Transcript Computer Network 101

CS105 INTRODUCTION TO
COMPUTER CONCEPTS
COMPUTER NETWORKS 101
Instructor: Cuong (Charlie) Pham
Computer Network
2
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

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Network Devices
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
To connect multiple
segments of networks
into a larger one
 Hub:
A multiport
repeater to enhance
signal within the same
network
 Switch: Like hub but
with intelligent 
Better performance
 Router: Forward
packets from one
network to another
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Cabling
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
Coaxial Cable



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:



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..
Shielded Twisted Pair (STP). STP is commonly used in Token Ring networks
Unshielded 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.
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Cabling
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

Top: Unshielded Twisted Pair and Shielded Twisted Pair Cable
Bottom: Coaxial and Optical Fiber Cable
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Network Types
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




LAN (Local Area Network)
WAN (Wide …)
MAN (Metropolitan …)
PAN (…)
Internet
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LAN
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

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
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


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
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
The industry
standard bus (star)
technology for LAN
 10BaseT
 10Mbps
(Mega bits
per second)
 100BaseT
 100Mbps
 1000BaseT
 1000Mbps
or 1Gbps
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WLAN (Wireless LAN)
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
Wi-Fi (Wireless Fidelity)


Access Point (AP)



A device (base station) that
connects wireless devices
together
Usually connected to a wirednetwork
SSID (Service Set ID)


A wireless technology that
connects computers without
cables
A “name” for the AP, eg.
mobilenet
Hotspot

The area covered by wireless
access points
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WLAN (Wireless LAN)
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
Standard
 802.11b
- 11Mbps
 802.11g - 54Mbps
 802.11a - 54Mbps

2.4G
5G
Security
 WEP
(Wired Equivalent Privacy)
 WPA (Wi-Fi Protected Access)
 To prevent wardriving
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WAN/MAN
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
Wide-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 cities
Internet A wide area
network that spans the
planet
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Gateway
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One particular set up to handle all communication going between that LAN and other
networks
Figure 15.1 Local-area networks connected across a
distance to create a wide-area network
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Internet Connections
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

Internet 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
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Dial-up Services
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
Modem
 Modulator/demodulator
A
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 Services
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
ISDN
 Integrated
Services Digital Network
 2 data channel (56K each)
 1 voice channel
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Broadband Services
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
xDSL (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 - 800Kbps
Need a DSL modem
 Splitters are needed to separate the voice and data signal

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Broadband Services
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Cable


A technology that provides digital data transmission over cable TV
infrastructure
Speed
 Downlink


Uplink


128Kbps - 3~5Mbps
64Kbps - 128Kbps~1Mbps
Need a cable modem
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Broadband Services
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Satellite


A technology that provide digital data transmission over satellites
Speed
 Downlink


Uplink


500Kbps - 1Mbps
50Kbps - 100Kbps
Need a satellite dish
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Home Network (single machine)
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Wall Jack
DSL/Cable
Modem
USB/Ethernet
Cable
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Home Network (multiple machines)
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Wall Jack
DSL/Cable
Modem
Hub/Switch/Router
USB/Ethernet
Cable
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Home Network (multiple machines)
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Wall Jack
Ethernet Cable
DSL/Cable
Modem
Hub/Switch/Router
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Home Wireless Network
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Wall Jack
Ethernet Cable
DSL/Cable
Modem
Hub/Switch/Router
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Network Security
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Firewall A gateway machine and its software that
protects a network by filtering the traffic it allows
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Network Addresses
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Hostname
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
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Network Addresses
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Figure 15.9
An IP address is
stored in four
bytes
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
Where does the host number
come from?
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Domain Name System
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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 System
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matisse.csc.villanova.edu
Computer
name
Domain name
TLD
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Domain Name System
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Figure 15.10 Top-level domains, including some relatively new ones
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Domain Name System
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Organizations based in countries other than the United States use
a top-level domain that corresponds to their two-letter country
codes
Do you
email
someone
in another
country?
Figure 15.11
Some of the top-level domain
names based on country codes
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Domain Name System
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Domain 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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References
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

Computer 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_Introductio
nToNetworking.ppt

Basic Computer Network by Weesan Lee
 http://www.cs.ucr.edu/~weesan/cs6/03_basic_computer
_network.ppt
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References (cont)
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
Domain Names
 http://www.icann.org/topics/new-gtld-strategy-
faq.htm
 http://www.iana.org/root-whois/index.html
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