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5 Software Architecture
SWAP devices are supported in
Microsoft Windows via the NDIS driver library. SWAP is designed for use
mainly in Windows 2000, but can also be used in Windows 98 with some minor
modifications. The NDIS library performs many functions common to all
networking device drivers, such as synchronisation. It also provides a
standard interface that higher-level applications can access.
NDIS exports two distinct
interfaces. A connectionless interface used by broadcast media like
Ethernet, and a connection oriented interface used by media that have
explicit connections between endpoints like ATM.
Manufacturers of asynchronous node
devices should write a connectionless miniport that declares itself as a
member of the Ethernet media type. To higher level protocols, SWAP
asynchronous nodes are indistinguishable from regular Ethernet adapters.
Manufacturers of Isochronous node
devices should write a miniport that declares itself as a member of the
Ethernet media type. It should display a connection oriented interface
however, not the connectionless interface used. NDIS works in Windows 98
and in Windows 2000. Isonchronous node drivers must also provide call
management functions to enable the setting up and terminating of calls.
Isonchronous node call control should be done through TAPI. TAPI is a
simple set of object interfaces and methods for establishing connections
between devices. The TAPI proxy is freely available in Windows 2000, while
in Windows 98 it can easily be obtained.
Figure 5.1: Software Architecture Diagram
Some device designers may wish to
stream voice conversations between the SWAP adapter and another adapter
within the PC in real time. In Windows 98 and Windows 2000 voice streams
coming in through NDIS are redirected to the Raw Channel Access filter,
which then sends them into Directshow, as illustrated in figure 5 of the
software architecture diagram above.
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