Results 11 - 20
of
99
Multiple Time Scale Redundancy Control for QoS-sensitive Transport of Real-time Traffic
- Proc. IEEE INFOCOM '00
, 2000
"... End-to-end QoS control over best-effort and differentiated service networks which exhibit variability in their exported service properties looms as an important challenge. In previous work, we have shown how packet-level adaptive FEC can be used in dynamic networks to facilitate invariant user-speci ..."
Abstract
-
Cited by 12 (6 self)
- Add to MetaCart
(Show Context)
End-to-end QoS control over best-effort and differentiated service networks which exhibit variability in their exported service properties looms as an important challenge. In previous work, we have shown how packet-level adaptive FEC can be used in dynamic networks to facilitate invariant user-specified QoS in an end-to-end manner. This paper addresses two important problems---self-similar burstiness and performance degradation of reactive controls subject to long feedback loops---complementing the stability/optimality considerations studied earlier. First, for adaptive redundancy control to be effective, its susceptibility to correlated packet drops and queueing delays stemming from selfsimilar burstiness must be fortified. Second, to preserve FEC's viability over ARQ when transporting real-time traffic in WANs, proactivity must be injected to offset the performance degradation of reactive feedback controls when subject to long RTTs. In this paper, we use the recently advanced multi...
A contrasting look at self-organization in the Internet and next-generation communication networks
- IEEE Communications Magazine
"... The rapid development of new networking tech-nologies, ranging from advances in the physical/ link layer (e.g., ad hoc wireless networks) to innovations in the application layer (e.g., peer- ..."
Abstract
-
Cited by 11 (3 self)
- Add to MetaCart
The rapid development of new networking tech-nologies, ranging from advances in the physical/ link layer (e.g., ad hoc wireless networks) to innovations in the application layer (e.g., peer-
Scheduling Policies for Single-Hop Networks with Heavy-Tailed Traffic
"... Abstract—In the first part of the paper, we study the impact of scheduling, in a setting of parallel queues with a mix of heavy-tailed and light-tailed traffic. We analyze queue-length unaware scheduling policies, such as round-robin, randomized, and priority, and characterize their performance. We ..."
Abstract
-
Cited by 11 (3 self)
- Add to MetaCart
(Show Context)
Abstract—In the first part of the paper, we study the impact of scheduling, in a setting of parallel queues with a mix of heavy-tailed and light-tailed traffic. We analyze queue-length unaware scheduling policies, such as round-robin, randomized, and priority, and characterize their performance. We prove the queue-length instability of Max-Weight scheduling, in the presence of heavy-tailed traffic. Motivated by this, we analyze the performance of Max-Weight-α scheduling, and establish conditions on the α-parameters, under which the system is queue-length stable. We also introduce the Max-Weight-log policy, which provides performance guarantees, without any knowledge of the arriving traffic. In the second part of the paper, we extend the results on Max-Weight and Max-Weightα scheduling to a single-hop network, with arbitrary topology and scheduling constraints. I.
Modeling and characterization of traffic in a public safety wireless network
, 2006
"... ..."
(Show Context)
A Novel Approach to the Estimation of the Long-Range Dependence Parameter
, 2002
"... A new model-testing paradigm is introduced. This paradigm is illustrated through the two long-range dependent models: Second-order self-similar, and fractional ARIMA. We then consider the parameter-estimation problem when the process is known to follow a certain model. We illustrate this new estimat ..."
Abstract
-
Cited by 9 (1 self)
- Add to MetaCart
A new model-testing paradigm is introduced. This paradigm is illustrated through the two long-range dependent models: Second-order self-similar, and fractional ARIMA. We then consider the parameter-estimation problem when the process is known to follow a certain model. We illustrate this new estimation method on the two aformentioned long-range dependent models. The confidence intervals and biasedness are obtained for the estimates using the new method. This new method is then applied to pseudo-random data and to real traffic data. We compare the performance of the new method to that of the widely-used wavelet method, and demonstrate that the former is much faster and produces much smaller confidence intervals of the long-range dependence parameter estimate. We believe that the new method can be used as an on-line estimation tool for the long-range dependence parameter and thus be incorporated in the new TCP algorithms that exploit the known self-similar and long-range dependent nature of network traffic.
Workload flurries
, 2003
"... The performance of computer systems depends, among other things, on the workload. Performance evaluations are therefore often done using logs of workloads on current productions systems, under the assumption that such real workloads are representative and reliable; likewise, workload modeling is typ ..."
Abstract
-
Cited by 9 (3 self)
- Add to MetaCart
(Show Context)
The performance of computer systems depends, among other things, on the workload. Performance evaluations are therefore often done using logs of workloads on current productions systems, under the assumption that such real workloads are representative and reliable; likewise, workload modeling is typically based on real workloads. However, real workloads may also contain anomalies that make them non-representative and unreliable. A previously unrecognized type of anomaly is workload flurries: surges of activity with a repetitive nature, caused by a single user, that dominate the workload for a relatively short period. Under suitable conditions, such flurries can have a decisive effect on performance evaluation results. The problem is that workloads containing such a flurry are not representative of normal usage. Moreover, creating a statistical model based on such a workload or using it directly is also not representative of flurries in general. This motivates the approach of identifying and removing the flurries, so as to allow for an evaluation under normal conditions. We demonstrate this for several evaluations of parallel systems, showing that the anomalies in the workload as embodied by flurries carry over to anomalies in the evaluation results, which disappear when the flurries are removed. Such an evaluation can then be augmented by a separate evaluation of the deviation caused by the flurry.
Performance evaluation of multiple time scale TCP under self-similar traffic conditions
- ACM Transactions on Modeling and Computer Simulation
, 1999
"... Measurements of network tra c have shown that self-similarity is a ubiquitous phenomenon spanning across diverse network environments. In previous work, we have explored the feasibility of exploiting long-range correlation structure in self-similar tra c for congestion control. We have advanced the ..."
Abstract
-
Cited by 8 (5 self)
- Add to MetaCart
Measurements of network tra c have shown that self-similarity is a ubiquitous phenomenon spanning across diverse network environments. In previous work, we have explored the feasibility of exploiting long-range correlation structure in self-similar tra c for congestion control. We have advanced the framework of multiple time scale congestion control and shown its e ectiveness at enhancing performance for rate-based feedback control. In this paper, we extend the multiple time scale control framework to window-based congestion control, in particular, TCP. This is performed by interfacing TCP with a large time scale control module which adjusts the aggressiveness of bandwidth consumption behavior exhibited by TCP as a function of \large time scale " network state, i.e., information that exceeds the horizon of the feedback loop as determined by RTT. How to e ectively utilize such information|due to its probabilistic nature, dispersion over multiple time scales, and a ection on top of existing window-based congestion controls|is a nontrivial problem. Our contribution is threefold. First, we de ne a modular extension of TCP|a function call with a simple interface|that applies to various avours of TCP|e.g., Tahoe, Reno, Vegas|
Un-mixing mix traffic
- In Proc. of Privacy Enhancing Technologies workshop (PET 2005
, 2005
"... Abstract. We apply blind source separation techniques from statistical signal processing to separate the traffic in a mix network into either individual flows or groups of flows. This separation requires no a priori information about the individual flows. As a result, unlinkability can be compromise ..."
Abstract
-
Cited by 8 (2 self)
- Add to MetaCart
(Show Context)
Abstract. We apply blind source separation techniques from statistical signal processing to separate the traffic in a mix network into either individual flows or groups of flows. This separation requires no a priori information about the individual flows. As a result, unlinkability can be compromised without ever observing individual flows. Our experiments show that this attack is effective and scalable. By correlating separated groups of flows across nodes, a passive attacker can get an accurate traffic map of the mix network. We use a non-trivial network to show that the combined attack works. The experiments also show that multicast traffic can be dangerous for anonymity networks. 1
Cross-Layer Analysis of Rate Adaptation, DCF and TCP in Multi-Rate WLANs
"... Abstract—Wireless Internet access is facilitated by IEEE 802.11 WLANs that, in addition to realizing a specific form of CSMA/CA—distributed coordination function (DCF)— implement a range of performance enhancement features such as multi-rate adaptation that induce cross-layer protocol coupling. Rece ..."
Abstract
-
Cited by 8 (0 self)
- Add to MetaCart
(Show Context)
Abstract—Wireless Internet access is facilitated by IEEE 802.11 WLANs that, in addition to realizing a specific form of CSMA/CA—distributed coordination function (DCF)— implement a range of performance enhancement features such as multi-rate adaptation that induce cross-layer protocol coupling. Recent works in empirical WLAN performance evaluation have shown that cross-layer interactions can be subtle, sometimes leading to unexpected outcomes. Two such instances are: significant throughput degradation (a bell-shaped throughput curve) resulting from automatic rate fallback (ARF) having difficulty distinguishing collision from channel noise, and scalable TCP performance over DCF that is able to curtail effective multiple access contention in the presence of many contending stations. The latter also mitigates the negative performance effect of ARF. In this paper, we present station-centric Markov chain models of WLAN cross-layer performance aimed at capturing complex interactions between ARF, DCF, and TCP. Our performance analyses may be viewed as multi-protocol extensions of Bianchi’s IEEE 802.11 model that, despite significantly increased complexity, lead to tractable and accurate performance predictions due to modular coupling. Our results complement empirical and simulation-based findings, demonstrating the versatility and efficacy of station-centric Markov chain analysis for capturing cross-layer WLAN dynamics.
Performance Impact of Inter-Layer Dependence in Infrastructure WLANs
"... Widespread deployment of infrastructure WLANs has made Wi-Fi an integral part of today’s Internet access technology. Despite its crucial role in affecting end-to-end performance, past research has focused on MAC protocol enhancement, analysis and simulation-based performance evaluation without suffi ..."
Abstract
-
Cited by 8 (3 self)
- Add to MetaCart
(Show Context)
Widespread deployment of infrastructure WLANs has made Wi-Fi an integral part of today’s Internet access technology. Despite its crucial role in affecting end-to-end performance, past research has focused on MAC protocol enhancement, analysis and simulation-based performance evaluation without sufficient consideration for modeling inaccuracies stemming from inter-layer dependencies, including physical layer diversity, that significantly impact performance. We take a fresh look at IEEE 802.11 WLANs, and using experiment, simulation, and analysis demonstrate its surprisingly agile performance traits. Our findings are two-fold. First, contention-based MAC throughput degrades gracefully under congested conditions, enabled by physical layer channel diversity that reduces the effective level of MAC contention. In contrast, fairness degrades and jitter increases significantly at a critical offered load. This duality obviates the need for link layer flow control for throughput improvement. Second, TCP-over-WLAN achieves high throughput commensurate with that of wireline TCP under saturated conditions, challenging the widely held perception that TCP throughput fares poorly over WLANs when subject to heavy contention. We show that TCP-over-WLAN prowess is facilitated by the self-regulating actions of DCF and TCP feedback control that jointly drive the shared channel at an effective load of 2–3 wireless stations, even when the number of active stations is large. We show that the mitigating influence of TCP extends to unfairness and adverse impact of dynamic rate shifting under multiple access contention. We use experimentation and simulation in a complementary fashion, pointing out performance characteristics where they agree and differ. Keywords: Wireless communication, access schemes, physical layer diversity, TCP-over-WLAN perfor-mance, experimentation vs. simulation 1 A. Background and Motivation
