ADTRAN 550 user manual Appendix B OSI Model and Frame Relay Technology Overview

Appendix B OSI Model and Frame Relay

Technology Overview

This chapter discusses the OSI Model, Frame Relay Protocol, and Transpar- ent Bit Oriented Protocol (TBOP).

OSI MODEL

		The Open Systems Interconnection (OSI) model is an internationally accept-
		ed standard for communication between multiple vendors’ communication
		equipment. It relies on a seven-layer model to allow communication be-
		tween communication equipment. Table B-1 describes these layers.
		Table B-1. Seven-Layer OSI Model
Layer	Title	Description
Layer 7	Application	Contains functions for end-user services. These include FTP, remote file
		access, and network management. This is not the application, but the
		interface.
Layer 6	Presentation	Provides transparent communication by creating code and syntax
		compatibility between systems.
Layer 5	Session	Takes care of the communication facility provided by the transport layer
		(layer 4). Allows sessions to be established, recovered, and terminated.
Layer 4	Transport	Provides some error correction and end-to-end flow control. Also decides
		best route for the information being transmitted.
Layer 3	Network	Determines the method for transmitting data and also deals with routing
		the data between networks. Moves data based on addressing.
Layer 2	Data Link	Deals with procedures and protocols for controlling the transmission line.
		Provides some error detection and correction.
Layer 1	Physical	Deals with the electrical, mechanical, and functional control of sending
		data over the transmission lines.
		By defining standard interfaces between each of the seven layers, an individ-
		ual layer only has to know about the interface to the layer above, to the layer
		below, and to the same layer on the other end of the network. This interface
		definition simplifies the process of networking.

61200305L1-1 ATLAS 550 User Manual B-1