The Role of Responsive Pricing in the Internet

The Internet continues to evolve as it reaches out to a wider user population. The recent introduction of user-friendly navigation and retrieval tools for the World Wide Web has triggered an unprecedented level of interest in the Internet among the media and the general public, as well as in the technical community. It seems inevitable that some changes or additions are needed in the control mechanisms used to allocate usage of Internet resources. In this paper, we argue that a feedback signal in the form of a variable price for network service is a workable tool to aid network operators in controlling Internet traffic. We suggest that these prices should vary dynamically based on the current utilization of network resources. We show how this responsive pricing puts control of network service back where it belongs: with the users.Internet, pricing, feedback, networks

An Improved Link Model for Window Flow Control and Its Application to FAST TCP

This paper presents a link model which captures the queue dynamics in response to a change in a transmission control protocol (TCP) source's congestion window. By considering both self-clocking and the link integrator effect, the model generalizes existing models and is shown to be more accurate by both open loop and closed loop packet level simulations. It reduces to the known static link model when flows' round trip delays are identical, and approximates the standard integrator link model when there is significant cross traffic. We apply this model to the stability analysis of fast active queue management scalable TCP (FAST TCP) including its filter dynamics. Under this model, the FAST control law is linearly stable for a single bottleneck link with an arbitrary distribution of round trip delays. This result resolves the notable discrepancy between empirical observations and previous theoretical predictions. The analysis highlights the critical role of self-clocking in TCP stability, and the proof technique is new and less conservative than existing ones

A study of the coexistence of heterogeneous flows on data networks.

Tam Sai-Wah.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.Includes bibliographical references (leaves [103]-104) and index.Abstracts in English and Chinese.Abstract --- p.x摘要 --- p.xiAbbreviations --- p.xiiSymbols --- p.xivChapter Part I --- BackgroundChapter 1 --- Background on coexistence --- p.2Chapter 1.1 --- Data network --- p.2Chapter 1.1.1 --- Telephone network vs. data network --- p.2Chapter 1.1.2 --- Bandwidth in networks --- p.3Chapter 1.2 --- Taxonomy of flows --- p.4Chapter 1.3 --- Effect of heterogeneity and proposed solution --- p.4Chapter 1.3.1 --- Cause and effect of heterogeneity --- p.4Chapter 1.3.2 --- TCP-friendly congestion control as a solution --- p.5Chapter 1.3.3 --- Distributed admission control as a solution --- p.6Chapter 1.3.4 --- Evaluation methodology and organisation of this thesis --- p.6Chapter 2 --- Model of Heterogeneous Flows --- p.8Chapter 2.1 --- The network --- p.8Chapter 2.2 --- Elastic flows --- p.8Chapter 2.3 --- Inelastic flows --- p.10Chapter 2.4 --- Stochastic Flows --- p.11Chapter 2.5 --- Controls --- p.12Chapter 2.5.1 --- Congestion control for elastic flows --- p.12Chapter 2.5.2 --- No control for inelastic flows --- p.13Chapter 2.5.3 --- Congestion control for inelastic flows --- p.14Chapter 2.5.4 --- Admission control for inelastic flows --- p.15Chapter 2.5.5 --- Admission control for inelastic flows with continuous assurance --- p.16Chapter 2.6 --- Markov chain model of control schemes --- p.17Chapter 2.6.1 --- Normalisation --- p.17Chapter 2.6.2 --- Control schemes and Markov chains --- p.18Chapter Part II --- EvaluationChapter 3 --- Stability of network under different controls --- p.29Chapter 3.1 --- Stability of queues --- p.29Chapter 3.2 --- Stability of the Markov chain models --- p.30Chapter 3.2.1 --- Observation of stability from simulation --- p.30Chapter 3.3 --- Informal discussion of stability --- p.33Chapter 4 --- Bandwidth allocation --- p.35Chapter 4.1 --- Aggregated bandwidth --- p.35Chapter 4.2 --- Bandwidth per flow --- p.37Chapter 5 --- Evaluation based on utility functions --- p.40Chapter 5.1 --- Properties of utility function --- p.40Chapter 5.1.1 --- Utility for elastic flows --- p.40Chapter 5.1.2 --- Utility for inelastic flows --- p.41Chapter 5.1.3 --- Utility throughput --- p.41Chapter 5.1.4 --- Choice of utility function --- p.43Chapter 5.2 --- Degree of elasticity --- p.45Chapter 5.3 --- Homogeneous environment --- p.46Chapter 5.4 --- Heterogeneous environment --- p.49Chapter 5.4.1 --- Comparison for different offered load --- p.50Chapter 5.4.2 --- Effect of scaling --- p.52Chapter 5.4.3 --- Sensitivity to α and ε --- p.57Chapter 6 --- Blocking probability --- p.62Chapter 6.1 --- Formulating admission behaviour into PCDSDE --- p.62Chapter 6.2 --- Evaluation of the blocking probability --- p.64Chapter 6.3 --- Verification by simulation --- p.66Chapter 6.3.1 --- Comparison for different offered load --- p.66Chapter 6.3.2 --- Effect of scaling --- p.68Chapter 6.3.3 --- Sensitivity to α and ε --- p.68Chapter 7 --- Population --- p.74Chapter 7.1 --- Mean number of inelastic flows --- p.74Chapter 7.2 --- Mean number of elastic flows --- p.75Chapter 7.2.1 --- Elastic population after scaling --- p.79Chapter 7.2.2 --- Effect of aggressiveness --- p.79Chapter 7.2.3 --- Effect of α --- p.82Chapter Part III --- ConclusionChapter 8 --- Conclusion --- p.85Chapter 8.1 --- Summary --- p.85Chapter 8.2 --- Implication --- p.87Chapter 8.3 --- Future Work --- p.88AppendicesChapter A --- Glossary --- p.91Chapter B --- Introduction to Poisson counter driven stochastic differential equations --- p.97Chapter C --- Simulation --- p.101References --- p.103Index --- p.10

A novel multimedia adaptation architecture and congestion control mechanism designed for real-time interactive applications

PhDThe increasing use of interactive multimedia applications over the Internet has created a problem of congestion. This is because a majority of these applications do not respond to congestion indicators. This leads to resource starvation for responsive flows, and ultimately excessive delay and losses for all flows therefore loss of quality. This results in unfair sharing of network resources and increasing the risk of network ‘congestion collapse’. Current Congestion Control Mechanisms such as ‘TCP-Friendly Rate Control’ (TFRC) have been able to achieve ‘fair-share’ of network resource when competing with responsive flows such as TCP, but TFRC’s method of congestion response (i.e. to reduce Packet Rate) is not ideally matched for interactive multimedia applications which maintain a fixed Frame Rate. This mismatch of the two rates (Packet Rate and Frame Rate) leads to buffering of frames at the Sender Buffer resulting in delay and loss, and an unacceptable reduction of quality or complete loss of service for the end-user. To address this issue, this thesis proposes a novel Congestion Control Mechanism which is referred to as ‘TCP-friendly rate control – Fine Grain Scalable’ (TFGS) for interactive multimedia applications. This new approach allows multimedia frames (data) to be sent as soon as they are generated, so that the multimedia frames can reach the destination as quickly as possible, in order to provide an isochronous interactive service. This is done by maintaining the Packet Rate of the Congestion Control Mechanism (CCM) at a level equivalent to the Frame Rate of the Multimedia Encoder.The response to congestion is to truncate the Packet Size, hence reducing the overall bitrate of the multimedia stream. This functionality of the Congestion Control Mechanism is referred to as Packet Size Truncation (PST), and takes advantage of adaptive multimedia encoding, such as Fine Grain Scalable (FGS), where the multimedia frame is encoded in order of significance, Most to Least Significant Bits. The Multimedia Adaptation Manager (MAM) truncates the multimedia frame to the size indicated by the Packet Size Truncation function of the CCM, accurately mapping user demand to available network resource. Additionally Fine Grain Scalable encoding can offer scalability at byte level granularity, providing a true match to available network resources. This approach has the benefits of achieving a ‘fair-share’ of network resource when competing with responsive flows (as similar to TFRC CCM), but it also provides an isochronous service which is of crucial benefit to real-time interactive services. Furthermore, results illustrate that an increased number of interactive multimedia flows (such as voice) can be carried over congested networks whilst maintaining a quality level equivalent to that of a standard landline telephone. This is because the loss and delay arising from the buffering of frames at the Sender Buffer is completely removed. Packets sent maintain a fixed inter-packet-gap-spacing (IPGS). This results in a majority of packets arriving at the receiving end at tight time intervals. Hence, this avoids the need of using large Playout (de-jitter) Buffer sizes and adaptive Playout Buffer configurations. As a result this reduces delay, improves interactivity and Quality of Experience (QoE) of the multimedia application

Layering as Optimization Decomposition: Questions and Answers

Network protocols in layered architectures have historically been obtained on an ad-hoc basis, and much of the recent cross-layer designs are conducted through piecemeal approaches. Network protocols may instead be holistically analyzed and systematically designed as distributed solutions to some global optimization problems in the form of generalized Network Utility Maximization (NUM), providing insight on what they optimize and on the structures of network protocol stacks. In the form of 10 Questions and Answers, this paper presents a short survey of the recent efforts towards a systematic understanding of "layering" as "optimization decomposition". The overall communication network is modeled by a generalized NUM problem, each layer corresponds to a decomposed subproblem, and the interfaces among layers are quantified as functions of the optimization variables coordinating the subproblems. Furthermore, there are many alternative decompositions, each leading to a different layering architecture. Industry adoption of this unifying framework has also started. Here we summarize the current status of horizontal decomposition into distributed computation and vertical decomposition into functional modules such as congestion control, routing, scheduling, random access, power control, and coding. We also discuss under-explored future research directions in this area. More importantly than proposing any particular crosslayer design, this framework is working towards a mathematical foundation of network architectures and the design process of modularization

Cooperation Strategies for Enhanced Connectivity at Home

WHILE AT HOME , USERS MAY EXPERIENCE A POOR I NTERNET SERVICE while being connected to their 802.11 Access Points (APs). The AP is just one component of the Internet Gateway (GW) that generally includes a backhaul connection (ADSL, fiber,etc..) and a router providing a LAN. The root cause of performance degradation may be poor/congested wireless channel between the user and the GW or congested/bandwidth limited backhaul connection. The latter is a serious issue for DSL users that are located far from the central office because the greater the distance the lesser the achievable physical datarate. Furthermore, the GW is one of the few devices in the home that is left always on, resulting in energy waste and electromagnetic pollution increase. This thesis proposes two strategies to enhance Internet connectivity at home by (i) creating a wireless resource sharing scheme through the federation and the coordination of neighboring GWs in order to achieve energy efficiency while avoiding congestion, (ii) exploiting different king of connectivities, i.e., the wired plus the cellular (3G/4G) connections, through the aggregation of the available bandwidth across multiple access technologies. In order to achieve the aforementioned strategies we study and develop: • A viable interference estimation technique for 802.11 BSSes that can be implemented on commodity hardware at the MAC layer, without requiring active measurements, changes in the 802.11 standard, cooperation from the wireless stations (WSs). We extend previous theoretical results on the saturation throughput in order to quantify the impact in term of throughput loss of any kind of interferer. We im- plement and extensively evaluate our estimation technique with a real testbed and with different kind of interferer, achieving always good accuracy. • Two available bandwidth estimation algorithms for 802.11 BSSes that rely only on passive measurements and that account for different kind of interferers on the ISM band. This algorithms can be implemented on commodity hardware, as they require only software modifications. The first algorithm applies to intra-GW while the second one applies to inter-GW available bandwidth estimation. Indeed, we use the first algorithm to compute the metric for assessing the Wi-Fi load of a GW and the second one to compute the metric to decide whether accept incoming WSs from neighboring GWs or not. Note that in the latter case it is assumed that one or more WSs with known traffic profile are requested to relocate from one GW to another one. We evaluate both algorithms with simulation as well as with a real test-bed for different traffic patterns, achieving high precision. • A fully distributed and decentralized inter-access point protocol for federated GWs that allows to dynamically manage the associations of the wireless stations (WSs) in the federated network in order to achieve energy efficiency and offloading con- gested GWs, i.e, we keep a minimum number of GWs ON while avoiding to create congestion and real-time throughput loss. We evaluate this protocol in a federated scenario, using both simulation and a real test-bed, achieving up to 65% of energy saving in the simulated setting. We compare the energy saving achieved by our protocol against a centralized optimal scheme, obtaining close to optimal results. • An application level solution that accelerates slow ADSL connections with the parallel use of cellular (3G/4G) connections. We study the feasibility and the potential performance of this scheme at scale using both extensive throughput measurement of the cellular network and trace driven analysis. We validate our solution by implementing a real test bed and evaluating it “in the wild, at several residential locations of a major European city. We test two applications: Video-on-Demand (VoD) and picture upload, obtaining remarkable throughput increase for both applications at all locations. Our implementation features a multipath scheduler which we compare to other scheduling policies as well as to transport level solution like MTCP, obtaining always better results

Dynamic bandwidth allocation in multi-class IP networks using utility functions.

PhDAbstact not availableFujitsu Telecommunications Europe Lt