3Com Switch 8800 Family IPsec Module Configuration and Command reference Guide

Classification of VPN 101
Normally, layer 2 Tunneling protocols and layer 3 Tunneling protocols are used
separately. The reasonable combination of two types of protocols, however, may
deliver better security and functions (e.g. using L2TP and IPsec together).
Classification of VPN IP VPN means emulating private line service of WAN (e.g. remote dial-up, DDN,
etc.) over IP networks (including the Internet or dedicated IP backbone). IP VPN is
classified as follows:
Classified by operation mode
1 CPE-based VPN (Customer Premises Equipment based VPN)
Users not only have to install expensive devices and special authentication tools,
but also maintain complex VPN (e.g. channel maintenance, bandwidth
management, etc.). Networking in this way features both high complexity and low
service scalability.
2 NBIP-VPN (Network-based VPN)
The maintenance of VPN (permitting users to conduct service management and
control to some extent) is conducted by ISP, and all functions are implemented at
network device side, so as to reduce users’ investment, reinforce the flexibility and
scalability of services, and bring new incomes to ISP.
Classified by service application
1 Intranet VPN
Intranet VPN interconnects points distributed inside an enterprise by making use
of public network. It is an extended or substitute form of traditional private
network or other enterprise network.
2 Access VPN
Access VPN allows remote users like staff traveling on business and remote small
offices to establish private network connections with the intranet and extranet of
their enterprise over a public network. Access VPN provides two types of
connections: client-initiated VPN connection and NAS-initiated VPN connection.
3 Extranet VPN
Extranet VPN extends an enterprise network to suppliers, cooperators and clients
by using VPN, allowing different enterprises to construct VPN over public
networks.
Classified by networking model
1 VLL
Virtual Leased Line (VLL) is emulation to traditional leased line services. By
emulating leased line over IP networks, it provides asymmetric and low cost
"DDN" service. From the view of end users of VLL, it is similar to traditional leased
lines.
2 VPDN