The Point to Point Protocol

PPP has the distinction of being used on both the slowest and fastest Internet links. PPP is sometimes used with the newer home technologies such as DSL and cable modems. Encapsulation is typically performed by the interface device, and the traffic is bridged to Ethernet.

To connect a host to a network with PPP;

• Kernel must be able to send IP packets across a serial line as specified by the PPP protocol standard. Linux systems, PPP is a loadable kernel module that places network packets in the serial device output queue. This module usually pretends to be just another network interface, so it can be manipulated with 'ifconfig'.
• A user level program that allows to establish and maintain PPP connections. WvDial PPP driver for Linux, with an emphasis on simplicity.
• Both host must understand the protocol used.

Linux uses a daemon called pppd and most of its configuaration files in /etc/ppp

#apt-get install ppp

#apt-get install ipppd

PPP related commands and configuration files by system
/usr/sbin/pppd PPP daemon program.
/usr/sbin/chat Talk to modem.
/usr/sbin/pppstats Show statistics of PPP link.
/usr/sbin/pppdump Makes PPP packets readable ASCII.
/etc/ppp/options Configuration files for pppd.
/usr/bin/pon Starts up a PPP connection.
/usr/bin/poff Shutdown a PPP connection.
/usr/bin/plog Show the tail end of ppp.log
/usr/sbin/pppconfig Configures pppd.
/etc/ppp/peers/provider Options for pon to contact your ISP.
/etc/chatscripts/provider Chat script for pon to talk to the ISP.

Global options are set in the file /etc/PPP/options and options for particular connections can be stored in the directories /etc/ppp/peers and /etc/chatscripts

The active options for /etc/ppp/options
asyncmap 0x00000000 By default, don't escape anything
auth Authentication method.
crtscts Use hardware flow control.
lock Always lock the device which using.
hide-password
modem Device serial numver
proxyarp
lcp-echo-interval 30
lcp-echo-failure 4
noipx
mru 552 MRU.MTU 512 (date) + 40 (header)
mtu 552

WvDial
It is a PPP dialer with built-in intelligence. It dials a modem and starts PPP in order to connect to the Internet. The connection started with wvdial can be dropped by switching back to the terminal from where it was started and pressing ctrl-C.

The default configuration file is: /etc/wvdial.conf. 
#apt-get install wvdial

First, make sure modem is installed and type the following command to configure the modem:
#wvdialconf /etc/wvdial.conf
#nano /etc/wvdial.conf
[Dialer Defaults]
Modem = /dev/ttyS1
Baud = 115200
Init1 = ATZ
Phone = 172226
Username = Your-USERNAME
Username = {Username}
Password = {Password}
 
To connect Internet
#wvdial