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Although the Internet is not a new creation arose 95th year, friendly graphical user interface focused towards ordinary principles of HID (Human Interface Device), enabled the Internet 'suddenly' become very popular and widespread, almost inevitable way of communication. As local networks in addition to its internal protocols like NetBEUI or IPX / SPX or another, to communicate to the world as well as within their infrastructure using TCP / IP protocol and they are an integral part of the Internet. As yet they have some of their characteristics are called INTRANET, or simply the Internet in a small.

The appearance of the Windows 9X and Windows NT operating system, which implements the TCP / IP protocol suite has prompted manufacturers of software for creating client and server applications of all kinds, in which they emphasized the Netscape and IE, if in nothing else, then the well-known mutual competition.

Administrators of local networks have been successfully used TCP / IP suite of protocols (HTTP, FTP, SMTP, POP3, NNTP, and more) to your local area network to enable the exchange of e-mail messages, documents, web access, file transfer, and more. Realized in the form of more physically separate computers as servers or a single server with all these capabilities, along with work stations that can access it, forming a small local Internet - INTRANET.

Intranet is essentially a function of the company, an institution or an organization for its own purposes, but with the possibility of controlled access from the outside and to the outside. As already quite all types of business applications with Microsoft Office or Lotus Domino Web-like, their use is very simple and almost accessible to everyone. To all the local network could act as Internet, the Web server is necessary. Everyone else is able to enrich. The structure of the local network - LAN (Local Area Network), it could look like the following picture.

 Intranet - LAN
Figure 7.5.1 Local network connected to the Internet.  

Network infrastructure, at the picture shown in red is just an illustration of the data flow, not their physical structure (UPS, switch, hub, etc.). Relationship with the world allows the router. As in the above manner local area network becomes the target of every curious in the world, and it is necessary to protect some content locally as opposed to the other in order to promote sales, or made accessible, a peculiar problem that arises is the security of the local system. By placing the 'Firewall' of local users can allow limited access to the Internet, and incoming requests from the Internet can be directed only to certain materials do not contain any trade secrets.

Firewall protection system involves the use of a proxy server to be able to communicate with the Internet. Administration of the firewall will allow the individual port or partially or completely disabled. Part of why we perform the configuration of the router, and part of the award appropriate rights to certain content servers.

As Web technology as the basis of documents and communication is not dependent on the platform on which it is used, and, because of its flexibility to interconnect different systems. Apparently scattered system based on different operating systems and programming support type 'office' can be transformed into a single functional environment.

Which allows all intranet? Almost the same services as the Internet, but at the local level, as a function of successful communication and thus professionalism in all segments of the IT system. 25% of successful global companies already using it and about 50% carried out the implementation. For the other 25% have no hope if they do not focus on the future. Applications for group work (groupware) are relatively new, but the leading producers of software (such as Lotus and Novell) have started to make networking applications where the main communication protocol just HTTP. Successful big companies already have hundreds of different dedicate our own servers with hundreds of thousands of HTML documents on them. HTML as the standard daily in construction and is progressing and offers more options. Integrates text, images and movies in the simplest terms. Classic LAN network become increasingly intranet.

Size of the local network is a relative term. The basic difference between the Internet, intranets large and small intranets in structure and function. Although the concept is basically the same, the difference between mass and class. Broad user intranets tend to offer all things to all people for all reasons, while dimensional intranets, for example, a particular company, focused on the final number of people who require a certain range of possibilities in order to achieve the set goals. The Internet is not owned by any one company or person while the company's intranet, a private network or organization which is accessible by persons authorized to be opposed to the Internet which has access to any person who has appropriate technical capabilities (via modem to a computer at home is sufficient).

Only the introduction of an intranet for every organization poses a security risk but also a necessity in electronic business. Increases the likelihood intentional or accidental incidents because the data can be accessed from any number of locations, and what is the significance of the intranet. People that could cause such security incidents can be alone company employees, cooperation partners, clients, and hackers. However, there is no single tool as the solution to a security problem intranet and protection of the network so that the reduced security risks commonly used firewall, encryption and authentication. The highest security is achieved through a combination of hardware, software, organizational and administrative solutions. And the doorman at the entrance gate and institutions, with clearly defined tasks is part of the quality of security policy.

Computer networks called intranets, therefore, is an independent, internal (at the level of an organization), a computer network that connects customers using Internet technologies. Actually, intranet put a fence around it boundless territory, establishing a 'local' network with controlled access, in which users can interact in the same way as on the Internet. Most often this network consists of one computer organization, and is often built around the World Wide Web interface that allows communication between authorized users regardless of platform or operating system on which they work, in real time.

Each device in the network has its own unique IP address. But the service providers for Internet connection is often not able to provide the entire class to use the address of the user, and in this case resorted NAT (Network Address Translation) mechanism of transferring public address for private use as a bar to any class of computer. For public address said that it is 'external' network, and private addresses that it is 'internal' network. This is usually concerned dedicated device router / firewall that besides translating an IP address has other elements protect internal networks, such as protection from DoS attacks and more. According to the scheme in Figure servers in the internal network. But that does not mean that the NAT device can not be configured to one public address always translates into the same home address, which auto attendant with such address it publicly available. So, it's logical address space is divided into two zones: a public-private-visible and invisible, and using the same physical infrastructure. But public-visible address, to which the public can be connected to a Web server, it remains under the control device that supports NAT and supervising operations. Although the server is publicly available, is further protected. This zone-set of publicly-visible address is called the DMZ - demilitarized zone. Which of the classes used for NAT depends on the router / firewall device. One Windows server with two network cards can be used to monitor the entire NAT with a private A-class, and using Linux server with two or more high-quality network cards and free software support for firewall, Shorewall as software support, we can accomplish an effective and inexpensive NAT-firewall device, and safe when login on it to allow only console.

An intranet is basically a private network institution or firm. Using a firewall can be organized so that it is completely 'invisible' to other participants of Internet, or are only visible to the world some of the possible resources. It all depends on the type of business owners LAN. But it may happen that the network owner has a need to connect with your other subsidiary network or allow a business partner access to part of its network. Such a structure is called a dislocated EXTRANET (EXtended InTRANET) is linked to the main network through existing public network infrastructure, but the overall traffic encrypted.

Extranet is an electronic business connections between organizations based on an open standard Internet protocols. Using an extranet organizations can share private information that is stored and running on their intranets with his business associates. Extranets can be conceptualized as a reciprocal and center. The reciprocal extranet each organization makes your partner access to specific organizations from their own intranet, extranet, while the central one organization allows its business partners access to its information.

If it is a unified functional whole multiple LANs, for the purpose of operating the services of particular units whether a particular service or a common or separate, which again can be as common as a whole monitor LAN, then there is a network of a larger company or campus (CAN - Campus Area Network). When more dislocated LANs interconnected in a single network over an existing public network systems, but the traffic between them is encrypted and used by strong security mechanisms, uses the term VPN (Virtual Private Network), which seeks to easily and inexpensively connect dislocated local business systems. The notebook will use VPN software support for a relationship with with the parent system over the public Internet infrastructure.

Dedicated network system Storage Area Network - SAN, very fast, scalable network for connecting computers provided for data storage (servers with SAS drives in a RAID array for example), usually based on optical networking technology, it can not be strictly classified as LAN, MAN or WAN . Very fast optical communication allowing it to be outside the local network infrastructure, available for several institutions and for different functions. It is better for intranet use NAS (Network Attached Storage) system, a local RAID storage system.

SAN disk offers huge resources for use, but under the supervision of operating system monitoring devices, which means that the file system is used by the operating system monitoring devices to be a file system SAN system. For SOHO (Small Office / Home Office) environment is friendly NAS (Network Attached Storage) system. NAS has its own operating system and hence its own file system that monitors the disks. Windows OS users can not even know what to do with him. Therefore, the system is being installed on the user's specific 'client' software support to us was available. This means that the NAS independent of the operating system (OS) users, but users must have OS software support that will allow communication with the NAS included. So, through the NAS network infrastructure can be used by different OS (Windows, Linux, Mac OS ...), but with the condition that an appropriate program of support for the approach. This is a good deal resembles the Novell NetWare client-server (client-server) concept. In Figure 7.5.1 is shown SAN but one can imagine further environment as if the NAS does not enter into its structure. NAS could be another 'box' that stands by servers, and basically conceived as a server.


IT potent weapon of today is just the Internet. The two most important services offered by the WWW and E-mail. Does anyone remember the B.B.S. (Bulletin Board System)? Still find a few active.

The World Wide Web is now the most powerful and flexible Internet navigation system that exists. To use the WWW to be available on the computer have installed the software support for reading web presentations. It has not been a problem since many of these software tools are offered for free, and market competition makes them all the more powerful and effective.

Electronic mail (e-mail) is a way of communicating electronically between Internet users who have an open e-mail address with an Internet Service Provider (ISP). Very efficient service unquestioned future.

Without of Internet can not imagine doing productive work in any business environment, whether it is a small office, an institution or a full ministry. Since the work in these business environments already can not imagine without local network, its symbiosis with the Internet becomes inevitable. The result is an INTRANET, the Internet in a small completely under local control.

The problem nowadays is of Internet with us most evident in throughput abroad. Just access to all possible knowledge bases of the world should be the strategic orientation of each company if does not want to fall behind in the great race of IT. As the number of Internet users is steadily increasing there is a constant need to expand capacity links that connect users with other countries. It is in the mutual interest.

The opposite of all these networks is the PAN (Personal Area Network). PAN network is limited to just a few meters distance between nodes. Most often it's about communication between small devices (mobile phone, PDA ...) or peripherals (printer) with a PC or notebook (laptop) or between themselves computer using wired, wireless or infrared technology, all in order to satisfy personal needs of the user. In this context, the same could be used for a small accounting firm. These are the SOHO (Small Office / Home Office) environments. Consequently, it can be stated that all those who have a computer at home with additional equipment, have PAN :-).


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