The Study on State Transition Behavior of The Shared Buffer Switch and Call Admission Control Criterion in the ATM Network

• Main Author: 吳建翰
• Other Authors: Zhang, Wen-Zhong
• Format: Others
• Language: en_US
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/65632145045719692456

碩士 === 國立交通大學 === 電信工程研究所 === 86 === 　　For years, efforts have been made to improve the communication quality and bandwidth for the increasong traffic volumn of the communication needs. However, today the transmission and switching for multimedia data have met big problem since it contains a large variety of traffic sources, with many sources different characteristics. With the introduction of B - ISDN, the problem seems to be solved well. Among the techniques used to implement the B - ISDN architecture, the ATM (Asynchronous Transfer Mode) is found to be the most promising protocol due to its high efficiency and flexibility. 　　In an ATM network, the transmission speed is much higher than that in the traditional networks. But some problems are also met in the network. For example, if the traffic state of the network is at serios condition that is, too many cells generated from the transmitted sources are discarded due to netowork congestion, then in most cases it is hard to recover the netoork to normal state. Therefore, a good way for the network system to keep the network under control is very important. One of the important topic for congestion avoidance is the CAC (Call Admission Control). The admission decision should be made based on some convincing factors, such as Qos. 　　Here we will propose a method for estimating instantaneous cell loss rate and thus use the result to determine whether or not to accept a new call. The original cell loss rate is measured based on the current traffics tate of the ATM network. And the increment in the instantaneous cell loss rate when a new call asks for connection is then calculated based on some mathematical analysis. 　　We use some mathematical models to describe the ATM network, so that analysis on instantaneous cell loss rate could be proceeded well. What is amazing is that the result of the estimated formula is quite simple. This would do help to the call admission control since the calculation work for the system to make the decision could be much lessen.