COMPUTER MONITORING SYSTEM
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates a computer system, and more particularly to a
monitoring system for computer system.
Discussion of the Related Art
Computer networks conventionally consist of a server computer and a plurality of
client computers. Each of the client computers is connected to the server computer that
operates the network. Server and client computers communicate by sending and receiving
bi-directional digital signals through a transmission line. If the transmission line is
disrupted in any way, communication between the computers will be affected.
Accordingly, methods are needed to inform computer systems managers that the
transmission line is disrupted. Usually, this is accomplished by determining if no signals
have been received by the server computer over a sufficiently long period of time.
However, false notifications will result from normal idle intervals if the period is too
short, and many lost transmissions may occur during undetected outages if the period is
too long. Alternatively, the server may regularly send coded polling signals to client
computers which return coded polling responses. The server computer then determines if
the polling response in correct. However, this method is not satisfactory.
SIJMMARY OF THE INVENTION
Accordingly, the present invention is directed to a computer monitoring system
that substantially obviates one or more of the problems due to limitations and
disadvantages of the related art.
An object of the present invention is to provide a reliable and economical system
to monitor the integrity of transmission lines linking at least two computers.
Additional features and advantages of the invention will be set forth in the
description which follows, and in part will be apparent from the description, or may be
learned by practice of the invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed out in the written
description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the
present invention, as embodied and broadly described, the computer monitoring system
includes a first computer; a second computer; a transmission line for passing data between
the first and second computers, the first computer connected to a first end of the
transmission line and the second computer connected to a second end of the transmission
line; an impedance load at the second end of the transmission line, the impedance load
being impedance matched with the transmission line; and monitoring circuitry which
provides at least one oscillatory voltage to the transmission line at the first end, the
monitoring circuitry detecting an impedance mismatch between the impedance load and
the transmission line.
In another aspect, the computer monitoring system, for monitoring a transmission
line between a first computer and a second computer, includes an impedance load at a
first end of the transmission line, the impedance load being impedance matched with the
transmission line; and monitoring circuitry which provides at least one oscillatory voltage
to the transmission line at a second end of the transmission line, the monitoring circuitry
detecting an impedance mismatch between the impedance load and the transmission line.
It is to be understood that both the foregoing general description and the following
detailed description are exemplary and explanatory and are intended to provide further
explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWING
The accompanying drawing, which is included to provide a further understanding
of the invention and is incorporated in and constitutes a part of this specification,
illustrates an embodiment of the invention and together with the description serves to
explain the principles of the invention.
In the drawing, FIG. 1 is a block diagram of a computer monitoring system
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
U.S. Patent Application No. 08/845,866 (Jackson) filed April 28, 1997, is hereby
incorporated by reference.
Reference will now be made in detail to the preferred embodiments of the present
invention, an example of which is illustrated in the accompanying drawing.
The present invention provides a system which monitors a computer system. In
the system, the transmission line is impedance matched with an impedance load.
Monitoring circuity is used to determine if an impedance mismatch occurs. Thus, the
detection of an impedance mismatch indicates that the transmission line may be disrupted
or disturbed.
Referring to FIG. 1, the monitored computer network includes a server computer
101 at a first end of a transmission line 103 and a client computer 105 at a second end of a
transmission line 103. Of course, the present invention should not be limited to
computers configured for use in client-server relation, but may be used with any two
computers connected together. The system further includes monitoring circuitry, such as
a mismatch detector 107 and an oscillator 109, at the first end of the transmission line 103
and a load impedance 111 at the second end of the transmission line 103. Here, the
mismatch detector 107 may be a voltage standing wave ratio (VSWR) meter.
Alternatively, the monitoring circuitry may be a network analyzer. Preferably, the
oscillator 109 transmits a single radio frequency voltage over the transmission line 103.
However, non-radio frequency voltages can be used, and more than one frequency can be
used. The impedance load 111 preferably matches the characteristic impedance of the
transmission line 103. For example, if the characteristic impedance of the transmission
line is 50 Ω, then the impedance load 111 should also be 50 Ω.
In the system, signals transmitted over the transmission line 103 from the first end
will be transmitted without any reflection. However, if the transmission line 103 is
disrupted or disturbed, an impedance mismatch will occur and a detectable reflection of
the oscillatory voltage will result. Thus, the oscillatory voltage is used to monitor
transmission line integrity through impedance matching detection. In the preferred
embodiment, the oscillatory voltage from an oscillator 109 is sent on the transmission line
with the data. For example, the oscillatory voltage may be a carrier frequency for the data
signal.
If the mismatch detector 107 measures a VSWR of 1.5:1 or less, an impedance
matched condition exists. However, if the mismatch detector measures a VSWR greater
than 1.5:1, an impedance mismatch has occurred, and a fault is signaled to a security
system or the server computer. Of course, the VSWR threshold may be set to other ratios
consistent with the present invention, for example, between 1.0: 1 and 2.0: 1. Also, the
monitoring circuitry can be used to measure S-parameters, Z-parameters, Y-parameters,
image impedance, or the like. These parameters are determined by some combination of
reflected and transmitted waves.
In the one embodiment, the system may include a plurality of filters. For
example, FIG. 1 shows a first low pass filter 113 connected serially with the server
computer 101, a first high pass filter 115 connected serially with the mismatch detector
107, a second low pass filter 117 connected serially with the client computer 105, and a
second high pass filter 119 connected serially the impedance load 111. Here, the first and
second low pass filters 113 and 117 pass the data signal from the server and client
computers 101 and 105 but block the oscillatory voltage of the oscillator 109. In contrast,
the first and second high pass filters 115 and 119 block the data signal from the server and
client computers 101 and 105 but pass the oscillatory voltage of the oscillator 109. The
first and second low pass filters 113 and 117 should have the same cut-off frequency.
Also, the first and second high pass filters 115 and 119 should have the same cut-off
frequency which is preferably higher than the cut-off frequency of the low pass filters.
Alternatively, band pass filters with similar frequency characteristics can be
substituted for first and second high pass filters 115 and 119. In this case, the band pass
filters should have the same center frequency corresponding to the frequency of the
oscillator 109 and a lower cut-off frequency that is higher than the cut-off frequency of
the first and second low pass filters 113 and 117.
As described, the present invention provides a reliable and economical system to
determine if the integrity of a transmission line between computers is maintained.
According to the system, if the mismatch detector observes an impedance change, the
transmission line has been altered or damaged. The impedance change may signal
evidence of damage or unauthorized tampering.
It will be apparent to those skilled in the art that various modifications and
variations can be made in the computer monitoring system of the present invention
without departing from the spirit or scope of the invention. Thus, it is intended that the
present invention cover the modifications and variations of this invention provided they
come within the scope of the appended claims and their equivalents.