WO1998049570A1 - Computer monitoring system - Google Patents

Abstract

A computer monitoring system monitors a transmission line between a first computer and a second computer. The system includes an impedance load at a first end of the transmission line and monitoring circuitry. The impedance load is impedance matched with the transmission line. The monitoring circuitry provides at least one oscillatory voltage to the transmission line at a second end of the transmission line and detects an impedance mismatch between the impendance load and the transmission line.

Description

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.

Claims

What Is Claimed Is:

1. A computer monitoring system, comprising:

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.

2. The computer monitoring system according to claim 1, further comprising:

a first filter serially connected with the first computer, the first filter blocking the

oscillatory voltage and passing the data;

a second filter serially connected with the second computer, the second filter

blocking the oscillatory voltage and passing the data;

a third filter serially connected with the monitoring circuitry, the third filter

blocking the data voltage and passing the oscillatory voltage; and a fourth filter serially connected with the impedance load, the fourth filter

blocking the data voltage and passing the oscillatory voltage.

3. The computer monitoring system according to claim 2, wherein the first

and second filters include low pass filters, and wherein the third and fourth filters include

high pass filters.

4. The computer monitoring system according to claim 3, wherein each of the

first and second filters define an upper cut-off frequency, wherein each of the third and

fourth filters define a lower cut-off frequency, and wherein the upper cut-off frequency is

less than the lower cut-off frequency.

5. The computer monitoring system according to claim 4, wherein the at least

one oscillatory voltage includes a radio frequency oscillatory voltage.

6. The computer monitoring system according to claim 5, wherein the

monitoring circuitry includes and oscillator and a mismatch detector.

7. The computer monitoring system according to claim 6, wherein the

oscillator is a voltage controlled oscillator.

8. The computer monitoring system according to claim 7, wherein the

monitoring circuitry determines whether a voltage standing wave ratio measured from the

transmission line changes.

9. The computer monitoring system according to claim 2, wherein the first

and second filters include low pass filters, and wherein the third and fourth filters include

band pass filters.

10. The computer monitoring system according to claim 9, wherein a center

frequency of the band pass filters is substantially the same as a frequency of the

oscillatory voltage.

11. The computer monitoring system according to claim 9, wherein each of the

first and second filters define an upper cut-off frequency, wherein each of the third and

fourth filters define a lower cut-off frequency, and wherein the upper cut-off frequency is

less than the lower cut-off frequency.

12. The computer monitoring system according to claim 11, wherein a center

frequency of the band pass filters is substantially the same as a frequency of the

oscillatory voltage.

13. The computer monitoring system according to claim 1 , wherein the at least

one oscillatory voltage includes a radio frequency oscillatory voltage.

14. The computer monitoring system according to claims 1, wherein the

monitoring circuitry includes and oscillator and a mismatch detector.

15. The computer monitoring system according to claim 14, wherein the

oscillator is a voltage controlled oscillator.

16. The computer monitoring system according to claim 1 , wherein the

monitoring circuitry includes a network analyzer.

17. The computer monitoring system according to claim 1, wherein the

monitoring circuitry determines whether a reflected oscillatory voltage is received from

the transmission line.

18. The computer monitoring system according to claim 1 , wherein the

transmission line has a characteristic impedance of 50 Ω.

19. The computer monitoring system according to claim 1 , wherein the first

computer includes a server computer and the second computer includes a client computer.

20. A computer monitoring system coupled to a first computer for monitoring

a transmission line between the first computer and a second computer, comprising:

monitoring circuitry which provides at least one oscillatory voltage to the

transmission line at a first end of the transmission line, the monitoring circuitry detecting

an impedance mismatch between the transmission line and an impedance load at a second

end of the transmission line.

21. The computer monitoring system according to claim 20, further

comprising:

a first filter serially connected with the first computer, the first filter blocking the

oscillatory voltage and passing the data;

a second filter serially connected with the second computer, the second filter

blocking the oscillatory voltage and passing the data;

a third filter serially connected with the monitoring circuitry, the third filter

blocking the data voltage and passing the oscillatory voltage; and

a fourth filter serially connected with the impedance load, the fourth filter

blocking the data voltage and passing the oscillatory voltage.

22. The computer monitoring system according to claim 20, wherein the first

and second filters include low pass filters, and wherein the third and fourth filters include

high pass filters.

23. The computer monitoring system according to claim 22, wherein each of

the first and second filters define an upper cut-off frequency, wherein each of the third

and fourth filters define a lower cut-off frequency, and wherein the upper cut-off

frequency is less than the lower cut-off frequency.

24. The computer monitoring system according to claim 23, wherein the at

least one oscillatory voltage includes a radio frequency oscillatory voltage.

25. The computer monitoring system according to claim 24, wherein the

monitoring circuitry includes and oscillator and a mismatch detector.

26. The computer monitoring system according to claim 25, wherein the

oscillator is a voltage controlled oscillator.

27. The computer monitoring system according to claim 26, wherein the

monitoring circuitry determines whether a voltage standing wave ratio measured from the

transmission line changes.

28. The computer monitoring system according to claim 21 , wherein the first

and second filters include low pass filters, and wherein the third and fourth filters include

band pass filters.

29. The computer monitoring system according to claim 28, wherein a center

frequency of the band pass filters is substantially the same as a frequency of the

oscillatory voltage.

30. The computer monitoring system according to claim 28, wherein each of

the first and second filters define an upper cut-off frequency, wherein each of the third

and fourth filters define a lower cut-off frequency, and wherein the upper cut-off

frequency is less than the lower cut-off frequency.

31. The computer monitoring system according to claim 30, wherein a center

frequency of the band pass filters is substantially the same as a frequency of the

oscillatory voltage.

32. The computer monitoring system according to claim 20, wherein the at

least one oscillatory voltage includes a radio frequency oscillatory voltage.

33. The computer monitoring system according to claims 20, wherein the

monitoring circuitry includes and oscillator and a mismatch detector.

34. The computer monitoring system according to claim 33, wherein the

oscillator is a voltage controlled oscillator.

35. The computer monitoring system according to claim 20, wherein the

monitoring circuitry includes a network analyzer.

36. The computer monitoring system according to claim 20, wherein the

monitoring circuitry determines whether a voltage standing wave ratio measured from the

transmission line changes.