3Com 10014299 manual Basic Networking, Applications of VPN, Classification of IP

598CHAPTER 42: CONFIGURING VPN

	The VPN with service quality guarantee can provide different levels of service
	quality guarantees for users by charging for different services.
Basic Networking	An enterprise that has an intranet established with VPN is shown in the following
Applications of VPN	figure.
	Figure 178 Schematic diagram of VPN networking

	Remote user
	PSTN/ISDN
	PC	Internet	POP
		POP	Headquarters
	Partner		Internal server
	In this configuration, the users who need the internal resources of enterprises, can
	access the POP (Point of Presence) server of local ISP via PSTN or ISDN, and further
	access the internal resources of the enterprises. Traditional WAN construction
	techniques only supply the service with the aid of leased line between them. After
	a VPN is established, the remote users and the clients in other places can access
	internal resources of enterprises even if they do not have the Internet access
	authority given by local ISP.
	VPN services of enterprises only require a server supporting VPN (a Windows NT
	server or a router). After connecting the local POP server via PSTN or ISDN, the
	users who want a resource directly call the remote servers of enterprises (VPN
	servers). The access server of ISP along with the VPN server accomplishes the call
	process.
Classification of IP	IP VPN is the emulation of leased line services (remote dial-up and DDN) of WAN
VPN	equipment using IP facilities (including public Internet or private IP backbone
	network). IP VPN classification is based on:

■Operation Mode

■Tunnel Protocols

■Service Purpose

■Networking Model

Operation Mode VPNs can be CPE- or network-based. CPE-based VPN's require installation of networking and authentication equipment to support establishment of the VPN. It requires configuration and administration of WAN resources and bandwidth management.

In a network-based VPN, the maintenance of VPN is allocated to the ISP, although users are allowed to manage and control services to some extent. VPN functions are mainly fulfilled on the equipment at the network side. This type of service reduces the investments of the users, increases the flexibility and scalability of services, bringing profits to the service providers.