Classification Of Vpn - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
which may not only overload the system but also decrease the scalability. The
introduction of tunneling latency may incur such problems as PPP session timeout in
time sensitive LCP and NCP negotiations of PPP. On the contrary, layer 3 tunnel
terminates within ISP gateway, and PPP session terminates at NAS; thus user gateway
needs not to manage and maintain status of each PPP session, and thereby reduces
system load.
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).

1.3 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:
I. 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.
II. 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.
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Chapter 1 VPN Overview