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Appendix E: Using the Optional Modem Feature
Appendix E. Using the Optional Modem Feature
E.1 Background
The modem option allows the ServSwitch to act as an Internet connection server
that increases security and flexibility when connecting with the managed
computers. Unlike the TCP/IP connection used with the standard Web
configuration and VNC clients, the modem creates a one-to-one connection
between the ServSwitch and the computer you are using to manage your
network. This connection is essentially private, since it bypasses the public Internet
completely. This option requires both an external modem (most standard
connection protocols are supported) and a dedicated phone line that can be
connected to the modem for external access. While it is technically possible
to use the modem feature through some PBX systems, this increases the
connection’s complexity and reduces its performance. For clarity, the instructions
presented here assume that the modem is connected to a typical POTS (plain old
telephone system) line that is not routed through a phone management system or
shared with other devices. If you want to use this feature through a PBX system,
you might need additional support from your telecom services provider.
E.2 Connecting a Modem
The ServSwitch works with virtually any Hayes® compatible modem that recog-
nizes the standard AT command set. Some modem manufacturers offer “enter-
prise” modems that include technology to improve the connections’ stability. To
determine whether or not you need this type of modem, ask yourself:
1. Is the modem connection mission-critical?
2. Will your telecom infrastructure support such a modem?
3. Will your budget provide a higher-quality modem?
NOTE: Modems that offer “56K” (or 56,000 bps) connections often achieve
connection speeds that are far lower than their maximum capabilities.
Given the limitations of telecom infrastructure (many locations have yet to
implement fully digital switching technology, and still rely on older analog
technology for some segments), the maximum “upstream” transfer rate is
limited to a maximum of 33,600 bps between two modems; the
“downstream” rate is often within a similar range for a typical connection.
Therefore, speeds below 56,000 bps do not indicate a problem with the
modem or the line but simply reflect the line conditions at the time the
connection is made. Use the ServSwitch unit’s rear-panel serial port and a
null-modem serial cable for the modem connection.
