Queuing theory is the mathematical study of queuing, or waiting in lines.Queues contain customers such as people, objects, or information. Queuesform when there are limited resources for providing a service. A basic queuingsystem consists of an arrival process (how customers arrive at the queue, howmany customers are present in total), the queue itself, the service process forattending to those customers, and departures from the system. Essentials inmodern life would not be possible without queueing theory.The purpose of this thesis is to address the inferential problems associatedwith various single/multi-server queueing models. It is mainly focused on theestimation of queue parameters like arrival rate, service rate and some importantsteady state queue characteristics such as traffic intensity, expected queuesize, expected system size and expected waiting time. The study of queueingmodel is basically motivated by its use in communication system and computernetworks. The development of an appropriate stochastic models is one of themajor problem associated with the study of communication systems as it requiresmore and more sophistication to manage their complexity.Queueing theory was developed to provide models to predict the behaviorof the systems that attempt to provide service for randomly arising demand.The earliest problems studied were those of telephone traffic congestion. Thepioneer investigator was the Danish mathematician, A. K. Erlang, who, in1909, published "The theory of Probabilities and Telephone Conversations".In later works he observed that a telephone system was generally characterizedby either Poisson input, exponential service times, and multiple serversor Poisson input, constant service times, and a single channel. Thereare many valuable applications of the theory, most of which have been welldocumented in the literature of probability, operations research, managementscience, and industrial engineering. Some examples are traffic flow (vehiclesaircraft, people, communications), scheduling (patients in hospitals, jobs onmachines, programs on a computer), and facility design (bank, post officesamusement parks, fast-food restaurants).