User Manual

Additional Remote Networking Using the SCS Without Dialup Modems
5-13
If the last connection attempt succeeded and the success timer is set to a high value (for example, 20
minutes), the SCS will wait for a longer period of time before attempting a new connection. If the SCS was
not able to connect for some reason, setting the failure timer to a low value (for example, 5 seconds) will
cause the SCS to retry the connection at short intervals until it succeeds.
In Figure 5-20, the SCS is configured to allow a new connection attempt almost immediately upon
completion of a successful connection. If the last attempt to connect to the site failed, the SCS will wait 30
seconds before attempting another connection. It will continue to retry the connection every 30 seconds
until it succeeds.
5.6 Using the SCS Without Dialup Modems
The SCS may be configured to allow Remote Node and LAN to LAN functionality without using modems;
dial-on demand features will be ignored.
5.6.1 Situations Where Dialup Modems Are Not Used
There are four primary situations in which the SCS may be used without modems:
Direct connections Two SCS units are linked with a serial cable.
Statistical multiplexors Multiplexors (stat-mux) allow multiple serial lines to run over a single
leased line. The stat-mux must support asynchronous serial
communication.
Synchronous leased line Lines are leased from the telephone company and dedicated to
synchronous serial communication between two fixed locations.
Analog leased lines Analog lines are ordinary telephone lines leased from the telephone
company and used in conjunction with standard modems. The modems
must have leased line capabilities.
5.6.1.1 Direct Connections
Two buildings may be linked with a serial cable. Two SCS units may use the serial cable to connect two
networks together.
5.6.1.2 Statistical Multiplexors
Two locations may have statistical multiplexors (commonly called stat-muxes) in place. These stat-muxes
may be used to connect to SCS units. A series of commands may have to be sent to the stat-mux to connect
to the remote SCS; chat scripts make sending these commands easy and relatively error-free.
Note: See Chat Scripts on page 5-3 for more information.
The SCS assumes an 8-bit data path. If you are using SLIP, all characters must be sent and received
unchanged by the intervening communications equipment. PPP has a feature called ACCM which causes
the SCS to avoid sending user-specified control characters. If the equipment connecting the SCS cannot
send certain control characters, configure PPP and ACCM on the SCS port.