Operation Manual

Connecting to the Internet
NT/MPRI – 3 Configuration and Operation of the NT/MPRI: The Basics 40
3.5 Connecting to the Internet
The NT/MPRI creates a PPP connection to what is called a PoP (Point of
Presence) of an Internet provider. The connection between the PoP and
your local network is established either via an ISDN dial-in connection,
which is established and cleared automatically depending on the
amount of data transferred; via an ISDN leased line or an ADSL connec-
tion. The NT/MPRI routes the data packets between your local network
and the router of your Internet provider.
For connections to the Internet with the NT/MPRI, either access with a
dynamic IP address or access with a static IP address can be used.
The connection between the NT/MPRI and the PoP of your Internet pro-
vider is generally initiated by the end at which data are awaiting trans-
mission. This is imperative for certain applications like the E-mail serv-
er, which use SMTP.
In order for incoming calls to be recognized by your Internet provider,
and assigned to a configured call destination, the local router also can
require either an “Authentication at Local Site” with PAP or CHAP or the
D-channel number transmitted by the remote site.
If the Internet provider requires authentication from your site, simply
activate the function “Authentication at Remote Site” in the NT/MPRI.
Here, too, the PAP and CHAP procedures are supported.
Access with a Dynamic IP Address
Accesses with a dynamic IP address are generally more economical
than accesses with a static IP address, as an Internet-compliant IP ad-
dress is assigned by the Internet provider each time a connection is es-
tablished. This IP address is supplied to the NT/MPRI during PPP nego-
tiation. In order to guarantee access to the Internet for all computers in
the local network, “IP Masquerading” must be activated in the call des-
tination settings. Masquerading is the process of hiding an internal
network and mapping all IP addresses in the LAN to a single IP address
so that the same IP address is used for all requests from the Internet.
The connection is initiated only by the NT/MPRI.
As an example, this section describes access via UUNet and ISDN as
well as UUNet and ADSL. In both cases a dynamic IP address is as-
signed each time a connection is established to UUNet.
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