ATM is a connection-oriented, unreliable (does not acknowledge the receipt of cells sent), virtual circuit packet switching technology.
The cost of maintaining separate, specialized networks for computer, voice, and video is high. To reduce networking costs, ATM enables integration of all of these services on a single network and the combination of existing networks into a single infrastructure. In particular, Windows operating systems provide rich connectivity using Asynchronous Transfer Mode (ATM) while maintaining support for legacy systems.
To support ATM, Network Driver Interface Specification (NDIS) has been updated with ATM commands. Because many applications do not yet use ATM services, Windows Server 2003 includes support for LAN Emulation (LANE) for LAN applications, such as Ethernet. Similarly, IP over ATM support has been added, eliminating the additional header cost of LAN packets. Winsock 2.0 native ATM has also been added to support the many applications that use Windows Sockets (Winsock).
Unlike most connectionless networking protocols, ATM is a deterministic networking system — it provides predictable, guaranteed quality of service. From end to end, every component in an ATM network provides a high level of control. ATM technology includes:
- Scalable performance. ATM can send data across a network quickly and accurately, regardless of the size of the network. ATM works well on both very low and very high-speed media.
- Flexible, guaranteed Quality of Service (QoS). ATM allows the accuracy and speed of data transfer to be specified by the client. This feature distinguishes ATM from other high-speed LAN technologies such as gigabit Ethernet. The QoS feature of ATM also supports time dependent (or isochronous) traffic. Traffic management at the hardware level ensures that quality service exists end-to-end. Each virtual circuit in an ATM network is unaffected by traffic on other virtual circuits. Small packet size and a simple header structure ensure that switching is done quickly and that delays due to high traffic are minimized.
- Unobstructed speed. ATM imposes no architectural speed limitations. Its pre-negotiated virtual circuits, fixed-length cells, message segmentation and re-assembly in hardware, and hardware-level switching all help support extremely fast forwarding of data.
- Integration of different traffic types. ATM supports integration of voice, video, and data services on a single network. ATM over Asymmetric Digital Subscriber Line (ADSL) enables residential access to these services.