VPNs and their functions

Posted by Thomas Tanner on January 24th, 2020

At the link layer, L2TP and PPTP data tunneling protocols can be used, which use authorization and authentication.

PPTP

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. In practice, PPP and remains the communication protocol of the PPTP connection session. PPTP creates a tunnel through the network to the <a href="https://chrome.google.com/webstore/detail/veepn-unlimited-free-fast/majdfhpaihoncoakbjgbdhglocklcgno?hl=en/"> VeePN vpn</a> server of the recipient and transmits through it the PPP packets of the remote user. Server and production stations use a virtual private network and do not pay attention to how much safe or accessible is the global network between them. End a connection session by server driven, unlike specialized remote access servers, allows LAN administrators do not allow remote users to leave the system Windows Server Security.

Although the competence of the PPTP protocol applies only to devices operating under running Windows, it gives companies the ability to interact with existing network infrastructures and not harm your own security system.

Thus, 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 server NT. At the same time, the company does not have to spend large amounts on organization and maintenance a pool of modems that provides remote access services.

Next, the work of RTRT is considered. PPTP encapsulates IP packets for transmission over an IP network.

PPTP clients use the destination port to create the tunnel control connection. This the process takes place at the OSI model transport layer. After creating the tunnel, the client computer and the server begins to exchange service packets. In addition to the <a href="https://en.wikipedia.org/wiki/Point-to-Point_Tunneling_Protocol/"> PPTP</a> control connection, to ensure the channel is working, a connection is created for forwarding through the tunnel data. Encapsulating data before forwarding through a tunnel is slightly different than in normal transmission. Encapsulating data before sending it to the tunnel involves two steps:

1. First, the PPP information part is created. Data flows from top to bottom, from OSI application layer to channel.

2. Then the received data is sent up the OSI model and encapsulated upper level protocols.

Thus, during the second pass, data reaches the transport layer. However information cannot be sent as intended, as the link layer is responsible for this OSI Therefore, PPTP encrypts the packet payload field and takes over the functions of the second tiers typically owned by PPP, i.e. Adds a PPP header and ending to the PPTP packet. On thethis creates the link layer frame.

Next, PPTP encapsulates the PPP frame in the Generic Routing Encapsulation (GRE) packet, which belongs to the network layer. GRE encapsulates network layer protocols such as

IPX, AppleTalk, DECnet, to ensure the possibility of their transmission over IP networks. However GRE is not. It has the ability to establish sessions and protect data from intruders. For This uses PPTP's ability to create a connection for tunnel management. Application GRE as an encapsulation method limits the PPTP scope to IP networks only.

After the PPP frame has been encapsulated in a frame with the GRE header, it is executed encapsulation in a frame with an IP header. IP header contains sender and receiver addressespackage. In conclusion, PPTP adds a PPP header and ending.

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