The Communication Protocols specified in this Part of PS3 closely fit the ISO Open Systems Interconnection Basic Reference Model (ISO 7498-1, see Figure 1-1). They relate to the following layers: Physical, Data Link, Network, Transport, Session, Presentation and the Association Control Services (ACSE) of the Application layer. The communication protocols specified by this Part are general purpose communication protocols (TCP/IP) and not specific to this Standard. The other aspects of the Application Layer protocols are addressed in other parts of this Standard as discussed in PS3.1 “PS3.1”.