Address Format

Two address formats for the OSI protocol are defined in this section. The SOCKADDR_TP format is retained for compatibility with Windows Sockets 1.1-OSI protocols. Windows Sockets 2 OSI protocols support the SOCKADDR_OSITP format. It contains:

• A Transport Selector (TSEL)
• Network Service Access Point (NSAP)
• Sub Network address (SNPA),
• Extended addressing information
• The option profile name.

The SNPA follows the rules of the Sub Network in use. For example, an SNPA would contain a 6-byte MAC address followed by a 1-byte Link Service Access Point (LSAP) giving a 7-byte SNPA.

Some X.25 protocols use connect user data to select the listening socket. The extended addressing information contains connect user data. This field must not be specified for other OSI protocols.

The address structure also contains the option profile name. If the name length is zero, the default option profile is used.

The TP4/NULL OSI-protocol profile is selected by using the TP4/CLNS protocol, selecting a zero-length NSAP, and specifying the MAC address and LSAP in the Sub Network address field.