Open Systems Interconnection (OSI)

Supplemental Material

Internetworking

Open Systems Interconnection (OSI)

Developed by the International Organization for Standardization (ISO) in 1984

The primary architectural model for intercomputer communications.

A conceptual model composed of seven layers, each specifying particular network functions.

Describes how information from a software application in one computer moves through a network medium to a software application in another computer.

OSI Model

Applicationlayer

Networklayer

Data Link layer

Physical layer

OSI Model F-D’s Model

Application layer: http, telnet, snmp,smtp, nfs, ftp

TCP, UDP

Data Link Layer

Physical layer

Internet Model

IPv4, IPv6

(HDLC)

OSI Model

Network layer provides routing and related functions

Transport layer implements reliable internetwork data transport services

Session layer establishes, manages and terminates communication

sessions between presentation layer entities

Presentation layer provides a variety of coding and conversion functions

Application layer closest to the end user

Protocols

Protocols fall into one of the following groups: LAN protocols WAN protocols Network protocols Routing protocols

Interaction between Layers

A data link layer contact three other layers

Headers and Data

Physical-layer Implementation

OSI Data Link Layer

IEEE has subdivided data link layer into two sub-layers.