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A dynamic document is created by a Web server whenever a browser requests the document. When a request arrives, the Web server runs an application program that creates the dynamic document.

Common Gateway Interface (CGI) is a technology that creates and handles dynamic documents.

CGI is a set of standards that defines how a dynamic document should be written, how the input data should be supplied to the program and how the output result should be used.

CGI is not a new language, but it allows programmers to use any of several languages such as C, C++, Bourne Shell, Korn Shell or Perl.A CGI program in its simplest form is code written in one of the languages supporting the CGI.


This is what all about the CGI for the internet.
Enjoy.....

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File Transfer Protocol (FTP) is the standard mechanism provided by TCP/IP for copying a file from one host to another. The FTP protocol is defined in RFC959. It is further defined in RFC 2227, 2640, 2773 for updated documentation.

In transferring files from one system to another, two systems may have different ways to represent text and data. Two systems may have different directory structures. All of these problems have been solved by FTP in a very simple and elegant way.

FTP differs from other client–server applications in that it establishes two connections between the hosts. One connection is used for data transfer (port 20), he other for control information (port 21). The control connection port remains open during the entire FTP session and is used to send control messages and client commands between the client and server. A data connection is established using an ephemeral port.

The data connection is created each time a file is transferred between the client and server. Separation of commands and data transfer makes FTP more efficient. FTP allows the client to specify whether a file contains text (ASCII or EBCDIC character sets) or binary integers. FTP requires clients to authorise themselves by sending a log name and password to the server before requesting file transfers.

Since FTP is used only to send and receive files, it is very difficult for hackers to exploit.

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The Internet Group Management Protocol (IGMP) is used to facilitate the simultaneous transmission of a message to a group of recipients. IGMP helps multicast routers to maintain a list of multicast addresses of groups. ‘Multicasting’ means sending of the same message to more than one receiver simultaneously. When the router receives a message with a destination address that matches one on the list, it forwards the message, converting the IP multicast address to a physical multicast address. To participate in IP on a local network, the host must inform local multicast routers. The local routers contact other multicast routers, passing on the membership information and establishing route. IGMP has only two types of messages: report and query. The report message is sent from the host to the router. The query message is sent from the router to the host.

A router sends in an IGMP query to determine if a host wishes to continue membership in a group. The query message is multicast using the multicast address 244.0.0.1. The report message is multicast using a destination address equal to the multicast address being reported. IP addresses that start with 1110(2) are multicast addresses. Multicast addresses are class D addresses. The IGMP message is encapsulated in an IP datagram with the protocol value of two. When the message is encapsulated in the IP datagram, the value of TTL must be one. This is required because the domain of IGMP is the LAN. The multicast backbone (MBONE) is a set of routers on the Internet that supports multicasting. MBONE is based on the multicasting capability of IP. Today MBONE uses the services of UDP at the transport layer.

This is what all about the IGMP. The protocols are the set of rules for working. Enjoy.....

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The protocol used to transfer a Web page between a browser and a Web server is known as Hypertext Transfer Protocol (HTTP). HTTP operates at the application level. HTTP is a protocol used mainly to access data on the World Wide Web. HTTP functions like a combination of FTP and SMTP. It is similar to FTP because it transfers files, while HTTP is like SMTP because the data transferred between the client and the server looks like SMTP messages. However, HTTP differs from SMTP in the way that SMTP messages are stored and forwarded; HTTP messages are delivered immediately. As a simple example, a browser sends an HTTP GET command to request a Web page from a server. A browser contacts a Web server directly to obtain a page. The browser begins with a URL, extracts the hostname section, uses DNS to map the name
into an equivalent IP address, and uses the IP address to form a TCP connection to the server. Once the TCP connection is in place, the browser and Web server use HTTP to communicate. Thus, if the browser sends a request to retrieve a specific page, the server responds by sending a copy of the page.

A browser requests a Web page, and the server transfers a copy to the browser. HTTP also allows transfer from a browser to a server. HTTP allows browsers and servers to negotiate details such as the character set to be used during transfers. To improve response time, a browser caches a copy of each Web page it retrieves. HTTP allows a machine
along the path between a browser and a server to act as a proxy server that caches Web pages and answers a browser’s request from its cache. Proxy servers are an important part of the Web architecture because they reduce the load on servers. In summary, a browser and server use HTTP to communicate. HTTP is an applicationlevel protocol with explicit support for negotiation, proxy servers, caching and persistent connections.

This is what all about the HTTP. The protocols are set of rules for working. Enjoy.....

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The browser architecture is composed of the controller and the interpreters to display a Web document on the screen. The controller can be one of the protocols such as HTTP, FTP, Gopher or TELNET. The interpreter can be HTML or Java, depending on the type of document.
The Hypertext Markup Language (HTML) is a language used to create Web pages. A markup language such as HTML is embedded in the file itself, and formatting instructions are stored with the text. Thus, any browser can read the instructions and format the text according to the workstation being used. Suppose a user creates formatted text on a Macintosh computer and stores it in a Web page, so another user who is on an IBM computer is not able to receive the Web page because the two computers are using different formatting procedures. Consider a case where different word processors use different techniques or procedures to format text. To overcome these difficulties, uses only ASCII characters for both main text and formatting instructions. Therefore, every computer can receive the whole document as an ASCII document. Web page.

Web page consists of two parts: the head and body. The head is the first part of a Web page. The head contains the file of the page and other parameters that the browser will use. The body contains the actual content of a page. The body includes the text and tags (marks). The text is the information contained in a page, whereas the tags define the appearance of the document.

Tags :
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Tags are marks that are embedded into the text. Every HTML tag is a name followed by an optional list of attributes. An attribute is followed by an equals sign (=) and the value of the attribute. Some tags are used alone; some are used in pairs. The tags used in pairs are called starting and ending tags. The starting tag can have attributes and values. The ending tag cannot have attributes or values, but must have a slash before the name. An example of starting and ending tags is shown below :

< attribute =" Value" attribute =" Value"> (Starting tag)
<> (Ending tag)
A tag is enclosed in two angled brackets like and usually comes in pairs as and . The starting tag starts with the name of the tag, and the ending tag starts with a backslash followed by the name of the tag. A tag can have a list of attributes, each of which can be followed by an equals sign and a value associated with the attribute.

This is what all about the HTML. The protocols are set of rule for working.

Internet Control Message Protocol (ICMP) The ICMP is an extension to the Internet Protocol which is used to communicate between a gateway and a source host, to manage errors and generate control messages. The Internet Protocol (IP) is not designed to be absolutely reliable. The purpose of control messages (ICMP) is to provide feedback about problems in the communication environment, not to make IP reliable. There are still no guarantees that a datagram will be delivered or a control message will be returned. Some datagrams may still be undelivered without any report of their loss. The higher-level protocols that use TCP/IP must implement their own reliability procedures if reliable communication is required. IP is an unreliable protocol that has no mechanisms for error checking or error control. ICMP was designed to compensate for this IP deficiency. However, ICMP does not correct errors, simply reports them. ICMP uses the source IP address to send the error message to the source of the datagram. ICMP messages consist of error-reporting messages and query messages. The error-reporting messages report problems that a router or a destination host may encounter when it processes an IP packet. In addition to error reporting, ICMP can diagnose some network problems through the query messages. The query messages (in pairs) give a host or a network manager specific information from a router or another host


This is all about ICMP its workin rules and way to working. Enjoy.....

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The evolution of TCP/IP technology has led on to attempts to solve problems that improve service and extend functionalities. Most researchers seek new ways to develop and extend the improved technology, and millions of users want to solve new networking problems and improve the underlying mechanisms. The motivation behind revising the protocols arises from changes in underlying technology: first, computer and network hardware continues to evolve; second, as programmers invent new ways to use TCP/IP, additional protocol support is needed; third, the global Internet has experienced huge growth in size and use. This section examines a proposed revision of the Internet protocol which is one of the most significant engineering efforts so far. The network layer protocol is currently IPv4. IPv4 provides the basic communication mechanism of the TCP/IP suite. Although IPv4 is well designed, data communication has evolved since the inception of IPv4 in the 1970s. Despite its sound design, IPv4 has some deficiencies that make it unsuitable for the fast-growing Internet. The IETF decided to assign the new version of IP and to name it IPv6 to distinguish it from the current IPv4. The proposed IPv6 protocol retains many of the features that contributed to the success of IPv4. In fact, the designers have characterised IPv6 as being basically the same as IPv4 with a few modifications: IPv6 still supports connectionless delivery, allows the sender to choose the size of a datagram, and requires the sender to specify the maximum number of hops a datagram can make before being terminated. In addition, IPv6 also retains most of IPv4’s options, including facilities for fragmentation and source routing. IP version 6 (IPv6), also known as the Internet Protocol next generation (IPng), is the new version of the Internet Protocol, designed to be a full replacement for IPv4. IPv6 has an 128-bit address space, a revised header format, new options, an allowance for extension, support for resource allocation and increased security measures. However, due to the huge number of systems on the Internet, the transition from IPv4 to IPv6 cannot occur at once. It will take a considerable amount of time before every system in the Internet can move from IPv4 to IPv6. RFC 2460 defines the new IPv6 protocol.

IPv6 differs from IPv4 in a number of significant ways :
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• The IP address length in IPv6 is increased from 32 to 128 bits.
• IPv6 can automatically configure local addresses and locate IP routers to reduce configuration and setup problems.
• The IPv6 header format is simplified and some header fields dropped. This new header format improves router performance and make it easier to add new header types.
• Support for authentication, data integrity and data confidentiality are part of the IPv6 architecture.
• A new concept of flows has been added to IPv6 to enable the sender to request special
handling of datagrams.


This is all about the IP Version. Its working description and all that. Enjoy......

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In December 1995, the network working group of IETF proposed a longer-term solution for specifying and allocating IP addresses. RFC 2373 describes the address space associated with the IPv6. The biggest concern with Internet developers will be the migration process from IPv4 to IPv6. IPv4 addressing has the following shortcoming: IPv4 was defined when the Internet was small and consisted of networks of limited size and complexity. It offered two layers of address hierarchy (netid and hostid) with three address formats (class A, B and C) to accommodate varying network sizes. Both the limited address space and the 32-bit address size in IPv4 proved to be inadequate for handling the increase in the size of the routing table caused by the immense numbers of active hosts and servers. IPv6 is designed to improve upon IPv4 in each of these areas. IPv6 allocates 128 bits for addresses. Analysis shows that this address space will suffice to incorporate flexible hierarchies and to distribute the responsibility for allocation and management of the IP address space. Like IPv4, IPv6 addresses are represented as string of digits (128 bits or 32 hex digits) which are further broken down into eight 16-bit integers separated by colons (:). The basic representation takes the form of eight sections, each two bytes in length. xx:xx:xx:xx:xx:xx:xx:xx
where each xx represents the hexadecimal form of 16 bits of address. IPv6 uses hexadecimal colon notation with abbreviation methods.


This is all about the IPv 6 Addressing. Enjoy......

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CIDR is the standard that specifies the details of both classless addressing and an associated routing scheme. Accordingly, the name is slightly inaccurate designation because CIDR specifies addressing as well as routing. The original IPv4 model built on network classes was a useful mechanism for allocating identifiers (netid and hostid) when the primary users of the Internet were academic and research organisations. But, this mode proved insufficiently flexible and inefficient as the Internet grew rapidly to include gateways into corporate enterprises with complex networks. By September 1993, it was clear that the growth in Internet users would require an interim solution while the details of IPv6 were being finalised. The resulting proposal
was submitted as RFC 1519 titled ‘Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy.’ CIDR is classless, representing a move away from the original IPv4 network class model. CIDR is concerned with interdomain routing rather than host identification. CIDR has a strategy for the allocation and use of IPv4 addresses, rather than a new proposal.


This is all about the CIDR - Classless Interdomain Routiong.