OSI Model-Data Communication-Lecture Slides, Slides of Data Communication Systems and Computer Networks

This lecture is part of lecture series delivered by Dr. Siddanth Suri at Cochin University of Science and Technology for Data Communication course. Its main points are: Open, System, Interconnection, Communication, Architecture, Layers, Model, Data, Link, Protocol

Typology: Slides

2011/2012

Uploaded on 07/07/2012

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Data Communication
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Download OSI Model-Data Communication-Lecture Slides and more Slides Data Communication Systems and Computer Networks in PDF only on Docsity!

Data Communication

Lect-

by

Previous Lecture

• Protocol Architecture

 Protocol Layers

 Inter Layer Communication

 Ports / Service Access Points

 Protocol Data Units PDUs

• Protocol Standards

 Defacto, De-Jure

 Regulatory Authorities, Forums,

 Interoperability

• Open System Interconnection

OSI Layers

• Seven Layers

 Application Layer

 Presentation Layer

 Session Layer

 Transport Layer

 Network Layer

 Data Link Layer

 Physical Layer

Physical Layer

• Concerned with protocols, standards and functions of

physical interface between two devices

• Characteristics of interface covered

 Mechanical

• Shape, size, medium, etc..

 Electrical

• Bits representation in terms of voltages and flow rate

 Functional

• Function of the device/interface

 Procedural

• How various functions of the device/interface will be executed to

perform a useful task.

Example Physical Layer..

  • EIA-232 Electrical specifications

Data Link Layer

• Typical Functions

 Framing

• Conversion of raw bit stream into manageable units called “Frames”

 Physical Addressing

• Adds physical address of source and destination device to each frame

 Flow Control

• Responsible for controlling flow of data between two devices

 Error Control

• Additional information is added with data to detect transmission error,

correct errors in some cases request is send to retransmit the data

 Access Control

• If more than one devices uses the communication medium, this layer

defines the procedure to use a shared medium

Network Layer

• Functions

 Addressing

• Providing a mechanism to uniquely identify systems connected

to a communication network, systems on a network are

identify by an IP address

 Routing ~ Path selection in a communication network

• Providing a mechanism to find a suitable path in the

communication network so that systems across the network

can communicate

network layer.. Network / Routing Node Network Network 2

Transport Layer

 Provide end to end reliable data transmission

mechanism

 End to end Transmission modes

 Connection oriented

• An end to end connection is established before communication

takes place

• E.g. Telephonic Conversation

 Connection less

• No prior end to end connection

Data Link Vs Transport Layer

Error free link, reliable

communication with

with adjacent nodes

Reliable error free

transmission across the

network

Session Layer

 Control of dialogues between applications

 Dialogue discipline

• Half Duplex

• Full Duplex

 Synchronization

• Recovery of broken session

 Example:

• Log in session of any email system.

In some cases session Layer may not be required at all

Presentation Layer

 Data formats and coding

• What character should be formed by the bits received

• E.g. UTF-8 (Unicode), English, Arabic etc..

 Data compression

• Data compression is commonly done to increase the

transmission rates, sender and receiver need to know

compression methods of each other

 Encryption

• To provide security data is seldom encrypted,