NDIS(Network Driver Interface Specifation)

NDIS (Network Driver Interface Specification) is a Windows specification for how communication protocol programs (such as TCP/IP) and network device driver should communicate with each other. NDIS specifies interfaces for:

1. The program that sends and receives data by constructing or extracting it from the formatted units called frame (and sometimes packet or datagram). This program, usually called a protocol stack, is layering and generally corresponds to layers 3 and 4 (the Network Addressing and Transport layers) of the Open Systems Interconnection (OSI) reference model. Examples are TCP/IP and Internetwork Packet Exchange.
2. The program, usually called a device driver, that interacts directly with the network interface card (NIC)or other adapter hardware, which sends or receives the data on thecommunications line in the form of electronic signals. The driverprogram and the NIC interact at the Media Access Control (MAC address)sublayer of layer-2 level of OSI, which is called Data-Link Control.(Putting the signal on the line is the layer-1 or the Physical layer ofOSI.) Examples of MAC drivers are those for Ethernet, Fiber Distributed-Data Interface, and Token Ring.
3. A program called the Protocol Manager that assists theprotocol stack program and the MAC driver program by telling each ofthem the computer location of the other when the operating system is started or, in some cases, when a new device is added to the computer. This is called bind.A system file called PROTOCOL.INI identifies which protocol stacks usewhich MAC drivers and where each is located. A protocol stack can bebound to more than one MAC driver where a computer is connected tomultiple networks. And a single MAC driver can be bound to more thanone protocol stack in a computer.

NDIS was developed by Microsoft and 3Com. Using NDIS, Windowssoftware developers can develop protocol stacks that work with the MACdriver for any hardware manufacturer's communications adapter. By thesame token, any adapter maker can write a MAC driver software that cancommunicate with any protocol stack program.

A similar interface, called Open Data-Link Interface (ODI), is provided by Novell for its NetWare local area network operating system.

The latest version of NDIS, NDIS 5.0, specifies the interface for Windows 98 and Windows NT 5.0. A new kind of device model called the miniport driver model is specified that facilitates plug-and-play device features.