Nirwan Ansari - Academia.edu (original) (raw)

Papers by Nirwan Ansari

IEEE Communications Surveys and Tutorials, 2012

Applications, deployed over a wide area network (WAN) which may connect across metropolitan, regi... more Applications, deployed over a wide area network (WAN) which may connect across metropolitan, regional or national boundaries, suffer performance degradation owing to unavoidable natural characteristics of WANs such as high latency and high packet loss rate. WAN optimization, also known as WAN acceleration, aims to accelerate a broad range of applications and protocols over a WAN. In this paper, we provide a survey on the state of the art of WAN optimization or WAN acceleration techniques, and illustrate how these acceleration techniques can improve application performance, mitigate the impact of latency and loss, and minimize bandwidth consumption. We begin by reviewing the obstacles in efficiently delivering applications over a WAN. Furthermore, we provide a comprehensive survey of the most recent content delivery acceleration techniques in WANs from the networking and optimization point of view. Finally, we discuss major WAN optimization techniques which have been incorporated in widely deployed WAN acceleration productsmultiple optimization techniques are leveraged by a single WAN accelerator to improve application performance in general.

IEEE ACM Transactions on Networking, Jun 1, 2019

The concept of fog computing is centered around providing computation resources at the edge of ne... more The concept of fog computing is centered around providing computation resources at the edge of network, thereby reducing the latency and improving the quality of service. However, it is still desirable to investigate how and where at the edge of the network the computation capacity should be provisioned. To this end, we propose a hierarchical capacity provisioning scheme. In particular, we consider a two-tier network architecture consisting of shallow and deep cloudlets and explore the benefits of hierarchical capacity provisioning based on queueing analysis. Moreover, we explore two different network scenarios in which the network delay between the two tiers is negligible as well as the case that the deep cloudlet is located somewhere deeper in the network and thus the delay is significant. More importantly, we model the first network delay scenario with bufferless shallow cloudlets as well as the second scenario with finite-size buffer shallow cloudlets, and formulate an optimization problem for each model. We also use stochastic ordering to solve the optimization problem formulated for the first model and an upper bound based technique is proposed for the second model. The performance of the proposed scheme is evaluated via simulations in which we show the accuracy of the proposed upper bound technique as well as the queue length estimation approach for both randomly generated input and real trace data.

arXiv (Cornell University), Dec 23, 2010

Traditional network security protocols depend mainly on developing cryptographic schemes and on u... more Traditional network security protocols depend mainly on developing cryptographic schemes and on using biometric methods. These have led to several network security protocols that are unbreakable based on difficulty of solving untractable mathematical problems such as factoring large integers. In this paper, Security of Networks Employing Encoding and Decoding (SNEED) is developed to mitigate single and multiple link attacks. Network coding and shared capacity among the working paths are used to provide data protection and data integrity against network attackers and eavesdroppers. SNEED can be incorporated into various applications in on-demand TV, satellite communications and multimedia security. Finally, It is shown that SNEED can be implemented easily where there are k edge disjoint paths between two core nodes (routers or switches) in an enterprize network.

To support different QoS requirements of heterogeneous and bursty traffic, Weighted Minmax algori... more To support different QoS requirements of heterogeneous and bursty traffic, Weighted Minmax algorithm (WMinmax) is proposed in this paper to efficiently and dynamically allocate network resources. In WMinmax, heterogeneous and regulated traffic are grouped into several classes according to their negotiated QoS parameters. For different classes, resources are allocated in proportion to their corresponding weights.

GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270)

Scheduling algorithms are implemented in highspeed switches to provision Quality-of-Service guara... more Scheduling algorithms are implemented in highspeed switches to provision Quality-of-Service guarantees in both cell-based and packet-based networks. Being able to guarantee end-to-end delay and fairness, timestamp-based fair queuing algorithms have received much attention in the past few years. In timestamp-based fair queuing algorithms, the size of timestamp and period determines the supportable rates in terms of the range and accuracy. Furthermore, it also determines the scheduler's memory in terms of access bandwidth and storage space. An efficient expression can reduce the size of the timestamp and period without compromising the supportable rate range and the accuracy. In this paper, we propose a compressed and dynamic-range-based expression of the timestamp and period, which can be readily implemented in hardware for both high-speed packet-based and cell-based schedulers. As compared to fixed-point and floating-point number expression, when the size is fixed, the proposed expression has a better accuracy. Regarding to efficiency and relative error consistency, it is even better than our earlier proposal.

2010 IEEE International Conference on Communications, 2010

Driven by emerging bandwidth-hungry applications, next generation passive optical networks (NG-PO... more Driven by emerging bandwidth-hungry applications, next generation passive optical networks (NG-PONs) provide higher bandwidth to users by using more wavelengths and increasing data rates of optical network units (ONUs). On the other hand, for smooth upgrading, NG-PON is desired to be backward compatible with the current TDM PONs where data rates of ONUs remain unchanged. Thus, both high-rate ONUs and low-rate ONUs may coexist in NG-PON. The key parameters of bandwidth allocation in this multi-rate multiwavelength network include achieving fairness among all ONUs, encouraging low-rate ONUs to increase their data rates, and utilizing wavelength resources efficiently. This paper illustrates contributions in three main aspects. First, we define rate-dependent utilities for ONUs, which serve as the basis for bandwidth arbitration among low-rate and high-rate ONUs. Second, to achieve fairness among ONUs, we employ water-filling idea and formulate a utility max-min fair bandwidth allocation scheme. Third, to efficiently utilize the wavelengths, we map the resource allocation problem in multiwavelength PON into a multi-processor scheduling problem and employ a heuristic algorithm to address the NP-hard wavelength assignment problem.

Proceedings from the Fifth Annual IEEE SMC Information Assurance Workshop, 2004.

Journal of Optical Communications and Networking, 2010

Most broadband access networks such as passive optical networks (PONs) adopt the point-to-multipo... more Most broadband access networks such as passive optical networks (PONs) adopt the point-to-multipoint (P2MP) topology. One critical issue in such networks is the upstream resource management and allocation mechanism. Nonlinear predictor-based dynamic resource allocation (NLPDRA) schemes for improving the P2MP network upstream transmission efficiency have been investigated in an ad hoc manner. In this paper, we establish a general state space model to analyze the controllability and stability of the NLPDRA schemes from the P2MP network system's point of view and propose controller design guidelines to maintain the system stability under different scenarios. Analytical results show that NLPDRA maintains the P2MP network system controllability even when the loaded network traffic changes drastically. We further prove that a P2MP network system with NLPDRA is stable by proper pole placements as the traffic changes. Finally, we provide guidelines to design a optimal compensator to achieve system accuracy.

Journal of Optical Communications and Networking, 2012

In this paper, we investigate the wavelength scheduling problem in hybrid wavelength division mul... more In this paper, we investigate the wavelength scheduling problem in hybrid wavelength division multiplexing/time division multiplexing passive optical networks (WDM/TDM PONs), which can be mapped into multiprocessor scheduling problems with wavelengths and optical network unit (ONU) requests being considered as machines and jobs, respectively. To achieve high bandwidth utilization, guarantee low delay, and ensure short-term fairness, we try to construct a schedule with the minimum latest job completion time. First, we investigate the non-preemptive scheduling problem, which was shown to be NP-hard, and hence requires heuristic algorithms to approximate the optimal solution. The approximation ratio of the best heuristic algorithm is as large as 2 − 1/m, where m is the number of wavelengths. Motivated to achieve a smaller latest job completion time, we then investigate the preemptive scheduling problem. Preemption allows jobs to be scheduled more flexibly, and thus may yield a smaller makespan. However, with preemption, jobs may be split into subjobs and scheduled in discontinuous time durations at the expense of more guard time. We show that, with the consideration of guard time, the preemptive scheduling with the objective of minimizing the latest job completion time is NP-hard. To address the problem, we propose an approach by using linear programming with guard time supplement. It is shown that the proposed algorithm can ensure that the latest job completion time is no greater than the optimal value plus (m − 1)g/m, where g is the guard time between the scheduling of two ONUs. When the network is highly loaded, the approximation ratio is around 1.00061 and 1.002056 for hybrid WDM/TDM Ethernet PON (EPON) and Gigabit-capable PON (GPON), respectively.

IEEE Transactions on Smart Grid, 2016

This paper aims at maximizing the profit associated with running geographically dispersed green d... more This paper aims at maximizing the profit associated with running geographically dispersed green data centers, which offer multiple classes of service. To this end, we formulate an optimization framework which relies on the accuracy of the G/D/1 queue in characterizing the workload distribution, and taps on the merits of the workload decomposition into green and brown workload served by green and brown energy resources. Moreover, we take into account of not only the Service Level Agreements (SLAs) between the data centers and clients but also different deregulated electricity markets of data centers located at different regions. We prove the convexity of our optimization problem and the performance of the proposed workload distribution strategy is evaluated via simulations.

IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320), 1999

Input-queued switching architecture is becomingan attrac. tive alternative for designing very hig... more Input-queued switching architecture is becomingan attrac. tive alternative for designing very high speed switches owing to its scalability. Tremendous efforts have been made to overcome the throughput problem caused by contentions occurred at the input and output sides of the switches. However, no QoS guarantees can be provided by the current input-queued switch design. Iu this paper, a frame based scheduling algorithm, referred to as Store-Sort-and-Forward (SSF), is proposed to provide QoS guarantees for inputqueued switches without requiring speedup. SSF uses a framing strategy in which the time axis is divided into constant-length frames, each made up of an integer multiple of time slots. Celts arrived during a frame are first held in tbe input buffers, and are then "sorted-and-transmitted" within the next frame. A bandwidth allocation strategy and a cell admission poticy are adopted to regulate the traffic to conform to the (r, T) traffic model. A strict sense 100% throughput is proved to be achievable by rearranging the cell transmission orders in each input buffer, and a sorting algorithm is proposed to order the cell transmission. The SSF algorithm guarantees bounded end-to-end delay and delay jitter. It is proved that a perfect matching can be achieved within N(ln N + O (1)) effective moves.

2013 IEEE Global Communications Conference (GLOBECOM), 2013

Device to device (D2D) communications is a promising concept to improve data rates and the energy... more Device to device (D2D) communications is a promising concept to improve data rates and the energy efficiency of mobile networks. User devices (UEs) participated in D2D communications may increase their own data rates by retrieving the content from their neighboring peers instead of from the base stations. Meanwhile, UEs may drain their batteries while performing as content providers and transmitting the content to their peers. Increasing the data rates of D2D communications is desirable to alleviate the UEs' power consumption. In this paper, we propose a novel green relay assisted D2D communication architecture, in which the relay nodes powered by green energy are deployed to increase the data rates of D2D communications. However, achieving the optimal relay assignment for green relay assisted D2D communications is challenging. We propose a heuristic green relay assignment algorithm which maximizes the minimum data rates of the D2D pairs while considering the green load capacity of the relay nodes. We show that the proposed algorithm approximates the optimal solution with low computational complexity, and validate its performance by using simulation results.

2008 IEEE International Conference on Communications, 2008

Load-balanced switches have received much attention because they are more scalable than other swi... more Load-balanced switches have received much attention because they are more scalable than other switch architectures. However, a load-balanced switch has the problem of packet missequencing. In this paper, we propose a Dynamic Mailbox Sharing (DMS) scheme to eliminate the mis-sequencing problem of load-balanced switches only at the cost of a very small increase of delay. The key idea is to keep packets of the same flow in order in the load-balanced switch. The DMS scheme is based on two statistical facts in operational networks: the number of simultaneous active flows in the router buffer is far less than that of in-progress flows, and most of the intra-flow packet intervals are longer than the packet delay in the high speed router. In DMS, the packet sequence of the same flow arrived in the input ports is recorded in the mailbox maintained in the output ports. Then, packets of the same flow are delivered according to the order of their arrivals. The mailbox becomes the bottleneck in order to accommodate a large number of flows. We thus propose a dynamic sharing scheme to alleviate the bottleneck and greatly enhance the scalability of the mailbox. By simulations using the real internet traffic traces, we show that with a simple flow splitter mechanism restraining mis-sequencing, the average packet delay using DMS is considerably lower than that of other schemes including Uniform Frame Spreading, Padded Frame and the CR switch, and it is close to the ideal case without resequencing even when the load is very high. The results also demonstrate that the size of mailbox is in the hundreds.

Global Telecommunications Conference, 2002. GLOBECOM '02. IEEE

This paper addresses the issue of providing QoS services for Optical Burst Switching (OBS) system... more This paper addresses the issue of providing QoS services for Optical Burst Switching (OBS) systems. We propose a Linear Predictive Filter (LPF)-based Forward Resource Reservation method to reduce the burst delay at edge routers. An aggressive reservation method is proposed to increase the successful forward reservation probability and to improve the delay reduction performance. We also discuss a QoS strategy that achieves burst delay differentiation for different classes of traffic by extending the FRR scheme. We analyze the latency reduction improvement gained by our FRR scheme, and evaluate the bandwidth cost of the FRR-based QoS strategy. Our scheme yields significant delay reduction for time-critical traffic, while maintaining the bandwidth overhead within limits.

The Quality of Service (QoS) requirements such as delay and cell loss ratio (CLR) are very string... more The Quality of Service (QoS) requirements such as delay and cell loss ratio (CLR) are very stringent for video transmission. These constraints are difficult to meet if high network utilization is desired. Dynamic bandwidth allocation in which video traffic prediction can play an important role is thus needed. In this paper, we suggest to predict the variation of I frames instead of the actual size of I frames, and propose an algorithm that can achieve fast convergence and small prediction error, thus imposing QoS and attaining high network utilization. The performance of the scheme is studied using the renegotiated constant bit rate (RCBR) service model. The overall dynamic bandwidth allocation scheme based on our fast convergent algorithm is shown to be promising, and practically feasible for efficient transmission of real time videos.

IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference, 2007

With the general trend towards ubiquitous access to networks, more users will prefer to make voic... more With the general trend towards ubiquitous access to networks, more users will prefer to make voice calls through the Internet. Voice over IP (VoIP) as the application which facilitates voice calls through the Internet will increasingly occupy more traffic. The growth of delay sensitive traffic that requires special quality of service from the network will impose new constraints on network designers who should wisely allocate the limited resources to users based on their required quality of service. An efficient resource allocation depends upon gaining accurate information about the traffic profile of user applications. In this paper, we have studied the access level traffic profile of VoIP applications and proposed a realistic distribution model for VoIP traffic. Based on our model, we have introduced an algorithm for resource allocation in networks. It is shown that using our algorithm will enhance the delay and utilization performance of the network.

IEE Proceedings - Communications, 2006

The proportional differentiation service model has emerged as a refined version of the DiffServ q... more The proportional differentiation service model has emerged as a refined version of the DiffServ qualify of service (QoS) architecture. It relies on a series of parameters to enforce proportionally differentiated QoS criteria, such as queueing delay and packet loss. From the perspective of proportional loss differentiation, a large amount of work has been done on carrying out loss differentiation based on given parameters. Under certain network conditions, however, the loss differentiation cannot be met based on these hand picked parameters. While existing work focuses on enhancing dropping mechanisms themselves to honour the loss differentiation, the paper looks into calculating feasible differentiation parameters. By forming an optimisation problem based on multiple class blocking thresholds, the paper introduces a simple quantitative guideline to compute loss differentiation parameters. Derived closely related to network statuses and packet dropping mechanisms, these parameters ease the difficulty that dropping mechanisms may encounter when enforcing packet loss differentiation. Its finite computation time, moreover, makes practical implementation possible. Analytical and numerical results are given to substantiate the new approach and its merits.

IEE Proceedings - Communications, 2003

Random exponential marking (REM) is an attractive adaptive queue management algorithm. It uses th... more Random exponential marking (REM) is an attractive adaptive queue management algorithm. It uses the quantity known as 'price' to measure the congestion in a network. REM can achieve high utilisation, small queue length, and low buffer overflow probability. Many works have used control theory to provide the stable condition of REM without considering the feedback delay. Recently, sufficient conditions for local stability of REM have been provided when the sources have a uniform one-or two-step feedback delay. Nevertheless, no work has been done for the case of arbitrary uniform delay. The authors propose a continuous time model to generalise the local stable condition for REM in a multilink and multisource network with arbitrary uniform feedback delay.

IEEE Transactions on Neural Networks, 1998

In an integrated time-division multiple access (TDMA) communication system, voice and data are mu... more In an integrated time-division multiple access (TDMA) communication system, voice and data are multiplexed in time to share a common transmission link in a frame format in which time is divided into slots. A certain number of time slots in a frame are allocated to voice and the rest are used to transmit data. Maximum data throughput can be achieved by searching for the optimal configuration(s) of relative positions of voice and data transmissions in a frame (frame pattern). When the problem size becomes large, the computational complexity in searching for the optimal patterns becomes intractable. In this paper, mean field annealing (MFA), which provides near-optimal solutions with reasonable complexity, is proposed to solve this problem. The determination of the related parameters are addressed. Comparison with the random search and simulated annealing algorithm is made in terms of solution optimality and computational complexity. Simulation results show that the MFA approach exhibits a good tradeoff between performance and computational complexity.