waashk/dblp huggingface dataset:
statistical characteristics and multiplexing of mpeg streams. this paper presents a study of the statistical characteristics and multiplexing of variable-bit-rate (vbr) mpeg-coded video streams. our results are based on 23 minutes of video obtained from the entertainment movie, the wizard of oz. the experimental setup which was used to capture, digitize, and compress the video stream is described. although the study is conducted at the frame level (as opposed to the slice level), it is observed that the inter-frame correlation structure for the frame-size sequence involves complicated forms of pseudo-periodicity that are mainly affected by the compression pattern of the sequence. a simple model for an mpeg traffic source is developed in which frames are generated according to the compression pattern of the original captured video stream. the number of cells per frame is fitted by a lognormal distribution. simulations are used to study the performance of an atm multiplexer for mpeg streams.
exploiting the temporal structure of mpeg video for the reduction of bandwidth requirements. we present a novel bandwidth allocation scheme for transporting variable-bit-rate mpeg traffic from a video server. using time-varying envelopes to characterize the traffic, this scheme achieves significant bandwidth gain, via statistical multiplexing, while supporting stringent, deterministic qos guarantees. the gain can be maximized by allowing the server to appropriately schedule the starting times of video sources, at the expense of some negligible startup delay. for homogeneous streams, we give the optimal schedule that results in the minimum allocated bandwidth. a suboptimal schedule is given in the heterogeneous case, which is shown to be asymptotically optimal. efficient online procedures for bandwidth computation are provided. numerical examples based on traces of mpeg-coded movies are used to demonstrate the benefits of our allocation strategy.
performance analysis of rate based feedback control for atm networks. closed-loop input rate regulation schemes have come to play an important role in the transport of the available bit rate (abr) traffic service category for atm. in this paper, we present a numerical approach to the performance study of a delayed feedback system with one congested node and multiple connections. this approach consists in modeling the feedback system as a finite quasi-birth-death (qbd) process. due to the peculiar block tri-diagonol nature of its generator, efficient techniques exist for its steady-state and transient solutions. using these techniques, we examine a simple parsimonious feedback system for issues such as throughput/loss performance, fairness and stability.our approach has the flexibility to study the effect of several additional factors such as asynchronous feedback, two-level control and explicit rate notification in the presence of underlying high-priority traffic. this study brings to light the trade-offs between system performance and the complexity of the feedback scheme. our study shows that the time scales of correlation of the feedback system have a dominant effect on its performance. these time scales are associated with the feedback delay, the durations of active/idle periods of traffic sources and the time scales of the underlying high-priority traffic. we also examine the effect of the time scales on the convergence time for the transient queueing system.
new insights from a fixed point analysis of single cell ieee 802.11 wlans. we study a fixed-point formalization of the well-known analysis of bianchi. we provide a significant simplification and generalization of the analysis. in this more general framework, the fixed-point solution and performance measures resulting from it are studied. uniqueness of the fixed point is established. simple and general throughput formulas are provided. it is shown that the throughput of any flow will be bounded by the one with the smallest transmission rate. the aggregate throughput is bounded by the reciprocal of the harmonic mean of the transmission rates. in an asymptotic regime with a large number of nodes, explicit formulas for the collision probability, the aggregate attempt rate, and the aggregate throughput are provided. the results from the analysis are compared with ns2 simulations and also with an exact markov model of the backoff process. it is shown how the saturated network analysis can be used to obtain tcp transfer throughputs in some cases.
an access protection solution for heavy load unfairness in dqdb. the authors discuss the unfairness issue arising in a 802.6 distributed queue dual bus (dqdb) network at heavy loads. based on the 802.6 protocol, the end-nodes along a bus experience longer delays than the other nodes. the origin and remedy for this heavy load unfairness problem are discussed. an access control scheme is proposed as a solution. a comparison of the proposed scheme with the 802.6 protocol is presented. the simulation results and performance characteristics are discussed under several types of loads. with symmetric load conditions under the proposed scheme, all active nodes along a bus experience almost the same access delay and packet loss characteristics. the performance under several other load conditions was also found to be satisfactory
fairness by demand and service pattern match: the alpha tuning mechanism for dqdb mans. this paper proposes a dynamic bandwidth control scheme for the distributed queue dual bus (dqdb) networks. the heavy load unfairness is effectively addressed. the match of demand and service patterns is achieved at fairly uniform delays and success rates of transmission at every node. using a tunable parameter (/spl alpha/), the proposed scheme perceives the presence of several fictitious nodes at the end of the bus and applies access protection. analysis and simulation studies for three standard load patterns, viz., symmetric, asymmetric and equal probability loads, show that it outperforms the bandwidth balancing mechanism.
performance and fluid simulations of a novel shared buffer management system. we consider a switching system that has multiple ports that share a common buffer, in which there is a fifo logical queue for each port. each port may support a large number of flows or connections, which are approximately homogeneous in their statistical characteristics, with common qos requirements in cell loss and maximum delay. heterogeneity may exist across ports. our first contribution is a buffer management scheme based on buffer admission control, which is integrated with connection admission control at the switch. at the same time, this scheme is fair, efficient, and robust in sharing the buffer resources across ports. our scheme is based on the resource-sharing technique of virtual partitioning. our second major contribution is to advance the practice of discrete-event fluid simulations. such simulations are approximations to cell-level simulations and offer orders of magnitude speed-up. a third contribution of the paper is the formulation and solution of a problem of optimal allocation of bandwidth and buffers to each port having specific delay bounds, in a lossless multiplexing framework. finally, we report on extensive simulation results. the scheme is found to be effective, efficient, and robust.
uplink scheduling in cdma packet-data systems. uplink scheduling in wireless systems is gaining importance due to arising uplink intensive data services (ftp, image uploads etc.), which could be hampered by the currently in-built asymmetry in favor of the downlink. in this work, we propose and study algorithms for efficient uplink packet-data scheduling in a cdma cell. the algorithms attempt to maximize system throughput under transmit power limitations on the mobiles assuming instantaneous knowledge of user queues and channels. however no channel statistics or traffic characterization is necessary. apart from increasing throughput, the algorithms also improve fairness of service among users, hence reducing chances of buffer overflows for poorly located users.the major observation arising from our analysis is that it is advantageous on the uplink to schedule "strong" users one-at-a-time, and "weak" users in larger groups. this contrasts with the downlink where one-at-a-time transmission for all users has shown to be the preferred mode in much previous work. based on the optimal schedules, we propose less complex and more practical approximate methods, both of which offer significant performance improvement compared to one-at-a-time transmission, and the widely acclaimed proportional fair (pf) algorithm, in simulations. when queue content cannot be fed back, we propose a simple modification of pf, uplink pf (upf), that offers similar improvement.
receiver-oriented adaptive buffer allocation in credit-based flow control for atm networks. in credit-based flow control for atm networks, a buffer is first allocated to each vc (virtual circuit) and then credit control is applied to the vc for avoiding possible buffer overflow. receiver-oriented, adaptive buffer allocation allows a receiver to allocate its buffer dynamically, to vcs from multiple upstream nodes based on their bandwidth usage. the paper describes, in detail, such an adaptive algorithm capable of supporting a wide range of link speeds and propagation delays, and also packing multiple allocation and credit records in a single message. analysis and simulation results show that even under highly bursty traffic, the adaptive scheme guarantees no cell loss due to congestion, and achieves excellent performance in utilization, fairness, ramp-up and packing, while requiring only relatively small node memory and bandwidth overhead. the required memory need only be 4*rtt+2*n, where rtt is the link round-trip time in cell cycles and n is the number of vcs.
client-server performance on flow-controlled atm networks: a web database of simulation results. extensive simulation has demonstrated the effectiveness of credit-based atm flow control in supporting client-server applications. in particular, request/response protocols used in these applications allow efficient sharing of switch buffer, for the case when all the vcs sharing the same buffer are subject to the same degree of downstream congestion. the required buffer size can be as small as the minimum of bandwidth*rtt for the link and #clients*reply_size. request/response protocols generally tolerate congestion better than greedy loads. being able to avoid synchronization, fifo scheduling is sometimes more efficient than vc round-robin scheduling. these findings are derived from an online web database of simulation results covering more than 10,000 network and load configurations. the web database approach has proven to be effective in managing and navigating a large set of simulation results.
end-to-end congestion control schemes: utility functions, random losses and ecn marks. we present a framework for designing end-to-end congestion control schemes in a network where each user may have a different utility function and may experience noncongestion-related losses. we first show that there exists an additive-increase-multiplicative-decrease scheme using only end-to-end measurable losses such that a socially optimal solution can be reached. we incorporate round-trip delay in this model, and show that one can generalize observations regarding tcp-type congestion avoidance to more general window flow control schemes. we then consider explicit congestion notification (ecn) as an alternate mechanism (instead of losses) for signaling congestion and show that ecn marking levels can be designed to nearly eliminate losses in the network by choosing the marking level independently for each node in the network. while the ecn marking level at each node may depend on the number of flows through the node, the appropriate marking level can be estimated using only aggregate flow measurements, i.e., per-flow measurements are not required.
reliable multicast in multi-access wireless lans. multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. in this paper, we focus on multicast in single channel multi-access wireless local area networks (lans) comprising several small cells. in such a system, a receiver cannot correctly receive a packet if two or more packets are sent to it at the same time, because the ackets "collide". therefore, one has to ensure that only one node sends at a time. we look at two important issues.first, we consider the problem of the sender acquiring the multi-access channel for multicast transmission. second, for reliable multicast in each cell of the wireless lan, we examine arq-based approaches. the second issue is important because the wireless link error rates can be very high. we present a new approach to overcome the problem of feedback collision in single channel multi-access wireless lans, both for the purpose of acquiring the channel and for reliability. our approach involves the election of one of the multicast group members (receivers) as a "leader" or representative for the purpose of sending feedback to the sender. for reliable multicast, on erroneous reception of a packet, the leader does not send an acknowledgment, prompting a retransmission. on erroneous reception of the packet at receivers other than the leader, our protocol allows negative acknowledgments from these receivers to collide with the acknowledgment from the leader,thus destroying the acknowledgment and prompting the sender to retransmit the packet. using analytical models, we demonstrate that the leader-based protocol exhibits higher throughput in comparison to two other protocols which use traditional delayed feedback-based probabilistic methods. last, we present a simple scheme for leader election.
bounds and approximations for the periodic on/off queue with applications to atm traffic control. the authors consider statistical multiplexing of on/off sources in an asynchronous transfer mode (atm) network and its implications on traffic control. the periodic on/off source is used as a worst case output from the traffic enforcement algorithm, and the queue receiving information from a number of independent periodic on/off sources is studied with simulation results and analytical methods. the decomposition of the queuing process into a cell scale and a burst scale component is illustrated. a comparison with the exponentially distributed on/off queue is carried out, and a simple and versatile approximation is provided on which an admission control scheme based on peak, mean and burst duration can be based. some implications on buffer dimensioning and traffic control are discussed
an adaptable and reliable authentication protocol for communication networks. in this paper, we propose a new authentication and key distribution protocol which is adaptable and reliable for communication networks. the secrets for authentication, which are chosen from a relatively small space by common users, are easy to guess. our protocol gives a solution to protect the weak secrets from guessing attacks.compared with other related work, our protocol is more reliable because it is resistant to various kinds of attacks including guessing attacks, and more adaptable because it reduces several overheads which make the existing protocols more expensive. we show how to apply our protocol to the q.931 calling sequences and to the world wide web model.
performance impact of partial reconfigurability in lightwave networks. rearrangeable multihop lightwave networks can be dynamically reconfigured to adapt the connectivity among network stations to prevailing traffic conditions. most of the literature has analyzed the performance of such networks assuming no limitations on the range of tunability of the transmitters and/or receivers allocated to each network station. therefore, all connection diagrams could be realized among network stations, within the constraints of the number of transmitters and receivers at each station. since the number of wavelengths in use may be very large, a practical implementation would restrict the tunability range of each transmitter and receiver to some limited set of contiguous wavelengths, or waveband. however, there is a penalty associated with such restrictions in that all connection diagrams might not be achievable and the network performances could degrade. the author derives lower bounds on the performance degradation experienced by the network when there are tunability limitations. he then proposes and analyzes a waveband assignment and grouping scheme, illustrating that one can design networks with good performance even though there are tunability constraints on the transceivers. he also describes other architectures (multi-fiber physical topology, subcarrier division multiplexing) for which the model and analysis readily apply.
reconfiguration algorithms for rearrangeable lightwave networks. the authors propose a minimally disruptive approach that transitions the network through a sequence of branch exchange operations, so that only two links are disrupted at any given time. it is shown that the problem of finding the shortest sequence, so as to minimize the duration of the reconfiguration phase, is equivalent to the problem of finding a decomposition of an auxiliary graph into the largest number of vertex-disjoint cycles. the authors then propose and compare three different polynomial-time greedy algorithms, on the basis of performance and time complexity. noticing that the length of a sequence increases at most linearly with the size of the network, the authors derived the average rate of growth from simulation results
a generalization of some policing mechanisms. the authors highlight the fact that most of the policing schemes proposed in the literature neglect important information on the past cell blocking behavior of the policing mechanism. they propose a modification of these schemes in which the discarded cell information is used, with almost no overhead compared to the usual strategies. the behavior of the modified policing mechanisms is discussed. this new behavior is illustrated by using the generalized leaky bucket to police the mean rate of a source. analysis using an on/off input process shows that the modified versions detect smaller-magnitude abuses, police the sources closer to their declared resources utilization, and have a faster response time. results are presented showing that the generalized sliding window exhibits the same kind of behavior
a framework for statistical multiplexing onto a variable-bit rate output channel. this paper investigates soft multiplexing, an issue that arises in vp-based atm networks. the main distinguishing feature of this form of multiplexing (as opposed to traditional statistical multiplexing) is that the output channel is a variable-bit rate vp. the concepts of work conservation and greediness were introduced to study soft multiplexing systematically. we assume that the overall multiplexed output traffic is regulated and policed by a leaky bucket. before being allowed to access the output channel, each input traffic stream is also controlled by a leaky bucket. it is shown that although strict performance guarantee can be provided to each input traffic stream by independent leaky bucket operation, output-channel utilization can be rather low, and it can be improved significantly if we allow some interactions among the leaky buckets of the input streams. in particular, we show that two simple soft-multiplexing schemes, excess token passing and token borrowing, can achieve higher output-channel utilization, better delay and loss performance without sacrificing guarantee to each session.
transporting compressed video over atm networks with explicit rate feedback control. we propose a scheme for transmission of variable-bit-rate compressed video over atm networks using the explicit-rate congestion control mechanisms proposed for the available bit rate (abr) service. compressed video is inherently bursty with rate fluctuations over both short and long time scales. we feel that this source behavior can naturally take advantage of the abr service, since the abr explicit-rate schemes allow sources to request varying amounts of bandwidth over time, while reserving a minimum for the entire duration of the connection. moreover when the bandwidth demand cannot be met, the network provides feedback indicating the bandwidth currently available to a connection. this information can be used to match the video source rate to the available bandwidth by modifying the quantization level used during compression. we use trace driven simulations to examine how effective the enhanced explicit rate scheme is in "rate matching" between the network and the source and the effect on end-end delay. we also look at the sensitivity of the proposed scheme to the estimates of the network round-trip times and to inaccuracies in the rate requests made by sources.
burst scheduling: architecture and algorithm for switching packet video. the authors observed that variable bit rate (vbr) video, which is a sequence of encoded pictures, has very large rate fluctuations from picture to picture. in designing a new traffic model, the authors retain the basic notion of a flow but allow the flow rate to fluctuate. in particular, they introduce the concept of a burst which, in a video flow, is a sequence of packets that carry the bits of an encoded picture. they present the architecture of a class of packet switching networks, called burst scheduling networks, for carrying video, audio, and data traffic. the class is characterized by (i) use of virtual clock value as priority in scheduling, (ii) end-to-end delay and delay jitter guarantees provided to flows conforming to the new traffic model, and (iii) traffic flows (in particular, video flows) scheduled efficiently in bursts. some experimental results are presented from a discrete-event simulation in which traces from several mpeg video sequences were used as video sources.
traffic shaping of a tagged stream in an atm network: approximate end-to-end analysis. traffic streams-originally shaped to comply with desired traffic descriptors-may suffer substantial distortion within an atm network due to statistical multiplexing. as a consequence, traffic re-shaping within the network may be necessary. in this work the modification of a tagged traffic stream due to a series of multiplexing operations is studied. the standard fcfs service policy, as well as a peak-rate enforcing multiplexing discipline, are considered. tagged cell delay, jitter and inter-departure processes are considered for the characterization of the tagged traffic stream.
analysis of packet discarding policies in high-speed networks. in this work, selective discarding policies, as a means for congestion avoidance, are studied and compared to non-discarding policies. the partial message discard policy discards packets of tails of corrupted messages. an improvement to this policy is the early message discard that drops entire messages and not just message-tails.a common performance measure of network elements is the effective throughput which measures the utilization of the network links but which neglects the application altogether. we adopt a new performance measure, goodput, which reflects the utilization of the network from the application's point of view and thus better describes network behavior.we develop and analyze a model for systems which employ discarding policies. the analysis shows a remarkable performance improvement when any message-based discarding policy is applied, and that the early message discard policy performs better, especially under high loads. we compute the optimal parameter setting for maximum goodput at different input loads and investigate the performance sensitivity to these parameters.