Unit 2072: Communications and Security

warmersafternoonNetworking and Communications

Oct 23, 2013 (3 years and 10 months ago)

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Unit 2072: Communications and Security

Session 5

The OSI Model

Unit 2072: Communications and Security


The OSI Model

Recap

What do you understanding about the causes of
errors in a communications system


What are the more common error correction and
detection methods


Unit 2072: Communications and Security


The OSI Model

The OSI Model

By the end of this session you will be able to …

identify the layers of the OSI Model

explain the purpose of the OSI Model

recognise some of the protocols and equipment used
at the levels of the OSI Model

Unit 2072: Communications and Security


The OSI Model

OSI



Open Systems Interconnection

A Standard from ISO



International Standards Organisation

Why?

To provide a framework for networking of systems



The

Open System Interconnection (OSI)

protocol suite is
comprised of numerous standard protocols that are based on
the OSI reference model.

http://www.cisco.com/en/US/docs/internetworking/technology/handbook/OSI
-
Protocols.html



Unit 2072: Communications and Security


The OSI Model

OSI Model

Seven layers one of which is subdivided into two sub
-
layers





Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Node A

Node B

Unit 2072: Communications and Security


The OSI Model

OSI Model

Data
-
link layer

Logical link Control sub
-
layer

MAC sub
-
layer





Application

Presentation

Session

Transport

Network

Data Link

Physical

Logical Link

MAC

7

6

5

4

3

2

1

Unit 2072: Communications and Security


The OSI Model

OSI Model

Refers to the physical attributes of the network

Procedural and functional specifications

Voltages/light waves

Encoding types

Data rates

Set up and end TX procedures

Maintenance of the connection

Mechanical

Connectors and terminators

Wiring/Fibre type

Transmission distances

The PDU is a bit

Physical

1

Unit 2072: Communications and Security


The OSI Model

OSI Model



Provides reliable transit of data across a network

Media Access Control
-

how to transmit data on the wire

Uses Physical addressing

Network media access

Network topology

Flow control

Error notification

Logical Link Control

Logically identifies different protocol types from upper layers

Ordered delivery of frames through identifiers

Protocols here are

Ethernet,

Token Ring,

ISDN,

PPP and

Frame Relay

2

Data Link

Logical Link

MAC

Unit 2072: Communications and Security


The OSI Model

OSI Model


Provides connectivity and path selection

Contains the logical addressing

THE PDU is a Frame

Protocols used

IP

IPX




Network

3

Unit 2072: Communications and Security


The OSI Model

OSI Model


Provides reliable virtual circuits

Establishes virtual circuits

Maintains virtual circuits

Closes virtual circuits

Segments upper layer data into Packets

THE PDU is a Packet

Highest level of data
-
flow protocols

Protocols used

TCP

UDP

SPX


Transport

4

Unit 2072: Communications and Security


The OSI Model

OSI Model


Creates sessions for upper layers by:

Establishing sessions

Maintaining sessions

Closing sessions

Offers

Efficient data transport

Class of service

Exception reporting

Start of application level protocols

Protocols used

X
-
Window system

ApplTalk Session Protocol (ASP)

Session

5

Unit 2072: Communications and Security


The OSI Model

OSI Model


Ensures that application data being sent can be read by the
application at the receiving end (Common formatting)

Provided encryption services

Protocols used

PICT, TIFF & JPEG for pictures

MIDI and MPEG for sound and movie

Presentation

6

Unit 2072: Communications and Security


The OSI Model

OSI Model


Closest layer to the user

Provides network services to user applications

Office suite

Network games

Establishes

availability of intended communication partner

agreed error recovery procedures

required control of data integrity

Protocols
-

Applications used

Telnet

HTTP

Application

7

Unit 2072: Communications and Security


The OSI Model

The TCP Model




Application

Presentation

Session

Transport

Network

Data Link

Physical

Internet


Network Access


Application


Transport

IP


Ethernet

I.e. FTP, HTTP,
SMTP, DNS,
TFTP

TCP/UDP

Unit 2072: Communications and Security


The OSI Model

Review

Are you able to …

identify the layers of the OSI Model

explain the purpose of the OSI Model

recognise some of the protocols and equipment used at
the levels of the OSI Model