ATM is a data transmission technology. Suitable for local area network and wide area network. It has high data transmission rate and supports many types of communication, such as voice, data, fax, real-time video, CD-quality audio and images.
ATM is a broadband technology to transmit sound, video images and data through local area network or wide area network. It is a cell relay technology, and the packet size is fixed. You can think of a cell as a transmission device, which can transmit data blocks from one device to another through ATM switching equipment. All cells have the same size, which is different from Frame Relay and LAN systems, and their packet size is uncertain. Using cells of the same size can provide a method to predict and guarantee the bandwidth required by the application. Just like a car waiting for a long truck to turn at a busy intersection, variable-length data packets can easily cause communication delay on switching equipment.
ATM does have the duality of circuit switching and packet switching;
ATM is connection-oriented. It needs to establish connections in both directions of communication, and then disconnect through signaling after the communication is over. However, it abandons synchronous time division multiplexing used in circuit switching and uses asynchronous time division multiplexing, so that the clocks of the sender and the receiver can be different and the bandwidth can be used more effectively.
The transmission unit of ATM is a cell with a fixed length of 53 bytes, and the header part contains VPI/VCI information for routing, so it has the characteristics of switching. It is a high-speed packet switching. In terms of protocol, it transfers the error correction and flow control functions of OSI layer 3 to intelligent terminals, which reduces network delay and improves switching speed.
Switching equipment is an important part of ATM, which can be used as a hub in an organization to quickly transmit data packets from one node to another. Or as a wide-area communication device to quickly transmit ATM cells between remote LANs. Traditional LANs such as Ethernet, optical fiber distributed data interface (FDD 1) and token ring network use * * * shared media, and only one node can transmit at any time, while ATM provides connections between any nodes, and nodes can transmit at the same time. Information from different nodes is multiplexed into the cell stream. In this system, ATM switches can be owned by public service providers or belong to an organization's intranet.
When ATM is the backbone network of a company, it can simplify the management of the network and eliminate many complicated problems caused by the interconnection of networks with different addressing schemes and routing mechanisms. An ATM hub can provide any two ports on the hub, regardless of the type of equipment connected. The addresses of these devices are pre-translated, for example, it is easy to send messages from one node to another, regardless of the network type to which the nodes are connected. ATM management software makes it very convenient for users and their physical workstations to move.
Through ATM technology, the local area network interconnection between corporate headquarters and offices and corporate branches can be completed, so as to realize internal data transmission, corporate mail service, voice service and so on. , and realize e-commerce and other applications through the Internet. At the same time, due to the statistical multiplexing technology, the access bandwidth of ATM has exceeded the original 2M, reaching 2M- 155M, which is suitable for applications with high bandwidth, low delay or high data burst.
(2) ATM
ATM is the abbreviation of Automatic Teller Machine, which means automatic teller machine, also known as ATM. It is an electronic device, which uses magnetic code card to work automatically instead of automaton to carry out the basic work of bank counter staff. You can withdraw cash, check deposit balance, transfer money between accounts, check balance and so on. Cardholders can use credit cards or savings cards to automatically withdraw money, check the balance, transfer money and modify the password according to the password.
1939, Luther George simkin invented the ATM. But the modern concept of ATM was put forward in 1968, and its embryonic form appeared in 1969. The first ATM was installed in New York Chemical Bank. At present, the development speed of ATM is quite fast, and the ratio with banking institutions has reached 4: 1. The us navy even installed ATM machines on warships.