waashk/dblp huggingface dataset:
mobility increases the capacity of ad-hoc wireless networks. the capacity of ad hoc wireless networks is constrained by the mutual interference of concurrent transmissions between nodes. we study a model of an ad hoc network where n nodes communicate in random source-destination pairs. these nodes are assumed to be mobile. we examine the per-session throughput for applications with loose delay constraints, such that the topology changes over the time-scale of packet delivery. under this assumption, the per-user throughput can increase dramatically when nodes are mobile rather than fixed. this improvement can be achieved by exploiting a form of multiuser diversity via packet relaying.
a time-scale decomposition approach to measurement-based admission control. we propose a time-scale decomposition approach to measurement-based admission control (mbac). we identify a critical time scale th such that: 1) aggregate traffic fluctuation slower than th can be tracked by the admission controller and compensated for by flow admissions and departures; and 2) fluctuations faster than th have to be absorbed by reserving spare bandwidth on the link. the critical time scale is shown to scale as th/√n, where th is the average flow duration and n is the size of the link in terms of number of flows it can carry. an mbac design is presented which filters aggregate measurements into low- and high-frequency components separated at the cutoff frequency 1/th, using the low-frequency component to track slow time-scale traffic fluctuations and the high-frequency component to estimate the spare bandwidth needed. our analysis shows that the scheme achieves high utilization and is robust to traffic heterogeneity, multiple time-scale fluctuations and measurement errors. the scheme uses only measurements of aggregate bandwidth and does not need to keep track of per-flow information.
measurement of atm traffic on the cell, burst and activity level by traffic sampling. the authors address the problem of measuring asynchronous transfer mode (atm) traffic on the cell, burst and activity level. with the aid of a traffic sampling mechanism it is shown that efficient data can be collected. these data are then used to estimate the spectral density on each level. it is shown that a forward-backward least square spectral estimator with prefiltering gives an accurate estimation even at low frequencies and that the power spectral density at frequency zero and the load are the most dominant parameters for the queue length and hence also for loss
project acorn and distributed approaches to atm networks. centralized and distributed approaches to the design and implementation of a multi-gigabit per second asynchronous transfer mode (atm) switch are discussed. the implementation constraints associated with a centralized switch are demonstrated and an alternative distributed optical network architecture is described. the distributed approach exploits unique opportunities presented through the use of a passive optical medium. a network based on these principles (teranet), has been implemented that offers user access rates of 1 gbit/s. the distributed atm switch fabric resides in small, geographically dispersed access stations interconnected by a shared, all-optical medium carrying many wavelength-multiplexed channels. although the underlying multihop architecture for the atm network produces a lower per-port throughput than that afforded by a large centralized atm switch, significant implementation advantages exist. possible techniques to yield a higher per-port throughput approaching that of a large centralized switch are also discussed
qos-based routing in networks with inaccurate information: theory and algorithms. we investigate the problem of routing connections with qos requirements across one or more networks, when the information available for making routing decisions is inaccurate and expressed in some probabilistic manner. this uncertainty about the actual state of a node or network arises naturally in a number of different environments, that are reviewed in the paper. the main focus is to determine the impact of such inaccuracies on the path selection process, whose goal is then to identify the path that is most likely to satisfy the qos requirements.
vbr over vbr: the homogeneous, loss-free case. we consider the multiplexing of several variable bit rate (vbr) connections over one variable bit rate connection where the multiplexing uses a multiplexing buffer of size b. the vbr trunk is itself a connection and has a multidimensional connection descriptor, reflecting peak and sustainable rates. given a cost function for the vbr trunk and a connection admission control (cac) method for the input connections, we focus on the problem of finding the vbr trunk connection descriptor that minimizes the cost function and is able to accept a given set of vbr input connections. first, we show that, under reasonable assumptions on the cost function, the optimization problem can be reduced to a simpler one. then we consider the homogeneous, loss-free case, for which we give an explicit cac method. in that case, we find that, for all reasonable cost functions, the optimal vbr trunk is either of the cbr type, or is truly vbr, with a burst duration equal to the burst duration of the input connections. we motivate this study by showing that the optimal peak cell rate is fixed for a given b (thus for a cbr trunk), and a vbr choice can only be an improvement. lastly, we take as example of cost function the equivalent capacity of the vbr trunk. those results are expected to form the basis for a general method for a connection manager at a multiplexing node in an integrated services packet network.
an analysis of internet inter-domain topology and route stability. the internet routing fabric is partitioned into several domains. each domain represents a region of the fabric administered by a single commercial entity. over the past two years, the routing fabric has experienced significant growth. from more than a year's worth of inter-domain routing traces, we analyze the internet inter-domain topology, its route stability behavior, and the effect of growth on these characteristics. our analysis reveals several interesting results. despite growth, the degree distribution and the diameter of the inter-domain topology have remained relatively unchanged. furthermore, there exists a four-level hierarchy of internet domains classified by degree. however, connectivity between domains is significantly non-hierarchical. despite increased connectivity at higher levels in the topology, the distribution of paths to prefixes from the backbone remained relatively unchanged. there is evidence that both route availability and the mean reachability duration have degraded with internet growth.
peak rate enforcement in atm networks. the authors address peak rate enforcement in asynchronous transfer mode (atm) networks by pick-up policing mechanisms. since the network cannot rely on user's compliance when declaring his traffic parameters, the policing function has been introduced to monitor the traffic characteristics of any connection. policing mechanisms proposed in the literature are actually pick-up mechanisms since cells can pass transparently through unless a policing action was performed according to some counting process. the authors analyze the impact of the cell multiplexing jitter on policing mechanism dimensioning. recognizing that dimensioning is a critical point for such mechanisms. it is shown that network buffer overflow cannot be avoided in certain conditions. therefore, a new policing scheme, called cell spacing, is introduced, and two spacing algorithms are presented
on characterizing an atm source via the sustainable cell rate traffic descriptor. the sustainable cell rate (scr) was introduced by the atm forum as a means of characterizing the statistical activity of atm vbr connections. the scr traffic descriptor (scr-td), composed of the sustainable cell rate 1/t/sub scr/ and the intrinsic burst tolerance /spl tau//sub ibt/, is defined with respect to an algorithmic characterization, the generic cell rate algorithm (gcra). this method makes source parameter enforcement straightforward. unfortunately, the current specification of the scr-td is incomplete, leaving the source with an infinite number of (t/sub scr/, /spl tau//sub ibt/) couples to choose from, this ambiguity could bear a negative impact on network efficiency. the authors investigate the issues involved in selecting suitable scr-td values for a given source, both from a user's perspective and from a networking point of view.
resource and connection admission control in real-time transport protocols with deterministic qos guarantees. real-time multimedia applications will require guaranteed quality of service (qos) such as a bound on the maximum message delay and/or on the maximum message loss rate. this poses an exciting challenge to the highspeed transport protocol design and implementations. in this paper, we study the resource and connection admission control algorithms, and give the necessary and sufficient conditions for the schedulability, of n real-time transport connections at a destination host under preemptive and non-preemptive deadline scheduling policy for deterministic qos guarantees. these necessary and sufficient conditions form the mathematical basis for the deterministic qos guarantees in real-time transport communication services. on the basis of these necessary and sufficient conditions, we give the connection admission control algorithms for deterministic qos guarantees. we also calculate the buffer space needed for each real-time transport connection. the results show that real-time transport connections with deterministic qos guarantees can reserve the buffer space at the establishment phase, and no flow control mechanism is required during the data transport phase. our results could be applied to other fields as well, such as real-time operating systems.
performance of a crosspoint buffered atm switch fabric. the authors present a queuing analysis and a simulation study of banyan switch fabrics based on 2&times;2 switching elements with crosspoint buffering. in particular, the results apply to the phoenix switching element based banyan fabrics. the results indicate that crosspoint buffering provides throughput approaching the offered load under uniform traffic conditions. the effect of bursty traffic on the performance of the switch is studied. it is shown that a speedup factor of three or more is required to achieve acceptable delay and packet loss probability. it is also shown that the amount of buffer space required per port increases linearly with the burst size for a desired packet loss performance. for a given burst size the packet loss rate decreases exponentially as the buffer size is increased. the impact of crosspoint buffering and shared buffering in the switching elements on the performance of the banyan fabric is analyzed
priority performance of atm packet switches. an asynchronous transfer mode (atm) packet switch should be capable of handling delay sensitive as well as loss sensitive traffic. the authors consider delinking handling of these two types of priorities in a switching system, and present an analysis of two classes of delay sensitive traffic in an n&times;n nonblocking switch with input queues. in such a switch, two variations of nonpreemptive priority are studied. a packet switch with input buffers has inadequate throughput. to enhance the performance and to provide low delay to high priority traffic, a dual plane switch architecture is examined, where each plane is a nonblocking switch with input buffers. the two planes are connected in parallel to form a load sharing arrangement. the analysis of a single plane nonblocking switch is extended to this architecture. in both cases, the performance is compared with the simulation results of a 64&times;64 switch
resource sharing for multi-party real-time communication. approaches to supporting real-time communication allocate network resources either to individual connections, or to aggregates of connections. resource sharing is a new approach that exploits known relationships between related connections to allow network resources to be shared between them without sacrificing well-defined guarantees. the authors present a fully distributed technique for using resource sharing to provide guaranteed performance communication in a heterogeneous internetwork. results show that resource sharing leads to a large gain in the connection acceptance rate, and a significant reduction in the computational overhead associated with admission control. thus, resource sharing is an important tool for providing real-time performance guarantees for large conferences.
design and performance analysis of a dynamic protocol achieving user fairness in high-speed dual-bus networks. the ieee 802-6 dqdb protocol solves the existing problems in prior round-robin high-speed mac protocols. however, it introduces a new performance unfairness problem when the network size or channel bandwidth increases. the pi-persistent protocol, on the other hand, does not pass any control information over the channels, and was shown capable of achieving various fairness criteria, when each station knows the loads of all other stations. the authors propose a dynamic pi-persistent protocol that is capable of adjusting the network to fair operation in an environment where the station loads change over time. the protocol requires passing of some control information through the network. the information passed is not as detailed as the request information in dqdb. the authors analyze the performance of the protocol in a batch arriving model for load increase. the results show that the protocol is both fast and accurate in responding to network load changes
network transparency: the planet approach. asynchronous transfer mode (atm) is being suggested as the basis for future high speed, universal networks. a key requirement for future atm networks will be transparency, i.e. for the network to alter or manipulate the user information as little as possible. a transparent transport mechanism, planet, based on extensions of the current atm standard and ibm's earlier paris technology, is proposed. it is shown how planet can satisfy the universal transport requirement of atm, while avoiding some demonstrated deficiencies. in fact, planet could be viewed as an enhanced version of atm that may be more suitable for the late 1990s than the current standard
performance of fddi under overload. the performance of the fiber distributed data interface (fddi) under overload is studied. it is well known that, under overload, fddi can settle into one of many recurrent sets of states. the idea of desirable and undesirable states is introduced. a desirable state is one where users share the capacity more or less equally in each token rotation. it is shown that the response times of interactive users are adversely affected if the system operates in an undesirable set of states. the waiting time of heavy users can be reduced by forcing the system to settle into the desirable states. simple control mechanisms are proposed to ensure that the system settle into the desirable states
fast simulation of a voice-data multiplexer. this paper considers the problem of estimating, via simulation, extremely low packet loss rates in a voice-data multiplexer. the multiplexer gives priority to voice packets, unless the data queue length exceeds a threshold. to efficiently simulate such low loss rates requires the proper use of importance sampling. in this paper we describe an importance sampling technique that is guaranteed to provide an exponential decrease in variance over standard simulation. this importance sampling technique has two phases, with a different importance sampling strategy in each phase. experimental results are presented that demonstrate the effectiveness of this approach.
gossip-based ad hoc routing. many ad hoc routing protocols are based on some variant of flooding. despite various optimizations of flooding, many routing messages are propagated unnecessarily. we propose a gossiping-based approach, where each node forwards a message with some probability, to reduce the overhead of the routing protocols. gossiping exhibits bimodal behavior in sufficienty large networks: in some executions, the gossip dies out quickly and hardly any node gets the message; in the remaining executions, a substantial fraction of the nodes gets the message. the fraction of executions in which most nodes get the message depends on the gossiping probability and the topology of the network. in the networks we have considered, using gossiping probability between 0.6 and 0.8 suffices to ensure that almost every node gets the message in almost every execution. for large networks, this simple gossiping protocol uses up to 35% fewer messages than flooding, with improved performance. gossiping can also be combined with various optimizations of flooding to yield further benefits. simulations show that adding gossiping to aodv results in significant performance improvement, even in networks as small as 150 nodes. our results suggest that the improvement should be even more significant in larger networks.
on slot allocation for time-constrained messages in dqdb networks. the paper addresses the issue of guaranteeing the timely delivery of isochronous messages with hard deadlines in a distributed queue dual bus (dqdb) network. the authors propose a slot allocation scheme which can allocate bandwidth for a set of isochronous message streams and provide deterministic deadline guarantees. the allocation scheme is guaranteed to find a feasible slot allocation (in the sense that all messages can be transmitted in a timely manner) as long as the total message density is less than or equal to a certain threshold, where the total message density is defined as the summation (over all message streams) of the ratio of maximum message size to message deadline. the implementation of this scheme is simple and does not require any change of the current dqdb standard.
a polynominal-time optimal synchronous bandwidth allocation scheme for the timed-token mac protocol. numerous methods have been proposed to integrate real-time and non-real-time services of the timed-token medium access control (mac) protocol. one of the key issues in tailoring the timed-token mac protocol for real-time applications is the synchronous bandwidth allocation (sea) problem whose objective is to meet both the protocol and deadline constraints. several non-optimal local sea schemes and an optimal global scheme have been proposed previously. local sea schemes use only information available locally to each node, and are thus preferred to global schemes because of their lower network-management overhead. unfortunately it has been formally proved in han et al. (1995) that there does not exist any optimal local sea scheme. chen et al. [1992] proposed the only-known optimal global sea scheme which is based on an iterative approach. however, their algorithm may not terminate theoretically. the present authors give an optimal global sea scheme of polynomial-time worst-case complexity.
toward formal ttcn-based test execution. formal test execution method is an important research field in formal protocol conformance testing. in this paper, we propose a formal test execution aapproach that is based on test notation ttcn's operational semantics, and describe its executing process by using input-output transition system(iots). we also give out a pratical design of this formal approach. this formal ttcn-based test execution method is very suitable for the construction of general protocol test system, and also an effective means of automatic test suite verification.
performance of alternative routing methods in all-optical switching networks. we study routing methods in all--optical switching networks. in all--optical switching networks, the connection with more hops encounters more call blocking, and it is especially true in optical networks with no wavelength conversions. we therefore consider an alternate routing method with limited trunk reservation in which connections with more hops are prepared more alternate routes. through developing an approximate analytic approach, we show that our method keeps good performance when compared with the existing alternate routing methods, and also that the fairness among connections can be improved. further performance improvement is investigated by introducing a wavelength assignment policy and a dynamic routing method. an effectiveness of the proposed method is investigated through simulation.
measuring bottleneck bandwidth of targeted path segments. abstract accurate measurement of network bandwidth is crucial for flexible internet applications and protocols which actively manage and dynamically adapt to changing utilization of network resources. these applications must do so to perform tasks such as distributing and delivering high-bandwidth media, scheduling service requests and performing admission control. extensive work has focused on two approaches to measuring bandwidth: measuring it hop-by-hop, and measuring it end-to-end along a path. unfortunately, best-practice techniques for the former are inefficient and techniques for the latter are only able to observe bottlenecks visible at end-to-end scope. in this paper, we develop and simulate end-to-end probing methods which can measure bottleneck bandwidth along arbitrary, targeted subpaths of a path in the network, including subpaths shared by a set of flows. as another important contribution, we describe a number of practical applications which we foresee as standing to benefit from solutions to this problem, especially in emerging, flexible network architectures such as overlay networks, ad-hoc networks, peer-to-peer architectures and massively accessed content servers.
comparisons of packet scheduling algorithms for fair service among connections on the internet. we investigate the performance of tcp under three representatives of packet scheduling algorithms at the router. our main focus is to investigate how fair service can be provided for elastic applications sharing the link. packet scheduling algorithms that we consider are fifo (first in first out), red (random early detection), and drr (deficit round robin). through simulation and analysis results, we discuss the degree of achieved fairness in those scheduling algorithms. furthermore, we propose a new algorithm which combines red and drr algorithms in order to prevent the unfairness property of the original drr algorithm, which appears in some circumstances where we want to resolve the scalability problem of the drr algorithm. in addition to tcp reno version, we consider tcp vegas to investigate its capability of providing the fairness. the results show that the principle of tcp vegas conforms to drr, but it cannot help improving the fairness among connections in fifo and red cases, which seems to be a substantial obstacle for the deployment of tcp vegas.
a general purpose cell sequencer/scheduler for atm switches. groups of cells, such as cells belonging to different priority levels, that are all placed in one queue, can be identified by using labels or tags to distinguish them from each other. in this paper we describe a buffering device called sequencer, which can distinguish logical queues within the same physical queue, and at the same time can successfully schedule the service among these logical queues. scheduling the service among cells, vc's, or groups of cells in atm switches is necessary to provide guaranteed qos for each connection which is a major goal of atm networks. the proposed sequencer is quite flexible and can realize different scheduling algorithms in different levels, including per vc scheduling.the sequencer can operate in real time and at very high speeds. it has a simple and modular architecture and can be implemented in a single chip. the size of the buffer can be increased simply by cascading several sequencers.the sequencer can be used as traffic shaper, input buffer, output buffer, or queue controller of ram-based switches.