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The need for standardsStandards organisationsOSI modelTCP/IP model

Network Standards and Models

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Standards

Processes or protocols that has been endorsed by the networking industry

Ratified by a standards organizationDocumented agreements containing

technical specifications or other precise criteria that stipulate how a particular product or service should be designed or performed

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

FCN week 10IEEE Networking Specifications

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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

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Different stages data must/may go through as it travels from one device to another

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

At the bottom, the Physical layer deals with wiring issues

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

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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

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OSI model – Why bother?Benefits include

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

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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

Applications HTTP Email Etc...

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The Presentation LayerThis layer “presents” data, which is to say it does

some pre-processing, such asdata compressionencryptioncharacter set conversion

Translates between the application and the network

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The Session LayerA communications management layerDefines how two computers synchronise, maintain

and close a communication sessionThis includes such things as

security authenticationacknowledgement of data transferestablishing and relinquishing a connection

identity

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The Transport LayerData packet managementEnsures that chunks of data have been transferred

without error – does lots of error and flow controlTakes data and packs it into chunks or chops it up

into chunks suitable for transmissionTakes chunks and unpacks them or combines them

into data streams

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The Network LayerThis is Internet Protocol address layer for path

selection around the networkRouting of packets uses IP addressesNetwork Layer Address

Resides at Network level of OSI ModelFollows hierarchical addressing schemeCan be assigned through operating system

software

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The Data Link Layer Decodes packets into what are called frames which contain

Physical source and destination addressingdata 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 sublayersLogical Link Control (LLC) sublayerMedia Access Control (MAC) sublayer

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The Physical LayerThis is the physical networking media layer which

includes the cabling technologyDefines 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

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FCN week 10Communication Between Two Systems

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TCP/IP

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

TCP/IP is a set of protocols used.

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What is TCP/IP? TCP/IP stands for Transport Control Protocol / Internet

Protocol suite. TCP/IP was created in 1983 to replace NCP. TCP/IP can successfully switch packets from all shapes and

sizes and varieties of networks. Therfore TCP/IP has become the backbone of the Internet

and its composite LANs and WANs, due to it's ability to switch packets from computer systems on any network to another network, regardless of network peculiarities, operating system differences and other packet differences

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What is TCP/IP? The higher layer, Transmission Control Protocol, manages

the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message.

The lower layer, Internet Protocol, handles the address part of each packet so that it gets to the right destination.

Each gateway computer on the network checks this address to see where to forward the message.

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What is TCP/IP? Even though some packets from the same message are routed

differently than others, they'll be reassembled at the destination. Uses the client/server model of communication in which a computer

user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network.

TCP/IP communication is primarily point-to-point, meaning each communication is from one point (or host computer) in the network to another point or host computer.

TCP/IP and the higher-level applications that use it are collectively said to be "stateless" because each client request is considered a new request unrelated to any previous one

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What is TCP/IP? Being stateless frees network paths so that everyone can use

them continuously. You will be familiar application protocols that use TCP/IP to

get to the Internet. These include the World Wide Web's Hypertext Transfer

Protocol (HTTP) File Transfer Protocol (FTP) Telnet (Telnet) which lets you logon to remote computers Simple Mail Transfer Protocol (SMTP).

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OSI Model TCP/IP

TCP/IP vs OSI

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Layers with TCP/IP and OSI Model

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Conclusion

We have discussed:-Organizations that set standards for networkingStandard “root concepts” of networkingLayered models of processes and layers in our

conceptual model of networkingWhy protocols are required for interoperabilityDetails of the seven layers of the OSI model