Enterasys Networks Security Router X-PeditionTM - Manual (Page 224)

Asynchronous and Synchronous Support
10-2 Configuring Dialer Services
Asynchronous and Synchronous Support
Synchronous and asynchronous interfaces can be configured for dialed connections to one or
more destination networks. When requested, the
XSR uses dialing commands to send the phone number of the destination network to a modem.
The modem then dials the destination modem and establishes a connection. Refer to
Figure 10-1 .
Calls can be placed using the following methods:
• AT commands on asynchronous ports
• V.25bis over synchronous interfaces
• DTR dialing for synchronous interfaces
Figure 10-1 Typical Dial Services Interconnection
AT Commands on Asynchronous Ports
On asynchronous ports, AT commands are used to establish and clear the call. Refer to your
modem documentation for a list of supported commands and options. The modem should be
configured to drive Data Carrier Detect and Clear To Send CCITT V.24 signals and accept input of
the Data Terminal Ready signal set by the XSR.
V.25bis over Synchronous Interfaces
Dial services also support connections from the synchronous serial interface to any modem that
supports V.25bis. V.25bis supports two modes of establishing or receiving calls: direct call and
addressed call. Dial services support connections using the addressed call mode and synchronous,
bit-oriented operation. The addressed call mode allows control signals and commands to be sent
over the modem interface to set up and terminate calls.
Devices used for dialing out must support certain hardware signals in addition to V.25bis. When
the XSR drops DTR, the device must disconnect any calls that are currently connected. When the
device connects to the remote end, Data Carrier Detect (DCD) must be automatically asserted. For
many V.25bis devices, raised DCD requires a special cable to crossover DCD and Data Set Ready
(DSR) signals.
XSR
Modem
Ethernet
Modem
Ethernet
PSTN
XSR