ncsweek2 osi model

04/13/23Mr.velu 13/04/23 Linton UniversitySchool of Computing

CN3044 Network Programming

Lans, Wans, Model and Procotols•Network Structures•Lans•Wans•Standards Protocols •OSI Model•TCP/IP Model

Slide 1


Network Types

Local Area Networks (LANs)– - A network serving a home, building or campus is

considered a Local Area Network (LAN)


Network Types Wide Area Networks (WANs)

– LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN)


Network Types

The internet is defined as a– global mesh of interconnected networks


Network Components


Standards

Standards • processes or protocols that has been endorsed by the

networking industry and ratified by a standards organization

• are documented agreements containing technical specifications or other precise criteria that stipulate how a particular product or service should be designed or performed

Organisations responsible for standards• American National Standards Institute (ANSI)• Electronics Industry Alliance (EIA)• Institute of Electrical and Electronic Engineers (IEEE)• International Organization for Standardization (ISO)• International Telecommunication Union (ITU)

Slide 6


IEEE Networking Specifications

Slide 7


Protocols A protocol:-

– “a mutually agreed treaty or diplomatic document”

– A set of predetermined rules• E. g. Traffic lights at a junction control the flow

of vehicles on a road system• This is a simple, world-wide protocol

– Although in France they do not use amber between red and green!

Slide 8


The Seven Layer OSI Model The OSI model breaks the process of communication down into

several layers

Application

Presentation

Session

Transport

Network

Data link

Physical

Slide 9

Nmemonics – Please do not throw sausage pizza away!All PC’s seem to network data poorly

At the top, the Application layer provides OS services for application software

At the bottom, the Physical layer deals with wiring issues


OSI model – Why bother? Real-world network protocols don’t implement the OSI seven layer

protocol stack model But nearly all network protocols are based on a simplified layered model The layered model helps us think about the many processes involved in

communicating over networks A good model provides support for thinking

Slide 10

Benefits include• assists in protocol design• fosters competition• changes in one layer do not affect other layers• provides a common language


A Fine-Grained Breakdown

This is a multilayer model

It shows two different “protocol stacks”

The courier service is analogous to network cabling (in a wired system)

President/CEO

Directors

Quality Control

Marketing

Clerical

Mail Room Mail Room

Courier or Postal Service

Clerical

Design

Manufacture

Slide 11


Communication Between Two Systems

Slide 12


Version2 04/13/23 Slide 13

ISO OSI Reference Model

Slide 13


Data Transformation

Slide 14


The Application Layer Provides interface to the software enabling programs

to use network devices Definition of the way that network services use the

network Defines how many services work, including

– File sharing, Network Printing, Message Services etc E.g Application Program Interface (API)

– Routine that allows a program to interact with the operating system

– Belongs to the Application layer of OSI Model Microsoft Message Queuing (MSMQ)

– Used in API network environment– Stores messages sent between nodes in queues– Forwards them to their destination

Slide 15


The Presentation Layer

This layer “presents” data, which is to say it does some pre-processing, such as– data compression– encryption– character set conversion

Translates between the application and the network

Slide 16


The Session Layer

A communications management layer Defines how two computers synchronise,

maintain and close a communication session This includes such things as

– security authentication– acknowledgement of data transfer– establishing and relinquishing a connection identity

Slide 17


The Transport Layer

Data packet management Ensures that chunks of data have been

transferred without error – does lots of error and flow control

Takes data and packs it into chunks or chops it up into chunks suitable for transmission

Takes chunks and unpacks them or combines them into data streams

Slide 18


The Network Layer

This is Internet Protocol address layer for path selection around the network

Routing of packets uses IP addresses Network Layer Address

– Resides at Network level of OSI Model– Follows hierarchical addressing scheme– Can be assigned through operating system software

Slide 19


The Data Link Layer

Decodes packets into what are called frames which contain– Physical source and destination addressing– data validity / error checking

The network technology being used will influence how this layer works e.g. Ethernet, token ring …..

To accommodate shared access for multiple network nodes, the IEEE expanded the OSI Model by separating the Data Link layer into two sublayers– Logical Link Control (LLC) sublayer– Media Access Control (MAC) sublayer

Slide 20


Subdivided Data Link Layer

LLC and MAC sublayers

Slide 21


Data Link Layer Sublayers

LLC – Upper sublayer– Provides common interface– Supplies reliability and flow control services

MAC – (Media Access Control)– Lower sublayer– Appends the physical address of the destination

computer onto the frame– Number uniquely defining a network node– Manufacturer-hard codes the address

• Block ID• Device ID

Slide 22


The Physical Layer

This is the physical networking media layer which includes the cabling technology

Defines the transmission technique and the hardware definitions (connectors and so on)

Networking may take place over copper cables, optical fibres, infra-red radiation, radio waves… and this variation should be transparent to the user

Slide 23


TCP/IP

The problem with the OSI model is a ‘concept’ not an actual implementation

TCP/IP is a set of protocols used.


OSI Model TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP)

Slide 25


Layers with TCP/IP and OSI Model


OSI Model Summary

Slide 27


Slide 28

Conclusion

We have discussed:- Organizations that set standards for

networking Standard “root concepts” of networking Layered models of processes and layers in our

conceptual model of networking Why protocols are required for interoperability Details of the seven layers of the OSI model

ncsweek2 osi model

Education

network slide

network services

layer osi model

network cabling

network printing

network technology

network components

network level of osi