Netopia Firmware 4000-Series - Manual (Page 104)

4-2 Firmware User Guide
The Netopia Firmware Version 5.4 can be used in VPNs either to initiate the connection or to answer it. When
used in this way, the routers are said to be tunnelling through the public network (Internet). The advantages are
that, like your long distance phone call, you don't need a direct line between one computer or LAN and the
other, but use the local connections, making it much cheaper; and the information you exchange through your
tunnel is private and secure.
Tunneling is a process of creating a private path between a remote user or private network and another private
network over some intermediate network, such as the IP-based Internet. A VPN allows remote offices or
employees access to your internal business LAN through means of encr yption allowing the use of the public
Internet to look “vir tually” like a private secure network. When two networks communicate with each other
through a network based on the Internet Protocol, they are said to be tunneling through the IP network.
Unlike the phone company, private and public computer networks can use more than one protocol to carr y your
information over the wires. Three such protocols are in common use for tunnelling, Point-to-Point Tunnelling
Protocol (PPTP), Ascend Tunnel Management Protocol (ATMP), and IP Security (IPsec). The Netopia Router can
use any one.
■ Point-to-Point Tunneling Protocol (PPTP) is an extension of Point-to-Point Protocol (PPP) and uses a client
and ser ver model. Netopia’s PPTP implementation is compatible with Microsoft’s and can function as
either the client (PAC) or the ser ver (PNS). As a client, a Netopia R-series router can provide all users on a
LAN with secure access over the Internet to the resources of another LAN by setting up a tunnel with a
Windows NT ser ver running Remote Access Ser vices (RAS) or with another Netopia Router. As a ser ver, a
Netopia R-series router can provide remote users a secure connection to the resources of the LAN over a
dial-up, cable, DSL, or any other type of Internet access. Because PPTP can create a VPN tunnel using the
Dial-Up Networking (DUN) (see
"Dial-Up Networking for VPN" on page 4-14) utility built into Windows 95,
98, or NT, no additional client software is required.
■ Ascend Tunnel Management Protocol (ATMP) is the protocol that is implemented in many Ascend routers.
ATMP is a simple protocol for connecting nodes and/or networks together over the Internet via a tunnel.
ATMP encapsulates IP or other user data without PPP headers within General Routing Encapsulation (GRE)
Transit Internetwork
Logical
Equivalent
Virtual Private Network