part 1.1 overview telecom network

8/13/2019 Part 1.1 Overview Telecom Network

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POST AND TELECOMMUNICATION

INSTITUTE OF TECHNOLOGY

1/31/2014Research Institute of Posts And Telecommunication1

PART 1

OVERVIEW OFTELECOMMUNICATION NETWORK


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What is a telecommunication network?

OVERVIEW OF TELECOMMUNICATION NETWORK


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Telecommunications Networks


Telecommunications are the means of electronic

transmission of information over distances. The

information may be in the form of voice telephone calls,

data, text, images, or video. Today, telecommunications are

used to organize more or less remote computer systems

into telecommunications networks. These networks

themselves are run by computers.

A telecommunications network is an arrangement of

computing and telecommunications resources for

communication of information between distant locations.


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Telecommunications Networks


A telecommunications network includes: Terminals for accessing the network

Computers that process information and are interconnected by thenetwork

Telecommunications links that form a channel through whichinformation is transmitted from a sending device to a receivingdevice.

Telecommunications equipment that facilitates the transmission ofinformation.

Telecommunications software that controls message transmissionover the network.


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Types of telecommunications networks



On the distance dimension;

Wide area networks (WAN) is a broad-band computer network thatspans a large geographical area (they serve greater distance).

Used by multinational companies. WANs transmit and receive information across cities and countries.

Some WANs are commercial, regulated networks while others areprivately owned (Ex: AT&T or Sprint). Some others are public in termsof their management, resources and access. One such public WAN is theInternet.


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Types of telecommunications networks (contd)

Local Area Networks (LANs)- A LAN connects two or morecommunicating devices within a short distance (One building orseveral buildings in close proximity).

It allows all computer users to connect with each other to shareinformation and devices, such as printers.

In an office a LAN can give users fast and efficient access to a commoncollection of information while also allowing the office to poolresources, such as printers.

Metropolitan Area Networks (MANs)- They serve a large city.


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Types of telecommunications networks (contd)

Virtual Private Networks (VPN): VPN is a private wide-areanetwork that connects an organization's LAN and users to anotherthrough a public network, usually the Internet.

A VPN provides long-distance connections virtually free of directcharges.

A VPN handles the security and it uses the Internet as its mainnetwork, but relies on firewalls and other security features of itsInternet and Intranet connections.

VNP is a means for allowing access to a private networkse-mail,shared files or intranet via an Internet connection.


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Telecommunications Links


Telecommunications links may be implemented withvarious communication media, with a correspondingvariety of characteristics. The main feature of a medium isits potential transmission speed, also known as channel

capacity, which for data transmission purposes isexpressed in bits per second (bps). An alternative measureof transmission channel capacity is bandwidth - the rangeof signal frequencies that can be transmitted over thechannel.

Two potential media are employed to implement: Wireless transmission

Wire transmission


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Six potential media are employed to implement

telecommunication links:

Twisted pair

Coaxial cable

Fiber Optics cable

Terrestrial Microwave

Satellite Transmission

Radio Transmission


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Wire transmission:

Twisted pair:

Consists of copper wire twisted in pairs.

It connects a telephone to its telephone jack in most homes

It is an older transmission medium. Used to transmit analog phone conversations but can be used for digital

communication as well.

Relatively slow for transmitting data.

Inexpensive.

Widely available.


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Coaxial cable:

Consists of thickly insulated copper wire.

Used by cable TV companies, bring television signals into thehome.


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Fiber optics fiber:

Has the greatest capacity of the telecommunications media.

A fast, light and durable transmission medium.

Can transfer large volume of data.

More expensive, harder to install.

Many long-distance companies use it.

Can carry digital signals as well as analog signals.

SIGNAL LASER CABLE PHOTODETECTOR

SIGNAL


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Telecommunications links

Research Institute of Posts And Telecommunication13 1/31/2014


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Wireless transmission: sends signals through air or space

without being tied to a physical line. Common technologies

for wireless data transmission include; Microwave:

Used for long-distance transmission.

Uses the atmosphere as the medium through which to transmit signals.

Can carry high-volume data.

Expensive.

Requires no cabling.


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Communication satellites :

The transmission of data using orbiting satellites.

Cost effective for transmitting large quantities of data over very longdistances.

Typically used for communications in large, geographically dispersed

organizations that would be difficult to tie together through cablingmedia.

Very expensive.

Signals weaken over long distances.

It is useful for only 7-10 years.


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Telecommunications media

UPLINK

MICROWAVE

TRANSMISSION

DOWNLINK

Research Institute of Posts And Telecommunication16 1/31/2014


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Cellular phones : Work by using radio waves to communicate withradio antennas placed within adjacent geographic area called cells. Ittransmits voice or data. It is for mobile voice and datacommunications.

Pagers: A wireless transmission technology in which the pager beeps

when the user receives a message. Used to transmit shortalphanumeric messages.


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Analog and Digital Communications

Types of Signals: Analog and Digital Information travels through a telecommunications system in the form of

electromagnetic signals.

Signals are represented in two ways: analog and digital signals.

An analog signal is a continuous waveform that passes through a

communications medium; used for voice communications. A digital signal is a discrete rather than continuous, waveform.

Most computers communicate with digital signals.

All digital signals must be translated into analog signals before they canbe transmitted in an analog system. The device that performs thistranslation is called a modem (Modem is an abbreviation forMOdulation/DEModulation).

A modem translates a computers digital signals into analog form fortransmission over ordinary telephone lines, or it translates analog signals

back into digital form for reception by a computer



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Open Systems Interconnection (OSI) model

OVERVIEW OF TELECOMMUNICATION NETWORK


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OSI Overview

OSI Overview

OSI - layered framework for the design of network systems that allows

communication across all types of computer systems.

The OSI 7 Layers. ( Brief functional overview. )

Vertical and horizontal communication between the layers usinginterfaces. (defines what information and services should the layer

provide to the layer above it. )

Data Encapsulation

PDU conception each protocol on the diff. layer has its own format.

Headers are added while a packet is going down the stack at each layer.

Trailers are usually added on the second layer.



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OSI Overview



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Comparison with TCP/IP

Comparison with TCP/IP

Pretty similar to OSI

TCP/IP has less layers(four)

Main difference in layers is after layer 4



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The OSI Layers



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Application layer(Layer 7)


Applications and Services run on it

Enables human network to interface the underlying data network

Applications on that layer (E-mail clients, web browsers, Chats, etc.)

top-stack applications (As people are on the top of the stack) Applications provide people with a way to create message

Application layer services establish an interface to the network

Protocols provide the rules and formats that govern how data is treated

Protocols on the destination and the host must match



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Presentation layer(Layer 6)


Coding and conversion of Application layer data to ensure that data from

the source device can be interpreted by the appropriate application on the

destination device.

Compression of the data in a manner that can be decompressed by thedestination device.

Encryption of the data for transmission and the decryption of data upon

receipt by the destination.

This is the layer at which application programmers consider data

structure and presentation Sometimes distinction is made between the presentation and application

layers.



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Session layer(Layer 5)


Functions at this layer create and maintain dialogs between source and

destination applications

Authentication

Permissions Session Restoration (Checkpoint or recovery)



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Transport layer(Layer 4)

Transport layer(Layer 4) Tracking the individual communication between applications on the source

and destination hosts

Segmenting data and managing each piece

Reassembling the segments into streams of application data

Identifying the different applications

Conversation Multiplexing Segments

Connection-oriented conversations

Reliable delivery

Ordered data reconstruction

Flow control

TCPWeb Browser UDP Video Streaming Applications



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Transport layer(Layer 4)



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Network layer(Layer 3)


Addressing (IPV4)

Encapsulation (Inserts a header with source and destination IPs)

Routing (Move a packet over the Internet)

Decapsulation (Open the packet and check the destination host)

IP is connectionless



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Data link layer(Layer 2)


It is the role of the OSI Data Link layer to prepare Network layer packets fortransmission and to control access to the physical media.

Allows the upper layers to access the media using techniques such as framing

Controls how data is placed onto the media and is received from the mediausing techniques such as media access control and error detection

Frame - The Data Link layer PDU Node - The Layer 2 notation for network devices connected to a common

medium

Media/medium - The physical means for the transfer of information betweentwo nodes

Network - Two or more nodes connected to a common medium

The Data Link layer is responsible for the exchange of frames between nodesover the media of a physical network.



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Physical layer (Layer 1)


The role of the Physical layer is to encode the binary digits that represent

Data Link layer frames into signals and to transmit and receive these

signals across the physical media that connect network devices.

Copper cable Fiber

Wireless



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Q & A



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1/31/2014R h I tit t f P t A d T l i ti39

Center of Consultancy and Technology Transfer

Research Institute of Posts And TelecommunicationTelephone: 84 4 3 756 0832/ 84 4 3 754 4486

Fax : 84 4 3 756 0833

Email [email protected], [email protected]
mailto:[email protected]:[email protected]

part 1.1 overview telecom network

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