Vandana Khaitan | University of Delhi (original) (raw)
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Papers by Vandana Khaitan
Mathematical and Computer Modelling, 2011
TCP (Transmission Control Protocol) is one of the protocols which are widely used in Internet env... more TCP (Transmission Control Protocol) is one of the protocols which are widely used in Internet environments. This paper presents an analytical model developed using the stochastic reward net (SRN) modeling technique for the TCP flow behavior in WLANs. The purpose of developing an analytical model is the evaluation of stationary TCP flow behavior. In this paper, we focus the attention on the TCP variant called TCP Reno which is implemented by most operating systems. The performance of TCP Reno is investigated through the SRN model. The model captures aspects such as congestion window (cwd) evolution, slow start and congestion avoidance phases, TCP packet transmissions, management of packet losses due to time-out, and due to generation of triple duplicate acknowledgements. The performance metrics such as throughput and delay of the TCP traffic are obtained using the SRN model. On the basis of these performance measures, the existing unfairness between the downstream and upstream flow at the AP in WLANs is also shown. The proposed analytical model is validated via simulation.
International Journal of Communication Systems, 2010
This paper presents an analytical approach to model the bi-directional multi-channel IEEE 802.11 ... more This paper presents an analytical approach to model the bi-directional multi-channel IEEE 802.11 MAC protocols (Bi-MCMAC) for ad hoc networks. Extensive simulation work has been done for the performance evaluation of IEEE 802.11 MAC protocols. Since simulation has several limitations, this work is primarily based on the analytical approach. The objective of this paper is to show analytically the performance advantages of Bi-MCMAC protocol over the classical IEEE 802.11 MAC protocol. The distributed coordination function (DCF) mode of medium access control (MAC) is considered in the modeling. Two different channel scheduling strategies, namely, random channel selection and fastest channel first selection strategy are also presented in the presence of multiple channels with different transmission rates. M/G/1 queue is used to model the protocols, and stochastic reward nets (SRNs) are employed as a modeling technique as it readily captures the synchronization between events in the DCF mode of access. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. We also validate our analytical model by comparison with simulation results. The results obtained through the analytical modeling approach illustrate the performance advantages of Bi-MCMAC protocols with the fastest channel first scheduling strategy over the classical IEEE 802.11 protocol for TCP traffic in wireless ad hoc networks.
Computers & Mathematics with Applications, 2010
We present a fluid queue model driven by two independent finite state birth-death processes with ... more We present a fluid queue model driven by two independent finite state birth-death processes with the objective to study the buffer occupancy distribution in any intermediate node in a communication network. In a communication network, at any node, the arrival and service of the packets are with variable rates. To model this scenario we develop a fluid queue with an infinite capacity buffer which receives fluid at variable rate and also releases fluid at variable rates. Because of variable inflow and outflow rates of the fluid, the proposed fluid queue is driven by the current states of two independent finite state birth-death processes evolving in the background which on merging give rise to a continuous time Markov chain which is not a birth-death process. Using the fluid queue model, we obtain the steady-state distribution of the buffer occupancy at any intermediate node during packet transmission in a communication network. As a special case, we consider a wireless network based on the IEEE 802.11 standard. We present the buffer occupancy distribution at any intermediate node in closed form with a numerical illustration. Along with buffer occupancy distribution, we also obtain various performance measures such as expected buffer content, average throughput, server utilization and mean delay which are relevant to packet transmission in such a communication network. Finally, we present numerical results to illustrate the feasibility of the proposed model. The results are in accordance with the expected behavior of these performance measures.
Wireless Personal Communications, 2022
In this paper, we develop a novel game theoretic model of the interactions between an EDoS attack... more In this paper, we develop a novel game theoretic model of the interactions between an EDoS attacker and the defender based on a signaling game that is a dynamic game of incomplete information. We then derive the best defense strategies for the network defender to respond to the EDoS attacks. That is, we compute the perfect Bayesian Nash Equilibrium (PBE) of the proposed game model such as the pooling PBE, separating PBE and mixed strategy PBE. In the pooling equilibrium, each type of the attacker takes the same action and the attacker's type is not revealed to the defender, whereas in the separating equilibrium, each type of the attacker uses different actions and hence the attacker's type is completely revealed to the defender. On the other hand, in the mixed strategy PBE, both the attacker and the defender randomize their strategies to optimize their payoffs. Numerical illustration is also presented to show the efficacy of the proposed model.
Journal of Network and Systems Management
Reliability Engineering & System Safety, 2011
Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very impor... more Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very important to study and enhance its dependability attributes. In this paper, an analytical dependability model for VoIP is proposed. The study is focused on analyzing the combined effects of resource degradation and security breaches on the Quality of Service (QoS) of VoIP, to enhance its overall dependability. As a preventive maintenance policy to prevent or postpone software failures which cause resource degradation, software rejuvenation is adopted. The dependability model is analyzed using semi-Markov process which captures the effects of non-Markovian nature of the time spent at various states of the system. The steady-state as well as the time-dependent analysis of the dependability model is presented. The steady-state results are obtained analytically, whereas the time-dependent results are obtained from simulation. Also, the analytical model is validated via simulation. The model analysis using a numerical example indicates the feasibility of our approach. Various dependability attributes such as availability, reliability and confidentiality are also obtained. A comparative study is also done between our proposed model and the existing models.
Reliability Engineering & System Safety, 2011
Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very impor... more Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very important to study and enhance its dependability attributes. In this paper, an analytical dependability model for VoIP is proposed. The study is focused on analyzing the combined effects of resource degradation and security breaches on the Quality of Service (QoS) of VoIP, to enhance its overall dependability.
International Journal of Reliability and Safety, 2013
Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Becaus... more Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Because of the increasing dependencies of people on VoIP for voice communication, it is important to design a reliable and performance oriented VoIP system. In this paper a hierarchical model combining reliability and performance is proposed for a server based VoIP system on a wireless network. The top level reliability model consists of only the basic components of a VoIP system. Simultaneous failure of multiple components is taken into modelling consideration. Component redundancies and software rejuvenation are employed to achieve higher system reliability. Assuming exponential failure and repair times of the components, continuous time Markov chain is used to develop the top level reliability model. In addition, a lower level performance model is constructed to obtain the performance metrics of the system at each state of the top level reliability model. Numerical results are provided for the quantitative analysis of the proposed model.
International Journal of Reliability and Safety
Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Becaus... more Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Because of the increasing dependencies of people on VoIP for voice communication, it is important to design a reliable and performance oriented VoIP system. In this paper a hierarchical model combining reliability and performance is proposed for a server based VoIP system on a wireless network. The top level reliability model consists of only the basic components of a VoIP system. Simultaneous failure of multiple components is taken into modelling consideration. Component redundancies and software rejuvenation are employed to achieve higher system reliability. Assuming exponential failure and repair times of the components, continuous time Markov chain is used to develop the top level reliability model. In addition, a lower level performance model is constructed to obtain the performance metrics of the system at each state of the top level reliability model. Numerical results are provided for ...
aging, 2009
Page 1. An Analytical Framework of Survivability Model for VoIP Vandana Gupta Department of Mathe... more Page 1. An Analytical Framework of Survivability Model for VoIP Vandana Gupta Department of Mathematics IIT Delhi, India vandana iitd@yahoo.com S. Dharmaraja Department of Mathematics IIT Delhi, India dharmar@maths.iitd.ernet.in ...
International Journal of Communication Systems, 2011
Gupta, V., Gong, M., Dharmaraja, S. and Williamson, C.(2011), Analytical modeling of bidirectiona... more Gupta, V., Gong, M., Dharmaraja, S. and Williamson, C.(2011), Analytical modeling of bidirectional multi-channel IEEE 802.11 MAC protocols. International Journal of Communication Systems, 24: 647665. doi: 10.1002/dac. 1183
Mathematical and Computer Modelling, 2011
TCP (Transmission Control Protocol) is one of the protocols which are widely used in Internet env... more TCP (Transmission Control Protocol) is one of the protocols which are widely used in Internet environments. This paper presents an analytical model developed using the stochastic reward net (SRN) modeling technique for the TCP flow behavior in WLANs. The purpose of developing an analytical model is the evaluation of stationary TCP flow behavior. In this paper, we focus the attention on the TCP variant called TCP Reno which is implemented by most operating systems. The performance of TCP Reno is investigated through the SRN model. The model captures aspects such as congestion window (cwd) evolution, slow start and congestion avoidance phases, TCP packet transmissions, management of packet losses due to time-out, and due to generation of triple duplicate acknowledgements. The performance metrics such as throughput and delay of the TCP traffic are obtained using the SRN model. On the basis of these performance measures, the existing unfairness between the downstream and upstream flow at the AP in WLANs is also shown. The proposed analytical model is validated via simulation.
International Journal of Communication Systems, 2010
This paper presents an analytical approach to model the bi-directional multi-channel IEEE 802.11 ... more This paper presents an analytical approach to model the bi-directional multi-channel IEEE 802.11 MAC protocols (Bi-MCMAC) for ad hoc networks. Extensive simulation work has been done for the performance evaluation of IEEE 802.11 MAC protocols. Since simulation has several limitations, this work is primarily based on the analytical approach. The objective of this paper is to show analytically the performance advantages of Bi-MCMAC protocol over the classical IEEE 802.11 MAC protocol. The distributed coordination function (DCF) mode of medium access control (MAC) is considered in the modeling. Two different channel scheduling strategies, namely, random channel selection and fastest channel first selection strategy are also presented in the presence of multiple channels with different transmission rates. M/G/1 queue is used to model the protocols, and stochastic reward nets (SRNs) are employed as a modeling technique as it readily captures the synchronization between events in the DCF mode of access. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. We also validate our analytical model by comparison with simulation results. The results obtained through the analytical modeling approach illustrate the performance advantages of Bi-MCMAC protocols with the fastest channel first scheduling strategy over the classical IEEE 802.11 protocol for TCP traffic in wireless ad hoc networks.
Computers & Mathematics with Applications, 2010
We present a fluid queue model driven by two independent finite state birth-death processes with ... more We present a fluid queue model driven by two independent finite state birth-death processes with the objective to study the buffer occupancy distribution in any intermediate node in a communication network. In a communication network, at any node, the arrival and service of the packets are with variable rates. To model this scenario we develop a fluid queue with an infinite capacity buffer which receives fluid at variable rate and also releases fluid at variable rates. Because of variable inflow and outflow rates of the fluid, the proposed fluid queue is driven by the current states of two independent finite state birth-death processes evolving in the background which on merging give rise to a continuous time Markov chain which is not a birth-death process. Using the fluid queue model, we obtain the steady-state distribution of the buffer occupancy at any intermediate node during packet transmission in a communication network. As a special case, we consider a wireless network based on the IEEE 802.11 standard. We present the buffer occupancy distribution at any intermediate node in closed form with a numerical illustration. Along with buffer occupancy distribution, we also obtain various performance measures such as expected buffer content, average throughput, server utilization and mean delay which are relevant to packet transmission in such a communication network. Finally, we present numerical results to illustrate the feasibility of the proposed model. The results are in accordance with the expected behavior of these performance measures.
Wireless Personal Communications, 2022
In this paper, we develop a novel game theoretic model of the interactions between an EDoS attack... more In this paper, we develop a novel game theoretic model of the interactions between an EDoS attacker and the defender based on a signaling game that is a dynamic game of incomplete information. We then derive the best defense strategies for the network defender to respond to the EDoS attacks. That is, we compute the perfect Bayesian Nash Equilibrium (PBE) of the proposed game model such as the pooling PBE, separating PBE and mixed strategy PBE. In the pooling equilibrium, each type of the attacker takes the same action and the attacker's type is not revealed to the defender, whereas in the separating equilibrium, each type of the attacker uses different actions and hence the attacker's type is completely revealed to the defender. On the other hand, in the mixed strategy PBE, both the attacker and the defender randomize their strategies to optimize their payoffs. Numerical illustration is also presented to show the efficacy of the proposed model.
Journal of Network and Systems Management
Reliability Engineering & System Safety, 2011
Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very impor... more Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very important to study and enhance its dependability attributes. In this paper, an analytical dependability model for VoIP is proposed. The study is focused on analyzing the combined effects of resource degradation and security breaches on the Quality of Service (QoS) of VoIP, to enhance its overall dependability. As a preventive maintenance policy to prevent or postpone software failures which cause resource degradation, software rejuvenation is adopted. The dependability model is analyzed using semi-Markov process which captures the effects of non-Markovian nature of the time spent at various states of the system. The steady-state as well as the time-dependent analysis of the dependability model is presented. The steady-state results are obtained analytically, whereas the time-dependent results are obtained from simulation. Also, the analytical model is validated via simulation. The model analysis using a numerical example indicates the feasibility of our approach. Various dependability attributes such as availability, reliability and confidentiality are also obtained. A comparative study is also done between our proposed model and the existing models.
Reliability Engineering & System Safety, 2011
Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very impor... more Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very important to study and enhance its dependability attributes. In this paper, an analytical dependability model for VoIP is proposed. The study is focused on analyzing the combined effects of resource degradation and security breaches on the Quality of Service (QoS) of VoIP, to enhance its overall dependability.
International Journal of Reliability and Safety, 2013
Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Becaus... more Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Because of the increasing dependencies of people on VoIP for voice communication, it is important to design a reliable and performance oriented VoIP system. In this paper a hierarchical model combining reliability and performance is proposed for a server based VoIP system on a wireless network. The top level reliability model consists of only the basic components of a VoIP system. Simultaneous failure of multiple components is taken into modelling consideration. Component redundancies and software rejuvenation are employed to achieve higher system reliability. Assuming exponential failure and repair times of the components, continuous time Markov chain is used to develop the top level reliability model. In addition, a lower level performance model is constructed to obtain the performance metrics of the system at each state of the top level reliability model. Numerical results are provided for the quantitative analysis of the proposed model.
International Journal of Reliability and Safety
Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Becaus... more Nowadays Voice over IP (VoIP) has become an evolutionary technology in telecommunications. Because of the increasing dependencies of people on VoIP for voice communication, it is important to design a reliable and performance oriented VoIP system. In this paper a hierarchical model combining reliability and performance is proposed for a server based VoIP system on a wireless network. The top level reliability model consists of only the basic components of a VoIP system. Simultaneous failure of multiple components is taken into modelling consideration. Component redundancies and software rejuvenation are employed to achieve higher system reliability. Assuming exponential failure and repair times of the components, continuous time Markov chain is used to develop the top level reliability model. In addition, a lower level performance model is constructed to obtain the performance metrics of the system at each state of the top level reliability model. Numerical results are provided for ...
aging, 2009
Page 1. An Analytical Framework of Survivability Model for VoIP Vandana Gupta Department of Mathe... more Page 1. An Analytical Framework of Survivability Model for VoIP Vandana Gupta Department of Mathematics IIT Delhi, India vandana iitd@yahoo.com S. Dharmaraja Department of Mathematics IIT Delhi, India dharmar@maths.iitd.ernet.in ...
International Journal of Communication Systems, 2011
Gupta, V., Gong, M., Dharmaraja, S. and Williamson, C.(2011), Analytical modeling of bidirectiona... more Gupta, V., Gong, M., Dharmaraja, S. and Williamson, C.(2011), Analytical modeling of bidirectional multi-channel IEEE 802.11 MAC protocols. International Journal of Communication Systems, 24: 647665. doi: 10.1002/dac. 1183