What is ATM

ATM (Asynchronous Transfer Mode) is a technological system developed for both local and wide area networks (LAN and WAN), and designed to handle data as well as video and voice traffic in real time, all at the same time. The system architecture makes use of switches that set up logical circuits at both ends of the data stream, which ensures unprecedented quality of service (QoS).

Network technology based on transferring data in cells or packets of a fixed size. The cell used with ATM is relatively small compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line.

Some people think that ATM holds the answer to the Internet bandwidth problem, but others are skeptical. ATM creates a fixed channel, or route, between two points whenever data transfer begins. This differs from TCP/IP, in which messages are divided into packets and each packet can take a different route from source to destination. This difference makes it easier to track and bill data usage across an ATM network, but it makes it less adaptable to sudden surges in network traffic.

When purchasing ATM service, you generally have a choice of four different types of service:

• constant bit rate (CBR): specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line.
• variable bit rate (VBR): provides a specified throughput capacity but data is not sent evenly. This is a popular choice for voice and videoconferencing data.
• available bit rate (ABR): provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free.
• unspecified bit rate (UBR): does not guarantee any throughput levels. This is used for applications, such as file transfer, that can tolerate delays.

ATM is a connection-oriented, unreliable (does not acknowledge the receipt of cells sent), virtual circuit packet switching technology. Unlike most connection-less networking protocols, ATM is a deterministic networking system ” it provides predictable, guaranteed quality of service. From end to end, every component in an ATM network provides a high level of control. ATM technology includes:

• Scalable performance. ATM can send data across a network quickly and accurately, regardless of the size of the network. ATM works well on both very low and very high-speed media.
  
• Flexible, guaranteed Quality of Service (QoS). ATM allows the accuracy and speed of data transfer to be specified by the client. This feature distinguishes ATM from other high-speed LAN technologies such as gigabit Ethernet. The QoS feature of ATM also supports time dependent (or isochronous) traffic. Traffic management at the hardware level ensures that quality service exists end-to-end. Each virtual circuit in an ATM network is unaffected by traffic on other virtual circuits. Small packet size and a simple header structure ensure that switching is done quickly and that delays due to high traffic are minimized.
  
• Unobstructed speed. ATM imposes no architectural speed limitations. Its pre-negotiated virtual circuits, fixed-length cells, message segmentation and re-assembly in hardware, and hardware-level switching all help support extremely fast forwarding of data.
  
• Integration of different traffic types. ATM supports integration of voice, video, and data services on a single network. ATM over Asymmetric Digital Subscriber Line (ADSL) enables residential access to these services.

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GCRA algorithm . please reply me. i'm need of it very urgently. thanx in advance......

ATM (Asynchronous Transfer Mode) is a technological system developed for both local and wide area networks (LAN and WAN), and designed to handle data as well as video and voice traffic in real time, all at the same time. The system architecture makes use of switches that set up logical circuits at both ends of the data stream, which ensures unprecedented quality of service

It is really a nice trivia for the meaning and relevant uses of ATM. This helps us know it better. I should be keeping this in my mind forever.