12-03-2011, 04:18 PM
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Introduction
ATM does not stand for automatic teller machine. In the telecommunication, it stands for Asynchronous Transfer Mode, in which data sends asynchronously. This mode is another fast packet switching mode.
ATM is regarded as the technology of the 21st century and its impact is expected to be similar to PCM (pulse code modulation) which is used widely around the world in telecommunication.
Asynchronous transfer mode (ATM) is a technology that has his its history in the development of broadband ISDN in the 1970s and 980s. Technically, it can be viewed as an evolution of pocket switching. Like packet switching for data , ATM integrates the multiplexing and switching functions, is well suited for bursty traffic and allows communications between devices that operate at different speeds . Unlike packet switching , ATM is designed for high-performance multimedia networking.
ATM is also a set of international interface and signaling standards defined by the International Telecommunication Union- Telecommunications (ITU-T) Standards Sector (formerly the CCITT). The ATM forum has played a pivotal role in the ATM market since its formulation in 1991.
The ATM forum is an international voluntary organization composed of vendors , service providers, research organization, and users. Its purpose is to accelerate the use of ATM products and services through the rapid convergence of interoperability specifications, promotion of industry cooperation , and other activities. Developing multivendor implementation agreements also furthers this goal.
What is ATM ?
Asynchronous transfer mode is a high speed; packet based multiplexing technique in which information flow is organized in short fixed length cells.
The cells are generated when there is new data to send, which allows an element of data compression (e.g there is no need to send the pauses that occurs in speech). It also means that cells with different bandwidth in each direction are possible- a fax connection, for example uses little bandwidth in return direction. This allows more efficient use of the network resourses.
ATM provides a way of multiplexing many sources of data onto a common cells stream. Regardless of speed of the inputs. This greatly improves flexibility, enabling provision of bandwidth on demand.
Asynchronous Transfer Mode Switching
Asynchronous Transfer Mode (ATM) an International Telecommunication Union-Telecommunications Standards Section (ITU-T) standard for cell relay wherein information for multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells. ATM networks are connection-oriented. This chapter provides summaries of ATM protocols, services, and operation. Figure illustrates a private ATM network and a public ATM network carrying voice, video, and data traffic.
Standards
ATM is based on the efforts of the ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard. It was originally conceived as a high-speed transfer technology for voice, video, and data over public networks. The ATM Forum extended the ITU-T's vision of ATM for use over public and private networks. The ATM Forum has released work on the following specifications:
User-to-Network Interface (UNI) 2.0
UNI 3.0
UNI 3.1
UNI 4.0
Public-Network Node Interface (P-NNI)
LAN Emulation (LANE)
Multiprotocol over ATM
ATM Devices and the Network Environment
ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching (guaranteed capacity and constant transmission delay) with those of packet switching (flexibility and efficiency for intermittent traffic). It provides scalable bandwidth from a few megabits per second (Mbps) to many gigabits per second (Gbps). Because of its asynchronous nature, ATM is more efficient than synchronous technologies, such as time-division multiplexing (TDM).
With TDM, each user is assigned to a time slot, and no other station send in that time slot. If a station has much data to send, it can send only when its time slot comes up, even if all other time slots are empty. However, if a station has nothing to transmit when its time slot comes up, the time slot is sent empty and is wasted. Because ATM is asynchronous, time slots are available on demand with information identifying the source of the transmission contained in the header of each ATM cell.
ATM Cell Basic Format
ATM transfers information in fixed-size units called cells. Each cell consists of 53 octets, or bytes. The first 5 bytes contain cell-header information, and the remaining 48 contain the payload (user information). Small, fixed-length cells are well suited to transferring voice and video traffic because such traffic is intolerant of delays that result from having to wait for a large data packet to download, among other things. Figure illustrates the basic format of an ATM cell.
Introduction
ATM does not stand for automatic teller machine. In the telecommunication, it stands for Asynchronous Transfer Mode, in which data sends asynchronously. This mode is another fast packet switching mode.
ATM is regarded as the technology of the 21st century and its impact is expected to be similar to PCM (pulse code modulation) which is used widely around the world in telecommunication.
Asynchronous transfer mode (ATM) is a technology that has his its history in the development of broadband ISDN in the 1970s and 980s. Technically, it can be viewed as an evolution of pocket switching. Like packet switching for data , ATM integrates the multiplexing and switching functions, is well suited for bursty traffic and allows communications between devices that operate at different speeds . Unlike packet switching , ATM is designed for high-performance multimedia networking.
ATM is also a set of international interface and signaling standards defined by the International Telecommunication Union- Telecommunications (ITU-T) Standards Sector (formerly the CCITT). The ATM forum has played a pivotal role in the ATM market since its formulation in 1991.
The ATM forum is an international voluntary organization composed of vendors , service providers, research organization, and users. Its purpose is to accelerate the use of ATM products and services through the rapid convergence of interoperability specifications, promotion of industry cooperation , and other activities. Developing multivendor implementation agreements also furthers this goal.
What is ATM ?
Asynchronous transfer mode is a high speed; packet based multiplexing technique in which information flow is organized in short fixed length cells.
The cells are generated when there is new data to send, which allows an element of data compression (e.g there is no need to send the pauses that occurs in speech). It also means that cells with different bandwidth in each direction are possible- a fax connection, for example uses little bandwidth in return direction. This allows more efficient use of the network resourses.
ATM provides a way of multiplexing many sources of data onto a common cells stream. Regardless of speed of the inputs. This greatly improves flexibility, enabling provision of bandwidth on demand.
Asynchronous Transfer Mode Switching
Asynchronous Transfer Mode (ATM) an International Telecommunication Union-Telecommunications Standards Section (ITU-T) standard for cell relay wherein information for multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells. ATM networks are connection-oriented. This chapter provides summaries of ATM protocols, services, and operation. Figure illustrates a private ATM network and a public ATM network carrying voice, video, and data traffic.
Standards
ATM is based on the efforts of the ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard. It was originally conceived as a high-speed transfer technology for voice, video, and data over public networks. The ATM Forum extended the ITU-T's vision of ATM for use over public and private networks. The ATM Forum has released work on the following specifications:
User-to-Network Interface (UNI) 2.0
UNI 3.0
UNI 3.1
UNI 4.0
Public-Network Node Interface (P-NNI)
LAN Emulation (LANE)
Multiprotocol over ATM
ATM Devices and the Network Environment
ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching (guaranteed capacity and constant transmission delay) with those of packet switching (flexibility and efficiency for intermittent traffic). It provides scalable bandwidth from a few megabits per second (Mbps) to many gigabits per second (Gbps). Because of its asynchronous nature, ATM is more efficient than synchronous technologies, such as time-division multiplexing (TDM).
With TDM, each user is assigned to a time slot, and no other station send in that time slot. If a station has much data to send, it can send only when its time slot comes up, even if all other time slots are empty. However, if a station has nothing to transmit when its time slot comes up, the time slot is sent empty and is wasted. Because ATM is asynchronous, time slots are available on demand with information identifying the source of the transmission contained in the header of each ATM cell.
ATM Cell Basic Format
ATM transfers information in fixed-size units called cells. Each cell consists of 53 octets, or bytes. The first 5 bytes contain cell-header information, and the remaining 48 contain the payload (user information). Small, fixed-length cells are well suited to transferring voice and video traffic because such traffic is intolerant of delays that result from having to wait for a large data packet to download, among other things. Figure illustrates the basic format of an ATM cell.
