Buffer Management

We consider the problem of interconnecting low speed LANs over a high-speed shared-memory ATM switch. A bottleneck is formed when more than one source originate traffic to the same destination LAN. In this case, a congestion may be created at the output gateway (destination LAN interface) and the required services are interrupted. In this paper we propose a new integrated scheme for call admission (CAC) and buffer management. The objective of the scheme is to prevent the congestion at the destination LANs, as well as within the ATM switch, while minimizing connection rejection rates (maximizing the utilization of the ATM switch). The scheme uses two types of parameters: first, the connection parameters which are estimated at the network interface unit and specified during connection set-up, and second, the actual traffic characteristics and buffer requirements. Therefore, the proposed scheme combines both parameter-based and measurement-based approaches to the problems of call admission and congestion control. The proposed scheme is shown not to require intensive computations and can be implemented in real time in a high-speed ATM switch. A simulation model for the system is developed from which the performance of our integrated CAC and buffer management scheme is evaluated. It is shown that the application of our CAC criteria maintains cell/packet dropping to within the same order of magnitude. It is also shown that using virtual buffer allocation, in conjunction with our CAC criteria, results in almost no cell/packet dropping. ᭧ 1998 Elsevier Science B.V.

Climate change, rapid urbanization, and population growth have intensified global water scarcity, increasing reliance on groundwater resources. One of the most effective solutions to this crisis is artificial groundwater recharge through floodwater harvesting, which captures surface runoff and facilitates controlled infiltration into aquifers. Floodwater harvesting techniques, such as check dams, recharge basins, and injection wells, are designed to capture and store excess runoff, allowing controlled percolation and groundwater replenishment. This study provides a comprehensive review of artificial groundwater recharge techniques, categorizing them into surface (spreading), sub-surface, and indirect methods. A total of eleven techniques were analyzed, including recharge basins, check dams, injection wells, and induced recharge methods, which have been successfully implemented in various regions. The review highlights the benefits of artificial recharge, such as improved groundwater storage, reduced soil erosion, and enhanced water quality. However, challenges such as aquifer contamination, sediment clogging, and inefficient recharge structures remain significant barriers to implementation. The study also examines the environmental impacts of artificial recharge, addressing both positive aspects (such as ecological restoration and energy savings) and potential drawbacks (including land subsidence and aquifer pollution risks). A special focus is given to Egypt, where floodwater harvesting has been implemented in Sinai using check dams and surface recharge techniques. Despite its potential, groundwater recharge in Egypt remains underutilized, necessitating further research into sub-surface recharge methods and alternative energy solutions such as solar-powered recharge systems. The findings

Pointer swizzling improves the performance of OODBMSs by reducing the number of table lookups. However, the object replacement incurs the unswizzling overhead. In this paper, we propose a new pointer swizzling strategy, the dynamic indirect pointer swizzling (DIPS). DIPS dynamically applies pointer swizzling techniques in order to reduce the overhead of unswizzling. DIPS uses the temporal locality information which is gathered by the object buffer manager. The information is used to select the object to whose pointers the pointer swizzling techniques are applied and to dynamically bind the pointer swizzling techniques using the virtual function mechanism. We show the efficiency of the proposed strategy through experiments over various object buffer sizes and workloads.

In spite of the larger performance gain such as higher throughput and almost zero packet retransmissions compared to TCP Reno, TCP Vegas still has a few obstacles for it to be deployed in the Internet. Studies have shown unfair treatment to Vegas connections when they compete with Reno connections. Other issues identified with TCP Vegas are problems of rerouting, persistent congestion, and discrepancy in flow rate tied with starting times and link bandwidth. We reinvestigate these issues and propose modifications to the congestion avoidance mechanism of the TCP Vegas, with the slow-start and congestion recovery algorithms of Vegas remaining untouched. Unlike the solutions proposed in the recent past to deal with some of these issues, our solution is neither dependent on any critical parameter values nor on the buffer management scheme at the routers (e.g., RED). Our experiments show that the modified TCP Vegas (Vegas-A) is able to obtain a fairer share of the network bandwidth when competing with other TCP flows. We also show that Vegas-A can tackle rerouting issues and rectify Vegas's bias against higher bandwidth flows. At the same time, our experiments prove that Vegas-A preserves the properties of Vegas that have made it a noteworthy protocol.

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.

In a Main Memory Database (MMDB) the primary copy of the database resides in volatile main memory. This makes MMDB systems more vulnerable to failures compared to the traditional Disk Resident Databases (DRDB). A backup copy of the database is maintained in secondary storage for recovery purposes. Recovery activities like logging, checkpointing and reloading are used to restore the database to a consistent state after a system crash has occurred. In this paper, we implement a recovery

Flash memory has characteristics of out-of-place update and asymmetric I/O latencies for read, write, and erase operations. Thus, the buffering policy for flash-based databases has to consider those properties to improve the overall performance. This article introduces a new approach to buffer management for flash-based databases, called AD-LRU (Adaptive Double LRU), which focuses on improving the overall runtime efficiency by reducing the number of write/erase operations and by retaining a high buffer hit ratio. We conduct trace-driven experiments both in a simulation environment and in a real DBMS, using a real OLTP trace and four kinds of synthetic traces: random, read-most, write-most, and Zipf. We make detailed comparisons between our algorithm and the best-known competitor methods. The experimental results show that AD-LRU is superior to its competitors in most cases.

Flash memory has characteristics of out-of-place update and asymmetric I/O latencies for read, write, and erase operations. Thus, the buffering policy for flash-based databases has to consider those properties to improve the overall performance. This article introduces a new approach to buffer management for flash-based databases, called AD-LRU (Adaptive Double LRU), which focuses on improving the overall runtime efficiency by reducing the number of write/erase operations and by retaining a high buffer hit ratio. We conduct trace-driven experiments both in a simulation environment and in a real DBMS, using a real OLTP trace and four kinds of synthetic traces: random, read-most, write-most, and Zipf. We make detailed comparisons between our algorithm and the best-known competitor methods. The experimental results show that AD-LRU is superior to its competitors in most cases.

Flash memory has characteristics of out-of-place update and asymmetric I/O latencies for read, write, and erase operations. Thus, the buffering policy for flash-based databases has to consider those properties to improve the overall performance. This article introduces a new approach to buffer management for flash-based databases, called AD-LRU (Adaptive Double LRU), which focuses on improving the overall runtime efficiency by reducing the number of write/erase operations and by retaining a high buffer hit ratio. We conduct trace-driven experiments both in a simulation environment and in a real DBMS, using a real OLTP trace and four kinds of synthetic traces: random, read-most, write-most, and Zipf. We make detailed comparisons between our algorithm and the best-known competitor methods. The experimental results show that AD-LRU is superior to its competitors in most cases.

Flash memory has characteristics of out-of-place update and asymmetric I/O latencies for read, write, and erase operations. Thus, the buffering policy for flash-based databases has to consider those properties to improve the overall performance. This article introduces a new approach to buffer management for flash-based databases, called AD-LRU (Adaptive Double LRU), which focuses on improving the overall runtime efficiency by reducing the number of write/erase operations and by retaining a high buffer hit ratio. We conduct trace-driven experiments both in a simulation environment and in a real DBMS, using a real OLTP trace and four kinds of synthetic traces: random, read-most, write-most, and Zipf. We make detailed comparisons between our algorithm and the best-known competitor methods. The experimental results show that AD-LRU is superior to its competitors in most cases.

Covert timing channels in real-time systems allow adversaries to not only exfiltrate application secrets but also to mount timing inference based attacks. Much effort has been put into improving real-time system predictability with the additional benefit of reducing the former class of confidentiality attacks. However, the more predictable the system behaves, the easier timing inference based attacks become. Time-triggered scheduling is particularly vulnerable to these types of attacks due to offline constructed tables that are scheduled with clock synchronization and OS-timer predictability. In this paper, we obfuscate timetriggered scheduling to complicate timing inference based attacks while maintaining strong protection against exfiltration attacks.

Real time audio transmission over the internet has become increasingly popular in many application areas, in particular in the commercial and entertainment sectors. However, the most challenging problem of end-to-end delay over an IP network needs to be addressed and is a topic of current ongoing research. In this paper various issues related to streaming real time audio in an IP network including the protocols used, problems faced in transmission and reception have been reviewed. A new scheme to evaluate the effect of buffer size during reception of an audio transmission in order to achieve an optimized playback is developed and tested. This method can be used to optimize the reception quality with respect to time and provide a way to reduce the noise effects at the receiver. It helps to stress out the factors affecting audio playback performance for the consumer.

Complex objects to support non-standard database applications require the use of substantial computing resources because their powerful operations must be performed and maintained in an interactive environment. Since the exploitation of parallelism within such operations seems to be promising, we investigate the principal approaches for processing a query on complex objects (molecules) in parallel. A number of arguments favor methods based on inter-molecule parallelism as against intra-molecule parallelism. Retrieval of molecules may be optimized by multiple storage structures and access paths. Hence, maintenance of such storage redundancy seems to be another good application area to explore the use of parallelism.

New database applications, primarily in the areas of engineering and knowledge-based systems, refer to complex objects (e.g. representation of a CAD workpiece or a VLSI chip) while performing their tasks. Retrieval, maintenance, and integrity checking of such complex objects consume substantial computing resources which were traditionally used by conventional database management systems in a sequential manner. Rigid performance goals dictated by interactive use and design environments imply new approaches to master the functionality of complex objects under satisfactory time restrictions. Because of the object granularity, the set orientation of the database interface, and the complicated algorithms for object handling, the exploitation of parallelism within such operations seems to be promising. Our main goal is the investigation and evaluation of different hardware architectures and their suitability to efficiently cope with workloads generated by database operations on complex objects. Apparently, employing just a number of processors is not a panacea for our database problem. The sheer horse power of machines does not help very much when data synchronization and event serialization requirements play a major role during object handling. What are the critical hardware architecture properties? How can the existing MIPS be best utilized for the data management functions when processing complex objects? To answer these questions and related issues, we discuss different kinds of architectures combining multiple processors: loosely-, tightly-, and closely-coupled. Furthermore, we consider parallelism at different levels of abstraction: the distribution of (sub-)queries or the decomposition of such queries and their concurrent evaluation at an inter-or intra-object level. Finally, we give some thoughts as to the problems of load control and transaction management.

Support for temporal data continues to be a requirement posed by many applications. We show that a complex object data model is an appropriate means for handling temporal data. Firstly, we describe the main features of temporal databases in terms of time sequences, valid time, etc. We then explain the mapping of time sequences onto recursively structured complex objects. Operations on temporal data are easily transformed into complex object operations. To cope with the huge storage requirements arising from temporal databases, we integrate the concept of storing logical differences into our approach. Here, we exploit the extensibility of the underlying complex object's database system PRIMA. Finally, we briefly sketch a further improvement to guarantee fast access to the present data by storing them apart from the historical data without loosing the connection between both.

❑ Propagation delay: 24 ms❑ Avg packetization delays: 6 ms+ 6 ms (PCM)❑ Assuming 5 switches on a typical path, delay variation allowed at each switch=(100-24-6-6)/5= 12.8 ms❑ For single switch bottleneck case, End-to-end delay= 12.8+ 24= 36.8 ms≈ 40 ms❑ We tried end-to-end delay bounds of 40 ms and 30 ms.

Background: Sorghum is an important source of fodder in the semi-arid areas of Kenya. However, its biomass yield has remained low due to the low soil moisture content which is associated with low rainfall. Objective: To evaluate the synergistic effects of combining rainwater harvesting practices on biomass yield and the morphometric traits of sorghum in semi-arid Kitui County. Methodology: The study was conducted in a randomized complete block design under rainfed conditions between March and August 2021 at the Research Farm of South Eastern Kenya University. It had twelve treatments, including three farming systems (conventional flat planting, ridge and furrow, and zai pits) with three soil mulching types (transparent plastic film mulch, black plastic film mulch, and grass mulch). The farming systems without mulching were used as control treatments. Data were subjected to analysis of variance and means were separated using Fisher’s protected Least Significant Difference test at 0.05 %. Results: The zai pits with black plastic film mulch and flat planting with grass mulch had the highest and lowest moisture content of 68.65% and 52.5% respectively compared to flat planting. The highest biomass yield was observed in ridge-furrow with black plastic film mulch (3283.33kg ha-1) and ridge–furrow with transparent plastic film mulch (3266.03) and was not significantly different. The lowest biomass yield was recorded in conventional flat planting and zai pits and was not significantly different. In all treatments, there was a significant increase (p ≤ 0.05) in morphometric traits. Implications: The farming system and the type of soil mulching determined the increase of soil moisture content, biomass yield, and morphometric traits. Conclusion: Combining ridge-furrow and black plastic mulch is recommended to improve the biomass yield of sorghum in semi-arid Kitui County, and other areas with similar agroecological conditions.
Key words: Drylands; cereals; water stress; climate change.

The objective of extensible DBMSs is to ease the construction of specialized DBMSs for nontraditional applications. Although much work has been done in providing various levels of extensibility (e.g., extensibility of data types and operators, query language extensibility, and query optimizer extensibility), there has been very limited research in providing extensibility at the buffer management level. Supporting extensibility at the buffer management level is important as it can contribute significantly to overall system performance. This paper addresses the problem of supporting extensibility of buffer replacement policies. The main contribution is the proposal of a framework for modeling buffer replacement policies. This work is novel in two aspects. First, by providing a uniform and generic specification of buffer replacement policies, the proposed framework unifies existing work in this area. Second, our work introduces a new level of extensibility. None of the existing extensible DBMSs, to our knowledge, provides extensibility at the buffer management level. The proposed framework provides a basis for the construction of an extensible buffer manager as part of a 100% Java-based storage manager. We conducted an extensive performance study to investigate the performance of the proposed framework. The experimental results demonstrate that the proposed framework is indeed feasible for existing DBMSs and improves system performance significantly without costing significant overhead.

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.

The performance of the proposed algorithm, FSAMAC, is compared with the TDFQ scheme. The simulation results are presented in the following section 6.5 EXPERIMENTAL RESULTS 6.5.1 Based on No. Of Flows In the experiment the numbers of flows are varied as 2,4,6,8 and 10.

Effective buffering of optical packets is essential to the efficient working of optical packet switches. In this paper three new schemes, which involve sorting and finding the least occupied buffer, are proposed. Their performance is compared with the common round-robin scheme. The results show that all these new schemes are able to enhance the optical packet switch performance significantly in terms of packet drop/loss probability. In addition, the results show that not all the newly arrived packets need to be sorted in order to obtain the minimum packet drop probability. As computation/processing time is significant in optical packet switching, partial sorting of the newly arrived packets with tolerable packet drop probability appears to be a viable proposition. Conversely, a complete sort of newly arrived packets wastes packet processing time unnecessarily while significantly increasing the packet drop probability.

En 3G UMTS, deux canaux principaux de transport ont été crées pour la transmission de données sur le lien descendant : un canal commun FACH et un canal dédié DCH. Le performance de TCP en UMTS dépend beaucoup de la politique de commutation de canal utilisée. Dans cet article, nous proposons et analysons trois nouvelles politiques de commutations de canal pour l'UMTS basées sur des seuils simples que nous appelons politique QS (Queue Size), FS (Flow Size) et QSFS (QS et FS combinés). Ces politiques améliorent de manière significative (environ 17%) le temps de réponse par rapport à la politique modifiée de seuil de . De plus, nous proposons et évaluons une nouvelle politique de commutation, plus performante, que nous appelons politique de FS-DCH (atleast flow-size threshold on DCH). Cette politique favorise les connexions TCP courtes (i.e., de peu de paquets) et est ainsi une politique inter-couche qui améliore le performance de TCP en donnant priorité aux premiers paquets des connexions sur le canal rapide DCH. De nombreux résultats de simulation illustrent ce gain de performance dans le cas d'un petit nombre de connexions TCP.

 This report provides a tool to support environmental assessment and risk screening activities for rural water supplies in low-income and fragile contexts.  It was developed by ODI, with support from Tearfund, for the Sustainable WASH in Fragile Contexts (SWIFT) consortium, providing water, sanitation and hygiene (WASH) services under the DFID WASH Results Programme funded by the UK Government.  This addresses the following questions regarding shallow groundwater sources (i.e., springs and wells) -both new and existing:  Is there enough water of suitable quality to meet demand across seasons for the long term?  What are the main environmental risks to ensuring a sustainable supply of safe water?  How can these risks be mitigated?  The tool proposes four main steps to do this: 1. Understand how much water is available by tapping local knowledge 2. Determine how much groundwater is needed to meet demand, and how big the catchment (recharge) area of a well will need to be to provide this water 3. Protect the sites and sources by identifying environmental hazards of, and measures for, site degradation and water supply contamination 4. Maintain records of the assessment, design and implementation of groundwater projects, so as to inform similar, future projects  Pages 10 and 11 of this report include a simple flow diagram of the tool that can be used to progress through each of these steps Comments and practical insights on ideas for this tool and on an early draft were provided by Tearfund and Oxfam country office staff in Goma and Kinshasa, DRC, and government and non-government partner organisations of SWIFT in Goma, DRC. Andy Bastable, Head of Water and Sanitation at Oxfam GB and Geraint Burrows, Hydrologists Without Borders (HWB), provided extremely valuable comments and critical reflections on early drafts of the tool and provided access to resources compiled by HWB-UK.

The media streaming technology is very appropriate for client applications running on mobile telephones due to its limited memory and bandwidth. A serious problem that has not been fully solved is the control of temporary client disconnections due to the lack of coverage, because it causes the closing of the current session and forces the opening of a new one with the corresponding loss of efficiency. Moreover, the software for developing a mobile telephone streaming client is in its infancy: The implementation of robust software that automatically recovers a streaming session is very difficult. The aim of this paper is to show a new light protocol and buffer management to efficiently support wireless multimedia communication disruptions and to recover the streaming session automatically. We are the first to obtain a working software in a commercial mobile telephone supporting disruption and maintaining constant the input throughput to the streaming Client.

We provide a competitive analysis framework for online prefetching and buffer management algorithms in parallel I/O systems, using a read-once model of block references. This has widespread applicability to key I/O-bound applications such as external merging and concurrent playback of multiple video streams. Two realistic lookahead models, global lookahead and local lookahead, are defined. Algorithms NOM and GREED based on these two forms of lookahead are analyzed for shared buffer and distributed buffer configurations, both of which occur frequently in existing systems. An important aspect of our work is that we show how to implement both the models of lookahead in practice using the simple techniques of forecasting and flushing. Given a ¤-disk parallel I/O system and a globally shared I/O buffer that can hold upto ¥ disk blocks, we derive a lower bound of ¦ § © ¤ on the competitive ratio of any deterministic online prefetching algorithm with § ¥ lookahead. NOM is shown to match the lower bound using global ¥-block lookahead. In contrast, using only local lookahead results in an ¦ § ¤ competitive ratio. When the buffer is distributed into

Buffer management for a D-disk parallel I/O system is considered in the context of randomized placement of data on the disks. A simple prefetching and caching algorithm PHASE-LRU using bounded lookahead is described and analyzed. It is shown that PHASE-LRU performs an expected number of I/Os that is within a factor (log D/ log log D) of the number performed by an optimal off-line algorithm. In contrast, any deterministic buffer management algorithm with the same amount of lookahead must do at least (√ D) times the number of I/Os of the optimal.

We address the problem of prefetching and caching in a parallel I/O system and present a new algorithm for parallel disk scheduling. Traditional buffer management algorithms that minimize the number of block misses are substantially suboptimal in a parallel I/O system where multiple I/Os can proceed simultaneously. We show that in the offline case, where a priori knowledge of all the requests is available, PC-OPT performs the minimum number of I/Os to service the given I/O requests. This is the first parallel I/O scheduling algorithm that is provably offline optimal in the parallel disk model. In the online case, we study the context of global L-block lookahead, which gives the buffer management algorithm a lookahead consisting of L distinct requests. We show that the competitive ratio of PC-OPT, with global L-block lookahead, is ÂðM À L þ DÞ, when L M, and ÂðMD=LÞ, when L > M, where the number of disks is D and buffer size is M.

The media streaming technology is very appropriate for client applications running on mobile telephones due to its limited memory and bandwidth. A serious problem that has not been fully solved is the control of temporary client disconnections due to the lack of coverage, because it causes the closing of the current session and forces the opening of a new one with the corresponding loss of efficiency. Moreover, the software for developing a mobile telephone streaming client is in its infancy: The implementation of robust software that automatically recovers a streaming session is very difficult. The aim of this paper is to show a new light protocol and buffer management to efficiently support wireless multimedia communication disruptions and to recover the streaming session automatically. We are the first to obtain a working software in a commercial mobile telephone supporting disruption and maintaining constant the input throughput to the streaming Client.

This paper reports the design and implementation of Platypus, a transactional object store. The twin goals of flexibility and performance dominate the design of Platypus. The design includes: support for SMP concurrency; standalone, client-server and client-peer distribution configurations; configurable logging and recovery; and object management which can accommodate garbage collection and clustering mechanisms. The first implementation of Platypus incorporates a number of innovations. (1) A new recovery algorithm derived from ARIES that removes the need for log sequence numbers to be present in store pages. (2) A zero-copy memory-mapped buffer manager with controlled write-back behavior. (3) A data structure for highly concurrent map querying. We present performance results comparing Platypus with SSM, the storage layer of the SHORE object store. For both medium and small OO7 workloads Platypus outperforms SHORE across a wide range of benchmark operations in both 'hot' and 'cold' settings. 1 We use the term byte store to describe untyped, unstructured data.

Data exchange within a Bluetooth piconet is masterdriven. The channel/slot utilization thus depends on the efficiency of the scheduling algorithm adopted by the master. In this paper, a novel MAC layer scheduling algorithm, called Floating Threshold (FT), is proposed. Unlike existing approaches, FT allows the master to estimate the backlog queue status at each slave accurately based only on a single feedback bit and a floating threshold. The master can then derive an optimized packet transmission schedule. Using simulations, we show that FT outperforms existing algorithms in terms of channel utilization, packet delay and packet dropping probability.

We study the issues of adaptive multicast wormhole routing in 2D mesh multicomputers. Three adaptive multicast wormhole routing strategies ;Lre proposed and studied~ which include miaitaal partial adaptive, minima] fuity adaptive anti nonminimal multicast routing methods. All the algorithms are shown to be deadlock-free. These are the first deadlock-free adaptive multicast wormhole routing algorithms ever proposed. A simulation study has been conducted that compares the performance of these multicast algorithms. The results show that the minimal fully adaptive routing method creates the least traffic~ however, double vertical channels are required in order to avoid deadlock. The nonminimal routing algorithin exhibit~ the best adaptivity, although it creates more network traffic than tile otlaer mettmds.

A critical component of subscriber management in a DOCSIS-based cable access network is the buffer management strategy that is in operation at the upstream service flow queue located in the cable modem. The strategy must contend with conflicting goals: large buffers might be required to ensure TCP flows can utilize available bandwidth, however large buffers can impact application flows that are latency sensitive. In this study, we have explored the relationship between application performance and upstream queue management. We define the optimal queue capacity as the buffer size that maximizes throughput and minimizes packet delay. Our results agree with previous work in wired Internet router contexts that suggest that the queue capacity should not exceed a bandwidth*delay product (BDP) amount of data. However, the upstream data rate available to a cable modem varies with the number of competing cable modems. Upstream service flow queues that are provisioned to hold a BDP of data might suffer queue delays exceeding several seconds during periods of congestion. Active queue management such as the Random Early Discard algorithm is able to reduce average queue levels but is not able to provide a consistent balance between the needs of both high throughput and latency sensitive applications. The conclusion is that an adaptive queue management algorithm is required to maintain a consistent balance between throughput and delay.

This work introduces two novel buffer management policies for inter-active VoD systems: Unique Buffer (UB) and Precise Buffer (PB). The former uses a buffer which is shared by all clients playing a same single object, and the latter is based on the idea of quantifying the information available in the local buffer before making any stream merge decisions. Through simulations we validate our proposals and carry out a detailed competitive analysis. The fi-nal results show for instance that, comparing to more conventional approaches, we may have optimizations in the range of 5%–98% at bandwidth peak values, bandwidth average values and system complexity. Resumo. Este trabalho apresenta duas novas estratégias de gerência de buffer de um sistema de VoD com interatividade: Unique Buffer (UB) e Precise Buffer (PB). A primeira tem por idéia principal o emprego de u unico buffer compar-tilhado por todos os clientes, e a segunda baseia-se na avalia ao da quantidade de informa ao disponível loc...

One of the challenges in the interconnection of LAN's and MAN's to ATM is the support of connectionless traffic in the ATM network. A commonly proposed strategy consists of maintaining a "thin" (i.e., low bandwidth) VP (virtual path) between each pair of gateways, and of requesting more bandwidth whenever a burst comes in from the LAN or MAN. Unfortunately, this strategy places a heavy burden on the ATM control processors; furthermore, it is overly conservative in the use of bandwidth. An alternative solution is proposed: on the-fly transmission of bursts without prior bandwidth reservation. The key conditions for this scheme to work are the use of the CLP (cell loss priority) bit in the ATM cell header, and the knowledge of available bandwidth on the path through "bandwidth advertising." An "on-the-fly'' strategy for connectionless traffic is described and is compared with a bandwidth renegotiation strategy.

In recent years, there has been a lot of interest in Quality of Service (QoS) networks. In regular IP networks, packets are indistinguishable and in case of overload any packet may be dropped. In a commercial environment, it is much more preferable to allow better service to higher-paying customers or customers with critical requirements. The idea of Quality of Service guarantees is that packets are marked with values which indicate their importance. This naturally leads to decision problems at network switches when many packets arrive and overload occurs. In this paper, we give an overview of several models that have been studied in this area from an online perspective. These models differ by restrictions such as bounded delay, bounded size of queue etc. We first present results for a single buffer in Section 1 and then for multiple buffers in Section 2. This paper is not meant as a comprehensive survey of the work in this area. There are many more variations of these problems that have been studied, for instance, multiple output buffers [14]. Our goal was merely to give a taste of this problem area, and we hope you enjoy it.

An objective of the next. generation network is the accommodation of services wit,h different QoS requirements. This indicates that the network should provide special mechanisms in order to prioritize the access to network node resources, such as link capacity and buffer space. We studied the performance of sharing buffer space and link capacity bet.ween sessions, the traffic of which is modeled by independent. general Markov-Modulated Fluid Process (MMFP) sources. For scheduling we use the Generalized Processor Sharing (G P S) policy, and improve previous upper bounds on the queue occupancy distributions. As an example of combining G P S with buffer management we apply our results to complete buffer sharing with virtual partitioning (VP+GPS). We also derive results on the resource allocation trade-off, with applications in traffic management and admission control. This work was supported in part by the NY State Center for Advanced Technologies in Telecommunications (C ATT) , and Sumitomo Electric Industries (USA). The work was done when G. Lapiotis was a research fellow in the NY State CATT, Polytechnic University.

Many works have studied the performance of TCP by modeling the network as a single bottleneck node. We present a more general model taking into account all the nodes on the path not only the main bottleneck. We show that, in addition to the main bottleneck, the other nodes can seriously affect the performance of TCP. They may cause an

Acknowledgement (ACK) filtering has been proposed as a technique to alleviate the congestion at the input of a slow channel located on the reverse path of a TCP connection. Old ACKs waiting at the input of the slow channel are erased when new ACKs are to be queued. In the literature the case of one‐ACK per connection at a time has been studied. In this paper we show that this is too aggressive for short transfers where ACKs arrive in bursts due to the slow start phase, and where the TCP source needs to receive the maximum number of ACKs to increase fast its window. We study first static filtering where a certain ACK queue length is allowed. We show analytically how this length needs to be chosen. We present then some algorithms that adapt the filtering of ACKs as a function of the slow channel utilization rather than the ACK queue length. These algorithms provide a good compromise between reducing the ACK queueing delay and passing a large number of ACKs that guarantee a fast window...

Several objectives have been identified in developing the random early drop (RED): decreasing queueing delay, increasing throughput, and increasing fairness between short and long lived connections. It has been believed that indeed the drop probability of a packet in RED does not depend on the size of the file to which it belongs. In this paper we study the fairness properties of RED where fairness is taken with respect to the size of the transferred file. We focus on short lived TCP sessions. Our findings are that (i) in terms of loss probabilities, RED is unfair: it favors short sessions, (ii) RED is fairer in terms of the average throughput of a session (as a function of its size) than in terms of loss probabilities. We study various loading regimes, with various versions of RED.

Access to the Internet is a crucial enabler for many of the Sustainable Development Goals (SDGs) of the United Nations. Unfortunately, a significant part of the world's population is left behind due to the lack of access to a reliable and affordable Internet connection. Satellites have the potential to impact the current market of Internet services significantly. In particular, Low Earth Orbit (LEO) satellites promise high-bandwidth without compromising latency. They can be employed in 5G Non-Terrestrial Networks (e.g., IoT connectivity, connected autonomous driving, communication in rural areas, and more). Smart farming and precise agriculture (even remotely controlled), especially in underdeveloped areas, are compelling use cases for LEO satellites. In these scenarios, high bandwidth and low latency are required to facilitate both quick transmission of images/videos and prompt remote control of drones, tractors, actuators, etc. This study compares different TCP protocols based on their performance over satellite communication in a smart farming case study. It also proposes and analyzes a solution leveraging on a limited buffer size to maintain a high throughput while lowering per-packet delays.

In this paper a special kind of buffer management policy is studied where the packet are preempted even when sufficient space is available in the buffer for incoming packets. This is done to congestion for future incoming packets to improve QoS for certain type of packets. This type of study has been done in past for ATM type of scenario. We extend the same for heterogeneous traffic where data rate and size of the packets are very versatile in nature. Typical example of this scenario is the buffer management in Differentiated Service Router. There are two aspects that are of interest. First is the packet size: whether all packets have same or different sizes. Second aspect is the value or space priority of the packets, do all packets have the same space priority or different packets have different space priorities. We present two types of policies to achieve QoS goals for packets with different priorities: the push out scheme and the expelling scheme. For this work the scenario of p...

A stable heap is storage that is managed automatically using garbage collection, manipulated using atomic transactions, and accessed using a uniform storage model. These featnres enhance reliability and simplify programming by preventing errors due to explicit deallocation, by masking failures and concurrency using transactions, and by eliminating the distinction between accessing temporary storage and permanent storage. Stable heap management is useful for programming languages for reliable distributed computing, programming languages with persistent storage, and object+riented database systems. Many applications that could benefit from a stable heap (e.g., computer-aided design, computer-aided software engineering, and office information systems) require large amounts of storage, timely responses for transactions, and high availability. We present garbage collection and recovery algorithms for a stable heap implementation that meet these goals and are appropriate for stock hardware. The collector is incremental it does not attempt to collect the whole heap at once. The collector is also atomic: it is coordinated with the recovery system to prevent problems when it moves and modifies objects. The time for recovery is independent of heap size, even if a failure occurs during garbage collection.

Effective buffer management is crucial for efficient inmemory and streaming XQuery processing. We propose a buffer management scheme which combines static and dynamic analysis to keep main memory consumption low. Our approach relies on a technique that we call active garbage collection and which actively purges buffers at runtime based on the current status of query evaluation. We have built a prototype system for a practical fragment of XQuery which employs our buffer management scheme. The experimental results demonstrate the significant impact of combined static and dynamic analysis on reducing main memory consumption and running time.