ensuring the Quality-of-Services for Voice-over-IP applications. We first address the motivations of QoS management for VoIP. We then partition the system into two management planes: data plane and control plane, and describe mechanisms in each plane respectively. In data plane, we cover several important techniques including packet classifier, buffer management, scheduling, loss recovery, and error concealment. In control plane, we describe admission control, resource provisioning, traffic engineering, and connection management etc. As we will see, admission control plays a critical role in QoS for VoIP. Thus, we will discuss methodologies used in admission control in detail. Specifically, we examine parameter-based and measurement-based admission control algorithms, and their use in VoIP. Finally, we discuss limitations of current technologies and future research issues in providing QoS to VoIP applications.

This paper deals with improving the lead-time performance of a small packaging manufacturer in the Netherlands that had already implemented several facets of Theory of Constraints (TOC) in 1997. Since then, delivery reliability and profits have increased and lead-times reduced substantially. In an attempt to achieve further lead-time improvements in 2001, the firm recently encountered some limitations of its partial TOC implementation. In this paper we focus on the modifications of its order acceptance and buffer management system that were necessary in order to obtain the desired lead-time reduction. We describe how Workload Control principles were introduced to improve the buffering approach and planning procedures the firm had been using since 1997. It shows that Workload Control provides effective tools that can be used in combination with the Drum-Buffer-Rope mechanism in order to balance the flow of work to the production floor.

State-of-the-art network technology has evolved to 10Gbps. However, TCP's high processing overhead and redundant data copies remain a major bottleneck for applications to fully benefit from such high speed technology. Remote Direct Memory Access (RDMA), as an emerging communication protocol, provides an opportunity for efficient storage system design by virtue of RDMA's semantics. Although RDMA based designs have been proposed to improve network file I/O protocols in several previous works, its benefit for cluster file system block I/O is not clear yet.

Asymmetric Digital Subscriber Line (ADSL) is an Internet access technology over copper wires which promises significant bandwidth compared to current modem or ISDN technology. However, the TCP/IP performance over ADSL is significantly diminished due to the effects of asymmetry. We introduce a new operational model called the "AMP model" which, with an understanding of TCP dynamics and buffer management techniques explains the performance effects seen. We apply this model to guide design improvements in buffer management (ack-regulation) and scheduling schemes to achieve performance improvements of an order of magnitude or more. The improvements observed are better than those proposed in earlier literature. General conference topics: Cable-Based Delivery & Access Systems, Quality of Service. Symposium: Global Internet 2000 (GI2000)

This paper concerns the mathematical formulation and optimal solutions for the Flexible Manufacturing Systems Scheduling Problem (FMSSP) with one vehicle. This linear formulation differs from the previously published ones as it takes into account the maximum number of jobs allowed in the system, limited input/output buffer capacities, empty vehicle trips and no-move-ahead trips simultaneously. Our objective is to propose optimal solutions for small and medium-sized instances and to examine a number of commonly used assumptions and heuristics. Computational experiments are carried out on instances adapted from Bilge and Ulusoy [Bilge, Ü., Ulusoy, G., 1995. A time window approach to simultaneous scheduling of machines and material handling system in an FMS. Operations Research 43, 1058-1070] and the following heuristics are evaluated: FIFO (First In First Out) rules for input/output buffer management; and FIFO, SPT (Shortest Processing Time), STT (Shortest Travel Time) and MOQS (Maximum Outgoing Queue Size) rules concerning the vehicle. The consequences of classical assumptions are also studied: ignoring empty trips, ignoring no-move-ahead constraints, and ignoring vehicle-disjunction constraints. The numerical experiments provide a set of optimal solutions and allow to evaluate the performances of heuristic search schemes.

Recently, there has been much interest in using active queue management in routers in order to protect users from connections that are not very responsive to congestion notification. A recent Internet draft recommends schemes based on random early detection for achieving these goals, to the extent that it is possible, in a system without "per-flow" state. However, a "stateless" system with first-in/first-out (FIFO) queueing is very much handicapped in the degree to which flow isolation and fairness can be achieved. Starting with the observation that a "stateless" system is but one extreme in a spectrum of design choices and that per-flow queueing for a large number of flows is possible, we present active queue management mechanisms that are tailored to provide a high degree of isolation and fairness for TCP connections in a gigabit IP router using per-flow queueing. We show that IP flow state in a router can be bounded if the scheduling discipline used has finite memory, and we investigate the performance implications of different buffer management strategies in such a system. We show that merely using perflow scheduling is not sufficient to achieve effective isolation and fairness, and it must be combined with appropriate buffer management strategies.

Destination-based forwarding in traditional IP routers has not been able to take full advantage of multiple paths that frequently exist in Internet Service Provider Networks. As a result, the networks may not operate efficiently, especially when the traffic patterns are dynamic. This paper describes a multipath adaptive traffic engineering mechanism, called MATE, which is targeted for switched networks such as MultiProtocol Label Switching (MPLS) networks. The main goal of MATE is to avoid network congestion by adaptively balancing the load among multiple paths based on measurement and analysis of path congestion. MATE adopts a minimalist approach in that intermediate nodes are not required to perform traffic engineering or measurements besides normal packet forwarding. Moreover, MATE does not impose any particular scheduling, buffer management, or a priori traffic characterization on the nodes. This paper presents an analytical model, derives a class of MATE algorithms, and proves their convergence. Several practical design techniques to implement MATE are described. Simulation results are provided to illustrate the efficacy of MATE under various network scenarios.

Traffic management (TM) mechanisms such as Call Admission Control (CAC), Scheduling, and Buffer Management (BM) play a key role in the design of multi-service wireless network by providing service differentiation from diverse applications and assigning the network resources (radio channels or buffer) according to the quality of service (QoS) requirements of each service class. We propose in this work two new models that integrate CAC, Scheduling, and BM in the design of multi-service wireless network. By presenting their Markovian models and their performance metrics, we investigate their respective design tradeoffs and compare their performance.

A wireless sensor network is constrained by computation capability, memory space, communication bandwidth, and above all, energy supply. When a critical event triggers a surge of data generated by the sensors, congestion may occur as data packets converge toward a sink. Congestion causes energy waste, throughput reduction, and information loss. However, the important problem of congestion avoidance in sensor networks is largely open. This paper proposes a congestion-avoidance scheme based on light-weight buffer management. We describe simple yet effective approaches that prevent data packets from overflowing the buffer space of the intermediate sensors. These approaches automatically adapt the sensors' forwarding rates to nearly optimal without causing congestion. We discuss how to implement buffer-based congestion avoidance with different MAC protocols.

In this paper, we analyze TCP performance in asymmetric networks, where the throughput significantly depends on the reverse direction and packet loss. We introduce a new operational model called the "AMP model" which, with an understanding of TCP dynamics and buffer management techniques, explains the performance effects observed. We apply this model to guide design improvements in buffer management (ack-regulation) and scheduling schemes to achieve performance improvements of an order of magnitude or more. The schemes have been tested through simulation and implementation, and the module driven improvements observed are better than those proposed in earlier literature.

The commercial deployment of LTE Release 8 is gaining significant momentum all over the globe, and LTE is evolving to LTE-Advanced which offers various new features to meet or exceed IMT-Advanced requirements. Since LTE-Advanced targets ambitious spectral efficiency and peak throughput, it poses tremendous system design challenges to operators and manufacturers, especially for mobile terminals. This article discusses modem design issues related to carrier aggregation, enhanced ICIC for HetNet, detection of eight layer transmission, reference signals for enhanced multi-antenna support, and HARQ buffer management. We provide an overview of technical challenges and sketch the perspectives for tackling them to exploit the full benefits of LTE-Advanced system.

We present a baseline MPEG-4 Advanced Video Coding (AVC) decoder based on the methodology of joint optimization of software and hardware. The software is first optimized with algorithm improvements for frame buffer management, boundary padding, content-aware inverse transform and context-based entropy decoding. The overall decoding throughput is further enhanced by pipelining the software and the dedicated hardware at macroblock level. The decoder is partitioned into the software and hardware modules according to the target frame rate and complexity profiles. The hardware acceleration modules include motion compensation, inverse transform and loop filtering. By comparing the optimized decoder with the committee reference decoder of Joint Video Team (JVT), the experimental results show improvement on the decoding throughput by 7 to 8 times. On an ARM966 board, the optimized software without hardware acceleration can achieve a decoding rate up to 5.9 frames per second (fps) for QCIF video source. The overall throughput is improved by another 27% to 7.4 fps on the average and up to 11.5 fps for slow motion video sequences. Finally, we provide a theoretical analysis of the ideal performance of the proposed decoder.

Power consumption and DRAM latencies are serious concerns in modern chip-multiprocessor (CMP or multi-core) based compute systems. The management of the DRAM row buffer can significantly impact both power consumption and latency. Modern DRAM systems read data from cell arrays and populate a row buffer as large as 8 KB on a memory request. But only a small fraction of these bits are ever returned back to the CPU. This ends up wasting energy and time to read (and subsequently write back) bits which are used rarely. Traditionally, an open-page policy has been used for uni-processor systems and it has worked well because of spatial and temporal locality in the access stream. In future multi-core processors, the possibly independent access streams of each core are interleaved, thus destroying the available locality and significantly under-utilizing the contents of the row buffer. In this work, we attempt to improve row-buffer utilization for future multi-core systems. The schemes present...

Supporting high transaction rates and high availability for on-line transaction processing and emerging applications requires systems consisting of multiple computing nodes. We outline various cluster architecturei and describe the factors that motivate the S/390 Parallel Sysplex™ architecture and its resulting advantages. We quantify the scalability of the S/390 Parallel Sysplex and show that the transaction rate supported is close to linear as nodes are added to the system. The key facet of the S/390 Parallel Sysplex architecture is the coupling facility. The coupling facility provides for very efficient intertransaction concurrency control, buffer cache coherency control, and shared buffer management, among other functions, that lead to the excellent scalability achieved. It also provides for effective dynamic load balancing, high data buffer hit ratios, and load balancing after a failure.

The Cambridge Research Laboratory was founded in 1987 to advance the state of the art in both core computing and human-computer interaction, and to use the knowledge so gained to support the Company's corporate objectives. We believe this is best accomplished through interconnected pursuits in technology creation, advanced systems engineering, and business development. We are actively investigating scalable computing; mobile computing; vision-based human and scene sensing; speech interaction; computer-animated synthetic persona; intelligent information appliances; and the capture, coding, storage, indexing, retrieval, decoding, and rendering of multimedia data. We recognize and embrace a technology creation model which is characterized by three major phases:

As one of the promising techniques in Broadband Wireless Access (BWA), IEEE 802.16 also namely WiMax provides wide-area, high-speed, and non-line-of-sight wireless transmission to support multimedia services. Four service types are defined in the specification of IEEE 802.16 for QoS support. In order to achieve end-to-end multimedia services, 802.16 QoS must be well integrated with IP QoS. In this paper, we propose a framework of cross-layer QoS support in the IEEE 802.16 network. Two novel mechanisms are proposed in the framework for performance improvement: Fragment Control and Remapping. Fragment Control handles the data frames that belong to the same IP datagram in an atomic manner to reduce useless transmission. Remapping is concerned with the mapping rules from IP QoS to 802.16 QoS and is designed to reduce the impact of traffic burstiness on buffer management. Simulation study has shown that the proposed scheme has higher goodput and throughput, and lower delay than the contrast.

In many applications the traffic traversing the network has inter-packet dependencies due to application-level encoding schemes. For some applications, e.g., multimedia streaming, dropping a single packet may render useless the delivery of a whole sequence. In such environments, the algorithm used to decide which packet to drop in case of buffer overflows must be carefully designed, to avoid goodput degradation.

Because organizations are open systems, environmental forces can both benefit the organization and cause it harm. The empirical theory of O'Toole and Meier suggests buffering is related to organizational performance in nonlinear ways by interacting with environmental forces, managerial networking, and organizational structures. This article examines the organization's history to generate an estimate of environmental buffering and then incorporates this measure to study buffering in a more contemporary data set. The authors find buffering is related to a variety of performance indicators and has an especially strong influence on performance in regard to a more disadvantaged clientele. The article then assesses the functional form of the buffering relationship and the potential interaction with other variables. Although the logic of Occam's razor implies that the simple linear relationship best fits the data, significant research needs to be done on other measures of buffering and other data sets before definitive conclusions can be drawn.

This paper investigates a novel active buffer management scheme, "Jitter Detection" (JD) for gateway-based congestion control to stream multimedia traffics in packet-switched networks. The quality of multimedia presentation can be greatly degraded due to network delay variation or jitter when transported over a packet-switched network. Jitter degrades the timing relationship among packets in a single media stream and between packets from different media streams and, hence, creates multimedia synchronization problems. Moreover, too much jitter will also degrade the performance of the streaming buffer in the client. Packets received by the client will be rendered useless if they have accumulated enough jitter. The proposed active buffer management scheme will improve the quality of service in multimedia networking by detecting and discarding packets that accumulated enough jitter, such as to maintain a high bandwidth for packets within the multimedia stream's jitter tolerance. Simulation results have shown that the proposed scheme can effectively lower the average received packet jitter and increase the goodput of the received packets when compared to random early detection (RED) and DropTail used in gateway-based congestion control. Furthermore, simulation results have also revealed that the proposed scheme can maintain the same TCP friendliness when compared to that of RED and DropTail used for multimedia streams.

Abstract: In this paper, we propose an adaptive and opportunistic forwarding mechanism that is able to match mobility characteristics in Delay Tolerant Networks (DTNs). Our pro- tocol, Seeker, empowers nodes with the ability to estimate future contact opportunities based on a history of pair-wise contacts. Furthermore, Seeker is able to adjust and rewind forwarding and buffering decisions on the fly.

Several satellite systems currently in operation or under development claim to support broadband Internet applications. In these scenarios, transmission control protocol (TCP) plays a critical role. Unfortunately, when used with satellite links, TCP suffers from a number of well-known performance problems, especially for higher data rates and high altitude satellites with longer delays. In response to these difficulties, the satellite and Internet research communities have developed a large gamut of solutions ranging from architectural modifications to changes in the TCP protocol. Among these, one approach requiring minimal modifications involves splitting the TCP connection in two or more segments with one segment connecting terrestrial nodes across the satellite network. In this paper, we consider an evolution of this idea: placing a TCP proxy on board the satellite that further subdivides the end-to-end connection into separate TCP connections between ground and space. We focus upon the efficient use of buffer resources on board the satellite, while at the same time enhancing TCP performance. We evaluate two TCP protocol versions, TCP NewReno and TCP Westwood. We consider various geosynchronous earth orbit satellite scenarios, with and without the split proxy, and with different channel error conditions (random errors, shadowing, etc). Using simulation, we show that an on-board proxy provides a number of distinct advantages and can enhance throughput up to threefold for both TCP New Reno and TCP Westwood, in some scenarios, with relatively modest on-board buffering requirements. The main contributions of this paper are: the on-board split proxy concept, the buffer management strategy, the use of a realistic "urban shadowing" model in the evaluation, and the extensive comparison of the recently announced TCP Westwood with the traditional TCP New Reno.

Packet buffers in a smart network interface card are managed in a way to reduce any packet losses from high-speed burst incoming data. Currently, two types of packet buffer management techniques are used. They are static buffer management and dynamic buffer management techniques. Dynamic buffer management techniques are more efficient than the static ones because they change the threshold value according to network traffic conditions. However, current dynamic techniques cannot adjust threshold instantaneously. Thus, packet losses with dynamic techniques are still high. We, therefore, propose a history-based buffer management scheme to address the issue. Our experiment results show that the history-based scheme reduces packet loss by 11% to 15.9% as compared to other conventional dynamic algorithms. Keywords -packet buffer; network interface card; layer 3 and 4 protocols; VHDL; static and dynamic buffer management.

In this paper, we formalize and prove the correctness of a concurrency control algorithm for an open and safe nested transaction using I/O automaton model. The model uses the notion of a recovery point subtransaction in the nested transaction tree. Our nested transaction model uses a prewrite operation before an actual write operation to increase the concurrency. It is termed "open and safe" as prewrites allow early reads (before database writes on disk) without cascading aborts. In our model we have also modeled the buffer management operations as nested transactions, and the concurrency control algorithm controls their executions. Non-access subtransactions, objects and the scheduler are modeled as I/O automata with the help of some pre and post conditions. These conditions capture the operational semantics and behavior of each automaton during the execution of transactions. While modeling we also take into account log activities, which occur during the execution of transactions. We also briefly sketch the recovery algorithm. The correctness proof shows that the concurrency control algorithm for our model is serially correct. Our proof makes use of assertional reasoning and provides many interesting invariant, thus gives a better understanding of our transaction model and the concurrency control algorithm. While proving correctness, we mapped our system to that of Moss's two phase locking system to show the relationships between the two algorithms.

High speed downlink packet access (HSDPA) was introduced to UMTS radio access segment to provide higher capacity for new packet switched services. As a result, packet switched sessions with multiple diverse traffic flows such as concurrent voice and data, or video and data being transmitted to the same user are a likely commonplace cellular packet data scenario. In HSDPA, radio access network (RAN) buffer management schemes are essential to support the end-to-end QoS of such sessions. Hence in this paper we present the end-to-end performance study of a proposed RAN buffer management scheme for multi-flow sessions via dynamic system-level HSDPA simulations. The scheme is an enhancement of a time-space priority (TSP) queuing strategy applied to the node B MAC-hs buffer allocated to an end user with concurrent real-time (RT) and non-real-time (NRT) flows during a multi-flow session. The experimental multi- flow scenario is a packet voice call with concurrent TCP-based file download to the same user. Results show that with the proposed enhancements to the TSP-based RAN buffer management, end-to-end QoS performance gains accrue to the NRT flow without compromising RT flow QoS of the same end user session.

infrastructure. However, in multi-hop networks, effective bandwidth decreases with increasing number of hops, mainly due to increased spatial contention. Longer hop length flows suffer from extremely low throughputs which is highly undesirable in the envisioned scenarios for mesh networks. In this paper, we show that Queue/Buffer management, at intermediate relay mesh nodes, plays an important role in limiting the performance of longer hop length flows. We propose a novel queue management algorithm for IEEE 802.11s based mesh networks that improves the performance of multihop flows by fairly sharing the available buffer at each mesh point among all the active source nodes whose flows are being forwarded. Extensive simulations reveal that our proposed scheme substantially improves the performance of multihop flows. We also identify some important design issues that should be considered for the practical deployment of such mesh networks. Nagesh S. Nandiraju et al.

One of the problems in future processors will be the resource conflicts caused by several load/store units competing to access the same cache bank. The traditional approach for handling this case is by introducing buffers combined with a cross-bar. This approach suffers from (i) the nondeterministic latency of a load/store and (ii) the extra latency caused by the cross-bar and the buffer management. A deterministic latency is of the utmost importance for the forwarding mechanism of out-of-order processors because it enables back-to-back operation of instructions. We propose a technique by which we eliminate the buffers and crossbars from the critical path of the load/store execution. This results in both, a low and a deterministic latency. Our solution consists of predicting which bank is to be accessed. Only in the case of a wrong prediction a penalty results.

This paper presents a Media Access Control (MAC) protocol for a WDM passive optical star. The protocol supports scalable service differentiation for Internet traf®c in the spirit of the IETF's Diffserv architecture. We describe the functional elements of the protocol (signaling, arbitration, service disciplines and buffer management techniques) and the way they interact to support the Diffserv's Expedited Forwarding (EF) PHB and Assured Forwarding (AF) PHB group, where PHB stands for Per-Hop-Behavior. Extensive simulation results give quantitative estimations of the performance of the protocol under combined EF/AF traf®c.

While it has been shown that TCP Vegas provides better performance compared to TCP Reno, studies have identified various issues associated with the protocol. We propose modifications to the congestion avoidance mechanism of the TCP Vegas to overcome these limitations. Unlike the solutions proposed in the past, our solution, named TCP Vegas-A, is neither dependent on optimising any critical parameter values nor on the buffer management scheme implemented at the routers and hence can be implemented solely at the end host. Our simulation experiments over wired as well as over geosynchronous and lower earth orbit satellite links show that TCP Vegas-A is able to overcome several of the identified problems-it can obtain a fairer share of the network bandwidth in wired and satellite scenarios, tackle rerouting issues, rectify Vegas's bias against higher bandwidth flows and prevail over fluctuating RTT conditions of a lower earth orbit satellite link. At the same time, Vegas-A is able to preserve the unique properties of Vegas that had made it a noteworthy protocol. q

The commercial deployment of LTE Release 8 is gaining significant momentum all over the globe, and LTE is evolving to LTE-Advanced, which offers various new features to meet or exceed IMT-Advanced requirements. Since LTE-Advanced targets ambitious spectral efficiency and peak throughput, it poses tremendous system design challenges to operators and manufacturers, especially for mobile terminals. This article discusses modem design issues related to carrier aggregation, enhanced ICIC for HetNet, detection of eight-layer transmission, reference signals for enhanced multi-antenna support, and HARQ buffer management. We provide an overview of technical challenges and sketch the perspectives for tackling them to exploit the full benefits of the LTE-Advanced system.

Traffic modeling is a fertile research area. This paper proposes a packet-level traffic model of traffic sources based on Hidden Markov Model. It has been developed by using real network traffic and estimating in a combined fashion Packet Size and Inter Packet Time. The effectiveness of the proposed model is evaluated by studying several traffic types with strong differences in terms of both applications/users and protocol behavior. Indeed, we applied our model to real traffic traces of Age of Mythology (a Multi Player Network Game), SMTP, and HTTP. An analytical basis and the mathematical details regarding the model are given. Results show how the proposed model captures first-order statistics, as well as temporal dynamics via auto-and cross-correlation. Also, the capability to accurately replicate the considered traffic sources is shown. Finally, preliminary results for model-based traffic prediction reveal encouraging.

The automated material handling system (AMHS) is a highly automated transport solution of actual 300mm semiconductor waferfabs. The big logistic challenge in such a running system is the just-in-time delivery of lots (carriers). Therefore, beside tracks and vehicles, there are different storages (stocker) and buffers (under track storages and load ports) integrated in such a transport system. To conquer the

To enhance performance characteristics of data transport over ATM-UBR service class, additional mechanisms, such as congestion control and buffer management, are required. In this paper, we investigate active queue management mechanisms that are designed to enable ATM switches to operate in the low delay/high throughput regime. In particular, we present an analytical framework for Random Early Detection (RED)-like congestion control mechanisms in an ATM multiplexer, and obtain closed form expressions for performance metrics such as throughput and average queueing delays. Based on this analysis, we propose an adaptive mechanism to select the parameters of the congestion control algorithm to optimize the system performance.

VDBMS research 1 is motivated by the requirements of video-based applications to search by content, and by the need for testbed facilities for research in video database management. Our fundamental concept is to provide a full range of functionality for video as a well-defined abstract data type. The research issues addressed include: MPEG7 for multimedia content representation, techniques for image processing, high-dimensional indexing, multimedia query processing and optimization, new query operators, real-time stream management, access control models for streaming, and search-based buffer management. VDBMS also provides an environment for testing and comparing algorithms in a standardized way. We are currently developing component wrappers with well-defined interfaces to facilitate the modification or replacement of components. Our ultimate goal is a flexible, extensible framework that can be used for developing, testing and benchmarking video database technologies.

There have been many debates about the feasibility of providing guaranteed Quality of Service (QoS) when network traffic travels beyond the enterprise domain and into the vast unknown of the Internet. Many mechanisms have been proposed to bring QoS to TCP/IP and the Internet (RSVP, DiffServ, 802.1p). However, until these techniques and the equipment to support them become ubiquitous, most enterprises will rely on local prioritization of the traffic to obtain the best performance for mission critical and time sensitive applications. This work explores prioritizing critical TCP/IP traffic using a multi-queue buffer management strategy that becomes biased against random low priority flows and remains biased while congestion exists in the network. This biasing implies a degree of unfairness but proves to be more advantageous to the overall throughput of the network than strategies that attempt to be fair. Only two classes of services are considered where TCP connections are assigned to these classes and mapped to two underlying queues with round robin scheduling and shared memory. In addition to improving the throughput, cell losses are minimized for the class of service (queue) with the higher priority.

Performance needs of many database applications dictate that the entire database be stored in main memory. The Dal system is a main memory storage manager designed to provide the persistence, availability and safety guarantees one typically expects from a diskresident database, while at the same time providing very high performance by virtue of being tuned to support in-memory data. User processes map the entire database into their address space and access data directly, thus avoiding expensive remote procedure calls and bu er manager interactions typical of accesses in disk-resident commercial systems available today.

In existing multicomputers, software overhead dominates the message-passing latency cost. Our research on the SHRIMP project at Princeton indicates that appropriate network interface support can signicantly reduce this software overhead. We have designed two network interfaces for the SHRIMP multicomputer. Both support virtual memory mapped communication allowing user processes to communicate without doing expensive buer management, and without using system calls to cross the protection boundary separating user processes from the operating system kernel. This paper describes and compares the two network interfaces, and discusses performance tradeos between them.

Emerging application domains such as interactive vision, animation, and multimedia collaboration display dynamic scalable parallelism and high-computational requirements, making them good candidates for executing on parallel architectures such as SMPs and clusters of SMPs. Stampede is a programming system that has many of the needed functionalities such as high-level data sharing, dynamic cluster-wide threads and their synchronization, support for task and data parallelism, handling of time-sequenced data items, and automatic buffer management. In this paper, we present an overview of Stampede, the primary data abstractions, the algorithmic basis of garbage collection, and the issues in implementing these abstractions on a cluster of SMPS. We also present a set of micromeasurements along with two multimedia applications implemented on top of Stampede, through which we demonstrate the low overhead of this runtime and that it is suitable for the streaming multimedia applications.

With the exponential increase in the integration of mobile communication devices with media communication over the Internet, the need to transmit high quality archived media clips and movies over limited bandwidth connections has increased. Archived movies have immense use for entertainment such as cartoon movies, news clips, and Internet based mobile instructions. In this paper, we describe an XML based Internet language for frame based transmission of object based movies over the Internet using STMD (Single Transmission Multiple Display) paradigm. The language and its implementation have been described, and the performance results for the implementation have been presented. The implementation benefits from the integration of static analysis of the movie and the predictive buffer management.

In this paper, we propose a novel external-memory algorithm to support view-dependent simplification for datasets much larger than main memory. In the preprocessing phase, we use a new spanned sub-meshes simplification technique to build view-dependence trees I/O-efficiently, which preserves the correct edge collapsing order and thus assures the run-time image quality. We further process the resulting view-dependence trees to build the meta-node trees, which can facilitate the run-time level-of-detail rendering and is kept in disk. During run-time navigation, we keep in main memory only the portions of the meta-node trees that are necessary to render the current level of details, plus some prefetched portions that are likely to be needed in the near future. The prefetching prediction takes advantage of the nature of the run-time traversal of the meta-node trees, and is both simple and accurate. We also employ the implicit dependencies for preventing incorrect foldovers, as well as main-memory buffer management and parallel processes scheme to separate the disk accesses from the navigation operations, all in an integrated manner. The experiments show that our approach scales well with respect to the main memory size available, with encouraging preprocessing and run-time rendering speeds and without sacrificing the image quality.

Current network processors (NPs) increasingly deal with packets with heterogeneous processing times. As a consequence, packets that require many processing cycles can significantly delay low-latency traffic, because the common approach in today's NPs is to employ run-to-completion processing. These difficulties have led to the emergence of the Multipass NP architecture, where after a processing cycle ends, all processed packets are recycled into the buffer and re-compete for processing resources.

End-user multi-flow services support is a crucial aspect of current and next generation mobile networks. This paper presents a dynamic buffer management strategy for HSDPA end-user multi-flow traffic with aggregated real-time and non-real-time flows. The scheme incorporates dynamic priority switching between the flows for transmission on the HSDPA radio channel. The end-to-end performance of the proposed strategy is investigated with an end-user multi-flow session of simultaneous VoIP and TCP-based downlink traffic using detailed HSDPA system-level simulations. Compared to an equivalent static buffer management scheme, the results show that end-to-end throughput performance gains in the non-real-time flow and better HSDPA channel utilization is attainable without compromising the real-time VoIP flow QoS constraints.