The PPP protocol supports TCP/IP communications over a serial interface. The PPP module is an optional add-on for RTIP-32 and must be purchased in addition to RTIP-32 to be available.

With the PPP protocol, each sent packet is encapsulated in a PPP header. Each end of the connection negotiates configuration parameters as specified by the options below. The options negotiated are set up by calling PPP API routines. If the two sides cannot agree upon the options, opening of the connection fails. If an option is not negotiated, default values are used (see the Default column in the table below). PPP can run in both server (passive) and client (active) modes.

RTIP-32's implementation of PPP supports the following options for the protocols specified by RFCs 1661 (Point-to-Point Protocol), 1172 (PPP Initial Options), 1334 (PPP Authentication) and 1332 (PPP IPCP):

Options	Defaults
LCP Maximum Receive Unit	150
LCP Async Control Character Map	-1
LCP Authentication Protocol (PAP, CHAP)	None
LCP Magic Number	None
LCP Protocol-Field-Compression	No Compression
LCP Address-and-Control-Field-Compression	No Compression
Password Authentication Protocol (PAP)	No Authentication
Challenge Handshake Authentication Protocol (CHAP)	No Authentication
IPCP IP-Address	Addresses set by xn_attach and xn_set_ip
DNS-IP-Address	No address
Van Jacobson Compression	No Compression

The routine xn_ppp_init must be called prior to calling any PPP routines. All PPP API functions are declared in header file Pppapi.h and are contained in library file Ppp.lib. The complete API documentation for PPP is included in the RTIP-32 Reference Manual. Please note that RTIP-32 also includes functions for modem dialing: xn_autoanswer, xn_autologin, xn_hangup, and xn_scriptlogin.

Demo program PPPDemo implements a complete PPP server or client with support for modem answering/dialing as well as Windows Direct Cable Connection.

Demo Programs

Right PPP Phases and States

Right PPP Commands

Right PPP Authentication

Down DHCP Client