ChorusOS 4.0 Network Administration Guide

PPP Configuration

This section explains how to configure Point-to-Point Protocol (PPP) with the ChorusOS 4.0 product standard interface and drivers. It assumes the serial line or modem is already physically connected. On some platforms, a unique serial line is used both for the console (accessed through tip), and for PPP. At boot time, the serial line connector must be connected to the host tip line.

Note -

Systems often have two IP addresses: one for Ethernet, one for PPP.

This document differentiates between Ethernet Internet addresses and PPP addresses. As you read, be aware that hostname refers to the Ethernet hostname corresponding to the Ethernet IP address, and that hostname_PPP refers to the hostname corresponding to the PPP address.

PPP as implemented in ChorusOS 4.0 handles IP traffic differently than previous releases.

First, you run pppstart, a daemon that listens for requests for connection.
Next, you use the pppd command to enable a connection to a specific serial line.
When finished with a PPP connection, you may close it using the pppclose command.
Finally, you can disable PPP services altogether using the pppstop command.

The process therefore remains the same whether you open one PPP line or multiple lines.

Figure 4-1 IP Traffic--PPP Only

In order to make sure the Ethernet interface can still be used for IP traffic, use different IP addresses for Ethernet and IP.

Figure 4-2 IP Traffic--Both Ethernet and PPP

It is strongly recommended for this release that you use different IP addresses for PPP and Ethernet.

As shown above, if each system has only one IP address, when an ifnet interface is set up between target_PPP and host_PPP, all traffic to host_PPP is routed through target_PPP. In other words, all IP traffic passes through the serial line.

How to Enable PPP Services

Enabling PPP services involves using the pppstart actor.

Enabling PPP at Boot Time by Including `pppstart` in the System Image

Change to the directory where you build system images:
host% cd build_dir

Ensure that both serial lines and network interfaces are available for PPP by including the necessary commands in the conf/sysadm.ini that you build into the system image. For example:

mkdev tty 0 /pci/pci-isa/ns16550-2      # Create a tty interface
                                        # using the second serial port
                                        # because the first is reserved
                                        # for the tip line

mkdev ppp 0                             # Create a PPP interface that is
                                        # not bound to the tty yet.

mknod /dev/tty01 c 0 0                  # Create a tty special file

#mknod /dev/ttyp0 c 5 0                # Pseudo tty devices, needed
#mknod /dev/ptyp0 c 6 0                # for dialup on demand.

# Enable PPP
# Requires pppstart.r in system image
#
arun /image/sys_bank/pppstart &

pppd /dev/tty01                         # Open a PPP line.

# Wait for the interface to be up.
#
ifwait ppp0

See the appropriate document in the ChorusOS 4.0 Target Family Documentation Collection for serial device IDs for other serial line hardware.

Start the ews configuration utility:
host% ews conf/ChorusOS.xml &

Use the hints in the table below to set system image features and tunables:

Set...	Comments
VTTY=true	PPP requires virtual ttys.
PPP=true
iom.nfs.rsize=1024	Optimizing NFS read and write buffer sizes for use with PPP by setting them to a maximum of `1024`
iom.nfs.wsize=1024

Include the pppstart.r actor in the system image.

Rebuild the system image.

Copy the system image to the boot server:

host% rcp system_image_name boot_server:/tftpboot

Reboot the target system:
host% rsh target reboot

Enabling PPP Manually

Ensure that both serial lines and network interfaces are available for PPP.

Run the actor:
host% rsh target arun /bin/pppstart &

How to Open PPP Lines

Opening an available PPP line involves the built-in C_INIT command, pppd.

Opening a PPP Line Manually

Run the built-in C_INIT command, pppd, on the target system:

host% rsh target pppd device
pppd device:info: Using interface ppp0
pppd device:notice: Connect: ppp0 <--> device
pppd device:notice: local  IP address local_addr
pppd device:notice: remote IP address remote_addr

where device is either /dev/tty01 or /dev/tty02.

See pppd(1M) for details.

How to Close PPP Lines

Closing an open PPP line involves using the pppclose command.

Closing a PPP Line Manually

Run the built-in C_INIT command, pppclose, on the target system:

host% rsh target pppclose device
pppd device:info: Terminating on signal 15.
pppd device:notice: Connection terminated, connected for 2 minutes
pppd device:info: Exit.