One of the last terms included in the networking environment is the word Extranet. An Extranet is nothing more than a virtual private network, using the Internet as a means of transporting information between the nodes of our private network. Thanks to an Extranet you can join two Intranets located anywhere in the world.
Traditionally, transport lines such as X.25, point-to-point connections or, more recently Frame-Relay, were used to link the networks of a corporation located in different cities, countries, and continents. An extranet can consider as part of a company's intranet that extended to users outside the company. It has also been described as a "state of mind" in which the Internet perceived as a way of doing business with other companies as well as selling products to its customers. The same benefits that HTML, HTTP, SMTP, and other Internet technologies have given the Network and corporate intranets now seem to accelerate business between companies. The advantages of an Extranet are mainly the reduction of costs and the high reliability that there is always an available link.
Reliability and low cost: Traditionally private networks implemented with dedicated lines between each headquarters of the company or corporation. A router capable of directing LAN traffic from one headquarters to the LAN of the nearest headquarters installed at each of these locations, always through the data transmission lines (WAN). In the absence of redundancy, the failure of a link prevents communication between sites. A more reliable system is to use a fully meshed network. That is, each headquarters communicates with each other through a link. It makes communications much more expensive, both in the rental of lines and in the cost of routers. Naturally, the additional cost implies an improvement in reliability: The failure of a link does not prevent communication to the other sites because alternative routes can establish. With an Extranet, it is only necessary that each site has a link, usually local, to an Internet access provider. Once on the Internet, the data will be transmitted to the destination headquarters. Naturally, the weak point is the link to the access provider, but the multiple alternative routes offered by the Internet ensure the existence of alternative routes. Therefore, it necessary for each site to have a reliable link to its provider.
With the extranet, reliability gained concerning the use of dedicated lines and costs reduced concerning the use of several dedicated lines (mesh). In many cases, due to international link costs, these options are virtually unfeasible. Only large multinationals can afford this luxury. For the rest of the companies, there is no better alternative, from the economic point of view than an extranet.
Security in Extranets: Firewalls and proxies allow you to protect extranets from unauthorized access by hackers and crackers — encryption used in packages that cross the Internet from one location to another. Authentication is also essential for services such as email. Hence the importance of systems such as SSL (Secure Socket Layer), capable of encrypting information packets and transferring them securely as well as the use of the PPTP protocol (Point-to-Point Tunneling Protocol) which is one of the methods to create a secure "tunnel" through the Internet which is an extension of the famous PPP. PPPT allows establishing multiprotocol virtual private networks over the Internet. The protocols that PPPT currently supports are IP, IPX, NetBIOS, and NetBEUI, that is, most of the protocols used in local area networks. As an extension of the PPP protocol, PPPT limited to point-to-point communications. However, several point-to-point communications can replace a multipoint. Based on the client-server model, it is necessary that the destination network also supports PPPT. Microsoft, with Windows NT Server 4.0 has been the first manufacturer to support this protocol. Applying all these techniques guarantees the security of the Extranet.
Disadvantage of Extranets
The delay in communication. The exponential growth of the Internet does not make it suitable for delay-sensitive traffic. For example, videoconferencing or telephony over the Internet, at present, do not offer the adequate quality of enterprise level. On the other hand, the Internet is a very suitable means for transporting email, file transfer, access to remote databases, etc. that is, traffic not sensitive to delays. Protocols indeed investigated that allow the necessary bandwidth to reserved for each service, but it takes years until it becomes operational and viable. Therefore, it is not advisable to use extranets as an internal telephone or videoconference network.
Purposes and Uses of An Extranet
As Intranets spread within corporations, it seems natural that if there is any need for information exchange between them: customers/suppliers, business partners, etc., the need to interconnect them through the Internet considered.
There is some inertia not to replace traditional EDI systems with "EDI Systems over the Internet", for some a vision of what an extranet is, especially for reasons of security and robustness of the first against a lack of confidence and normalization in the second. However, there is a field where the use of an extranet seems natural: in those EDI systems that need to reach a mass market. In this way, allowing you to launch an order or view the result of it from a Web browser, known as the Web-EDI model, does not require any specialized software, type EDI station, to enter the world of commercial exchanges without papers. Thus, it is feasible to extend EDI solutions to environments such as booksellers and publishers, pharmacies and pharmaceutical laboratories, etc.; where one of the parties has low investment capacity and is very numerous. However, exchanges of unstructured information such as email, news, etc .; between organizations that have an Intranet built or not, and connect through the Internet; It is as old as the existence of the Internet itself. From this point of view, extranets have always been part of the Internet.
Companies can use an extranet to:
• Exchange large volumes of data using Electronic Data Interchange (EDI).
• Share catalogs exclusively with wholesalers or people within your business or branch.
• Collaborate with other companies in joint development efforts.
• Develop and use training programs with other companies.
• Provide or access services offered by a company to another group of companies, such as the application of online banking managed by a company on behalf of banks affiliated with it.
• Share news of common interest exclusively with partner companies.
Microsoft supports the Point-to-Point Tunneling Protocol (PPTP) and is working with American Express and other companies on an Open Buying on the Internet (OBI) standard. Lotus Corporation is promoting its Notes group software product as a program well suited for use in extranets.