Dial-Up Networking

Reference Manual

HOW TO use NAT32 Dial-Up Networking.

NAT32 Version 1.8 (Build 1014 and later) contains advanced Dial-Up Networking support based on the Microsoft RAS API. Previous versions used the Microsoft Wininet API, which had several restrictions and bugs. The behaviour of the NAT32 Dialer is controlled by two distinct sets of variables: the master dialer variables and the interface-specific dialer variables.

Master Dialer Variables

Master Autodial is the master autodial switch. When this variable is 0, no autodial will take place, even if autodial is enabled on one or more PPP Client interfaces.

Autodial Default Connection is the name of the connection to be auto-dialled if no other connection name was specified. This variable defaults to the Windows Default Connection name as specified in the Internet Explorer settings on your computer. The global dialer variables can be viewed and modified using the autodial command.

Interface-specific Dialer Variables

Autodial controls autodialing on a specific PPP Client interface.

Autodial Connection is the name of the connection to be auto-dialled on this particular PPP Client interface. The interface-specific dialer variables can be viewed and modified using the dialcfg command.

Any connection can be dialled or disconnected at any time by using the dial or hangup commands. However, NAT32 will only bind to a connection if a PPP Client interface was configured for the particular Windows Dial-Up Networking Interface over which the connection is established. On Windows 2000 and higher platforms, there exists no way of specifying that a connection use a particular NDISWANIP Interface.

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Advanced Features

Multiple connections can be in place at any given time in order to boost Internet throughput. Booster connections can be dialed automatically when total load reaches a certain level for a certain period of time. The booster connections can also be disconnected automatically as the total load decreases.

Bandwidth Aggregation is supported (see the setis command), allowing multiple connections to be shared by all private machines, or certain connections to be reserved for use by specific private machines or subnets. Because of this route selection by source address capability, NAT32 bandwidth aggregation is superior to other forms of connection aggregation such as Multilink, which require ISP support and which cannot allocate bandwidth dynamically.

Keepalive is enabled per default and ensures that a connection, once established, is not disconnected when idle. This may result in excessive call charges in regions with timed local calls, so the command:

kill active

can be used to disable the feature.

An alternative keepalive method is to issue the command:

alive [off | minutes]

The alive thread will then regularly send a UDP packet to 137.92.11.80 (a non-existant Internet address) in order to force dialing or to keep an existing connection connected.

Script files are supported which allow user-defined actions to be carried out before a connection is dialled (dialup.txt) and after a connection has been established (connect). Similarly, file hangup.txt is executed before a hangup takes place and file disc is executed after a connection has been disconnected.

NDISWANIP Support

Whereas Windows 9X and NT4 support a static number of PPP Client and Server interfaces, Windows 2000 and higher supports a variable number of NDISWANIP interfaces. The implication of this is that NAT32 must recalculate interface bindings at runtime, i.e. when connections are established. NAT32 Build 1020 and higher therefore monitors the relevant TCP/IP Registry settings and recalculates all PPP Client Interface bindings whenever Windows changes those settings. The binding for an established connection remains fixed for the duration of that connection, but subsequent connections may use totally different NDISWANIP Interfaces. NAT32 will always attempt to bind an NDISWANIP Interface to the NAT32 interface with a matching connection name, but this is not possible if the connection was already in place when NAT32 started. In all other cases, the first NDISWANIP Interface found will be bound to the first available NAT32 PPP Client interface, the second to the second and so on. It can occur that Windows creates additional NDISWANIP interfaces at runtime, in which case NAT32 must be reconfigured, if those additional interfaces are to be used within NAT32. The maximum number of NAT32 PPP interfaces is 8.

Note that the connect file is not executed for PPP connections already in place when NAT32 starts. This is because, per definition, the connect file is executed only when a connection is established, and at no time thereafter. However, if such a connection is disconnected while NAT32 is running, the disc file will be executed.

RAS Phonebooks

This section applies only to Windows NT and higher. Windows 9X platforms do not support Phonebooks.

When NAT32 starts, it fetches the location of the file rasphone.pbk in a platform-independent manner. The current location of that file can be printed using the command: setpbkf.

All subsequent dialing and hangup operations depend on the settings in the current rasphone.pbk file. This can lead to problems on Windows 2000 and higher platforms, because they support an undocumented enhancement to the original Windows NT phonebook concept, in that they can access several phonebooks concurrently, if no particular phonebook file was specified. The following command can be used to enable this feature in NAT32:

if app setpbkf -d

The following command can be used to select a phonebook file:

setpbkf "path"

where path is the full pathname of the desired phonebook file.

When NAT32 runs as a service, the default phonebook file will depend on the account under which the service runs. If that account has no phonebook file, any available phonebook file can be selected by adding the following command to file startup:

if service setpbkf "path"

NAT32 also contains the following RAS Dialog commands for Windows 2000 and higher:

rasentry [name]

raspbk [name]

Command rasentry runs the Network Connection Wizard, while command rasentry name displays the Properties of the specified connection. Command raspbk displays the main Windows Dialing dialog box, which can be used to either dial a connection or view the Properties of a connection. Command raspbk name displays the same dialog box but selects the specified connection in the dialog box.

The commands described in this document allow very flexible configuration of Windows Dial-Up Networking, but always bear in mind that most of the commands depend entirely on the accessability of a valid RAS Phonebook file at run-time.