This chapter contains advanced information on the implementation of ISDN, and on using PPP. It contains these sections:
Your ISDN hardware provides a Basic Rate Interface (BRI) 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 hardware 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. Point-to-Point Protocol (PPP) is shipped with IRIX and can make ISDN calls and talk over ISDN B channels. Theisdnd daemon also accepts ASI messages from ASI program entities; see the ISDN Release Notes for details.
ISDN 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
CHAP authentication
IP address negotiation
demand dialing
a nonstandard (but not proprietary) multilink protocol
The remote system must use ISDN and 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.)
or
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 United States 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 be located in the same general geographic location (e.g., in the same city) and that the calls be 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 system 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 workstation.
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 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 the example below, 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 # Broadcast 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 a few common options for using PPP across an ISDN line. For more information, see the ppp man page.
You can authenticate the user name and password that your system will accept from a specific system by adding an incoming PPP connection as follows:
Open the Add an Incoming PPP Connection guide.
Select the Network and Connectivity category in the left-hand column of the System Manager window (see “Using the Interactive Guides” in Chapter 2). Select Add an Incoming PPP Connection and follow the steps.
 | Note: If you do not use Add an Incoming PPP Connection, any remote site can call your system. |
Give a password to each connection to make it secure and be sure that only the appropriate users know the user name and password.
Network routing can be very complex. Before you change your routing scheme, contact your network administrator.
You control network routing using either of the following:
a routing daemon (routed or gated)
or
a static route
To do so, follow the directions in “Setting Up Basic ISDN” to add a PPP connection and choose Add Route on page 9.
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 system supports a nonstandard method for optimizing connection speed that works best between two workstations. It uses both B channels simultaneously; consequently, it doubles your telephone usage costs.
Follow the directions to add a connection in “Using a System Security Scheme” and choose the Heavy Traffic option on page 6 of the guide.
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 inadvertently leave an idle connection open and incur unnecessary 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 a 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 a networking file that controls the behavior of the gated routing daemon. See also “Using ISDN and Other Networks Simultaneously.”