GLD implements both Style 1 and Style 2 providers. A physical point of attachment (PPA) is the point at which a system attaches itself to a physical communication medium. All communication on that physical medium funnels through the PPA. The Style 1 provider attaches the Stream to a particular PPA based on the major/minor device that has been opened. The Style 2 provider requires the DLS user to explicitly identify the desired PPA using DL_ATTACH_REQ. In this case, open(9E) creates a Stream between the user and GLD, and DL_ATTACH_REQ subsequently associates a particular PPA with that Stream. Style 2 is denoted by a minor number of zero. If a device node whose minor number is not zero is opened, Style 1 is indicated and the associated PPA is the minor number minus 1. If both Style 1 and Style 2 opens, the device is cloned.