Applied Queueing Systems
Traditional telephone networks were designed to implement a single type of communication service, i.e., the telephone service. Today’s telecommunication networks implement a wide range of communication services. In this section we introduce Markov models
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Applied Queueing Systems
11.1 Bandwidth Sharing of Finite-Capacity Links with Different Traffic Classes Traditional telephone networks were designed to implement a single type of communication service, i.e., the telephone service. Today’s telecommunication networks implement a wide range of communication services. In this section we introduce Markov models of communication services that compete for the bandwidth of a finite-capacity communication link.
11.1.1 Traffic Classes There are several important features of traffic sources of communication services that allow for their classification. Here assume that the traffic sources require the setting up of a connection for a finite period of time during which data communication is carried out between the parties of the communication service. We classify the traffic sources based on the bandwidth of the data transmission during a connection. The simplest case is where data are transmitted with a fixed bandwidth during a connection. This case is commonly referred to as constant bit rate (CBR). A more general traffic behavior is obtained when the bandwidth of data transmission varies during a connection. This case is commonly referred to as variable bit rate (VBR). The most common form of bandwidth variation is when the bandwidth alternates between 0 and a fixed bandwidth. These VBR sources are referred to as ON-OFF sources, and we restrict our attention to the ON-OFF case. The most complex traffic sources adjust their bandwidth according to the available capacities of the network resources. There are two classes of this kind of source. Adaptive traffic sources set up a connection for a given period of time and transmit data according to the available bandwidth in the network. If the network resources are occupied during the connection of an adaptive traffic L. Lakatos et al., Introduction to Queueing Systems with Telecommunication Applications, DOI 10.1007/978-1-4614-5317-8 11, © Springer Science+Business Media, LLC 2013
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11 Applied Queueing Systems
source, then the source transmits data with a low bandwidth, and the overall amount of transmitted data during a connection is low. Elastic traffic sources set up a connection for transmitting a given amount of data. The bandwidth of the data transmission depends on the available bandwidth in the network. If the network resources are occupied during the connection of an elastic connection, then the period of the connection is extended in such a way that the source transmits the required amount of data. In this section we assume that the traffic sources demonstrate a memoryless time-homogeneous stochastic behavior and, consequently, the arrival processes are Poisson processes and the connection times are exponentially distributed, except for the elastic class, where the amount of data to transmit is exponentially distributed. Additionally, the traffic sources are characterized by their bandwidth parameters. In the case of CBR and ON-OFF VBR sources, the bandwidth parameter is the bandwidth of the active period.
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