Internet concepts 1. What is client server architecture?

1. 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.

2. 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.

3. 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. 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

5. 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.

6. 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.

7. 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 ).

8. 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.

9. 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 connection-oriented 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.

10. 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;

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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)

21. 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 ...

22. 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.

23. 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

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. 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 Tier2. Application Tier/Logic Tier/Business Logic Tier3. Data Tier

31. 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.