Computer Concepts Computer networks 101 Instructor Cuong Charlie Pham Computer Network CS105 Section 2 Lecture 10 A collection of computing devices connected in order to communicate and share resources ID: 448874
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CS105 Introduction to Computer ConceptsComputer networks 101
Instructor:
Cuong
(Charlie) PhamSlide2
Computer NetworkCS105 Section 2 - Lecture 10
A collection of computing devices connected in order to communicate and share resources
Connections between computing devices can be physical using wires or cables or wireless using radio waves or infrared signals
2Slide3
Network DevicesTo connect multiple segments of networks into a larger oneHub:
A
multiport repeater to enhance signal within the same
network
Switch:
Like
hub but with
intelligent Better performanceRouter: Forward packets from one network to another
CS105 Section 2 - Lecture 10
3Slide4
CablingCoaxial Cable
Thinnet
looks like regular TV cable. It is about 1/4 inch in diameter and is very flexible and easy to work with.
Thicknet
is about 1/2 inch in diameter and not very flexible.
Thicknet
is older and not very common anymore except as a backbone within and between buildings. Coax transmits at 10 Mbps.. Twisted Pair. Twisted pair looks like telephone wire and consists of insulated strands of copper wire twisted together. There are two versions of twisted pair cable:
Shielded Twisted Pair (STP). STP is commonly used in Token Ring networksUnshielded Twisted Pair (UTP). UTP is used in Ethernet networks. Transmission rates vary between 10-100-1000-10000 Mbps.Fiber-Optic Cable. Fiber-optic cable consists of a thin cylinder of glass surrounded by glass cladding, encased in protective outer sheath. Fiber-optic cable is very fast (over 1Gbps). It can transmit over long distances (2 km +) but is expensive.
CS105 Section 2 - Lecture 104Slide5
Cabling Top: Unshielded Twisted Pair and Shielded Twisted Pair Cable
Bottom: Coaxial and Optical Fiber Cable
CS105 Section 2 - Lecture 10
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Network TypesCS105 Section 2 - Lecture 10LAN (Local Area Network)
WAN (Wide …)
MAN (Metropolitan …)
PAN (…)
Internet
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LANCS105 Section 2 - Lecture 10
A network that connects a relatively small number of machines in a relatively close geographical area
E.g., office buildings
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LAN Topologies Ring
topology
connects all nodes in a closed loop on which messages travel in one direction
Star topology
centers around one node to which all others are connected and through which all messages are sent
Bus
topology
nodes are connected to a single communication line that carries messages in both directions
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Ethernet The industry standard bus (star) technology for
LAN
10BaseT
10Mbps (Mega bits per second)
100BaseT
100Mbps
1000BaseT
1000Mbps or 1Gbps
CS105 Section 2 - Lecture 10
9Slide10
WLAN (Wireless LAN)Wi-Fi (Wireless Fidelity)A wireless technology that connects computers without cables
Access Point (AP)
A device (base station) that connects wireless devices together
Usually connected to a wired-network
SSID (Service
Set ID)
A “name” for the AP,
eg. mobilenetHotspot
The area covered by wireless access points
CS105 Section 2 - Lecture 10
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WLAN (Wireless LAN)Standard802.11b - 11Mbps802.11g - 54Mbps802.11a - 54MbpsSecurity
WEP (Wired
Equivalent
Privacy)
WPA (Wi-Fi Protected Access)To prevent
wardriving
2.4G
5G
CS105 Section 2 - Lecture 10
11Slide12
WAN/MANWide-area network
(WAN)
A network that connects local-area networks over a potentially large geographic distance
Metropolitan-area network
(MAN)
The communication infrastructures that have been developed in and around large citiesInternet
A wide area network that spans the planet
CS105 Section 2 - Lecture 1012Slide13
Gateway
Figure 15.1
Local-area networks connected across a distance to create a wide-area network
One particular set up to handle all communication going between that LAN and other networks
CS105 Section 2 - Lecture 10
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Internet ConnectionsInternet backbone A set of high-speed networks that carry Internet traffic, provided by companies such as AT&T, Verizon, GTE, British Telecom, and IBM
Internet service provider
(ISP)
A company that provides other companies or individuals with access to the Internet
CS105 Section 2 - Lecture 10
14Slide15
Dial-up ServicesModemModulator/demodulatorA device that converts analog signal to digital (modulation) and vice versa (demodulation)
Speed
1200/2400/9600 bps
14.4/28.8/33.6 Kbps
56 Kbps
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Dial-up ServicesISDNIntegrated Services Digital Network2 data channel (56K each)1 voice channel
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Broadband ServicesxDSL (Digital Subscriber Line)A technology that provides digital data transmission over unused frequencies on traditional telephone lines
For example, ADSL (Asymmetric
DSL)
Speed
Downlink
128Kbps - 4Mbps
Uplink
64Kbps - 800KbpsNeed a DSL modemSplitters are needed to separate the voice and data signal
CS105 Section 2 - Lecture 1017Slide18
Broadband ServicesCableA technology that provides digital data transmission over cable TV infrastructureSpeedDownlink
128Kbps - 3~5Mbps
Uplink
64Kbps - 128Kbps~1Mbps
Need a cable modem
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Broadband ServicesSatelliteA technology that provide digital data transmission over satellitesSpeedDownlink
500Kbps - 1Mbps
Uplink
50Kbps - 100Kbps
Need a satellite dish
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Home Network (single machine)
USB/Ethernet Cable
DSL/Cable Modem
Wall Jack
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Home Network (multiple machines)
USB/Ethernet Cable
DSL/Cable Modem
Wall Jack
Hub/Switch/Router
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Home Network (multiple machines)
Ethernet Cable
DSL/Cable Modem
Wall Jack
Hub/Switch/Router
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Home Wireless Network
Ethernet Cable
DSL/Cable Modem
Wall Jack
Hub/Switch/Router
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Network Security
Firewall
A gateway machine and its software that protects a network by filtering the traffic it allows
CS105 Section 2 - Lecture 10
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Network AddressesHostname
A name made up of words separated by dots that uniquely identifies a computer on the Internet
IP address
An address made up of four one-byte numeric values separated by dots that uniquely identifies a computer on the Internet
CS105 Section 2 - Lecture 10
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Network Addresses
Class A:
first byte for network address and three remaining bytes for host number
Class
B:
first
two bytes for network address and the last two bytes for host number
Class C:
first three bytes for network address and the last byte for host number
Figure 15.9
An IP address is stored in four bytes
Where does the host number
come from?
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Domain Name System
Host number
The part of the IP address that specifies a particular host (machine) on the network
Yes, but what is it?
Domain name
The part of a hostname that specifies a specific organization or group
Top-level domain (TLD)
The last section of a domain name that specifies the type of organization or its country of origin
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Domain Name Systemmatisse.csc.villanova.edu
Computer
name
Domain name
TLD
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Domain Name System
Figure 15.10
Top-level domains, including some relatively new ones
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Domain Name SystemOrganizations based in countries other than the United States use a top-level domain that corresponds to their two-letter country codes
Figure 15.11
Some of the top-level domain names based on country codes
Do you
email
someone
in another
country?
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Domain Name SystemDomain name system
(DNS)
A distributed system for managing hostname resolution
Domain name server
A computer that attempts to translate a hostname into an IP address
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ReferencesComputer Science Illuminated Ch 15 Slides
Modem
http://en.wikipedia.org/wiki/Modem
DSL
http://en.wikipedia.org/wiki/Digital_subscriber_line
Cabling
http://ww2.it.nuigalway.ie
/.../ct101/CT101
_IntroductionToNetworking.pptBasic Computer Network by Weesan Leehttp://www.cs.ucr.edu/~weesan/cs6/03_basic_computer_network.ppt
CS105 Section 2 - Lecture 1032Slide33
References (cont)Domain Nameshttp://www.icann.org/topics/new-gtld-strategy-faq.htm
http://www.iana.org/root-whois/index.html
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