What are the characteristics of atm technology

Characteristics of ATM technology: 1. Using fixed-length short message cells as transmission units, which is conducive to high-speed broadband switching; 2. Supports various services at different rates, using optical fiber transmission, and does not need to be performed at the data link layer Error control and flow control; 3. The lowest layer is connection-oriented transmission, and circuit switching ensures real-time and service quality.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

ATM is the abbreviation of Asynchronous Transfer Mode (ATM), which is one of the core technologies for realizing B-ISDN services. ATM is a packet switching and multiplexing technology based on cells.

It is a universal connection-oriented transmission mode designed for a variety of businesses. It is suitable for LAN and WAN, it has high-speed data transfer rate and supports many types of communication such as voice, data, fax, real-time video, CD-quality audio and images.

ATM uses a connection-oriented transmission method, dividing data into fixed-length cells and exchanging them through virtual connections. ATM integrates switching, multiplexing, and transmission. It uses asynchronous time division multiplexing for multiplexing, and distinguishes different channels through the header or header of the information.

Characteristics of ATM technology

ATM is a broadband technology that transmits voice, video images and data over LAN or WAN. It is a cell relay technology with fixed data packet size. You can think of a cell as a transport device that carries blocks of data from one device through an ATM switching device to another.

All cells have the same size, unlike frame relay and LAN system data packet sizes. Using cells of the same size provides a way to anticipate and guarantee the bandwidth required by an application. Just as a car must wait for a long truck to turn at a busy intersection, variable-length data packets tend to cause communication delays at switching equipment.

ATM is an asynchronous transmission mode, its characteristics are:

• Using fixed-length short cells as transmission units, which is conducive to high-speed broadband switching;

• Supports various services at different rates, using optical fiber transmission, without error control and flow control at the data link layer;

• Finally The bottom layer is connection-oriented and transmitted, and circuit switching ensures real-time and service quality.

Applications and advantages and disadvantages

ATM is a data transmission technology that implements B-ISDN services One of the core technologies. ATM is a packet switching and multiplexing technology based on cells. It is a universal connection-oriented transmission mode designed for a variety of services. It is suitable for LAN and WAN, it has high-speed data transfer 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 that transmits voice, video images and data over a LAN or WAN. It is a cell relay technology with fixed data packet size. You can think of a cell as a transport device that carries blocks of data from one device through an ATM switching device to another. All cells are of the same size, unlike frame relay and LAN systems where data packets are of variable size. Using cells of the same size provides a way to anticipate and guarantee the bandwidth required by an application. Just as a car must wait for a long truck to turn at a busy intersection, variable-length data packets tend to cause communication delays at switching equipment.

When used as a company's backbone network, ATM can simplify network management and eliminate many complex problems caused by network interconnection with different addressing schemes and routing mechanisms. An ATM hub can provide connection between any two ports on the hub, regardless of the type of connected device. The addresses of these devices are pre-mapped, making it easy, for example, to send a message from one node to another, regardless of the type of network the node is connected to. ATM management software makes it easy for users and their physical workstations to move around.

Using ATM technology, we can complete the LAN interconnection between the corporate headquarters and various offices and company branches, thereby realizing internal data transmission, corporate email services, voice services, etc., and realizing e-commerce through uplink INTERNET. application. At the same time, because ATM uses statistical multiplexing technology, and the access bandwidth exceeds the original 2M, reaching 2M-155M, it is suitable for applications such as high bandwidth, low latency or high data burst.

ATM is the best supporting technology for multimedia information transmission.

Advantages and Disadvantages

• Its characteristics: cell-based packet switching technology; fast switching technology; connection-oriented cell switching; reserved bandwidth .

• Its advantages: good real-time performance of circuit switching and strong flexibility of packet switching; using fixed-length packets (cells) as the unit of transmission and switching; excellent service quality; currently The highest speed is 10GB/S and will soon reach 40GB/S.

• The disadvantages are: the overhead of the cell header is too large; the technology is complex and expensive.

ATM layering

ATM procedures are divided into three levels: physical layer, ATM layer and ATM adaptation layer.

Physical layer: Specifies the interface between ATM data flow and physical media, including 2 sub-layers: physical media-related sub-layer and transmission convergence sub-layer. The former specifies the rate at which ATM data streams are transmitted through a given medium, and the latter specifies the procedures for transmitting cells through the relevant sublayer of the physical medium.

ATM layer: It is the core of ATM technology and is mainly responsible for the routing, multiplexing and repeated use of cells.

AAL (ATM Adaptation Layer, ATM Adaptation Layer): Converts user services from higher layers into the format and length of the payload in ATM, and then converts them into the original user services after arriving at the destination. AAL can be divided into 2 layers, including the convergence sublayer (CS) and the disassembly sublayer (SCR).

AAL has 4 protocol types: AAL1, AAL2, AAL3/AAL4 and AAL5 respectively support various AAL business types. The purpose of AAL is to allow existing protocols and applications to run on ATM. For this purpose AAL must convert the upper layer data into 48B in ATM cells. Common communication protocols (TCP/IP, Ethernet, Token Ring) use variable-length packets, and the packet lengths are larger than the data segments in ATM cells, but AAL can segment these larger high-level data packets. into cells that can be transmitted through the ATM network, or to reassemble cells received from the network into original data packets.

AAL consists of two sublayers, one called the Convergence Sublayer (CS) and the other called the Segmentation and Reassembly Sublayer (SAR). The CS sublayer first segments the high-level data and encapsulates it in CS-PDU (Convergence Sublayer Protocol Data Unit). Then, the SAR sublayer divides the CS-PDU into several data segments of the same size (not larger than 48B), so that it can be encapsulated in the cell.

The various services and corresponding AALs are as follows:

Class A, constant bit rate CBR service: AAL1 supports constant bit rate connection-oriented services. Examples of such services include 64Kb/ Dedicated lines for s-rate voice, fixed-rate uncompressed video, and private data networks.

Class B, variable bit rate VBR service: AAL2 supports connection-oriented services with variable bit rates, and cell transmission delays are required during the transmission process. Examples of such services include compressed packet voice or voice. The transmission delay process is necessary when the receiver reconstructs the original uncompressed speech or speech.

Category C, connection-oriented data service: used for connection-oriented file transfer and data network applications, in which the connection has been preset before data transmission. This service provides variable bit rates but does not require cell transmission delays for the transmission process. There are two protocols that support this type of service, and these two protocols have been merged into one, AAL3/4. However, due to its high complexity, the AAL5 protocol is often used to support this type of service.

Class D, connectionless data service: Examples of this service include datagram traffic and often data network applications in which no connection is pre-set up before data is transferred. Among them, AAL3/4 or AAL5 are used to support such services.

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