CIT-Dept-IFM 2006/7 Institute of Finance Management 2006 CIT232- Computer Networks 1/30 Protocols and Standards Protocols and Standards Protocols Standards

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CIT-Dept-IFM 2006/7 Institute of Finance Management 2006

CIT232- Computer Networks

ProtocolsProtocols and Standardsand Standards

• Protocols

• Standards

• Standards Organizations

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Protocols Definition and Need for Protocol

Elements of protocols Syntax Semantics Timing

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Standards

Standards and standards Marking organization

Categories of Standards De factor - meaning by fact or by

conversion De jure - meaning by law or organization

Standards Organizations Standards creation committees (ISO, ITU-

T, ANSI,IEEE & EIA) Forums Regulatory agencies (TRCA)

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Standards

Standards

De jure(by law)

De factor(by fact)

Proprietary Non-Proprietary

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NetworkModels

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Communication Model/Network Model

Model: -a frame or reference or set of guidelines on which communicating devices can understand each other.

Network Model: Open Systems Interconnection – OSI

Model Internet Model

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OSI model

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OSI is used as the theoretical model for how communication between devices, such as computer takes place. It define the way in which device interact

• There are seven layers in the OSI model: application, Presentation,

Session, Transport, Network, Data Link and Physical.

• These layers make up a framework that defines the way in which physical

hardware, media and software work together to communicate.

• Each layer of the OSI model is independent from every other in its purpose

and responsibilities.

• Each must do its own job, as well as provide services to the layers above

and below it.

• The model creates framework to understand how network communication

is taking place, as well as aid in troubleshooting problems that arise within

a network.

• The OSI model provides a structure for software programmers and Equipment

manufacturers to develop product that will work together [interoperability]

OSI Model

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These services can be divided into horizontal and vertical communication models.

The communication between layers in the same device is an

example of vertical communication model.

In the horizontal model, communication is between the same

layer on different devices.

This horizontal model is based on protocols that works at

specific layers of the model.

The top five layers of the OSI model are represented in software, while the lower layers are based on hardware.

OSI Model

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Sending a letter

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Application layer

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Presentation layer

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Session layer

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Transport layer

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Network layer

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Data link layer

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Physical layer

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Summary of layer functions

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Internet Model

Internet model is made up of five [5] layers

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An exchange using the Internet model

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Physical layer

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Physical layer

Physical layer is responsible for actual physical connection between devices.

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The physical layer is responsible for transmitting individual bits from one

node to the next.

Note:Note:

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Data link layer

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Data link Layer

Data link layer has two sublayers and each provides its own

services in the OSI model

Data link Sublayers

Logical Link Control [LLC]

Media Access Control [MAC]

LLC Sublayer: provides the interface between the media access

method and the network layer protocol.

MAC Sublayer: Is responsible for the connection to the physical

media

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The data link layer is responsible for transmitting frames from

one node to the next.

Note:Note:

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Node-to-node delivery

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Example 1

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Network layer

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Network Layer

This layer is responsible for the addressing and delivery of

packet.

Network address is a logical address based on numbering

scheme that is independent of a devices hardware or location.

Functions of the Network layer

Add the network address to the packet

Map the network to the device physical address

Determine the best path for the packet

Ensure that the packet is in the correct format for the

destination network

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The network layer is responsible for the delivery of packets from the original source to the final destination.

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Source-to-destination delivery

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Example 2

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Transport layer

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Transport Layer The function of the transport layer is to ensure that data

packets it receives from the session layer arrive reliably. Two type of transmission

Connection Oriented Connectionless

Transport layer also has the job of managing the speed of communication between devices: flow control

Features of Connection Oriented transmission Reliability Slower communication Packets are resent if a packet is un recognized or is not

received Features of connectionless transmission

Little or no Reliability Faster transmission Packet are not retransmitted

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The transport layer is responsible for delivery of a message from one process

to another.

Note:Note:

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Reliable process-to-process delivery of a message

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Example 3

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Application layer

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Application layer is the service provider. It gives service to the user of

the network.

Application layer works with the applications you use to communicate

over the network. Example: SMTP-simple mail transfer protocol to send

e-mail, HTTP (HyperText Transfer Protocol) to access the web page while

surfing the Internet, FTP (file transfer protocol) transfer protocol to

download a file from an FTP server.

Application Services:

File services

Electronic-mail services

Network printing services

Application services

Database services

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The application layer is responsible for providing services to the user.

Note:Note:

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Summary of duties

Documents

CIT-Dept-IFM 2006/7 Institute of Finance Management 2006 CIT232- Computer Networks 1/30 Protocols and Standards Protocols and Standards Protocols Standards