The channel layer can use the L2TP and PPTP data tunneling protocols, which use authorization and authentication.


PPTP.
Currently, the most common VPN Protocol is the point-to-Point tunneling Protocol (PPTP). It was developed by 3Com and Microsoft to provide secure remote access to corporate networks via the Internet. PPTP uses the existing open TCP/IP standards and relies heavily on the legacy point-to-point Protocol (PPTP). In practice, RRR remains the communication Protocol of the rrtr connection session. Rrtr creates a tunnel through the network to the recipient's NT server and passes RRR packets of the remote user over it. The server and workstation use a virtual private network and do not pay attention to how secure or accessible the global network is between them. Server-initiated termination of a connection session, unlike specialized remote access servers, allows local network administrators to prevent remote users from leaving the Windows Server security system.


Although the rrtd Protocol only applies to devices running Windows, it provides companies with the ability to interact with existing network infrastructures and not harm their own security system. In this way, a remote user can connect to the Internet using a local provider over an analog telephone line or ISDN channel and establish a connection to the NT server. At the same time, the company does not have to spend large amounts on organizing and maintaining a modem pool that provides remote access services.


Next, the work of the rrtr is considered. PPTP encapsulates IP packets for transmission over an IP network. PPTP clients use the destination port to create a tunnel management connection. This process occurs at the transport layer of the OSI model. After the tunnel is created, the client computer and server start exchanging service packages. In addition to the PPTP control connection that makes the channel work, a connection is created for sending data through the tunnel. Data is encapsulated before being sent through a tunnel in a slightly different way than during normal transmission. Data encapsulation before being sent to the tunnel includes two stages:


First, the PPP information part is created. Data flows from top to bottom, from the OSI application layer to the channel layer.
The resulting data is then sent up the OSI model and encapsulated by upper-level protocols.
Thus, during the second pass, the data reaches the transport level. However, the information cannot be sent to its intended destination, since the OSI channel layer is responsible for this. Therefore, PPTP encrypts the payload field of the packet and takes over the second-level functions that usually belong to PPP, i.e. it adds a PPP header and ending to the PPTP packet. This is the end of creating a channel-level frame.


Next, PPTP encapsulates the PPP frame in a Generic Routing Encapsulation (GRE) package that belongs to the network layer. GRE encapsulates network layer protocols, such as IPX, AppleTalk, and DECnet, to enable their transmission over IP networks. However, GRE does not have the ability to set sessions and protect data from hackers. This uses the ability of PPTP to create a connection for managing the tunnel. Using GRE as an encapsulation method restricts the PPTP action field to IP networks only.


After the PPP frame has been encapsulated in the frame with the GRE header, it is encapsulated in the frame with the IP header. The IP header contains the addresses of the sender and recipient of the packet. In conclusion, PPTP adds a PPP header and ending.


The sending system sends data through a tunnel. The receiving system deletes all service headers, leaving only the PPP data.


L2TP
In the near future, the number of virtual private networks deployed based on the new layer 2 tunneling Protocol (L2TP) is expected to grow.


L2TP was created by combining the PPTP and l2f (Layer 2 Forwarding) protocols. PPTP allows you to send PPP packets through the tunnel, and L2F allows you to send SLIP and PPP packets. In order to avoid confusion and problems of interaction of systems in the telecommunications market, the Internet Engineering Task Force (IETF) Committee recommended that Cisco Systems combine PPTP and L2F. it is generally agreed that the L2TP Protocol combines the best features of PPTP and L2F.the Main advantage of L2TP is that this Protocol allows you to create a tunnel not only in IP networks, but also in such as ATM, X. 25 and Frame Relay. Unfortunately, the L2TP implementation in Windows 2000 only supports IP.


L2TP uses the UDP Protocol as transport and uses the same message format for both tunnel management and data forwarding. L2TP in the Microsoft implementation uses UDP packets containing encrypted PPP packets as control messages. Delivery reliability is guaranteed by controlling the sequence of packages.


The functionality of PPTP and L2TP is different. L2TP can be used not only in IP networks, but service messages use the same format and protocols to create a tunnel and send data over it. PPTP can only be used in IP networks, and it needs a separate TCP connection to create and use the tunnel. L2TP over IPSec offers more security levels than PPTP, and can guarantee almost 100 percent security of important data for the organization. L2TP features make it a very promising Protocol for building virtual networks.

Harnessing the full potential of VPN technology offers many benefits. In all, regarding privacy, protection and accessibility on the Internet, VPN is simply unrivaled. Although this technology has evolved over the years, some of its aspects are still far from perfect. The disadvantages for each user will be different, but usually they are related to location, Internet channel and other factors.

VPN technology allows you to send encrypted data over unencrypted networks. In addition, it provides us with a confidential and secure web browsing and provides many other important advantages. Compared to a web proxy, VPN provides a greater degree of security on the Internet

Modern technologies allow you to access the Internet so that you don’t know where you are from and leave no traces on the Internet. For this, there is a service such as vpn that encrypts your IP address and it is not possible to calculate your IP address. This is good because if you need to go secretly, then turn on vpn, change the country and freely go there where it was impossible. Everything is simple and clear.

VPN allows you to create a virtual network as a local network but computers are not physically connected to each other.
Convenience lies in the fact that you can create an analogue of the local network between the computers of users from different countries and continents. The only negative is that such a network will not work without an Internet connection. But today, most online operators offer consistent and quality access to the World Wide Web. This is a high quality in the development of local networks and the careful organization of corporate networks.
At this stage, this direction is very popular. More and more companies are paying attention to their own VPN with all its capabilities. Of course, cash investments will be an important component of the success and quality of such a technology. You can browse the web anonymously and securely. During your surfing the Internet, your data will be encrypted and therefore impossible to download. Using VPN 翻牆 you can download torrent files without risk and can also circumvent censorship geographically thanks to a wide selection of IP addresses. You can also access all websites and blocked networks in your country. You can unlock the content of any video streaming site.

Currently, the most common VPN protocol is
Point-to-Point Tunneling Protocol - PPTP. Designed by him
3Com and Microsoft to provide secure remote access to
corporate networks over the Internet. PPTP leverages existing open TCP / IP standards
and relies heavily on the legacy PPP point-to-point protocol.