This chapter contains advanced information on the Indy implementation of ISDN, and on using PPP. It contains these sections:
The Indy provides a BRI (Basic Rate Interface) S/T interface. There are two B channels, each capable of transferring up to 64 Kbits/second and one D channel, capable of transferring 16 Kbits/second. For more information, see “About Transfer Rates.”
The B channels carry the actual data. The Indy supports only data communications (no voice communications) at this time. The D channel carries signaling and protocol data only. You cannot transmit user data over the D channel.
A daemon, isdnd, listens on the D channel for incoming calls. It also makes calls on behalf of local applications. PPP (Point-to-Point Protocol) is shipped with IRIX, and can make ISDN calls and talk over ISDN B channels. isdnd will also accept ASI messages from ASI program entities; see the ISDN Release Notes for details.
ISDN on the Indy supports both PPP and ASI. The implementation of PPP supports these standards:
magic numbers
LCP address and control field compression
LCP protocol field compression
Asynchronous Control Character Map
IP header compression (also called VJ compression)
PAP authentication
IP address negotiation
demand dialing
a non-standard (but not proprietary) multi-link protocol
The remote system must use ISDN and talk either:
IETF PPP ; if you're using the security scheme described in “Using a System Security Scheme”, it must support the PAP authentication/password scheme.
ASI
Although each B channel can transfer 64 Kbits/second, many U.S. and international calls cannot transfer at this rate because the telephone company uses 1 bit out of every 8 to send the data between switch hardware. This makes the actual rate on each B channel 56 Kbits/second.
You can transfer information within the U.S at 64 Kbits/second only if both your system and the remote ISDN system use the same physical switch hardware. In most cases, this would require that both systems are located in the same general geographic location (e.g., in the same city) and the calls are placed to each other in the same central switching office.
You can also increase your transfer rate by using both B channels simultaneously; see “Optimizing Connection Speed.”
If your Indy is connected to a standard Ethernet network, and you also want to use ISDN to connect to a different network, you must work closely with the administrator of the ISDN network to set up network routing on your Indy correctly.
This typically involves these steps:
Configure gated (the routing daemon you need to use when your system uses two or more networks simultaneously) by editing the /usr/etc/gated.conf file. A sample file appears at the end of these steps.
Turn off routed, turn on gated, and restart networking by logging in as root and typing:
/etc/chkconfig routed off
/etc/chkconfig gated on
/etc/init.d/network stop
/etc/init.d/network start
Delete the add_route line from every entry in the /etc/ppp.conf file.
Try out the connection. If you have routing problems (i.e., you see an error message that says <hostname>: Network is unreachable), contact the administrator of the remote system or network.
In this example, 192.0.1.1 is the IP address of the local system for both its PPP and Ethernet interfaces. 192.0.1 is the local Ethernet network. For more information, see the gated man page.
# gated.conf # # gated configuration file for automatic PPP RIP yes supplier HELLO no EGP no # Trace options traceflags internal external # Do not time out the PPP interface. This keeps gated # from timing out if it doesn't hear RIP packets from # the local system. passiveinterfaces 192.0.1.1 # Braodcast this system as a gateway at all times, # even when the PPP link is not active. net 192.0.1.0 gateway 192.0.1.1 metric 1 rip # Do not waste bandwidth by sending RIP packets to # the local system. noripoutinterface 192.0.1.1 |
This section covers only a few, common options for using PPP across an ISDN line. For more information, see the ppp man page.
As long as the remote system supports the PAP authentication/password scheme, you can add information to /etc/ppp.conf to allow only a select list of users to log in to your system. For example, assume that fred, joe, and mary all have user accounts on your system, but you want to allow only fred and mary to log in via ISDN. In this case, you would add one line in ppp.conf for each user under the _ISDN_INCOMING reconfigure line as shown here:
_ISDN_INCOMING reconfigure recv_username=fred recv_username=mary |
If you do not add any recv_username entries, all users who have a valid login account on your system can log in via ISDN.
Network routing can be very complex. Before you change your routing scheme, contact your network administrator.
You control network routing using either:
a routing daemon (routed or gated), or
a static route (the route add command or add_route in your ppp.conf file)
Do not use a static route and a routing daemon at the same time. This will disrupt the routing, and you will not be able to reach remote systems. For more information, see the routed, gated, and ppp man pages.
The Indy supports a non-standard method for optimizing connection speed which works best between two Indys. It uses both B channels simultaneously; consequently, it also doubles your telephone usage costs. To each entry in /etc/ppp.conf, add this line:
outdevs=2
For example, to optimize your connection speed to the host mars, its ppp.conf entry would look like this:
| mars | send_username=joe |
PPP's quiet mode starts PPP on demand (when you try to access a system using PPP) and closes the connection after a certain amount of idle time. This makes the PPP connection nearly as seamless as an Ethernet network connection, and also ensures that you do not inadvertantly leave an idle connection open and incur unneccessary telephone charges.
Quiet mode has complex routing implications. Contact your network administrator and see the ppp man page for more information.
This section summarizes the configuration files that you edit in Chapter 2 to set up your ISDN connection.
/etc/config/isdnd.options is an ISDN file in which you specify the switch software type that your telephone company uses.
/etc/uucp/Devices is a UUCP file in which you specify an ISDN line as an available device.
/etc/uucp/Systems is a UUCP file in which you specify the name and telephone numbers of systems to which you will connect via ISDN.
/etc/ppp.conf is a PPP file in which you can customize PPP for each system to which you will connect via ISDN. See also “Using Advanced ISDN Configuration Options.”
/etc/hosts is an IRIX networking file in which you specify the hostname, hostname alias, and IP address of each system to which you will connect via ISDN, as well as each system that you will access after establishing an ISDN connection.
/usr/etc/gated.conf is an IRIX networking file that controls the behavior of the gated routing daemon. See also “Using ISDN and Other Networks Simultaneously.”