User Manual - Configuration Guide (Volume 3)
Versatile Routing Platform Chapter 1
VPN Overview
1-1
Chapter 1 VPN Overview
Virtual Private Network, VPN for short, is one of the rapidly developin g technologies
along with the development of Internet in recent years. In the wake of enterprise
expansion, widely located clients and increasing partners, modern enterprises mak e
more and more use of Internet resources to conduct such activities as promotion,
marketing, after-sale service, training and cooperation. Many enterprises tend to
replace their private data network with Internet. Like the current private networks of
enterprises, VPN established on the public network is safe, reliable and manag eable.
This kind of logic network, which uses Internet to transmit private information, is called
VPN.

1.1 VPN features

VPN features the following:
1) Different from conventional networks, VPN does not actually exist; it is a virt ual
network formed by resource configuration of the existing network .So th e c arr iers
can make use of their spare network resources to provide VPN service and profit
from the network resources to the maximum extent.
2) VPN is specially used for specific enterprises or user groups. It makes no
difference to VPN users in using VPN and conventional private networks.
However, VPN is actually established on the public network or on the networks of
other carriers. In order to meet the requirements of private networks, some
technical means must be adopted to ensure the resource independence between
VPN and the public network or its bearing network. That is, the resources of a VPN
are not usually allowed to be used by other VPNs on the bearing network or
network members not belonging to the VPN. Another point is that VPN should be
safe enough, that is, the information from VPN users should not go out of VPN and
the external users can not generally access the information in VPN. T he above
mentioned two problems are the main problems to be solved in VPN protoco l.
3) VPN is not a s imple higher-level service. Network interconnection between the
users of private networks is required for VPN serv ice, including creation of VPN
internal network topology, route calculation, access and exit of members. So VPN
technology is much more complicated compared with the mechanism of various
ordinary point-to-point applications.
VPN has the following advantages:
1) With VPN, reliable and safe connection can be established between remote users,
branches of companies and commercial partners, and between suppliers a nd
companies. And security of data output can be ensured. The advantage is
especially significant in the integration of E-commer ce or financial network with the
communication network.
2) With VPN, IP network of lower cost can be used to transmit data stream so as to
downsize the cost to establish Intranet and to make effective use of the cur rently
idle network resources.
3) VPN users can be added and deleted with only relative configurations and without
changing hardware, making VPN applications highly flexible.
4) With VPN, a great amount of maintenance personnel of private network of the
enterprises can engage in more important services, leaving th e VPN management
and maintenance of ISP or other network companies.