These units had provided information on the TCP Five-Layer Network model as well as the OSI Networking Model.
The TCP model is based on a 5 layer system consisting of
5 Process & Applications Provide applications services to users and programs
4 Transport Handles data-consistency functions, i.e., provides a reliable byte stream between two nodes on a network. TCP and UDP work at this level.
3 Internet (sometimes called the Network Layer) Provides network addressing and routing, and does so in such a way as also to provide a common address space across multiple lower-level protocols. This makes possible the interconnection of networks that characterizes the Internet. The IP protocol operates at this level.
2 Network (sometimes called the Data Link Layer) This layer contains whatever IP will run over, e.g., Ethernet, token-ring, and Fiber Distributed Digital Interface (FDDI) networks. Individual network protocols, e.g., Ethernet, work at this level.
1 Physical Not really part of the model, since TCP and IP, as protocols, deal with software rather than hardware. This layer is generally thought of as referring to all hardware under the Network Layer.
The OSI networking model is based on a 7 layer model consisting of
Deals with the interface between a user and the host computer: e.g., Microsoft Word translating a signal, initiated by the user’s typing in a string of characters and then depressing the “Search” function key, into instructions to Windows (or System X) to try to find that string in a file.
6 Presentation Deals with syntactic representation of data: e.g., agreement on character code (e.g., ASCII, extensions to ASCII, Unicode), data-compression and data-encryption methods, representations of graphics (e.g., files using the .PIC or .BMP formats)
5 Session Deals with creating and managing sessions when one application process requests access to another applications process (e.g., Microsoft Word importing a chart from Excel)
4 Transport Deals with data transfer between end systems; flow control for two computers (e.g., how Netscape on your PC talks with the UT Libraries Online Webpage)
3 Network Deals with establishing paths for data between a pair of computers and handling any switching among alternative routes between the computers, as well as with definitions of how to break files (or messages) up into individual packets of data, in such a way that the packets can be transmitted and then reassembled.
2 Data-Link Deals with the transmission of data frames (e.g., packets) over a physical link between network entities, including the incorporation of error-correction coding into the data frames.
1 Physical Deals with the physical (i.e., electrical and mechanical) aspects of transmitting data (e.g., voltage levels, pin-connector design, cable lengths, and grounding arrangements).