Installing and Administering PPP

Chapter 2 31

Setting Up PPP Connections

Conﬁguring Your Modem

The following are general recommendations for conﬁguring modems to

use with PPP:

• Choose the highest asynchronous serial speed both modem and

computer can support.

• Enable error correction. If possible, choose CCITT V.42 for

compatibility with CCITT V.42bis data compression.

• Enable data compression. HP recommends CCITT V.42bis for higher

maximum compression ratios and handling of precompressed data

streams.

• Enable ﬂow control. Use hardware instead of software ﬂow control if

possible.

• Use default modem parameters for purposes outside PPP protocol,

including other inbound applications

• Set up dialers for UUCP or PPP outbound connections. Dialers'

PPP-speciﬁc register settings ensure that a general purpose modem

used for PPP will work as intended during an PPP session.

• Allow bidirectional connections over any available modem. Try the

following suggestions to conﬁgure bidirectional modems and to allow

modem use by other applications, such as uucp, tip, cu and remote

logins:

• Set S0 register value to 1 to answer after one ring.

• Lock the DTE interface to the selected speed. Many modems do not

support a speed register, but you can store the current value with the

&W command

• Disable modem printing of result codes when processing incoming

calls. You may have to disable result codes too. Start the dialer with

""ATE1 or its equivalent.

• Set the modem to print extended result codes, like Busy, when dialing

out. Better dialer performance is possible. Enter this in the

/etc/ppp/Dialers ﬁle, if necessary.

• Set the modem so it only asserts the Carrier Detect (CD) signal when

the carrier is established with another modem