MD01 Introduction

8/12/2019 MD01 Introduction

1/37

Module 1

1.1


2/37

1.2 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


3/37

Introduction

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


4/37

DATA COMMUNICATIONSDATA COMMUNICATIONS

The termThe termtelecommunicationtelecommunicationmeans communication at ameans communication at a

distance.distance.

The wordThe worddatadatarefers to information presented inrefers to information presented in

w a ever orm s agree upon y e par es crea ng anw a ever orm s agree upon y e par es crea ng an

using the data.using the data.

Data communicationsData communicationsare the exchange of data betweenare the exchange of data between

two devices via some form of transmission medium suchtwo devices via some form of transmission medium such

as a wire cable.as a wire cable.

1.4

ect venessect venesso commun cat on networ s s u ge yo commun cat on networ s s u ge y

DeliveryDelivery,,AccuracyAccuracy,, TimelinessTimeliness, and, andJitterJitter..


5/37

EffectivenessEffectiveness of communication networksof communication networks

Network effectiveness is judged byNetwork effectiveness is judged by

destination.destination. Lost or undelivered data should be avoided.Lost or undelivered data should be avoided.

AccuracyAccuracy: the delivered data should be accurate, i.e., should: the delivered data should be accurate, i.e., should

have not been altered in transmission.have not been altered in transmission.

TimelinessTimeliness: delivering data in a timely manner (without: delivering data in a timely manner (without--

applications.applications.

JitterJitter: jitter refers to the variation in: jitter refers to the variation in the datathe data arrival time toarrival time to

the destination. If some audio data are received after a delaythe destination. If some audio data are received after a delay

of 20 ms and some after a delay of 30 ms, the audio qualityof 20 ms and some after a delay of 30 ms, the audio quality

..

1.5


6/37

Five components of data communication

1.6


7/37

Five components of data communication

Message: is the information to be

Sender: is the device that sends the data

Receiver: is the device that receives the

Transmission medium: is the physical

sender to receiver.

1.7

data communication.


8/37

Data Representation

Text: is represented as a bit pattern using a

coding system, e.g., ASCII (American Standard

Code for Information Interchange) or Unicode.Numbers: is usually represented as a binary

va ue.

Images: is represented as a matrix of pixels.

and can be represented by an analog or digital

si nal.

Video: is continuous data for images and sound

and can be represented by an analog or digital

1.8

signal.


9/37

Data FlowSimplex: communication is unidirectional.

y w v

capability to transmit. The other device

can on y rece ve.

Half-duplex: each station can bothv , u

time. When one device is sending, the

.Full-Duplex: both devices can transmit

1.9

.


10/37

Data flow (simplex, half-duplex, and full-duplex)

1.10


11/37

NETWORKSNETWORKS

AAnetworknetwork isis aa setset ofof devicesdevices (often(often referredreferred

linkslinks..

AA nodenode cancan bebe aa computer,computer, printer,printer, oror anyanyotherother devicedevice capablecapable ofof endingending and/orand/or

receivinreceivin datadata eneratedenerated bb otherother nodesnodes onon

thethe networknetwork..

1.11


12/37


13/37

Types of connections: point-to-point and multipoint

1.13


14/37

Physical Topology

1.14


15/37

Mesh Topology

Properties: every device has a dedicated point-to- . ,

must be connected to n-1 nodes. We therefore needn*(n-1) physical unidirectional links or n*(n-1)/2 full

duplex l nks.

Advantages:1) traffic congestion from multiple

,

against link failure, 3) privacy and security are

improved, 4) fault identification is easy.

Disadvantages: the mesh topology requires largeramounts of cables and larger number of I/O ports in

1.15

.


16/37

A fully connected mesh topology (five devices)

# full-duplex links is

-

1.16


17/37

Star Topology

Properties: each device has a dedicated point-to-

hub; the controller acts as an exchange. The sendingdevice sends data to the controller which then relays it to

the rece v ng dev ce. The star topology s often used n

local area networks (LANs).

each device needs only one link and one port to connect

to any number of devices, 2) robust: if one link fails,

on y t at n s a ecte , au t ent cat on s easyDisadvantages: dependency of the whole topology

1.17

down.


18/37

A star topology connecting four stations

1.18


19/37

Bus Topology

Properties: unlike the mesh and the star topology,.

backbone to link all the devices in a network. Nodes areconnected to the bus by drop lines and taps.

Advantages: 1) ease of installation, 2) the bus usesless cabling than mesh or star topologies.

v : au en ca on s cu ,a fault or break in the cable stops all transmission.

1.19


20/37

A bus topology connecting three stations

1.20


21/37

Ring Topology

Properties: each device has a dedicated point-to-

of it. The signal travels along the ring in one direction,from device to device, until it reaches its destination.

Each dev ce has a repeater to send the s gnal to the next

device.

reconfiguration, 2) fault isolation is simple.

Disadvanta es: 1) unidirectional traffic decreasesefficiency , 2) a break in the ring, disables the entirenetwork if traffic flows only in one direction.

1.21


22/37

A ring topology connecting six stations

1.22


23/37

Hybrid Topology

The topology of a network can be hybrid, i.e., it

topologies discussed earlier.

1.23


24/37

Example of a hybrid topology:a star backbone with three bus networks

1.24


25/37

Types of Networks

Local Area Network (LAN): A LAN is a data

, ,

campus, or between nearby buildings.Metro olitan Network MAN : A MAN is a data

communication system covering an area the size of

a town or city.Wide Area Network (WAN): A WAN is a data

communication system spanning states, countries,

.

1.25


26/37

New Types of Networks

Wireless Local Area Network (WLAN): such as

s.

Personal Area Network (PAN): such as Bluetooth

.

Cluster Area Network (CAN): may also mean

Cam us Area Network. Storage Area Network (SAN): may also mean

Server Area Network.

Desk Area Network (DAN)

1.26


27/37

Local Area Network (LAN):

LAN size is limited to a few kilometers.

,

transmission medium. Common LAN to olo ies are star bus and rin .

Early LANS had data rates in the range 4-16 Mbps.

Today, LAN speeds are typically 100 Mbps to 1Gbps.

1.27


28/37

Example of LAN:

Note:

s as a s ar

topology, not a hybrid

topology.

1.28


29/37

Wide Area Network (WAN):

A WAN provides long-distance transmission of data

WANS can be of two types Switched WAN: connects end s stems via

routers.

Point-to-Point WAN: is normally a line leasedfrom a telephone or cable TV provider that

connects a home computer or a small LAN to an

of providing Internet access.

1.29


30/37

Example of WANs: a switched WAN and a point-to-point WAN

1.30


31/37

A heterogeneous network made of four WANs and two LANs

A company has two offices.

The east coast office has a

LAN of star topology and the

Three point-to-point

WANs are used to

connect the two offices

west coast office has a bus

LAN topology. The presidentof the company lives in the

an t e pres ent to a

switched WAN thatprovides connectivity

middle and uses a high-speed

DSL line.

.

1.31


32/37

THE INTERNETTHE INTERNET

TheThe InternetInternet hashas revolutionizedrevolutionized manymany aspectsaspects ofof

ourour a ya y vesves.. asas a ec ea ec e ee wayway wewe oo

businessbusiness asas wellwell asas thethe wayway wewe spendspend ourour leisureleisure

meme..

ee n ernen erne ss aa co ec onco ec on oo manymany separa esepara e

networksnetworks.. ItIt isis aa communicationcommunication systemsystem thatthat hashas

rougroug aa weawea oo n orma onn orma on oo ourour nger psnger psandand organizedorganized itit forfor ourour useuse..

1.32


33/37

The Internet today

Peeringpoint Peering

point

1.33


34/37

Internet Service Providers (ISPs)

International ISPs (Backbones): are large networksconnecting nations together. Backbones are connected

through complex switching systems called peering points.

Provider Networks: are smaller than backbones. They.

is connected to one or more backbone and may be

connected to other provider networks.at ona s: are argest type o prov er networ s.

Regional ISPs: are smaller than national ISPs. Each regional ISP

is connected to one or more national ISPs.

regional or national ISPs.

Customer Networks: are networks at the edge of the

1.34

Internet. They pay fees to providers for receiving services.


35/37

Note

The textbook (5th Ed) gives examples of companies that

are considered to be backbones including Sprint, AT&T,

and Verizon.

ccor ng o e ex oo , ese ac ones are no

providers. They only serve smaller ISPs and do not sell

services directl to customer networks.

In reality, however, these backbones serve regular

cus omers n a on o serv ng sma er s. obackbones are also provider networks.

1.35


36/37

Methods of Accessing the Internet

Dial-up Modem Services (Phone)

DSL Services Phone

Cable TV Services

Wireless Networks

rec onnec onDirect connection is when a large corporation becomes

similar to a local ISP by leasing a high-speed WAN linkfrom a provider.

1.36


37/37

Skip the following sections

Internet History

Standards and Administration or Protocols and

Standard, 4th Ed)

1.37

Documents

MD01 Introduction