Aun Haider

A Novel Proportional Fair Scheduling Algorithm for HSDPA in UMTS Networks

A utility function based perspective of packet scheduling in HSDPA is described and a new hybrid proportional fair scheduling algorithm has been developed. This algorithm employs a ratio of the instantaneous channel quality indicator to its mean value and an exponentially weighted moving average of the data rate to be transmitted at the base station (Node-B). Performance of the new algorithm has been compared with round robin, maximum carrier to interference ratio and proportional fair throughput schemes, under pedestrian A, vehicular A and vehicular B environments. The new algorithm has shown higher levels of total cell throughput than round robin and proportional fair throughput schedulers. Furthermore, it is shown that it has good fairness properties that are comparable with the round robin scheduler, and it exhibits low values of the mean end-to-end packet delay.

Auto-tuning RED for accurate queue control

One problem with a RED router with fixed parameter settings is that the buffer queue length varies markedly with the traffic level. In this paper, an algorithm is derived analytically for automatically tuning the key RED parameter max/sub p/ to keep the average queue length at the target value despite a varying traffic load. A control-theoretic stability analysis is performed to obtain guidelines for setting the remaining RED parameters and the adaptation frequency. Simulation results show that the new adaptive algorithm is faster acting and more accurate than previously proposed heuristic methods.

Transient fairness of optimized end-to-end window control

The paper is concerned with optimizing end-to-end window controls that achieve proportional fairness in the long run, and then investigating their transient or short-term fairness. An abstracted stochastic model of a bottlenecked connection is employed and the window control is designed to minimize the buffer queue variance while keeping the mean queue level at a target value, taking the round-trip delay into account. A generalized window control aimed at reducing window size fluctuations is also derived. The effects of both the target queue length and a weighting parameter on the short-term fairness, as measured by short-term fairness indices calculated over short time intervals, are investigated using ns-2 simulations.

Classification of malicious network streams using honeynets

Misuse-based intrusion detection systems alone cannot cope with the dynamic nature of the security threats faced today by organizations globally. Variants of malware and exploits are emerging on the global canvas at an ever-increasing rate. There is a need to automate their detection by observing their malicious footprints over network streams. In this paper we evaluate a proposed technique to measure the relative similarity or level of maliciousness between different categories of malicious network streams captured by honeynets. This is measured by quantifying areas of analogous information or entropy between incoming network streams and reference malicious samples. Machine learning methods are used to quickly cluster similar groups of streams from the datasets. This technique is then evaluated using a large dataset and the correctness of the classifier is verified by using ‘area under the receiver operating characteristic curves’(ROC AUC) measures across various string metric-based classifiers.

Algorithms for WiMAX scheduling

This paper reviews and compares various options for scheduling algorithms in WiMAX that are key to efficient operation of this technology. WiMAX multi-service environment is complex because of the various packet streams it needs to serve, their different quality of service (QoS) requirements and traffic behaviours. Therefore, the packet schedulers operating at the MAC layer are very important for QoS delivery. Although these schemes may be applicable to WiMAX, there are still certain issues that require attention, e.g., how much information is required by the grant scheduler at the BS, or how to allocate time-slots, as well as sub-channels, to different SSs when orthogonal-frequency division multiple access (OFDMA) is used.

On Path Switching in Overlay Networks

This paper investigates the stability characteristics of overlay networks performing switching between multiple virtual paths. A global stability condition for switched-control-systems has been applied to overlay path switching frequency, that can be incorporated into design of better routing protocols for overlay networks. Further, NS-2 based simulations have been carried out on an overlay network to evaluate the impact of round-trip-time, packet loss probability and throughput metrics on decisions regarding path selection. Throughput based switching decisions have shown to be resulting in lower number of path changes, which is desirable. Also, it has been observed that delay and loss based metrics can result into a large number of frequent path changes, which can push the overlay routing system into an instable oscillating state for a prolonged period of time.

A MAP-2 based quality of experience model for voice and multi-media services in next generation networks

In the past, single service networks such as the PSTN were relatively simple to design and dimension in order to meet specific service objectives. The arrival of next generation networks (NGN) based upon IP technology and supporting multiple service types has meant greater challenges for network designers, managers and planners as customers may experience a wide range of different performance levels depending on the nature of the service that they are using. NGN network services share network resources so they may be impacted on by failure of network elements that provide connectivity as well as by elements that are part of the service delivery - which in turn may be affected by traffic levels of completely different service types. This paper looks at voice and multi-media services and develops models for analytically estimating quality of experience measures so that they can be used in models to design and dimension next generation networks.

Stability Conditions For Scalable TCP-RED Based AQM

This paper investigates the stability of scalable transmission control protocol (TCP) with random early detection (RED) based active queue management (AQM). Dynamical modeling is used to analyze the stability of the closed loop system at the operating point in terms of the number of TCP connections. It is shown that period doubling bifurcations can occur by varying the system parameters. Two conditions for designing a stable Scalable TCP-RED system for a high capacity Gigabit network are also derived. Finally, Lyapunov Exponents are used to investigate the stability of a specific system.

An Evaluation of IP-Address Lookup Algorithms

Due to the manyfold increase in Internet traffic, backbone links and routers of multigigabit capacity are commonly deployed. One of the major bottlenecks in the optimum performance of such high-speed routers is address lookup while performing longest prefix match. The problem is further compounded by the introduction of 128 bit addresses in IPv6 technology. Due to the importance of the address lookup problem several algorithms have been proposed in recent years. This paper presents an evaluation of state-of-art IP address lookup algorithms. Both software and hardware based algorithms are discussed in terms of space/time complexity, lookup speed, scalability and update overheads

Control-Theoretic Design of RED AQM for Scalable TCP in High Speed Networks

Scalable TCP, based on a multiplicative-increase multiplicative-decrease congestion avoidance algorithm, has been proposed recently to overcome the inability of Standard TCP to utilize the full bandwidth in high-speed networks. This paper employs a novel approach to derive a transfer-function model of Scalable TCP that is then employed in a control-theoretic design of RED-based Active Queue Management for such a network. Robust stability of the proposed scheme is established under prescribed conditions and the design is validated by ns2 simulations.