Transcript TCP/IP suite of protocols

CHAPTER 2
PCs on the Internet
Suraya Alias
The TCP/IP Suite of Protocols
Internet applications – client/server applications
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The client requested data from the server
Example : a home user (client) requesting the facebook web
page from facebook application web server (web host)
Example of web servers : Apache HHTP Server and Internet
Information Services (IIS)
The server application is installed as a service in a computer
Using IP and Ports addresses to identify services
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Each services (email, web server) is addressed using unique port
number since they access to the same IP Address
So each server applications listens to the assigned port
Example: web server is assigned port 80, email server is port 25
So the web server will communicate at 136.60.30.5:80 and the email
server using 136.60.30.5:25
Common TCP/IP port assignment
Port
Protocol
Service
Description
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FTP
FTP
File transfer data
21
FTP
FTP
File transfer data
22
SSH
Secure Shell
23
Telnet
Telnet
Used by UNIX computers to control a computer
remotely
25
SMTP
E-mail
Simple Mail Transfer Protocol
80
HTTP
Web server
109
POP2
E-mail
Post Office Protocol,v2, used by client to receive
email
110
POP3
E-mail
Post Office Protocol,v3, used by client to receive
email
119
NNTP
News server
143
IMAP
E-mail
Internet Message Access Protocol, newer than
POP3
443
HTTPS
Web server
HTTP with security includes authentication and
encryption
Remote control to a networked computer
World Wide Web Protocol
New server, used for newsgroup
TCP/IP protocol layers
Applications
Email
HTTP
SMTP,
POP
Chat room
FTP
IRC
FTP
TCP Or UDP
IP, ARP,RARP,RIP or ICMP
Ethernet, PPP over telephone lines, Token
Ring, FDDI or wireless
Cabling/telephone lines
Applications
TCP/IP suite of protocols
Web server
Operating System
Physical Network
Application Protocols
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Four common applications that uses the internet is
Web browser, email, chat and FTP
Application Programming Interface (API) is used by
the OS in order to request or send data to another
host
For web browser and web servers, the OS
generates Hypertext Transfer Protocol (HTTP) in
order to communicate
A session is established after the response is
received from the web server
TCP/IP protocols used by OS
for network communication
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When a web browser make a request for a data to the
web server, a packet is created and is ready to be
delivered
Transmission Control Protocol (TCP) is the TCP/IP
protocol that guarantees the packet is delivered and will
resend if it fails
It is also called connection-oriented protocol and used
for email and web browsers, s
While UDP (User Datagram Protocol) does not
guarantee delivery by first connecting and checking
whether data is received or not
Its called a connectionless protocol or best-effort
protocol
TCP/IP protocols used by OS
for network communication
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Next, TCP & UDP pass the request to IP (Internet
Protocol) to breaks up and reassemble data into packets
and routing them to respective destination
Other available network protocols;
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ARP (Address resolution Protocol)
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RARP (Reverse Address resolution Protocol)
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Responsible for discovering the Internet Address of a host on a
local network
ICMP (Internet Control Message Protocol)
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Responsible to locate a host on a local network
Responsible for communicating problem with transmission
Example of TCP/IP utilities
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ARP, Getmac, IPconfig,FTP,NBstat,Netstat, NSLookup
Ping, route, telnet, tracert, winipcfg
TCP/IP Utilities
Connecting to the Internet
Computer or Local network can connect to Internet
by ISP using following technologies;
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Regular phone line - requires internal, external
modem
Cable modem - uses cable lines
DSL (Digital Subscriber Line) – uses copper phone
lines, same phone line for voice and DSL,
Asymmetric SDL,Symmetric DSL
ISDN (Integrated Services Digital Network)
Satellite access
Wireless access
Using Router
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Router is a device that manages traffic between
two network
2 major disadvantages of using host pc in sharing
internet connection
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Host comp must always be turned on
Security issues
Advantages of using router rather than host pc
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Less bottleneck of the host pc
Internet access not dependable to host pc
Router can serve as hardware firewall, better protection
that software firewall
Provide additional features such as DHCP server, switch,
wireless access point.
Virtual Private Network (VPN)
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Solution for securing private data travelling over a public network is using
VPN
VPN works by using encrypted data packets between a private network a
computer somewhere in the internet
Security methods with VPN
 User accounts and passwords are required, when the remote users
sends data to the authentication server, the data is encrypted using
protocols such as EAP (Extensible Authentication Protocol), SPAP
(Shiva Password Authentication Protocol) and others
 After the user is authenticated, a tunnel is created so that all data sent
between the user and the company is strongly encrypted
 There are 4 tunnels protocol that can be used
 PPTP (Point to Point Tunneling Protocol) - weakest
 L2TP (Layer Two Tunneling Protocol) – strongest is combined with
IPSec
 SSL (Secure Socket Layer )
 IPSec (IPSecurity)
Supporting Internet Client
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Web browser is a s/w application on client PC
used to request web pages from the web
server on the internet
URL (Uniform Resource Locator)
Domain Name
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http://www.facebook.com/photo/mypic.php
Protocol
Host
Name
Network
Name
folder
filename
Using Secured Web
Connection
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Using HTTPS (HTTP Secure)
For Internet Banking or private business
HTTP over SSL (Secure Socket Layer) or TSL (Transport Layer
Security)
The purpose of these security protocols is to prevent others from
the internet to eavesdropping on data or change the data
 SSL – uses an encryption system that uses a digital certificate.
Public Keys are secret codes used to encrypt and decrypt the
data. A digital certificate, or digital ID, digital signature is a code
assigned to you by a certificate authority such as Verisign that
uniquely identifies you on the net and includes a public key
 TSL – improved version of SSL