• Choose a category
• All
• Classic-Fiction

# Secrets for authentication using PAP

# client server secret IP or Domain

mdw * my-password

The first field is your system's name as expected by the remote system—usually your ISP username. The second field specifies the ISP's server name; an asterisk allows this entry to match all ISP servers to which you might connect. The third field specifies the shared secret provided by your ISP; as stated earlier, this is usually your ISP password. The fourth field is primarily used by PPP servers to limit the IP addresses to which users dialing in have access. These addresses can be specified as either IP addresses or domain names. For most PPP client configurations, however, this field is not required.

The chap-secrets file has the same four fields, but you need to include an entry other than * for the service provider's system; this is a secret the ISP shares with you when you establish the account.

If PAP or CHAP is being used, it's not necessary for the chat script to include handshaking information after CONNECT is received; pppd will take care of the rest. Therefore, you can edit /etc/ppp/my-chat-script to contain only the following lines:

#!/bin/sh

# my-chat-script: a program for dialing up your ISP

exec chat -v \

'' ATZ \

OK ATDT555-1212 \

CONNECT ''

You will also need to add the user option to the pppd command line in /etc/ppp/ppp-on, as so:

#!/bin/sh

# the ppp-on script

exec /usr/sbin/pppd /dev/modem 38400 lock crtscts noipdefault \

user mdw defaultroute 0.0.0.0:0.0.0.0 connect my-chat-script

* * *

[*] Older versions of Linux also used special "callout" devices, called /dev/cua0 through /dev/cua3. These are obsolete as of Linux kernel Version 2.2.

PPP over ISDN

ISDN has offered convenient, high-speed data communications—at a price—for many years; it is particularly popular in Europe, where rates and marketing have been more favorable to its use than in the U.S. ISDN, which integrates data and regular voice transmission over a single line, offers both a faster connection setup and much better throughput than traditional modems.

ISDN lines can transfer 64 kbits per second. And unlike analog lines, they can achieve this speed all the time because their transmission does not depend on the vagaries of analog transmission with interference by various kinds of noise. A newer protocol called ADSL (Asynchronous Digital Subscriber Line) is upping the ante for fast data access over phone lines and is taking over from ISDN in many regions of the world.

In this section, we describe how to configure dial-up access to your Internet provider over an ISDN line. We cover only the most common style of connection, synchronous PPP, not the special mode called raw IP. Furthermore, this section discusses just internal ISDN boards, which require a kind of setup that's different from the dial-up access covered in the previous section. To set up external ISDN devices, or the so-called ISDN modems (a term that is an oxymoron because there is no modulation and demodulation), you can use commands similar to those in the previous section because these devices present themselves to the computer and the operating system like a normal modem, albeit one that offers some additional commands, faster connection setup, and higher throughput.

If you want more information beyond what we present here, the source for all ISDN-related information for Linux is http://www.isdn4linux.de (despite this domain being registered in Germany, all the information here is in English).

In a way, setting up ISDN connections is much easier than setting up analog connections because many of the problems (bad lines, long connection setup times, and so on) simply cannot occur with digital lines. Once you dial the number, the connection is set up within milliseconds. But this can lead to problems. Because the connections are set up and shut down so fast, a misconfigured system that dials out again and again can cost you a fortune. This is even more problematic because with internal ISDN cards,