4.2 Identify the basic Internet protocols and terminologies. Identify procedures
for establishing Internet connectivity. In a given scenario, configure the
operating system to connect to and use Internet resources.
2. Connectivity technologies
3. Installing and Configuring browsers
4. Firewall protection under Windows XP
IP is responsible for moving packet of data from
node to node. IP forwards each packet based IP address provided in the
TCP is responsible for verifying the correct
delivery of data from host to host. Data can be lost in the intermediate
network. TCP adds support to detect errors or lost data and to trigger
retransmission until the data is completely received without errors, or
lost packets. The protocol is therefore known as connection oriented
POP: POP stands for Post Office Protocol. Version 3,
known as POP3 is the most widely used protocol. POP is used for
receiving email messages from a server to a client work station.On the
other hand, SMTP is used for sending messages from a client work station
to the server.
SMTP: Simple Mail Transfer
Protocol is the TCP/IP standard protocol for transferring electronic
mail messages from one machine to another. SMTP specifies how two mail
systems interact and the format of control messages they exchange to
IMAP: IMAP stands for Internet
Message Access Protocol. Similar to POP, it is used for accessing
electronic mail from a mail server. IMAP permits a "client"
email program (such as Outlook Express or Thunderbird) to access remote
message folders as if they were local. For example, email stored on an
IMAP server can be manipulated from a computer at home, a computer
at office, and a notebook computer while traveling, without any
need for transferring messages or files back and forth between these
computers. POP protocol on the other hand receives all the messages to
the local computer. This makes it difficult to work with email from
DNS: The Internet Domain Name
System (DNS) offers a hierarchical naming scheme. DNS uses distributed
lookup in which domain name servers map each domain name to an IP address or
main exchanger address. Clients begin by trying to resolve names locally.
When the local server cannot resolve the name, the client must choose to
work through the tree of name servers iteratively or request the local name
server to do it recursively.
HTML: It stands for Hyper Text Markup Language. HTML is the
language used widely for constructing web pages. When you see a web page
over the Internet, it contains HTML or a version of it. Other variations of
HTML include XML, XHTML,
HTTP: Stands for Hyper Text Transfer Protocol. The HTTP
protocol is a request/response protocol. A client sends a request to the
server in the form of a request method, URI (Universal Resource Indicator),
and protocol version, followed by a message containing client information
over a connection with a server. The server responds with a status line,
including the message's protocol version and a success or error code,
followed by a server information, and possible entity-body content. HTTP
communication normally uses port 80 of TCP/IP protocol suite.
HTTPS: This protocol is used for accessing a secure Web
server where authentication and encrypted communication is required. Using
HTTPS in the URL instead of HTTP directs the message to a secure port number
(normally, port number 443) rather than the default Web port number of 80.
The session is then managed by a security protocol. HTTPS encrypts the
session data using the SSL (Secure Socket Layer) protocol. HTTPS is the
preferred protocol when using credit card transactions.
An example format for secure URL is
SSL: Secure Socket Layer is a protocol for encrypting and
decrypting data across a secure connection from a client to a server. Both
the client browser, and the server should support SSL for the communication
to happen. The server is responsible for sending the client a
certificate and a public key for encryption. Upon validation of the
certificate, an SSL connection is established between the client and the
server. Once a secure session is established, all data passing either side
will be encrypted. Only the client and the server will be able to decrypt
Telnet: This is another client-server protocol that emulates
a terminal and used to execute commands on a server. You run commands on a
server without leaving your client work station, as if you were working
local to the server. Telenet uses port 23 of TCP. Typical telnet commands
include ls, cd, md, etc.
FTP: FTP stands for File Transfer
Protocol. Like any other protocol in TCP/IP suite of protocols, FTP is a
client-server protocol for transferring files between a client and the
server. FTP uses port number 21.
ISP: Short for Internet service provider. ISP is basically a
service entity (business or organisation) that provides consumers access to
the Internet and related services. ISPs maintain the infrastructure required
for access to the Internet. The infrastructure may include DNS servers, mail
servers, web servers, DHCP servers, remote access servers, etc. It is also
important that the facility has redundant hardware/software for providing
foolproof service. Major ISPs in US include MSN, EarthLink, AOL, etc.
Dial-up networking: As the name suggests, it is used to
connect a computer to an Internet service provider (ISP), or a remote
computer through an analog modem and POTS (plain old telephone system).
The following are the important features of dial-up
Uses a modem as the interface between a PC and a remote
access server, located at ISP.
The maximum speed at which you can upload or download data
is limited by the telephone system's analog bandwidth, and line quality.
Maximum speeds of up to 56 kbps are achievable.
Dial-up networking normally uses PPP (Point-to-Point
Protocol) protocol for accessing the Internet.
With the advent of broadband, dial-up networking is used
by smaller number of consumers. Broadband Internet enables speeds up to a
few Mbps (megabits per second) compared to 56 Kbps of dial-up.
DSL networking: DSL stands for Digital Subscriber Line. DSL
uses readily available telephone line for transmission of data to/from the
Internet. Unlike dial-up Internet connection, a DSL connection will not tie
up your telephone line. Though DSL uses the same telephone line, you can simultaneously
make or receive telephone calls. DSL is normally, an always ON connection.
You don't need to disconnect from the Internet when using DSL.
The two main categories of DSL for
home subscribers are called ADSL and SDSL.
ADSL, short for Asymmetric Digital Subscriber Line, supports data rates up to 9
Mbps when receiving data (known as the downstream rate) and up to 640 Kbps when
sending data (known as the upstream rate). ADSL requires a special ADSL
SDSL, short for Symmetric Digital Subscriber Line, a technology that allows
broadband connectivity over existing copper telephone lines (POTS). SDSL is
called symmetric because it supports the same data rates for upstream as well as
downstream traffic. SDSL supports data rates up to 3 Mbps. SDSL requires a
special SDSL modem.
Broadband Internet connection that is designed to operate
over cable TV lines is known as Cable Internet. It uses a modem, known as
Cable modem for receiving and transmitting data between the client, and the
ISP. Unlike DSL, Cable Internet uses shared medium. That is, all the
subscribers connected to a given cable share the Internet bandwidth
together. As a result, though the coaxial cable used by cable TV provides
much greater bandwidth than telephone lines (used by DSL), the speeds
achievable by Cable Internet are comparable to that of DSL.
far as data privacy and security are concerned, DSL is preferred over Cable,
due to the fact that data passing through cable is visible to all host
computers connected over the same cable segment. DSL on the other hand uses a
dedicated copper pair right from the telephone company up to the consumer.
Therefore, the signals that flow through the copper wire are secure, and not
shared over the media.
LAN: Stands for Local Area Networks. It is used for
connecting two or more computers for the purpose of sharing resources. Two
important versions of LANs are Peer-to-Peer networking, and Client-Server
Windows 9x supports Peer-to-Peer networking.
in Internet Explorer Version 5 and 6.:
In the Internet Explorer Menu go to Tools and then select
In the Internet Options window choose the Security tab
On the Security Window, choose Custom Level
In the Settings window scroll down to Active scripting.
Check Enable. Then Click on OK
You will get a warning message. Click on Yes
On the Security Window, click OK.
You may need to configure a Proxy server if not connected to
the Internet directly. A proxy server protects your computer from external
hacking, as well as allows a single Internet connection be shared among
For configuring Proxy, go to Tools in the main Menu of IE 6,
and select Internet Options. In the resulting Window, select
By clicking on "LAN Settings", another windows
opens as shown below.
You can check the box titles "Proxy server", and
enter the IP address, and Port number of the proxy server being used.
Internet Explorer offers security zones including Trusted and Restricted zones.
You can assign Web sites that you trust completely to trusted zones, and suspicious
websites to Restricted Zones.
For configuring Proxy, go to Tools in the main Menu of IE 6,
and select Internet Options. In the resulting Window, select Security.
As seen in the above figure, you can choose "Trusted
sites" and add some trust worthy sites there. Similarly, choose
restricted sites, and add some sites that you think need to be restricted
Windows XP Internet Connection Firewall is a software that you
can use to set restrictions on the information communicated between computer and
the Internet. If your computer uses Internet Connection Sharing to provide
Internet access to multiple computers, it is preferred to turn on Internet
Connection Firewall on the shared Internet connection.
To enable or disable Internet Connection Firewall
1.Open Network Connections
2.Click the LAN, Dial-up, or High-Speed Internet connection that you want to
protect, and then, under Network Tasks, click Change settings of this
3.On the Advanced tab, under Internet Connection Firewall, select one of the
1. To enable Internet Connection Firewall
(ICF), select the Protect my
computer and network by limiting or preventing access to this computer from
the Internet check box.
2. To disable Internet Connection Firewall, clear the Protect my computer
and network by limiting or preventing access to this computer from the
Internet check box.
Note that you should not use ICF when connecting to the Internet
using Virtual Private Network (VPN). You require administrative privileges to
enable or disable ICF.