Cognestion control in atm networks

Abstract

The Broadband Integrated Services Digital Network (BISDN) newlinesupports transmission of different types of data such as text, audio, newlineimages, video, and/or combination of these types of data at higher newlinetransmission rates. The Asynchronous Transfer Mode (ATM) was selected newlineby Telecommunication industry as the transfer technology to deliver newlineinteractive and distributive services through BISDN. newlineThe ATM network offers different types of services to the users newlinebased on the type of traffic and the way the information is to be newlinetransmitted, like Constant Bit Rate (CBR), real time Variable Bit Rate (rt- newlineVBR), non real time Variable Bit Rate (nrt-VBR), Unspecified Bit Rate newline(UBR), and Available Bit Rate (ABR) services. Among these services, the newlineABR service provides better service for data traffic by periodically newlineadvising the sources about the rate at which they should transmit. In newlinethis thesis, ABR service has been considered for transmission of data in newlineATM networks. newlineTraffic management and congestion control are major issues in newlineATM networks. Traffic management functions refer to set of actions taken newlineby the network to meet various Quality of Service (QoS) parameters while newlineefficiently utilizing the available network resources. Congestion occurs newlinewhen the aggregate demand for a resource, typically link bandwidth, newlineexceeds the available capacity. Congestion is very much undesirable, newlinebecause it results larger queue length in shorter time, cell losses, and newlineii newlinereduced throughput. Congestion control mechanisms are required to newlineregulate traffic flow in the network in order to prevent the performance newlinedegradation in the network. newlineIn ATM networks, congestion control mechanisms have mainly newlinecategorized into credit based and rate based mechanisms. There are newlinesome reasons for non adoption of credit based schemes, as it has newlineconstraint of reserving the resources in advance for each virtual newlineconnection and involving high transmission delay. On other hand, the newlinerate based schemes are popular, as they have end-to-end feedback newlinemechanism, and capable of dynamicall