The Figure shows one of the
modem-control functions terminating a connection. Either the DTE
device or the DCE device may signal for the connection to be
terminated. The signals that are used for this function are DTR from
the DTE or the modem recognizing the loss of the CD signal.
Therefore, a modem connection can be terminated in two ways:
- DTE initiated—The access
server or computer can drop the DTR signal. The modem must be
programmed to terminate the connection on loss of DTR and
restore to saved settings in its nonvolatile RAM (NVRAM).
- DCE initiated—The
access server detects CD low and terminates the connection. The
modem must be programmed so that the CD reflects the state of
the carrier.
When modem control is not configured properly, the following symptoms might occur:
- The modem does not hang up when
you quit your session, meaning the DTR is not dropped or
recognized, so the modem is not aware that it should break the
connection.
- You end up in someone else's
session, meaning that the CD is not dropped or recognized. This
scenario happens when Caller A terminates his/her dialup
session, and the modem does not pass the true state of the CD to
the DTE. The access server is not aware that Caller A terminated
his/her session, so it maintains the line for Caller A. When a
new caller, Caller B, comes in by the same line (interface), the
access server continues with the session previously initiated by
Caller A, instead of starting a new one. Thus, Caller B ends up
in Caller A's session without having to authenticate. It is,
therefore, very important that the true state of CD is always
passed back to the DTE, so the access server terminates sessions
when callers hang up.
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