Just as Windows Sockets 2 allows the basic data transport capabilities of numerous transport protocols to be accessed in a generic manner, it also provides a generic way to utilize multipoint and multicast capabilities of transports that implement these features. To simplify, the term multipoint is used hereafter to refer to both multicast and multipoint communications.
Current multipoint implementations (e.g. IP multicast, ST-II, T.120, ATM UNI, etc.) vary widely with respect to how nodes join a multipoint session, whether a particular node is designated as a central or root node, and whether data is exchanged between all nodes or only between a root node and the various leaf nodes. Windows Sockets 2's WSAPROTOCOL_INFOW struct is used to declare the various multipoint attributes of a protocol. By examining these attributes the programmer will know what conventions to follow in utilizing the applicable Windows Sockets 2 functions to setup, utilize and teardown multipoint sessions.
The features of Windows Sockets 2 that support multicast can be summarized as follows:
Note The inclusion of these multipoint features in Windows Sockets 2 does not preclude a service provider from also supporting an existing protocol-dependent interface, such as the Deering socket options for IP multicast.