INTERNET-INTRANET-EXTRANET

 Unit-II 

INTERNET-INTRANET-EXTRANET 

The Internet, intranet, and extranet are the most popular platforms for e-commerce. In Internet is the most common platform for B2C e-commerce; the intranet is most the common for platform for corporate internal management; and the extranet is the most common platform for B2B e-commerce. Network Type Typical Users Access Type of information The Internet Any individual with dial-up access or LAN Unlimited public; no restrictions General public, and advertorial Intranet Authorized employees only Private and restricted Specific, corporate, and proprietary Extranet Authorized groups from collaborating companies Private and authorized outside partners Shared in authorized collaborating groups 

The Internet 

1. The Internet is a public and global communication network that provides direct connectivity to anyone over a local area network (LAN) or Internet Service Provider (ISP). 

2. The Internet is a public network that is connected and routed over gateways. End users are connected to local access providers (LANs or ISPs), who are connected to the Internet access providers, to network access providers, and eventually to the Internet backbone. 

 3. Since access to the Internet is open to all, there is a lack of control that may result in an unruly proliferation of information. 

The Intranet: 

1. An intranet is a corporate LAN or wide area network (WAN) that uses Internet technology and is secured behind company’s firewalls (see security and protection).

 2. The intranet links various servers, clients, databases, and application programs like Enterprise Resource Planning (ERP). Although intranets are developed on the same TCP/IP protocol as the Internet, they operate as a private network with limited access. 

 3. Only authorized employees are able to use it. Intranets are limited to information pertinent to the company and contain exclusive and often proprietary and sensitive information.

4. The firewalls protect the intranets from unauthorized outside access; the intranet can be used to enhance the communications and collaboration among authorized employees, customers, suppliers, and other business partners. 

 5. Since the intranet allows access through the Internet, it does not require any additional implementation of leased networks. This open and flexible connectivity is a major capability and advantage of intranet. Intranets provide the infrastructure for many intrabusiness commerce applications

The Extranet 

 1. An extranet, or “extended intranet”, uses the TCP/IP protocol network of the Internet, to link intranets in different locations. 

 2. Extranet transmission is usually conducted over the Internet, which offers little privacy or transmission security. 3

. Therefore, when using an extranet, it is necessary to improve the security of connecting portions of he Internet. This can be done by creating tunnels (see paragraph on security and protection) of secured data flows, using cryptography and authorization algorithm. 

 4. The Internet with tunneling technology is known as a virtually private network (VPN). 

5. Extranets provide secured connectivity between corporation’s intranets and the intranets of its business partners, material suppliers, financial services, government, and customers. 

 6. Access to intranets is usually limited by agreements of the collaborating parties, is strictly controlled, and is only available to authorized personnel. 

 7. The protected environment of the extranet allows groups to collaborate, sharing information exclusively, and exchanging it securely. 

 8. Since an extranet allows connectivity between businesses through the Internet, it is an open and flexible platform suitable for supply chain management. 

 9. To increase security, many companies replicate the database they are willing to share with their business partners and separate them physically from their regular intranets.

Benefits or advantages of firewalls: 

1. Internet firewalls allow the network administrator to define a centralized ‘choke point’ that keeps unauthorized users such as hackers, crackers, vandals and spies and providing protection from various types of routing attacks. 

2. Firewalls offer a convenient point where internet security can be monitored and alarms generated. 

3. An internet firewall is a logical place to deploy a network address translator (NAT) that can help alleviate the address space shortage and eliminate the need to re-number when an organization changes its ISP’s. 

4. An internet firewall is the perfect point to audit or log internet usage.

5. An internet firewall can also offer a central point of contract for information delivery service to customers. 

Types of firewalls: 

1. Application Gateways: the first firewalls were application gateways, and are sometimes known as proxy gateways. These are sun with special software to act as a proxy server. 

2. Packet filtering: packet filtering is a techniques where by routers have ACLs(Access Control Lists) turned on. By default, a router will pass all traffic sent it, and will do so without any sort of restrictions. 3

. Hybrid Systems: in an attempt to marry the security of the application layer gateways with the flexibility and speed of packet filtering, some vendors have created systems that use the principles of both.

SMTP (Simple Mail Transfer Protocol): 

Simple Mail Transfer Protocol (SMTP) is a protocol designed to transfer electronic mail reliably and efficiently. SMTP is a mail service modeled on the FTP file transfer service. SMTP transfers mail messages between systems and provides notification regarding incoming mail. SMTP is independent of the particular transmission subsystem and requires only a reliable ordered data stream channel. 

 An important feature of SMTP is its capability to transport mail across networks, usually referred to as “SMTP mail relaying”. A network consists of the mutually-TCP-accessible hosts on the public Internet, the mutually-TCP-accessible hosts on a firewall-isolated TCP/IP Intranet, or hosts in some other LAN or WAN environment utilizing a non-TCP transport-level protocol. 

Using SMTP, a process can transfer mail to another process on the same network or to some other network via a relay or gateway process accessible to both networks. In this way, a mail message may pass through a number of intermediate relay or gateway hosts on its path from sender to ultimate recipient. 3.FTP(File Transfer Protocol): 1. File Transfer Protocol (FTP) enables file sharing between hosts. 

FTP uses TCP to create a virtual connection for control information and then creates a separate TCP connection for data transfers. 3. The control connection uses an image of the TELNET protocol to exchange commands and messages between hosts. The key functions of FTP are: 8 

1) to promote sharing of files (computer programs and/or data); 

2) to encourage indirect or implicit (via programs) use of remote computers; 

3) to shield a user from variations in file storage systems among hosts; and 

4) to transfer data reliably and efficiently. FTP, though usable directly by a user at a terminal, is designed mainly for use by programs. 

FTP control frames are TELNET exchanges and can contain TELNET commands and option negotiation. However, most FTP control frames are simple ASCII text and can be classified as FTP commands or FTP messages. FTP messages are responses to FTP commands and consist of a response code followed by