Comparison of DDN and VPN technologies

Advantages of VPN Technology
Security
VPN: very high, protecting the integrity, confidentiality, and non-repudiation of data transmission; security control is in the hands of users;
DDN: relatively high. However, security is built on the trust of the Telecom Department, and there is no security for telecom operators.
Scalability
VPN: Based on the TCP/IP technology, the access method is flexible, as long as the network is reachable, it can be easily expanded.
DDN: Since the support of local operators, expansion is inconvenient.
Investment Cost
VPN: one-time device investment, which does not require monthly operation fees. In the long term, it seems that the cost is greatly reduced.
DDN: the leased line fee is very high. You need to pay an expensive leased line rental fee every month, and you need to invest the router fee in the initial stage.
Support for mobile users
VPN: secure access to internal mobile users on the internet to completely eliminate regional differences. Construct a global virtual private network.
DDN: only the network connected by the leased line is supported. It does not support private network access by internal users who leave the LAN.
Bandwidth
VPN: use various low-cost broadband intervention methods, such as ADSL and Ethernet, generally ranging from 1 ~ 100 M.
DDN: because the price is high, the bandwidth is generally narrower than 2 M ).
Upgrade
VPN: It depends on device upgrades and is very convenient.
DDN: dependent on the telecommunications department.