Applicable to End Systems concerned with operating in the Open Systems Interconnection (OSI) environment. Specifies a combination of OSI standards, which collectively provide the connection-mode Transport Service using the connection-mode Network Service. Defines the TC51 profile which is applicable to the provision of the OSI connection-mode Transport Service using the OSI connection-mode Network Service in an End System attached to a CSMA/CD LAN subnetwork. Specifies the required functions from the supporting protocol stack shown in figure 2.