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Asynchronous Transfer Mode (ATM) in Computer Network

We use an Asynchronous Transfer Mode (ATM) network because it is driven by the integration of performance and service, which is the requirement for both data network and telephony. It also provides network support for the single quality of the service, and these services are very expensive. It is very cheap and flexible. It also supports some ranges of services at a reasonable cost.

Asynchronous Transfer Mode (ATM)

Asynchronous Transfer Mode (ATM) is an International Telecommunication Union- Telecommunications Standards Section (ITU-T) that is very efficient for the relay of calling. Also, it is used to transfer all the services like voice, data, or video. These services can be conveyed in a small fixed-sized packet called the cell. These cells are connected in a network that transmits the data asynchronously.

Asynchronous transfer mode (ATM) is a technology that was developed in the year between 1970 and 1980. This was considered the revolution in packet switching. Each cell consists of 53 bytes longs. Further, the 53 bytes long can be divided into 5 bytes header and 48 bytes payload. Before making an ATM call, we need to send a message to set up the connection.

All the cells follow the same path connected to the destination. The cell can also handle both variable and constant rate traffic. Thus it has multiple types of traffic with end-to-end encryption. Asynchronous transfer mode (ATM) does not depend on the transmission medium. Asynchronous transfer mode (ATM) uses cell or packet switching and virtual circuits to switch the transmission medium. The main purpose of designing the Asynchronous transfer mode (ATM) is to help implement high-performance multimedia networking.

ATM Cell Format

In Asynchronous transfer mode (ATM), the data are transmitted through a fixed-size unit called cells. As we know, each cell has 53 bytes long. There are two types of Asynchronous transfer modes (ATM). These are as follows:

1. UNI header

This is used in the private connection in the Asynchronous transfer mode (ATM) network between ATM switches and ATM endpoints.

2. NNI header

It communicates between the Asynchronous Transfer Mode (ATM) switches.

Working of ATM

Two types of connection use the Asynchronous transfer mode (ATM). A virtual path can be created end-to-end across an ATM network, as it does not route the cells to a particular virtual circuit. In case of major failure, all cells belonging to a particular virtual path are routed the same way through the ATM network, thus helping faster recovery.

Switches connected to subscribers use both VPIs and VCIs to switch the cells, which are Virtual Path and Virtual Connection switches that can have different virtual channel connections between them, serving the purpose of creating a virtual trunk between the switches, which can be handled as a single entity. Its basic operation is straightforward looking up the connection value in the local translation table, determining the outgoing port of the connection, and the new VPI/VCI value of the connection on that link.

ATM vs. DATA Networks (Internet)

  • ATM is a "virtual circuit" based: Here, the path is reserved before transmission. While Internet Protocol (IP) is connectionless, end-to-end resource reservations are impossible. RSVP is a new signaling protocol on the internet.
  • ATM Cells: Fixed or small, and the Tradeoff is between voice or data. At the same time, IP packets are of variable size.
  • Addressing: ATM uses 20-byte global NSAP addresses for signaling and 32-bit locally assigned labels in cells. At the same time, IP uses 32-bit global addresses in all packets.

ATM Applications


To send the data over a long distance, we use WAN and a router to connect ATMs and other networks.

2. Multimedia virtual private networks and managed services

It helps manage ATM, LAN, voice, and video services and is capable of full-service virtual private networking, including integrated multimedia access.

3. Frame relay backbone

Frame relay services are a networking infrastructure for a range of data services and enable frame-relay ATM service to Internetworking services.

4. Residential broadband networks

ATM by choice provides the networking infrastructure for establishing residential broadband services in search of highly scalable solutions.

5. Carrier infrastructure for telephone and private line networks

To make more effective use of SONET/SDH fiber infrastructures we build the ATM infrastructure to carry out the telephonic and private-line traffic.

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