Fixed IP Addresses

Introduction

TSX-Online has support for fixed IP addresses but, if your customers dial into the modems directly connectd to the TSX-32 system, there is an important limitation. If your system uses terminal servers the limitation does not apply.

This web page provides instructions on assigning fixed IP addresses to your users and explains the restrictions which apply.

Steps For Assigning Fixed IP Addresses

To give a customer a fixed IP address you must take two steps. First, you must declare, in the SERVICE PROVIDER block which defines the interface to which this TCP/IP address is assigned, that the IP address is a "Fixed address" and not a "floater". This prevents the IP address from being given away to remote computers who ask for "just any IP address", hence reserving it for your important (and hopefully more profitable) customer. Here's an example:

SERVICE PASSTHRU
        LOCALIP 208.324.2.187
        REMOTEIP 208.324.2.188
        LINENAME Ajax Corp
	IPFIXED

The second thing that you must do is inform TSX-Online who this IP address "belongs to". To do this, use the SYSOP program and go to page two of the user's account screen. There's a field for IP address on this page; fill it in with the ip address you have reserved.

Usage of Fixed IP Addresses for Modem Customers

The way TSX-Online was originally designed was as an ANSI based BBS, with no PPP support. To convert this time sharing line into a network connection required the user to navigate menus and engage SLIP mode. During this phase of the the industry's history, many people were still using DOS or Windows 3.11 based systems at home in conjunction with a TCP/IP implemenation named "Trumpet Winsock", which had a very nice scripting language built into it.

The same approach can be used today, with Windows 95/98/NT, and PPP connections. You can write a script to nagivate the menus but you don't even have to really NAVIGATE, since the logon prompt can be responded to with a string like this one:

   Dan Cappannari;DansPassword;PPP

Alternatively, you can use the post terminal dial up screen and enter this by hand.

What you CAN NOT D0 with tsx-32 ppp connections and fixed ip addresses is take advantage of "ppp autodetect" to permit the Windows system to go into "network packet mode" immediately after dialing. You MUST log in before going into PPP mode.

Why is this? The PTY server responds to a request to go into PPP packet mode by selecting an interface defined in SY:SERVICES.PTY. These interfaces are defined with IP addresses, so by the time you begin doing PPP packets, you already have an ip address. PAP authorization uses PPP packets to transmit names and passwords. But by then it's too late for the PTY server to decide "hey, this is a customer with a fixed IP address, I'll find his reserved interface for him". It's too late because one of the "floating" interfaces was ALREADY assigned and the PPP packets are ALREADY flowing through it.

There ARE systems that can do this. How do they do it? Do they change the IP address of the interface "on the fly"? We don't know.

Now, if your customers are authenticated using RADIUS, you don't have this problem, since the interface pool is managed by the terminal server (or whatever you call your RADIUS client). The RADIUS server can advise a RADIUS client on an IP address the server wants the client to assign. Note, however, that since the RADIUS client is ultimately responsible for managing the pool of interfaces, this directive from the server is "advise at best" (much the same as people tend to regard stop signs!). There may be some way to tell some RADIUS clients to reserve IP addresses for such directives, but we don't know.