ZyXEL Communications Prestige 128Plus, User Manual, Page: 134 / 203

Prestige 128+ ISDN Router
10-4 L2TP
The remote user dials in to an ISP. A tunnel is then set up from the ISP across the
Internet to a corporate gateway server. Once the tunnel is set up, mobile users
access the corporate network as if they had dialed directly into that network.
10.3.3 Internet-based tunnel process:
1. The remote user dials the ISP and the ISP collects logon information from the
user.
2. The ISP inspects the user name in the logon information and determines whether
a virtual dial-up service is required. The ISP maintains a database (endpoint
table) for a corporation that associates the user name (the realm or domain name)
with a specific endpoint (i.e., the corporate gateway).
3. The ISP establishes a tunnel by contacting the corporate gateway.
4. The authentication information that was initially collected from the remote user
in Step 1 is forwarded to the corporate gateway. Now the remote user is
authenticated by the corporate LNS.
5.
Now the user has an end-to-end PPP link.
At this point, the connection between the remote user and the corporate network
is like any PPP connection. When the ISP receives frames from the remote user
over the PPP link, they are encapsulated in L2TP, and forwarded over the tunnel
to the LNS. The corporate gateway receives these frames, strips L2TP, and
processes them as normal incoming PPP frames.
10.4 The Prestige and L2TP
We will describe scenarios where we use the Prestige as a LNS and/or LAC for
both outgoing and incoming calls.