VPN's "life" Exploration

VPN is an extension of a private network, that is, a temporary and secure private network connection created on a private and public network (usually the Internet. Currently, VPN is mainly used in the following three aspects: First, remote user access is achieved through the Internet, and VPN can support secure remote access to the enterprise LAN through the Internet; the second is network interconnection through the Internet, which can be achieved through leased line connection and dial-up connection respectively, in this way, the connection established with the local ISP and the Internet can be created between the Enterprise Branch and the enterprise side router. The third is to connect the enterprise's internal network computer, VPN servers are used to connect to the entire enterprise LAN and ensure data security. There are four VPN tunnel protocols: point-to-point tunnel protocol PPTP, L2 tunnel protocol L2TP, network layer tunnel protocol IPSec and SOCKS v5. 1. PPTP: PPTP is a new enhanced security protocol developed on the basis of PPP. It allows remote users to access the enterprise network through direct connection to the Internet or other networks through the ISP. Due to its low performance, the PPTP protocol has been basically eliminated and is no longer used in VPN products. 2. L2TP: Unlike PPTP, it only requires a dedicated L2TP tunnel for point-to-point connection. Combining the advantages of the PPTP protocol and the L2 forwarding L2F protocol, L2TP can tunnel PPP packets through various network protocols, including ATM, SONET, and FR. However, L2TP does not have any encryption measures. It is used in conjunction with the IPSec protocol to provide tunneling verification. 3. IPSec: an extensive and open security protocol. It works at the network layer and provides all data protection and transparent secure communication at the network layer. The IPSec protocol can be set to run in two modes: tunnel mode and transmission mode. In tunneling mode, IPSec encapsulates IPv4 packets in Secure IP frames. The transmission mode protects the end-to-end security and does not hide route information. In addition to packet filtering, this technology does not specify other access control methods. It is difficult to handle NAT-based access to public networks. Therefore, it is most suitable for building a VPN between a trusted LAN and a LAN. 4. SOCKS v5: works on the Session Layer and serves as the basis for establishing a highly secure VPN. SOCKS v5 protocol has advantages in access control, so it is suitable for VPN with high security. The disadvantage is that the performance is worse than the low-level VPN protocol, and more complex security management policies must be developed. This Protocol is most suitable for the connection mode from the client to the server and for external Network VPN And Remote Access VPN.