Download - CCN Lecture 3(2)
-
8/3/2019 CCN Lecture 3(2)
1/15
-
8/3/2019 CCN Lecture 3(2)
2/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
LAN and WAN
Local Area Network (LAN)
Smallnetwork,short distance A room, a floor, a building
Limited byno. ofcomputers anddistancecovered
Usually one kind oftechnology throughout the LAN
Serve a department within an organization Examples:
Networkinside the Student Computer Room
Networkinside University
Networkinsideyour home
-
8/3/2019 CCN Lecture 3(2)
3/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Wide Area Network (WAN) A network that useslong-rangetelecommunicationlinks
to connect 2 or more LANs/computers housedindifferentplacesfar apart.
Towns,states,countries Examples:
Network ofour Campus
Internet
WAN
Student
Computer
Centre
Your home
USA
-
8/3/2019 CCN Lecture 3(2)
4/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Example WAN technologies:
ISDN Integrated ServiceDigital Network Basic rate: 192 Kbps Primary rate: 1.544Mbps
T-Carriers basicallydigitalphonelines T1: 1.544Mbps T3: 28vT1
Frame relay Each link offers 1.544Mbps or even higher
ATM Asynchronous Transfer Mode Support B-ISDN: 155Mbps or 622Mbps or higher
SONET Synchronous Optical Network Basic rate OC1: 51.84Mbps
Support OC12 andup to OC192 (9953.28Mbps) or
even higher in thefuture
-
8/3/2019 CCN Lecture 3(2)
5/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Example ofWAN: Broadband Cable Network
Cable TV services have beenextensivelydevelopedinmost
moderncities
Cable TV companies try to makeuse oftheir coaxialcable
installed (that aresupposed to carry TV signals) to deliver
broadbanddata services
Manycablenetwork wiring has been replaced with hybrid
fiber-coax (HFC)i.e. use offiber-opticcable to connect tothesubscribers buildings, and then the originalcoaxial
cable to connect to each household
-
8/3/2019 CCN Lecture 3(2)
6/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
The connection is shared by a
number of subscribers, hence
may raise performance and
security problems
Cable companyCoaxial
Cable
TV
PC
Cable
Drop
-
8/3/2019 CCN Lecture 3(2)
7/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Cableis anasymmetrical technology Downstream: max 36 Mbps Upstream: max 10 Mbps
May be reduced to 3 10 Mbpsdownstream and 2
Mbpsupstream,depending onno. ofsubscribers
Need a specialcablemodemEthernet
link to PC
Coaxiallink
fromcable TV
socket
Teryon Cable Modem
-
8/3/2019 CCN Lecture 3(2)
8/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Peer-to-Peer Networks
Peer-to-peer networkis also calledworkgroup
No h
ierar
chy
am
ong
compu
ters a
llareequ
al No administrator responsiblefor thenetwork
Peer-to-peer
-
8/3/2019 CCN Lecture 3(2)
9/15
-
8/3/2019 CCN Lecture 3(2)
10/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Clients and Servers Network ClientsClients (WorkstationWorkstation)
Computers that request network resources or services
Network ServersServers Computers that manage andprovidenetwork resources
andservices to clients
Usually havemoreprocessingpower,memory and
harddiskspace thanclients
RunNetwork Operating System that canmanagenot
onlydata, but also users,groups,security, and
applications on thenetwork
Servers often have a morestringent requirement onits
performance andreliability
-
8/3/2019 CCN Lecture 3(2)
11/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Advantages ofclient/server networks Facilitate resourcesharing centrally administrate and
control
Facilitatesystem backup andimprovefault tolerance
Enhancesecurity only administrator can have accessto Server
Support moreusers difficult to achieve with peer-to-
peer networks
Disadvantages ofclient/server networks High cost for Servers
Needexpert to configure thenetwork
Introduce a singlepoint offailure to thesystem
-
8/3/2019 CCN Lecture 3(2)
12/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Topology 3 basic types How so manycomputers areconnected together?
Bus Topology Ring Topology
Star Topology
Hub
-
8/3/2019 CCN Lecture 3(2)
13/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Bus Topology Simple andlow-cost
A singlecablecalled a trunk(backbone,segment)
Only onecomputer cansendmessages at a time
Passive topology - computer onlylistenfor,notregeneratedata
Star Topology Each computer has a cableconnected to a singlepoint
Morecabling, hence higher cost
Allsignals transmission through the hub; ifdown,entirenetworkdown
Depending on theintelligence ofhub, two or more
computersmaysendmessage at thesame time
-
8/3/2019 CCN Lecture 3(2)
14/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
How to construct a networkwith Bus / Star Topology?
Star Topology
Bus Topology
BNC T-Connector
Coaxial
cable
Network Card
-
8/3/2019 CCN Lecture 3(2)
15/15
ENG224
INFORMATION TECHNOLOGY Part II
5. Introduction to Networking
Ring Topology Everycomputer serves as
a repeater to boost signals
Typical way to senddata:
Tokenpassing
only thecomputer who
gets the tokencansend
data
Disadvantages
Difficult to addcomputers
Moreexpensive
Ifonecomputer fails, wholenetworkfails
TT
T
data
T
data
T
dataT data T data
T dataT Ack
T Ack
T Ack
TAck T