Download TCP/IP

3. Data
Communications
3.4 Internet –
Internet Connection
Internet/Intranet
The development of the Internet
 The development of IT as a timeline
 Difference between intranet and the
Internet
 Functions of a typical school intranet

The development of the
Internet
It was conceived by the Advanced Research
Projects Agency (ARPA) of the U.S.
government in 1969 and was first known as
the Advanced Research Projects Agency
Network. The original aim was to create a
network that would allow users of a
research computer at one university to be
able to "talk to" research computers at
other universities.
Extracted from whatis.com
The development of the
Internet
A side benefit of ARPANet's design was
that, because messages could be
routed or rerouted in more than one
direction, the network could continue
to function even if parts of it were
destroyed in the event of a military
attack or other disaster.
Extracted from whatis.com
The development of the
Internet

A global network connecting millions of
computers. As of 1999, the Internet
has more than 200 million users
worldwide, and that number is growing
rapidly. More than 100 countries are
linked into exchanges of data, news
and opinions.
Extracted from pcwebopaedia.com
The development of IT
as a timeline

Please refer to the following website
spider.georgetowncollege.edu/infoweb/
AcademicSupport/classes/ITClass/
Powerpoint/it1/sld007.htm
The development of IT
as a timeline
Cellular
Telephone
Telegraph
Television
Satellite
1800s
1880s
1840s
1970s
1930s
1890s
1950s
Computer Fibre Optics
Fax
Radio
Intranet
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Share information
Less expensive to build and manage than
private networks
A network based on TCP/IP protocols
Belong to an organisation, usually a corporation
Accessible only by the organisation’s members,
employees or others with authorisation
An intranet’s web sites look and act like any
other web sites
The firewall surrounding an intranet fends off
unauthorised access
Functions of a typical
school intranet
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E-mailing
Password
Chat room
Message board
Notice board
File cabinet
Question database
Library service
Internet Connection

Essential components:
–
–
–
–

Dial-up software
Telephone lines
ISP
Leased lines
Connection services:
– ISDN
– Cable
– ADSL
Dial-up software
Microsoft Dial-up program
Reference links: www.download.com, tucows.hkstar.com
Telephone lines
Registered Jack-11
(RJ-11)
www.techweb.com/encyclopedia/
ISPs in HK
ISP – Internet Services
Provider
HKIX – Hong Kong
Information
HKIX
Exchange
The
Internet
ISP
ISP
ISP
Leased lines
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a permanent telephone connection between
two points set up by a telecommunications
common carrier.
are typically used by businesses to connect
geographically distant offices
always active
The fee for the connection is a fixed monthly
rate
the carrier can assure a given level of
quality
Leased lines
a T-1 channel is a type of leased line
that provides a maximum transmission
speed of 1.544 Mbps
 You can divide the connection into
different lines for data and voice
communication or use the channel for
one high speed data circuit

ISDN
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Integrated Services Digital Network is an
international communications standard for
sending voice, video, and data over digital
telephone lines or normal telephone wires
ISDN supports data transfer rates of 64
Kbps
two lines at once, called B (bearer) channels
one for voice and the other for data, or you
can use both lines for data to give you data
rates of 128 Kbps
Detailed references: www.webopaedia.com,
www.techweb.com/encyclopedia
ISDN
ISDN
Cable modem
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A modem used to connect a computer to a
cable TV service that provides Internet
access.
Cable modems can dramatically increase
the bandwidth between the user's computer
and the Internet service provider
Cable modems link to the computer via
Ethernet, which makes the service online all
the time
the speed will vary depending on how many
customers on that cable segment are using
the Web at the same time
Cable modem
Cable modem
ADSL
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Asymmetric Digital Subscriber Line, a new
technology that allows more data to be sent
over existing copper telephone lines (POTS).
ADSL supports data rates of from 1.5 to 9
Mbps when receiving data (known as the
downstream rate) and from 16 to 640 Kbps
when sending data (known as the upstream
rate).
TCP/IP
A protocol is a set of special rules
governing transmitting and receiving of
data between end points
 TCP – Transmission Control Protocol
 IP – Internet Protocol
 Refer to the handouts of chapter 3.2
for the functions of TCP and IP

IP Address
An identifier for a computer or device
on a TCP/IP network
 The format of an IP address is a 32-bit
numeric address written as four
numbers separated by periods.
 Each number can be zero to 255. For
example, 1.160.10.240 could be an IP
address.

IP address classes
Class A addresses are for large
networks with many devices.
 Class B addresses are for mediumsized networks.
 Class C addresses are for small
networks (fewer than 256 devices).
 Class D addresses are multicast
addresses.

Class A IP addresses
Class
Max.
Max.
number networks hosts
1-127
127
Network Host ID
ID (bits) (bits)
16777214 7
0XXXXXXX.xxxxxxxx.xxxxxxxx.xxxxxxxx
Network ID
Host ID
24
Class B IP addresses
Class
Max.
Max.
number networks hosts
Network Host ID
ID (bits) (bits)
129191
14
16383
65534
16
10XXXXXX.XXXXXXXX.xxxxxxxx.xxxxxxxx
Network ID
Host ID
Class C IP addresses
Class
Max.
Max.
number networks hosts
Network Host ID
ID (bits) (bits)
192223
21
2097151
254
8
110XXXXX.XXXXXXXX.XXXXXXXX.xxxxxxxx
Network ID
Host ID
Class D IP addresses
1110xxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx
Multicast address
Subnet mask
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The method used for splitting IP networks
into a series of subgroups, or subnets.
The mask is a binary pattern that is matched
up with the IP address to turn part of the
host ID address field into a field for subnets.
It's called a mask because it can be used to
identify the subnet to which an IP address
belongs by performing a bitwise AND
operation on the mask and the IP address
Subnet mask
E.g. with explanations:
Subnet mask: 255.255.255.0
(11111111.11111111.11111111.00000000)
IP address: 150.215.17.9
(10010110.11010111.00010001.00001001)
Subnet address: 150.215.17.0
(10010110.11010111.00010001.00000000)
Subnet mask
E.g. with explanations:
Subnet mask: 255.255.240.0
(11111111.11111111.11110000.00000000)
IP address: 150.215.17.9
(10010110.11010111.00010001.00001001)
Subnet address: 150.215.16.0
(10010110.11010111.00010000.00000000)
Default subnet mask
numbers
Class
Default subnet mask numbers
A
255.0.0.0 (Dec)
B
255.255.0.0 (Dec)
C
255.255.255.0 (Dec)
Reserved IP addresses

127.X.X.X
– Loop back

X.X.X.0
– Network

X.X.X.255
– Broadcasting
DNS
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Short for Domain Name System (or Service), an
Internet service that translates domain names into
IP addresses
Because domain names are alphabetic, they're
easier to remember
The Internet however, is really based on IP
addresses
Every time you use a domain name, therefore, a
DNS service must translate the name into the
corresponding IP address. For example, the domain
name www.example.com might translate to
198.105.232.4.
DNS
The DNS system is, in fact, its own
network
 If one DNS server doesn't know how to
translate a particular domain name, it
asks another one, and so on, until the
correct IP address is returned
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Routers
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A device that forwards data packets from
one local area network (LAN) or wide area
network (WAN) to another
Based on routing tables and routing
protocols, routers read the network address
in each transmitted frame and make a
decision on how to send it based on the
most expedient route (traffic load, line costs,
speed, bad lines, etc.)
Install TCP/IP
Network
Fig. 1
Install TCP/IP
Add
Fig. 2
Install TCP/IP
Add
Protocol
Fig. 3
Install TCP/IP
TCP/IP protocol
Fig. 4
Configure TCP/IP
Dynamic Host
Configuration Protocol
(DHCP)
Fig. 5
Configure TCP/IP
IP address
Subnet mask
Fig. 6
TCP/IP Utilities
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ping (Packet Inter-Network Groper)
– This is used to test whether the host is
reachable or not.
– ping 10.123.48.173
– ping www.yahoo.com
TCP/IP Utilities

nslookup (name service lookup)
– This is used to find the web address from
the IP address or vice and versa
– nslookup 10.123.48.173
– nslookup www.yahoo.com
TCP/IP Utilities

tracert (trace route)
– This is used to show the path of the
packet which has passed through on its
way to destination.
– tracert www.koei.co.jp
– tracert www.netvigator.com
TCP/IP Utilities

netstat (network statistics)
– This is used to view TCP/IP statistics and
the current active TCP/IP connections
– netstat
TCP/IP Utilities
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ipconfig (IP configuration)
– This is used to list the IP configuration of
the current computer
– ipconfig
– ipconfig /all
TCP/IP Utilities

arp (Address Resolution Protocol)
– This is used to displays and modifies the
IP-to-Physical address translation tables
– arp -a
Firewall

A firewall is special software or
hardware designed to protect a private
computer network from unauthorized
access. Firewalls are used by
corporations, banks and research
facilities to keep information private
and secure.
Proxy Server

A proxy server stores web contents on
local hard disks so that the next visit of
the same web addresses will retrieve
faster.