DLPI Programmer's Guide

Chapter 1 25
Introduction to DLPI
The Data Link Layer
DLPI supports the ability to associate several streams with a single
DLSAP, where each stream may be a unique data link connection
endpoint. However, not all DLS providers can support such
configurations because some DLS providers may have no mechanism
beyond the DLSAP address for distinguishing multiple connections. In
such cases, the provider will restrict the DLS user to one stream per
DLSAP.