05-02-2013, 01:01 PM
The OSI Model
The OSI.ppt (Size: 1.44 MB / Downloads: 92)
INTRODUCTION
An ISO (International standard Organization) that covers all aspects of network communications is the Open System Interconnection (OSI) model.
An open system is a model that allows any two different systems to communicate regardless of their underlying architecture (hardware or software).
The OSI model is not a protocol; it is model for understanding and designing a network architecture that is flexible, robust and interoperable.
Peer-to-Peer Process
Within a single machine, each layer calls upon services of the layer just below it.
Layer 3, for example, uses the services provided by layer 2 and provides services for layer 4.
Between machines, layer x on one machine communicates with layer x on another machine, by using a protocol (this is Peer-to-Peer Process).
Communication between machines is therefore a peer-to-peer process using protocols appropriate to a given layer.
Physical Layer
The physical layer coordinates the functions required to transmit a bit stream over a physical medium. It also defines the procedures and functions that physical devices and interfaces have to perform for transmission occur.
Functions of the transport layer
Flow control: the transport layer performs a flow control end to end. The data link layer performs flow control across a single link.
Error control: the transport layer performs error control end to end. The data link layer performs control across a single link.