communications framework model (between different systems with different standards) that includes seven layers of communications organized according to events and occurrences
The transport layer of the OSI model, responsible for transparent transfer of data for a connection, including sequencing, retransmission, flow control and stream control
The session layer of the OSI model, (typically ignored in Internet protocols) providing full or half duplex checkpointing, adjournment, termination and restart procedures
The theoretical presentation layer of the OSI model, (typically handled by other levels in Internet protocols) responsible for delivery and formatting of messages, e.g. encryption/decryption, codeset conversions (ASCII to EBCDIC) or other abstraction manipulations
The application layer of the OSI model, responsible for common application services to application processes, e.g. the Mozilla HTML engine used by FireFox and Internet Explorer 4, or the SMTP protocol used by e-mail programs