ATM Network Adapter Integration in Windows 2000

Microsoft Windows 2000 handles Asynchronous Transfer Mode (ATM) network adapter integration through native, modular networking architecture powered by NDIS 5.0. By introducing Connection-Oriented NDIS (CoNDIS), the operating system natively bridges traditional packet-based network protocols with ATM’s connection-oriented, cell-switched transport. This integration enables features such as high-throughput data transfer, LAN Emulation (LANE), Classical IP over ATM (IPoATM), and hardware-level Quality of Service (QoS) directly within enterprise environments.

NDIS 5.0 and Connection-Oriented Architecture

Traditional local area networking relies on connectionless protocols where packets are routed independently. Because ATM establishes dedicated virtual circuits before transmitting data, Windows 2000 implemented Connection-Oriented NDIS (CoNDIS) within NDIS 5.0.

Under CoNDIS, the operating system separates the transmission of data from the signaling and call-management processes:

  • Miniport Drivers: The physical ATM network interface card (NIC) is controlled by an ATM miniport driver. This driver handles direct hardware communication, cell segmentation and reassembly (SAR), and physical transmission.
  • Call Managers: Connection setup, maintenance, and teardown are controlled by a Call Manager. The Call Manager handles ATM User-Network Interface (UNI) signaling (such as UNI 3.1 or 4.0). Windows 2000 allows the Call Manager to run as a separate driver or integrated directly into the miniport driver as a Miniport Call Manager (MCM).

Protocol Integration Models

Windows 2000 supports two primary mechanisms to allow traditional networking stacks (like TCP/IP) to communicate across an ATM fabric:

1. LAN Emulation (LANE)

LAN Emulation enables ATM adapters to appear as standard Ethernet or Token Ring adapters to the upper-layer operating system protocols.

  • The LANE client operates as an intermediate driver.
  • It translates MAC-layer broadcast and multicast traffic into ATM point-to-multipoint or point-to-point connections.
  • Upper-layer protocols—including TCP/IP, IPX/SPX, and NetBEUI—function over an ATM backbone without requiring modifications.

2. Classical IP over ATM (IPoATM / RFC 1577)

For environments seeking higher performance without MAC-layer overhead, Windows 2000 implements native Classical IP over ATM (CLIP).

  • The IP layer communicates directly with the ATM layer via an ATM ARP (Address Resolution Protocol) client.
  • IP addresses are resolved directly to ATM end-system addresses (NSAP format) rather than MAC addresses.
  • This removes framing overhead and maximizes throughput across Switched Virtual Circuits (SVCs) and Permanent Virtual Circuits (PVCs).

Quality of Service (QoS) Integration

ATM provides inherent Quality of Service capabilities, allowing bandwidth reservation and predictable latency. Windows 2000 integrates this hardware capability directly into its native QoS architecture:

  • Applications request bandwidth and latency parameters using the Generic QoS (GQoS) API or RSVP (Resource Reservation Protocol).
  • The Windows 2000 QoS packet scheduler maps these software requests directly to ATM traffic parameters, such as Constant Bit Rate (CBR), Variable Bit Rate (VBR), and Unspecified Bit Rate (UBR).
  • The ATM Call Manager negotiates these parameters with the ATM switch during the virtual circuit setup phase, guaranteeing network resources at the hardware layer.

Plug and Play and Configuration

Windows 2000 incorporates ATM adapters into its unified Plug and Play (PnP) subsystem and power management framework. When an ATM card is inserted:

  1. The PnP manager identifies the PCI hardware, assigns system resources (I/O ports, IRQs, and memory ranges), and loads the appropriate NDIS 5.0 miniport driver.
  2. The operating system automatically binds the default protocol stack, prompting configuration for ELAN (Emulated LAN) memberships or ATM ARP server addresses depending on whether LANE or RFC 1577 is selected.
  3. Network administrators manage ATM adapters through the centralized "Network and Dial-up Connections" interface, where virtual circuits, service categories, and signaling parameters can be defined.