MODELING AND SIMULATION OF A VIDEO ON DEMAND NETWORK -thesis
MODELING AND SIMULATION OF A VIDEO ON DEMAND NETWORK IMPLEMENTING ADAPTIVE SOURCE-LEVEL CONTROL AND RELATIVE RATE MARKING FLOW CONTROL FOR THE AVAILABLE BIT RATE SERVICE
The Available Bit Rate (ABR) service class for the Asynchronous Transfer Mode (ATM) protocol was originally designed to manage data traffic. ABR flow control makes no guarantees concerning cell transfer delay or cell delay variation. A closed-loop feedback mechanism is used for traffic management. To use this class of service for video transport, the video source will accept feedback from the network and adapt its source rate based on this status information. The objective of this research is to assess the ability of the ATM ABR service class to deliver Moving Picture Experts Group version 1 (MPEG-1) video. Three approaches to source-level control are compared: (i) arbitrary loss or no control method, (ii) selective discard of MPEG B-pictures, and (iii) selective discard of MPEG Band P-pictures. Performance is evaluated based on end-to-end delay, congested queue occupancy levels, network utilization, and jitter. A description of the investigation, assumptions, limitations, and results of the simulation study are included
The Broadband Integrated Services Digital Network (B-ISDN) concept is a world-wide effort to merge data (packet-switched), voice (circuit-switched), and video (e.g., cable television) networks [LAPO94].This move to produce a single network capable of providing services for computer communications, telecommunications, and video delivery, has been widely accepted. The Asynchronous Transfer Mode (ATM) has been chosen as the connection-oriented, cell-based, switching and (de)multiplexing method for B-ISDN. Of the three services mentioned above, providing video service, such as videoon-demand, video-conferencing, and real-time broadcasts, is the most challenging because of its high bandwidth requirements and fixed delay bounds. To handle video service, ATM designates the Constant Bit Rate (CBR) and the Variable Bit Rate (VBR) service classes. These service categories guarantee strict contract requirements, agreed to by the source and the network, before the network establishes the connection. The Available Bit Rate (ABR) service class, which was originally designed to handle data traffic, meets less stringent requirements. The ABR class makes no guarantees concerning cell transfer delay or cell delay variation. A closed-loop feedback mechanism is used for traffic management. To use this class for video service, however, requires that the video source interact with the network. More specifically, the video source must accept feedback from the network and adapt its source rate based on this status information. If the network status indicates congestion, then the source must lower its rate.
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