Rabu, 10 Agustus 2011


This tutorial provides the basic introduction to atm network technology, packet switching, cell base, telecommmunication technology, high speed bandwidth usage in this technology. ATM (Asynchronous Transfer Mode) is a high speed network technology that has become the standardized solution for the telecommunication industry, teleconferencing, videoconferencing, telemedicine, HDTV, distance learning and where high speed data transfer is required.

ATM technology integrates voice, data and video at the same time. ATM uses fixed size packets called cells of 55 bytes in length. ATM network is a high speed circuit switched network that is capable of transferring one million signals using ATM protocol. ATM is a connection oriented technology in which logical connections are established for the data communication. ATM is implemented in the WAN and telecommunication sectors. Small data cells are used for communication and ATM is designed for high speed and high traffic networks. ATM cells allow voice, data and video transfer at the same time. ATM operates on the data link layer of the OSI model and it uses UTP/STP, fiber optic or air as a communication medium.

It is a small unit of 55 bytes fixed length and it contains the users and signaling information in it. It has a header with very limited functionality to reduce the internal buffer and to provide the high speed transfer. ATM cell identify the cells that belongs to the same virtual channels and perform easy routing.

Various switching technologies have been developed in the past to provide the high speed data transfer and secure communication. ATM switching technology provides high speed data transfer due to the connection oriented technology. ATM switching technology uses the predefined routing table so guarantees the fast data communication.
ATM basically uses two types of devices such as ATM switch and end systems. The function of the switch is to handle the transmission of the cells throughout the network. Switches accept the incoming cells from the ATM end station or another ATM switch. On the other hand, ATM end systems contain the ATM adaptors.
ATM supports two types of connections point to point and point to multi point connections. In the point to point connections, two end systems are connected bi directionally or uni directionally. The point to multi point system connects one source to the number of destinations in uni directional. The source sends the information and switch replicates it to the destinations. Unidirectional network connects two switches. A typical ATM network consists of a set of the switches interconnected by point to point links. Switch support two types of interfaces user network and network node interface. Asynchronous transfer mode technology is designed for the reliability, performance, utilization and QOS and it creates fixed channels and routes when data travels between two points. There are four types of the choice when purchasing a connection.
Constant Bit Rate: It specifies fixed size rate and data is transferred in a steady form. Variable bit rate.Variable Bit Rate: It provides specified throughput and it is best for videoconferencing. Available bit rate. It provides guaranteed minimum capacity but high rate is also possible when the network is free. 
Unspecified bit rate. It does not provide any fixed throughput level and it is best for the file transfer where delay can occurred.

It provides fixed bandwidth and simple routing is possible due to the connection oriented technology. High bandwidth utilization can be possible so it is the best solution for the telecommunication sector, videoconferencing and QOS. There are some of the disadvantages of this technology such as high cost, cell loss due to the high congestion in the network.

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