Transcript Internet Concepts

Internet concepts
1. What is client server architecture?
Client server is network architecture which separates a client (often an
application that uses a graphical user interface) from a server. Each
instance of the client software can send requests to a server. Specific
types of servers include web servers, application servers, file servers,
terminal servers, and mail servers. While their purposes vary somewhat,
the basic architecture remains the same.
Although this idea is applied in a variety of ways, on many different
kinds of applications, the easiest example to visualize is the current use
of web pages on the internet. For example, if you are reading this article
on Wikipedia, your computer and web browser would be considered a
client, and the computers, databases, and applications that make up
Wikipedia would be considered the server. When your web browser
requests a particular article from Wikipedia, the Wikipedia server finds
all of the information required to display the article in the Wikipedia
database, assembles it into a web page, and sends it back to your web
browser for you to look at.
Characteristics of a server:
Passive (slave)
Waits for requests
Upon receipt of requests, processes them and then serves replies
Characteristics of a client:
Active (master)
Sends requests
Waits for and receives server replies
Servers can be stateless or stateful. A stateless server does not keep
any information between requests. A stateful server can remember
information between requests. The scope of this information can be
global or session-specific. An HTTP server for static HTML pages is an
example of a stateless server while Apache Tomcat is an example of a
stateful server.
The interaction between client and server is often described using
sequence diagrams. Sequence diagrams are standardized in the UML.
Another type of network architecture is known as a peer-to-peer
architecture because each node or instance of the program is both a
"client" and a "server" and each has equivalent responsibilities. Both
architectures are in wide use.
2. What is a thin client?
A network computer without a hard disk drive, which, in client/server
applications, is designed to be especially small so that the bulk of the
data processing occurs on the server
3. What is a fat client?
In computing, a Fat Client (also known as Rich-Client) is a term from
client-server architecture for a client that performs the bulk of the data
processing operations. The data itself is stored on the server.
4. What is a web server?
A computer, including software package, that provides a specific kind
of service to client software running on other computers. More
specifically, a server is a computer that manages and shares web
based applications accessible anytime from any computer connected
to the Internet.
5. What is OSI model?
The Open Systems Interconnection Basic Reference Model (OSI
Reference Model or OSI Model for short) is a layered, abstract
description for communications and computer network protocol
design, developed as part of the Open Systems Interconnection
initiative. It is also called the OSI seven layer model.
OSI Model
7, Application layer 6, Presentation layer 5, Session layer 4,
Transport layer 3, Network layer 2, Data link layer LLC sublayer
MAC sublayer 1, Physical layer
6.What is TCP/IP model?
The TCP/IP model or Internet reference model, sometimes called the
DoD model (DoD, Department of Defense), ARPANET reference model,
is a layered abstract description for communications and computer
network protocol design. It was created in the 1970s by DARPA for use
in developing the Internet's protocols, and the structure of the Internet is
still closely reflected by the TCP/IP model. It has fewer, less rigidly
defined layers than the commonly referenced OSI model, and thus
provides an easier fit for real-world protocols]
The layers
Application layer
Transport layer
Network layer
Data link layer
Physical layer
7. What is network?
A group of computers, connected by a telecommunications link, that
share information
A network may be composed of any combination of LANs, or WANs.
8. What is browser?
Software program used to view and interact with various types of
Internet resources available on the World Wide Web. Netscape and
Internet Explorer are two common examples
9. What is topology?
the geometric configuration of a computer network, or how the network
is physically laid out. Common topologies are star (centralized), bus
(decentralized), and ring (decentralized).
10. Internet adheres to which topology?
11. What are the services available on internet?
It is a "network of networks" that consists of millions of smaller domestic,
academic, business, and government networks, which together carry
various information and services, such as electronic mail, online chat,
file transfer, and the interlinked Web pages and other documents of the
World Wide Web.
12. What is the difference between internet and intranet?
There's one major distinction between an intranet and the Internet:
The Internet is an open, public space, while an intranet is designed to
be a private space. An intranet may be accessible from the Internet,
but as a rule it's protected by a password and accessible only to
employees or other authorized
13.What is a search engine ? What are different search engines used
now-a-days?
Internet search engines (eg Google, AltaVista) help users find web
pages on a given subject. The search engines maintain databases of
web sites and use programs (often referred to as "spiders" or "robots")
to collect information, which is then indexed by the search engine.
Similar services are provided by "directories," which maintain ordered
lists of websites, eg Yahoo!
www
Ans: World wide web
hypertext
Ans: Hypertext is text which is not constrained to be linear.
Hypertext is text which contains links to other texts. The term was
coined by Ted Nelson around 1965 (see History ).
HyperMedia is a term used for hypertext which is not constrained to be
text: it can include graphics, video and sound , for example. Apparently
Ted Nelson was the first to use this term too.
how can a page linked with other pages
Ans:
19. PORTAL
Ans: A Personal Portal is a site on the World Wide Web that typically
provides personalized capabilities to its visitors, providing a pathway to
other content. It is designed to use distributed applications, different
numbers and types of middleware and hardware to provide services
from a number of different sources. In addition, business portals are
designed to share collaboration in workplaces. A further business-driven
requirement of portals is that the content be able to work on multiple
platforms such as personal computers, personal digital assistants
(PDAs), and cell phones.
protocol in email
Ans : IMAP, POP3, SMTP and HTTP Email Protocols
connectionless service
Ans: A service that allows the transfer of information among subscribers without the
need for end-to-end establishment procedures
connection oriented service
Ans : connection-oriented describes a means of transmitting data in which the
devices at the end points use a preliminary protocol to establish an end-to-end
connection before any data is sent. Connection-oriented protocol service is
sometimes called a "reliable" network service, because it guarantees that data will
arrive in the proper sequence. Transmission Control Protocol (TCP) is a connectionoriented protocol.
protocol
Ans: In information technology, a protocol (from the Greek protocollon, which was a
leaf of paper glued to a manuscript volume, describing its contents) is the special set
of rules that end points in a telecommunication connection use when they
communicate. Protocols exist at several levels in a telecommunication connection.
For example, there are protocols for the data interchange at the hardware device
level and protocols for data interchange at the application program level. In the
standard model known as Open Systems Interconnection (OSI), there are one or
more protocols at each layer in the telecommunication exchange that both ends of
the exchange must recognize and observe. Protocols are often described in an
industry or international standard.
On the Internet, there are the TCP/IP protocols, consisting of:
Transmission Control Protocol (TCP), which uses a set of rules to
exchange messages with other Internet points at the information packet
level
Internet Protocol (IP), which uses a set of rules to send and receive
messages at the Internet address level
Additional protocols that include the Hypertext Transfer Protocol (HTTP)
and File Transfer Protocol (FTP), each with defined sets of rules to use
with corresponding programs elsewhere on the Internet
HTTP
Ans: Hypertext Transfer Protocol
URL relevance
Ans: in popular usage, it is a widespread synonym for Uniform Resource
Identifier (URI) — many popular and technical texts will use the term
"URL" when referring to URI;
IP Address
Ans: An identifier for a computer or device on a TCP/IP network. Networks
using the TCP/IP protocol route messages based on the IP address of the
destination. 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.
Within an isolated network, you can assign IP addresses at random as long as
each one is unique. However, connecting a private network to the Internet
requires using registered IP addresses (called Internet addresses) to avoid
duplicates.
Classes
Ans: The four numbers in an IP address are used in different ways to identify a
particular network and a host on that network. Four regional Internet registries - ARIN, RIPE NCC, LACNIC and APNIC -- assign Internet addresses from the
following three classes.
· Class A - supports 16 million hosts on each of 126 networks
· Class B - supports 65,000 hosts on each of 16,000 networks
· Class C - supports 254 hosts on each of 2 million networks
The number of unassigned Internet addresses is running out, so a new
classless scheme called CIDR is gradually replacing the system based on
classes A, B, and C and is tied to adoption of IPv6.
HTML
Ans: HTML stands for Hyper Text Markup Language
An HTML file is a text file containing small markup tags
The markup tags tell the Web browser how to display the page
An HTML file must have an htm or html file extension
An HTML file can be created using a simple text editor
stateless protocol
Ans: Stateless
This does not require the user to start an instance of the application as all
access to the application is via a web browser. The application, which is
running under a web server, knows nothing about any particular client
until it receives an HTTP request. When it receives a request the
following happens:
The web server creates and activates a child process to deal with the
request, or it may reactivate an existing process which is currently
"sleeping".
The child process deals with the request and generates a response,
which the web server will send back to the client device.
The child process then dies, or puts itself in a "sleep" condition.
The idea behind a child process going to sleep instead of dying is to
avoid the overhead of creating and activating a brand new process each
time. With this method a process is created just once, and while it is not
actively dealing with a request it sits in a queue of sleeping processes
which are waiting to be reactivated.
It should be noted here that even if a child process does not die but
merely goes to sleep it loses all memory of the request it just processed
and the response which it generated. Even if the next request from the
same client is given to the same child process there is no memory of
any state left by the previous request. This is the stateless nature of the
HTTP protocol.
The HTTP protocol does not allow a process on the web server to be
permanently allocated to a particular client.
After dealing with a request from one client a child process may deal
with many requests from many other clients before it receives the next
request from the original client.
When the web server receives a request from a client there is no way to
guarantee that it will allocate the same child process that dealt with the
previous request from that client.
If that website is operating a server farm there is no way to guarantee
that a subsequent request from a client will be allocated to the same
server that dealt with any previous request.
This means that a client is only consuming resources on the web server
during the processing of a request-response cycle. When a client
receives a response there is usually a time delay before the next
request is issued (if any), and during this time the web server can deal
with many other requests from many other clients.
The advantage of this approach is that although there is a limit on the
number of child processes which can be active at any one time, the
number of active clients can be considerably greater due to the fact that
the requests are usually staggered instead of transmitted all at the same
instant.
The disadvantage of this approach is that the web server does not
maintain any memory of the activities of any particular client, so each
request is treated as a new request and not as a follow-up to a previous
request.
There is no state maintained at the server end, but what about at the
client end? It is true that the browser maintains a history, but this is
nothing more than a history of requests that have been sent. If a request
is re-transmitted it is treated as if it were a new request. The responses
may be cached, but while stepping through the browser's cache there is
no communication with the server, so what is being viewed is from the
browser's memory on the client, not the server's memory.
cookie
Ans: HTTP cookies, sometimes known as web cookies or just
cookies, are parcels of text sent by a server to a web browser and then
sent back unchanged by the browser each time it accesses that server.
HTTP cookies are used for authenticating, tracking, and maintaining
specific information about users, such as site preferences and the
contents of their electronic shopping carts. The term "cookie" is derived
from "magic cookie," a well-known concept in Unix computing which
inspired both the idea and the name of HTTP cookies.
Cookies have been of concern for Internet privacy, since they can be
used for tracking browsing behavior. As a result, they have been subject
to legislation in various countries such as the United States and in the
European Union. Cookies have also been criticised because the
identification of users they provide is not always accurate and because
they could potentially be used for network attacks. Some alternatives to
cookies exist, but each has its own drawbacks.
Cookies are also subject to a number of misconceptions, mostly based
on the erroneous notion that they are computer programs. In fact,
cookies are simple pieces of data unable to perform any operation by
themselves. In particular, they are neither spyware nor viruses, despite
the detection of cookies from certain sites by many anti-spyware
products.
Most modern browsers allow users to decide whether to accept cookies,
but rejection makes some websites unusable. For example, shopping
baskets implemented using cookies do not work if cookies are rejected.
port
Ans: An interface on a computer to which you can connect a device. Personal
computers have various types of ports. Internally, there are several ports for
connecting disk drives, display screens, and keyboards. Externally, personal
computers have ports for connecting modems, printers, mice, and other
peripheral devices.
Almost all personal computers come with a serial RS-232C port or RS-422 port
for connecting a modem or mouse and a parallel port for connecting a printer.
On PCs, the parallel port is a Centronics interface that uses a 25-pin connector.
SCSI (Small Computer System Interface) ports support higher transmission
speeds than do conventional ports and enable you to attach up to seven
devices to the same port.
reserved ports
Ans : The Well Known Ports /Reserved Ports are those in the range 0–1023.
email
Ans Electronic mail (abbreviated "e-mail" or, often, "email") is a store and
forward method of composing, sending, storing, and receiving messages over
electronic communication systems. The term "e-mail" (as a noun or verb)
applies both to the Internet e-mail system based on the Simple Mail Transfer
Protocol (SMTP) and to intranet systems allowing users within one organization
to e-mail each other. Often these workgroup collaboration organizations may
use the Internet protocols for internal e-mail service.
What is WAIS?
IS (Wide Area Information Servers) is an Internet system in which
specialized subject databases are created at multiple server locations,
kept track of by a directory of servers at one location, and made
accessible for searching by users with WAIS client programs. The user
of WAIS is provided with or obtains a list of distributed databases. The
user enters a search argument for a selected database and the client
then accesses all the servers on which the database is distributed. The
results provide a description of each text that meets the search
requirements. The user can then retrieve the full text.
WAIS (pronounced "ways") uses its own Internet protocol, an extension
of the Z39.50 standard (Information Retrieval Service Definition and
Protocol Specification for Library Applications) of the National
Information Standards Organization. Web users can use WAIS by either
downloading a WAIS client and a "gateway" to the Web browser or by
using Telnet to connect to a public WAIS client.
What is VRML?
VRML, the Virtual Reality Modeling Language, is an attempt to extend
the web into the domain of three-dimensional graphics. VRML "worlds"
can depict realistic or otherworldly places, which can contain objects
that link to other documents or VRML worlds on the web.
What is Virtual Private Network?
A data network that uses the public telecommunications infrastructure,
but maintains privacy through the use of a tunneling protocol and
security procedures. A VPN gives a company the same capabilities as
a system of owned or leased lines to which that company has
exclusive access. However, costs are much lower because the VPN
uses the shared public infrastructure rather than exclusive line access.
Who runs the internet?
The Internet is unlike most hierarchical organizations we deal with in
life, because there is no one "in charge" as the single top authority.
But there is order as well as chaos:
Yes, it's true. No one is in charge of the Internet.
Even Larry Landweber, president of the Internet Society, admits that. "But
anarchy? That is incorrect," he said of the other popular belief -- that no
one maintains law and order on the 'net.
In reality, a number of dedicated volunteer groups keeps the Internet
working through their efforts at standards development and consensus
building. <ComputerWorld, January 2, 1996, p. 12.>
Groups that contribute to the Internet architecture and use.
Internet2 Project (UCAID)
for development of advanced network services for higher education and
research and the VBNS highspeed backbone on which it will run. See
also Abilene and QBone and VBNS+. And there is the Canadian CA*net 3
which is discussed in the Chronicle of Higher Education.
Internet Society
Concerned with the evolution of the Internet and its social, political, and
technical issues.
Internet Engineering Task Force (IETF)
Develops technical standards for the Internet.
Internet Architecture Board (IAB)
Oversees Internet protocols and procedures and the creation of Internet
standards.
Internet Assigned Numbers Authority (IANA)
Coordinates assignment of protocol numbers. See ICANN (below) for domain
name name assignments.
Commercial Internet Exchange Association (CIX)
Nonprofit trade association for public data internetworking service providers.
CommerceNet
Nonprofit group that works to accelerate the application of electronic
commerce on the Internet.
W3C, World Wide Web Consortium
An industry consoritum run by MIT that develops standards for the evolution
of the Web. Registrars ...
ICANN
Internet Corporation for Assigned Names and Numbers (supersedes some
IANA functions) and list of Accredited Registrars.
InterNIC at Network Solutions
Directory and Databases.
Domain Name Buyers Guide.
And ...
Internet responsiveness or weather as maps from MIDS.
Internet Domain Survey
run in January and July.
IP Next Generation (IPng).
What is FTP?ON which port it is available?
File Transfer Protocol. This is the language used for file transfer from
computer to computer across the WWW. An anonymous FTP is a file
transfer between locations that does not require users to identify
themselves with a password or log-in. An anonymous FTP is not secure,
because it can be accessed by any other user of the WWW.
Port number 21 is utilized by the File Transfer Protocol for control traffic.
What is SMTP?On which port SMTP works?
SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in
sending and receiving e-mail.
The SMTP standard specifies that all SMTP servers must use port 25.
What is an intranet?
An intranet is a private computer network that uses Internet protocols,
network connectivity, and possibly the public telecommunication system
to securely share part of an organization's information or operations with
its employees. Sometimes the term refers only to the most visible
service, the internal website. The same concepts and technologies of
the Internet such as clients and servers running on the Internet protocol
suite are used to build an intranet. HTTP and other Internet protocols
are commonly used as well, especially FTP and e-mail. There is often
an attempt to use Internet technologies to provide new interfaces with
corporate 'legacy' data and information systems.
Briefly, an intranet can be understood as "a private version of the
Internet," or as a version of the internet confined to an organization
What is a database server?
Manages data queries
What is an application server?
A "middle-tier" software and hardware combination that lies between the
Web server and the corporate network and systems.
An application server is a server computer on a computer network
dedicated to running certain software applications (as opposed to e.g. a
file server or print server).
Generally, an application server is a software engine that delivers
applications to client computers. Moreover, an application server should
handle most, if not all, of the business logic and data access of the
application. The main benefits of application server technology are ease
of application development and centralization.
Although the term application server applies to all platforms, it has
become heavily identified with the Sun Microsystems J2EE platform;
however, it has also come to encompass servers of web-based
applications, such as integrated platforms for e-commerce, content
management systems, affiliate management systems and occasionally,
even applied to simplistic web-site page builders. The paradigm is more
similar to mainframe based applications than traditional client-server.
What is CGI?What is a CGI script?
CGI stands for Common Gateway Interface. CGI allows HTML pages to
interact with programming applications.
The Common Gateway Interface (CGI) is a method of allowing a
hyperlink to refer to a program rather than a static web page. The
easiest way to understand how a CGI works is by contrast with an
ordinary web page.
Common Gateway Interface script; a script that takes data from a web
form and converts it.
(Common Gateway Interface script) A small program written in a
language such as Perl, Tcl, C or C++, it functions as the glue between
HTML pages and other programs on the Web server. For example, a
CGI script would allow search data entered on a Web page to be sent to
the DBMS (database management system) for lookup. It would also
format the results of that search as an HTML page and send it back to
the user.
What is server side script?
A server side script is a program that is processed on the SERVER, before the
information ever reaches the viewer's computer. Compared to a client side script,
which is processed on the CLIENT's computer. Examples of languages commonly
used as server side scripts: php, jsp, asp, perl. Examples of client side script: Java
Script.
What is style sheet? What is cascading style sheet?
A set of formatting or style commands that are kept separate from the actual
content of a web page. This makes formatting easier as it can be defined globally,
rather than each time a particular element occurs.
a block of text in which one or more formats for webpage display are defined. This
may include redefinitions of standard formats such as <H1> or new formats specific
to that page or site. Style sheets may be embedded in a particular webpage or
stored as a separate text file to which some or all of the webpages on a site are
linked.
Cascading style sheets is a style sheet language that enables authors and users to
attach style (fonts, spacing and aural cues) to structure that include HTML and XML
applications.
CSSs allow authors and users to attach style (eg, fonts, spacing, and aural cues) to
structured documents (eg, HTML documents and XML applications). CSSs
separate the presentation style of documents from the content of documents, and
thereby simplify Web authoring and site maintenance. Both Netscape and IE now
support CSSs.
What is scripting language?
The programming language in which a script is written.
A (relatively) simple programming language eg JavaScript and Visual
Basic which can be used to create a script, which is a set of instructions
for a computer. VBS is much favoured by virus writers seeking to exploit
certain vulnerabilities in some Microsoft programs.
What is IPV4?How many bytes it take?
The Internet Protocol version 4. This is the current version. IPv4
addresses are 32 bits(4 bytes) wide. Its headers are 20 bytes at
minimum, and grow in chunks of 4 bytes.
What is IPV6?How many bytes it take?
Internet Protocol Version 6. Next generation version of the internet
protocol. Includes improved address space, quality of service and data
security over IPv4
Internet Protocol version 6”. A replacement for the aging IPv4, which
was released in the early 1980s. IPv6 will increase the number of
available Internet addresses (from 32 to 128 bits), resolving a problem
associated with the growth of the number of computers attached to the
Internet.
What is email?
Electronic mail. Mail composed and transmitted on a computer system
or network
Electronic mail) The exchange of electronic messages and computer
files between computers that are connected to the Internet or some
other computer network
What is ecommerce?
Electric commerce: the conducting of business communication and
transactions over networks and through computers. Specifically,
ecommerce is the buying and selling of goods and services, and the
transfer of funds, through digital communications
What is SGML?
Standard Generalized Markup Language. SGML is both a language and
an ISO standard for describing information embedded within a
document. HyperText Markup Language (HTML) is based on the SGML
standard. SGML itself does not specify any particular formatting; rather,
it specifies the rules for tagging elements. These tags can then be
interpreted to format elements in different ways.
What is a web server?
A computer, including software package, that provides a specific kind of
service to client software running on other computers. More specifically,
a server is a computer that manages and shares web based
applications accessible anytime from any computer connected to the
Internet.
What is single tier architecture?
a central computer served the whole business community and was
accessed via dumb terminals. All processing took place on a single
computer - and therefore in one place. All resources associated with the
computer (tape and disk drives, printers etc.) were attached to this same
computer. This is single tier (or 1-tier) computing. It is simple, efficient,
uncomplicated, but terribly expensive to run.
What is 2 tier architecture? what are its advantages and disadvantages?
Refers to client/server architectures in which the user interface runs on
the client and the database is stored on the server. The actual
application logic can run on either the client or the server.
Advantages and Disadvantages
The advantage of the two-tier design is its simplicity. The TopLink
database session that builds the two-tier architecture provides all the
TopLink features in a single session type, thereby making the two-tier
architecture simple to build and use.
The most important limitation of the two-tier architecture is that it is not
scalable, because each client requires its own database session.
What is 3 tier architecture? what are its advantages and disadvantages?
In computing, Three-tier is a client-server architecture in which the user
interface, functional process logic ("business rules"), data storage and
data access are developed and maintained as independent modules,
most often on separate platforms. The term "three-tier" or "three-layer",
as well as the concept of multi tier architectures, seems to have
originated within Rational Software.
The 3-Tier architecture has the following 3-tiers.
1. Presentation Tier
2. Application Tier/Logic Tier/Business Logic Tier
3. Data Tier
What is n tier architecture? What are its advantages and disadvantages?
An N-tier architecture uses several "tiers" of computers (servers) to interpret
requests and transfer data between one place and another. The 0th tier is at
the source of the data. Each tier is completely independent of all the other
tiers, except for those immediately above and below it. The nth tier only has
to know how to handle a request from the n+1th tier, and how to forward
that request onto the n-1th tier (if there is one), and handle the results of the
request
Presentation Tier
caching service tier
Application server Tier/Logic Tier/Business Logic Tier
integration service tier
Data Tier
The big advantage to using such an architecture is that the client does not
need to know anything about the database. The client is completely
removed from the database. The middle tier (our Frontier server) contains
all the information about how to connect to the database, how to send a
request, what the result will look like, etc; as well as information on how to
send that result back to the client.