2. Recap
In the previous class, you have learnt about
• ISP
• Typical ISPs
• Types of ISPs
• ISP connection options
• Internal Architecture of ISP
* 2
3. Objectives
On completion of this topic, you would be able to
understand about
• ISP
• Pre-requisites of ISP
• High level architecture of ISP
* 3
4. ISP Recap
• ISP is a internet Service Provider
• It can also called as Internet Access provider
• It provide internet access to the individuals as well as
companies
• It provides home users as well as business connections
cont….
* 4
5. The ISP Architecture Consists of
• Set of modems
• Remote access server
• SMTP server
• Web server and
• Routers
* 5
6. Pre-requisites of ISP
• ISP purchases certain IP address to its subscribes
• ISP allocates IP address to its subscriber on connection
requirements
• IP address is added bad to the list when the connection
breaks
Cont....
* 6
7. • When the subscribes obtain an internet connection from
an ISP the subscriber gets user id & password
• RAS maintains the data base of all users ids and
passwords
contd….
* 7
8. Fig.1 High Level Architecture
RAS
SUBSCRIBERS SET OF MODEMS
MODEMS
NTERNET
* 8
9. • Clint dial-up program at High Level Architecture of ISP
the subscribers end dials
the number provided by RAS
the ISP via the modem SET OF
MODEMS
MODEMS
NTERNET
• The subscriber’s modem
uses the telephone
connection to call the ISP
number
* 9
10. • Subscriber’s modem
hunts for a free modem High Level Architecture of ISP
from set of modems of
ISP
RAS
• A dedicated line is MODEMS
SET OF
MODEMS
established between
NTERNET
the subscriber’s
modem and ISP
modems
* 10
11. • ISP modem is responds to High Level Architecture of ISP
the subscriber’s modems
with an acknowledgement
signal
RAS
SET OF
MODEMS
MODEMS
• Subscriber’s modem NTERNET
passes the
acknowledgement
message to the dial-up
program of the subscriber
* 11
12. • This is the indication for High Level Architecture of ISP
the application program
at the subscriber end that
the
RAS
SET OF
MODEMS
MODEMS
• ISP is ready to accept NTERNET
connection from the
subscriber
* 12
13. • The dial-up program High Level Architecture of ISP
sends user id and
password as message for
authentication
RAS
SET OF
MODEMS
MODEMS
•ISP’s modem receives
this information and NTERNET
passes to RAS
* 13
14. • RAS checks user id and High Level Architecture of ISP
password for
authentication
RAS
SET OF
MODEMS
• If he is a valid user, MODEMS
sends valid message NTERNET
other wise sends error
message back to the
subscriber modem
* 14
15. • The subscriber is virtually High Level Architecture of ISP
connected to the internet
through the ISP
RAS
SET OF
MODEMS
• The subscriber can MODEMS
access the internet NTERNET
services such as HTTP,
FTP, email and so on
* 15
16. Summary
In this class, you have learnt about
• High Level Architecture of an ISP
• How the Subscribers are connected to the Internet
through ISP
* 16
17. Quiz
(1) ISP can also be called as
(a) internet source provide
(b) Internet access provider
(c) Internet subscriber provider
* 17
18. Frequency Asked Questions
(1) What is an ISP ?
(2) Explain briefly about the high level architecture of ISP
(3) Explain briefly how the subscribers are connected to
the inter net by using ISP
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