Key points of ATM technology

ATM is based on a set of technological innovations that allow it meets the requirements demanded.
Standardization
Although its origins date back to the 60, is from 1988 when the CCITT ratifies ATM as the technology for the development of broadband networks (B-ISDN), appearing the first standards in 1990.
From then until now ATM has been subjected to a rigorous process of standardization, not only for simple interoperability at the physical level (SONET and SDH speeds ...) but to ensure multifabricantes networking service level, issues such as standardizing Signaling (UNI, NNI), congestion control, LAN integration, and so on.
This feature ensures multivendor networking, guaranteeing investment and allow a strong market development, thereby reducing costs.
Cell based multiplexing
To be able to properly manage the bandwidth on a link, it is necessary that the different sources that submit their data used in minimum units of information.
For ATM was decided a minimum unit of 53 bytes fixed size. The use of a fixed size can develop very specialized hardware modules that switch these cells at the speeds required in broadband (and future). The length of the unit should be small so quickly can be multiplexed on the same link cells from different sources and to guarantee service quality for sensitive traffic (voice, video, ...)
Connection-oriented
ATM out that a connection-oriented technology allowing, among other things, to achieve a minimum information unit of small size. As mentioned earlier, growth forecasts for ATM required the use of a numbering system terminals 20 bytes. Technologies do not require connection-oriented that each unit of information contains the addresses within both origin and destination. Obviously, they could not devote 40 bytes of the cell for that purpose (for header overhead would be unacceptable).
Addressing the only data that is included in the cell is the virtual channel identification means, only, five byte header (48 bytes for transmitting useful information).
Quality of Service (QoS)
Defines four basic categories of traffic: CBR (Constant Bit Rate), VBR (Variable Bit Rate), UBR (Undefined Bit Rate) and AVR (Available Bit Rate)
At the time of creation, the DTE characterizes the traffic to be sent through the circuit using four parameters (PCR, SCR, and MBS CDVT) within one of these four categories. The network propagates the request to its destination and internally valid if the requirements will be required to comply. If so, the network accepts the circuit and from that time, ensures that traffic be treated according to the terms negotiated in the establishment.
The ATM switches run an algorithm called dual leaky buckets guarantees, cell by cell, which is offering the required quality of service. Is it permissible for the DTE to send data over a circuit of the negotiated rate. In that case the ATM switch can proceed to discard the cells concerned in the case of saturation at any point in the network.
Intelligent Network
ATM transport network is an intelligent network where each node that composes a separate item. As mentioned above, the switches forming the ATM network individually discover the network topology of your environment through a dialog protocol between nodes.
This type of approach, novel in broadband networks, open the door to a new world of functionality (different speed links, flexible topology, traffic balancing, scalability, ...) and is without a doubt, the cornerstone ATM technology.