This document provides a specification for a STREAMS based implementation of the SS7 protocol stack. Although there exsits specifications for OSI protocol layers, the SS7 protocol does not map one-to-one onto OSI layers, and, as such, it is necessary to implement different protocol layers for the various modules of the SS7 stack. Nevertheless, there is a rough correspondence between the protocol modules of this SS7 specification and the protocol modules of the OSI stack (illustrated in Figure 1 below) which is useful when considering SS7 implementations in comparison to existing OSI implementations on STREAMS.