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Claims  |
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We claim:
1. In a local area networked computer system having a plurality of nodes
each connected to a first network cable by an input/output line from a
network connector board within the node to a first interfacing transceiver
operably attached to the first network cable, the improvement for
permitting more error-free operation of the networked computer system
comprising:
(a) a second network cable disposed in parallel with the first cable, said
second network cable including a plurality of second interfacing
transceivers attached thereto;
(b) a plurality of three position switches each having a signal input,
three outputs for individual selective connection to said input, and a
control input for receiving signals designating which of said outputs is
to be connected to said signal input, each of said switches including
means for designating a response address for responding to addressed
signals appearing at said control input, each of said switches further
having its said signal input connected to a respective one of the
input/output lines from the odes, one of said three outputs being
connected to a respective one of the plurality of first interfacing
transceivers, and another of said three outputs being connected to a
respective one of said plurality of second interfacing transceivers;
(c) master switch control means having an output connected to said control
inputs of said plurality of three position switches and an input for
receiving directive signals for outputting addressed switch position
signals to said three position switches; and,
(d) monitor and control computer means having a pair of network connector
boards therein connected to respective ones of one of the first
interforcing transceivers and one of said second interfacing transceivers
and an output connected to said input of said master switch means for
monitoring the status of the networked computer system by sending messages
to the nodes and receiving and verifying messages therefrom and for
sending control signals to said master switch to cause said master switch
to cause respective ones of the nodes to use a desired one of the first
cable and said second cable for transmitting and receiving messages and
for disconnecting desired ones of the nodes from both cables.
2. The improvement to a local area networked computer system of claim 1
wherein:
said plurality of three position switches each includes indicator means for
indicating which of said outputs is presently connected to said signal
input.
3. The improvement to a local area networked computer system of claim 1
wherein:
said master switch control means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded to be connected to said signal input.
4. The improvement to a local area networked computer system of claim 1
wherein:
said monitor and control computer means includes gateway program logic
means between the first cable and said second cable for sensing messages
being transmitted from one cable to the other and for bridging said
messages between the first cable and said second cable.
5. The improvement to a local area networked computer system of claim 4
wherein:
said gateway program logic means includes means for sensing excessive
gateway activity between nodes on different cables and for switching said
nodes to the same cable to reduce gateway activity therebetween.
6. The improvement to a local area networked computer system of claim 1
wherein:
said monitor and control computer means includes network status monitor
means for displaying to service personnel the present connections of the
nodes to the cables.
7. The improvement to a local area networked computer system of claim 6
wherein:
said network status monitor means includes means for service personnel to
override said master switch control means and manually connect and
disconnect selected ones of the nodes to and from a selected cable.
8. The improvement to a local area networked computer system of claim 6
wherein:
said network status monitor means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded via said master switch control means to be
connected to said signal input.
9. In a local area networked computer system having a plurality of nodes
each connected to a first network cable by an input/output line from a
network connector board within the node to a first interfacing transceiver
operably attached to the first network cable, the improvement for
permitting more error-free operation of the networked computer system
comprising:
(a) a second network cable disposed in parallel with the first cable, said
second network cable including a plurality of second interfacing
transceivers attached thereto;
(b) a plurality of three position switches each having a signal input,
three outputs for individual selective connection to said input, and a
control input for receiving signals designating which of said outputs is
to be connected to said signal input, each of said switches further having
its said signal input connected to a respective one of the input/output
lines from the nodes, one of said three outputs being connected to a
respective one of the plurality of first interfacing transceivers, and
another of said three outputs being connected to a respective one of said
plurality of second interfacing transceivers; and,
(c) master switch control means having an output connected to said control
inputs of said plurality of three position switches for outputting switch
position signals to said three position switches.
10. The improvement to a local area networked computer system of claim 9
wherein:
(a) each of said switches includes means for designating a response address
for responding to addressed signals appearing at said control input;
(b) said master switch control means includes an input for receiving
directive signals; and additionally comprising,
(c) monitor and control computer means having a pair of network connector
boards therein connected to respective ones of one of the first
interfacing transceivers and one of said second interfacing transceivers
and an output connected to said input of said master switch means for
monitoring the status of the networked computer system by sending messages
to the nodes and receiving and verifying messages therefrom and for
sending control signals to said master switch to cause said master switch
to cause respective ones of the nodes to use a desired one of the first
cable and said second cable for transmitting and receiving messages and
for disconnecting desired ones of the nodes from both cables.
11. The improvement to a local area networked computer system of claim 10
wherein:
said monitor and control computer means includes gateway program logic
means between the first cable and said second cable for sensing messages
being transmitted from one cable to the other and for bridging said
messages between the first cable and said second cable.
12. The improvement to a local area networked computer system of claim 11
wherein:
said gateway program logic means includes means for sensing excessive
gateway activity between nodes on different cables and for switching said
nodes to the same cable to reduce gateway activity therebetween.
13. The improvement to a local area networked computer system of claim 10
wherein:
said monitor and control computer means includes network status monitor
means for displaying to service personnel the present connections of the
nodes to the cables.
14. The improvement to a local area networked computer system of claim 13
wherein:
said network status monitor means includes means for service personnel to
override said master switch control means and manually connect and
disconnect selected ones of the nodes to and from a selected cable.
15. The improvement to a local area networked computer system of claim 13
wherein:
said network status monitor means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded via said master switch control means to be
connected to said signal input.
16. The improvement to a local area networked computer system of claim 9
wherein:
said plurality of three position switches each includes indicator means for
indicating which of said outputs is presently connected to said signal
input.
17. The improvement to a local area networked computer system of claim 9
wherein:
said master switch control means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded to be connected to said signal input.
18. A redundant error-detecting and correcting local area networked
computer system having a plurality of nodes each including a network
connector board within the node for connecting to an interfacing
transceiver operably attached to a network cable, said system comprising:
(a) a first network cable disposed along a path to interconnect the nodes,
said first network cable including a plurality of first interfacing
transceivers attached thereto;
(b) a second network cable disposed in parallel with said first cable, said
second network cable including a plurality of second interfacing
transceivers attached thereto;
(c) a plurality of three position switches each having a signal input,
three outputs for individual selective connection to said input, and a
control input for receiving signals designating which of said outputs is
to be connected to said signal input, each of said switches including
means for designating a response address for responding to addressed
signals appearing at said control input, each of said switches further
having its said signal input connected to a respective one of the
input/output lines from the nodes, one of said three outputs being
connected to a respective one of said plurality of first interfacing
transceivers, and another of said three outputs being connected to a
respective one of said plurality of second interfacing transceivers;
(d) master switch control means having an output connected to said control
inputs of said plurality of three position switches and an input for
receiving directive signals for outputting addressed switch position
signals to said three position switches; and,
(e) monitor and control computer means having a pair of network connector
boards therein connected to respective ones of one of said first
interfacing transceivers and one of said second interfacing transceivers
and an output connected to said input of said master switch means for
monitoring the status of the networked computer system by sending messages
to the nodes and receiving and verifying messages therefrom and for
sending control signals to said master switch to cause said master switch
to cause respective ones of the nodes to use a desired one of said first
cable and said second cable for transmitting and receiving messages and
for disconnecting desired ones of the nodes from both cables.
19. The improved local area networked computer system of claim 18 wherein:
said plurality of three position switches each includes indicator means for
indicating which of said outputs is presently connected to said signal
input.
20. The improved local area networked computer system of claim 18 wherein:
said master switch control means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded to be connected to said signal input.
21. The improved local area networked computer system of claim 18 wherein:
said monitor and control computer means includes gateway program logic
means between said first cable and said second cable for sensing messages
being transmitted from one cable to the other and for bridging said
messages between said first cable and said second cable.
22. The improved local area networked computer system of claim 21 wherein:
said gateway program logic means includes means for sensing excessive
gateway activity between nodes on different cables and for switching said
nodes to the same cable to reduce gateway activity therebetween.
23. The improved local area networked computer system of claim 18 wherein:
said monitor and control computer means includes network status monitor
means for displaying to service personnel the present connections of the
nodes to said cables.
24. The improved local area networked computer system of claim 23 wherein:
said network status monitor means includes means for service personnel to
override said master switch control means and manually connect and
disconnect selected ones of the nodes to and from a selected cable.
25. The improved local area networked computer system of claim 23 wherein:
said network status monitor means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded via said master switch control means to be
connected to said signal input.
26. A redundant error-detecting and correcting local area networked
computer system having a plurality of nodes each including network
connector means within the node for connecting to an interfacing
transceiver operably attached to a network cable, said system comprising:
(a) a first network cable disposed along a path to interconnect the nodes,
said first network cable including a plurality of first interfacing
transceivers attached thereto;
(b) a second network cable disposed in parallel with said first cable, said
second network cable including a plurality of second interfacing
transceivers attached thereto;
(c) a plurality of three position switches each having a signal input,
three outputs for individual selective connection to said input, and a
control input for receiving signals designating which of said outputs is
to be connected to said signal input, each of said switches including
means for designating a response address for responding to addressed
signals appearing at said control input, each of said switches further
having its said signal input connected to a respective one of the
input/output lines from the nodes, one of said three outputs being
connected to a respective one of said plurality of first interfacing
transceivers, and another of said three outputs being connected to a
respective one of said plurality of second interfacing transceivers; and,
(d) master switch control means having an output connected to said control
inputs of said plurality of three position switches for outputting switch
position signals to said three position switches.
27. The improved local area networked computer system of claim 26 wherein:
(a) each of said switches includes means for designating a response address
for responding to addressed signals appearing at said control input;
(b) said master switch control means includes an input for receiving
directive signals; and additionally comprising,
(c) monitor and control computer means having a pair of network connector
means therein for connecting to respective ones of one of the first
interfacing transceivers and one of said second interfacing transceivers
and an output connected to said input of said master switch means for
monitoring the status of the networked computer system by sending messages
to the nodes and receiving and verifying messages therefrom and for
sending control signals to said master switch to cause said master switch
to cause respective ones of the nodes to use a desired one of the first
cable and said second cable for transmitting and receiving messages and
for disconnecting desired ones of the nodes from both cables.
28. The improved local area networked computer system of claim 27 wherein:
said monitor and control computer means includes gateway program logic
means between the first cable and said second cable for sensing messages
being transmitted from one cable to the other and for bridging said
messages between the first cable and said second cable.
29. The improved local area networked computer system of claim 28 wherein:
said gateway program logic means includes means for sensing excessive
gateway activity between nodes on different cables and for switching said
nodes to the same cable to reduce gateway activity therebetween.
30. The improved local area networked computer system of claim 27 wherein:
said monitor and control computer means includes network status monitor
means for displaying to service personnel the present connections of the
nodes to the cables.
31. The improved local area networked computer system of claim 30 wherein:
said network status monitor means includes means for service personnel to
override said master switch control means and manually connect and
disconnect selected ones of the nodes to and from a selected cable.
different cables and for switching said nodes to the same cable to reduce
gateway activity therebetween.
32. The improved local area networked computer system of claim 30 wherein:
said network status monitor means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded via said master switch control to be connected
to said signal input.
33. The improved local area networked computer system of claim 26 wherein:
said plurality of three position switches each includes indicator means for
indicating which of said outputs is presently connected to said signal
input.
34. The improved local area networked computer system of claim 26 wherein:
said master switch control means includes indicator means for indicating
which of said outputs of said plurality of three position switches is
presently being commanded to be connected to said signal input.
35. The method of operating a local area network having simultaneously
operating first and second communications paths for the transfer of
messages between a plurality of nodes selectively connectable to either of
the paths to provide better and more reliable operation of the network
comprising the steps of:
(a) monitoring the messages on the paths independent of the nodes to
identify messages requiring bridging between nodes connected to one path
and nodes connected to the other path; and,
(b) when the number of messages between a pair of nodes requiring bridging
exceeds a preset limit during a pre-established period, connecting the
pair of nodes to the same path to reduce the amount of bridging required.
36. The method of operating a local area network having simultaneously
operating first and second communications paths for the transfer of
messages between a plurality of nodes selectively connectable to either of
the paths to provide better and more reliable operation of the network
comprising the steps of:
(a) connecting the nodes to the two paths in substantially equal numbers so
that the message traffic between the nodes is split between the two paths
and both paths are always active;
(b) periodically sending, receiving, and verifying pre-established messages
with all the nodes on the paths from an independent control computer to
verify that the network is still operating normally and accurately.
37. The method of operating a local area network of claim 36 and
additionally comprising the steps of:
(a) switching a node that does not properly send and receive the
pre-established message to the other path;
(b) repeating the sending and receiving of the pre-established message with
the switched node to verify if the node or its connection to the network
is improperly functioning;
(c) notifying maintenance personnel of a node malfunction if the
pre-established message is not properly sent over the other path; and,
(d) notifying maintenance personnel of a network connection malfunction if
the pre-established message is properly sent over the other path
38. The method of operating a local area network having a plurality of
simultaneously operating communications paths for the transfer of messages
between a plurality of nodes selectively connectable to any one of the
paths to provide better and more reliable operation of the network
comprising the steps of:
(a) monitoring the messages on the paths independent of the nodes to
identify the sending and receiving nodes of the messages; and,
(b) when the number of messages between a plurality of nodes exceeds a
preset limit during a pre-established time period, transferring that
plurality of nodes to a dedicated path not shared with other nodes.
39. The method of operating a local area network of claim 38 wherein:
said step (a) thereof includes monitoring for nodes designated as high
priority nodes and switching high priority nodes to a common path not
shared with other non-high priority nodes. |
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Claims |
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Description |
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TECHNICAL FIELD
The present invention relates to local area networks and, more
particularly, to a local area network having the ability to find, isolate,
and aid in the correction of network faults. In particular, it relates to
a redundant error-detecting and correcting local area networked computer
system having a plurality of nodes each including a network connector
board within the node for connecting to an interfacing transceiver
operably attached to a network cable and comprising a first network cable
disposed along a path to interconnect the nodes, the first network cable
including a plurality of first interfacing transceivers attached thereto;
a second network cable disposed in combination with the first cable, the
second network cable including a plurality of second interfacing
transceivers attached thereto; a plurality of three position switches each
having a signal input, three outputs for individual selective connection
to the input, and a control input for receiving signals designating which
of the outputs is to be connected to the signal input, each of the
switches including means for designating a response address for responding
to addressed signals appearing at the control input, each of the switches
further having its signal input connected to a respective one of the
input/output lines from the nodes, one of the three outputs being
connected to a respective one of the plurality of first interfacing
transceivers, and another of the three outputs being connected to a
respective one of the plurality of second interfacing transceivers; master
switch control means having an output connected to the control inputs of
the plurality of three position switches and an input for receiving
directive signals for outputting addressed switch position signals to the
three position switches; and, monitor and control computer means having a
pair of network connector boards therein connected to respective ones of
one of the first interfacing transceiver and one of the second interfacing
transceivers and an output connected to the input of the master switch
means for monitoring the status of the networked computer system by
sending messages to the nodes and receiving and verifying messages
therefrom and for sending control signals to the master switch to cause
the master switch to cause respective ones of the nodes to use a desired
one of the first and second cables for transmitting and receiving messages
and for disconnecting desired ones of the nodes from both cables.
DESCRIPTION OF THE PRIOR ART
The networking of workstations, nodes, and other computer entities has
grown rapidly in user acceptance. So called "local area networks" (LAN's)
come in numerous configurations. There are straight lines, stars, and
rings or loops. Regardless of the type of physical cabling (electrical,
shielded coaxial, fiber optic, or the like) the end result is the same.
The computers are individually hooked to the LAN through an interface by
which they can put messages onto the LAN and read messages from the LAN.
Despite high interest in and acceptance of LANs, the technology has grown
with tunnel vision; that is, much energy has been devoted to the
technology of the electronics and the software associated with the LAN and
its use but virtually no effort has been expended in monitoring and
controlling the moment-to-moment health of the LAN so as to prevent errors
and downtime.
The use of redundant LANs is old in the art. Other electronic and
telecommunications applications employed redundant cabling for backup
capabilities and, therefore, it was a logical extension to apply this
technology to LANs. In a ring or loop LAN, communications are only in one
direction so duplex operation is not a consideration. In non-looped
networks, the use of a pair of single-direction cables (i.e., one for
transmitting and one for receiving) has been a common approach to
eliminating duplex mode considerations.
Despite the modern technology of electronics and software which has been
developed, prior art LANs depend on user dissatisfaction and stone axe
approaches to discover problems with the LAN and to effect isolation and
correction thereof. As individual users notice erroneous or strange
behavior at their workstation, they call the central service department to
inquire as to whether not there are problems with the network. A multitude
of calls alerts the service department that there may be a problem
somewhere on the network. The type of complaints and locality of the
complained about workstations gives a first indication of a probable
source of the problem, if any. A service engineer is then dispatched to
the area to attempt to isolate, identify, and solve the problem. Few tools
are available to the service engineer to isolate LAN problems; typically,
each node is removed one by one until the problem (hopefully) goes away.
Because these blind trouble shooting techniques are the only ones
available, the duration of the LAN's down time can never be predicted. As
can be realized, such an approach is far from satisfactory--particularly
in applications of a critical nature.
A typical prior art LAN having redundant backup capability is shown in FIG.
1. The network, generally indicated as 10, comprises two LAN cables 12,
14, labelled "LAN1" "LAN2", respectively. A plurality of workstations 16
are attached to LANs 12, 14 by interfacing transceivers 18. Each
workstation 16 has a pair of network interface boards 20, 22 for
connecting to respective ones of the LAN cables 12, 14. An internet router
24 is also provided for communicating with other LANs (not shown). The
internet router 24 also includes network interfacing boards 20, 22
connecting the LANs 12, 14 with interfacing transceivers 18. Additionally,
the internet router 24 connects to a pair of modems 26 which are connected
to the other networks (not shown) through lines 28.
In this prior art configuration, it is proposed to have a system monitoring
computer (SMC) 30 including network interfacing transceiver boards 20, 22
and connected to respective ones of the LANs 12, 14 in order to monitor
the status of the network 10. Unfortunately, in a configuration such as
that shown in FIG. 1, there is very little the SMC 30 could do in the way
of monitoring and acting on the health of the network. Moreover, computers
incorporating two network interfacing transceiver boards such as 20 and 22
are rare if they exist at all. Obviously, more space and expense is
required for duplicate boards. To employ such a duplicate configuration in
each computer element of the network would be difficult at best.
Additionally, the associated software for interfacing with the network
becomes much more complicated and prone to errors since multiple addresses
for inputting and outputting must now be employed and maintained. Many
times, each backup interfacing transceiver board 20, 22 must be put into
action manually, via software commands, making for a slow transition
(especially if the LAN spans several floors and/or several buildings)
which does not guarantee system recovery.
Thus, while there are redundant LANs and attempts to monitor them, there is
no LAN configuration in the art having simplified software and electronics
in the existing equipment which allows for continuous monitoring of the
health of the network. Likewise, there is no LAN which can rapidly
identify the existence of a fault or error condition in the network,
isolate it, and alert service personnel to the existence and location of
the problem so that it can be rapidly resolved.
DISCLOSURE OF THE INVENTION
This invention is a redundant error-detecting and correcting local area
networked computer system having a plurality of nodes each including a
network connector board within the node for connecting to an interfacing
transceiver operably attached to a network cable. There is a first network
cable disposed along a path to interconnect the nodes. The first network
cable includes a plurality of first interfacing transceivers attached
thereto. A second network cable is disposed in parallel with the first
cable and, in like manner, includes a plurality of second interfacing
transceivers attached thereto. There are a plurality of three position
switches each having a signal input, three outputs for individual
selective connection to the input, and a control input for receiving
signals designating which of the outputs is to be connected to the signal
input. Each of the switches includes means for designating a response
address for responding to addressed signals appearing at the control input
and each of the switches further has its signal input connected to a
respective one of the input/output lines from the nodes. Also, one of the
three outputs is connected to a respective one of the plurality of first
interfacing transceivers, and another of the three outputs is connected to
a respective one of the plurality of second interfacing transceivers.
There is master switch control means having an output connected to the
control inputs of the plurality of three position switches and an input
for receiving directive signals for outputting addressed switch position
signals to the three position switches as well as monitor and control
computer means having a pair of network connector boards therein connected
to respective ones of one of the first interfacing transceivers and one of
the second interfacing transceivers and an output connected to the input
of the master switch means for monitoring the status of the networked
computer system by sending messages to the nodes and receiving and
verifying messages therefrom and for sending control signals to the master
switch to cause the master switch to cause respective ones of the nodes to
use a desired one of the first and second cables for transmitting and
receiving messages and for disconnecting desired ones of the nodes from
both cables.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified block diagram drawing of a prior art approach to a
redundant local area network.
FIG. 2 is a simplified block diagram drawing of a redundant local area
network according to the present invention in its most basic form.
FIG. 3 is a simplified block diagram drawing of a redundant local area
network according to the present invention in its preferred embodiment.
FIG. 4 is a simplified block diagram drawing of a computer controlled
master switch as employed in the preferred embodiment of the present
invention.
FIG. 5 is a simplified block diagram drawing of one of the slave switches
employed in the preferred embodiment of the present invention.
FIG. 6 is a simplified drawing of a Network Status Monitor as might be
employed with a local area network according to the present invention to
allow service personnel to monitor the health of the network.
FIG. 7 is a simplified block diagram drawing of a redundant local area
network according to the present invention in an alternate embodiment with
a plurality of network cables and allowing priority levels within the
network.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 depicts the present invention in its most basic (and, therefore,
non-preferred) form. It should be noted that in the descriptions
hereinafter, only one type of interconnection between LANs is shown. It
should be understood that the interconnect router is just an example of
one type of LAN interconnection and does not preclude the use of any of
the many other types of possible interconnections, such as bridges,
repeaters, gateways, etc. The network 10 of FIG. 2 is an improvement over
the prior art network 10 of FIG. 1; however, due to its generally manual
nature, it falls short of the desired capability of rapidly and accurately
identifying and isolating errors in the network. It is worth investigating
briefly, however, since the changes incorporated therein form the basis
for the preferred embodiment to be described shortly.
In network 10', each workstation 16 needs only one network interfacing
transceiver board 20' in the usual and well known manner. The
bidirectional output line 32 from the interfacing transceiver board 20' is
connected as a bidirectional input to a three-position switch 34. Each
switch 34 has one bidirectional output 36 connected to a interfacing
transceiver 18 on LAN1 12 and a second output 38 connected to a
interfacing transceiver 18 on LAN2 14. All the switches 34 are connected
by a control line 40 to a master control line 42 which, in turn, is
connected to a three-position manual switch 44. An internet router 24 and
SMC 30 are, once again, provided and are connected in the same manner as
the workstations 16. By using the manual switch 44, the workstations 16,
internet router 24 and SMC 30 can be switched, collectively, from one LAN
12, 14 to the other or to a "neutral" position disconnected from either
LAN. In addition, by using the individual switches 34, the workstations
16, internet router 24, and SMC 30 can be switched individually from one
LAN 12, 14 to the other or to a neutral position disconnected from either
LAN. As will be appreciated, the complexity in the workstations 16 and
other components is reduced by this basic approach but, unfortunately,
little improvement is made in the capability of monitoring the health of
the network 10' over the prior art network 10 of FIG. 12 since the SMC 30
is not in control of the monitoring process. That is the very improvement
implemented by the preferred embodiment which will now be described.
The preferred network of the present invention is generally indicated as
10" in FIG. 3. As in the basic network 10' of FIG. 2, the workstations 16
and internet router 24 have a single interfacing transceiver board 20'
having a bidirectional output line 32 therefrom. Again, network 10" of the
present invention employs a three-position slave switch 48 which will be
discussed in greater detail shortly. As with the prior art network of FIG.
2, each slave switch 48 has its bidirectional output lines 36 and 38
connected to interfacing transceivers 18 on LANs 12, 14, respectively.
Additionally, however, each slave switch 48 has a control line 40 input
thereto which is connected to the master control line 42 which, in turn,
is connected to a master switch 50 which will also be described in greater
detail shortly. The master switch 50 has an input control line 2 which is
connected to an SMC 30. Unlike the other nodes of the network 10",
however, the SMC 30 of the present invention includes two network
interfacing transceiver boards 20, 22 in the manner of the prior art
network of FIG. 1. Thus, the SMC 30 is capable of simultaneously
monitoring both LANs 12, 14. These two LANs, in the present invention, are
concurrently active. As will be seen shortly, this permits a much broader
and useful capability in the SMC 30 not possible with the prior art
configuration of FIG. 1 as discussed above.
Turning now to FIG. 4, the master switch 50 of the present invention is
shown therein in greater detail. Master switch 50 comprises a one-chip CPU
54 of a type well known in the art and generally available commercially
which includes a memory (not shown) for holding the instructions to be
executed thereby. An RS422, or similar, output driver 56 interfaces
between the master control line 42 and one of the CPU's outputs as shown
and is used to send signals to the slave switches 48 in a manner to be
described shortly. An RS232, or similar, input receiver 58 interfaces
between the CPU and the input control line 52 over which control signals
are input by the SMC 30 to effect its various functions. It is preferred
that manual override switches 60 be provided so that all the components on
the network 10" can be connected to one of the LANs 12, 14 by manual
override such as for maintenance, and the like. As a visual indication to
the service personnel of the status of the system, LEDs 62, 64 are
connected to be driven by the one-chip CPU 54 so as to indicate the
presence of an output command to one LAN or the other. In the preferred
configuration, LED 62 is red and indicates that all nodes have been
commanded to switch to LAN1 12, while LED 64 is green and indicates a
similar result with respect to LAN2 14. If either of the two LEDs is ON,
it indicates a manual override status. Normally they will be OFF.
Turning now to FIG. 5, one of the slave switches 48 of the present
invention is shown therein in greater detail. As with the master switch
50, the heart of each slave switch 48 is a one-chip CPU 54. In this case,
the input receiver 58 is connected to control line 40 which, it will be
remembered, is connected to the master control line 42 connecting to the
master switch 50 of FIG. 4. The one-chip CPU 54 is also connected over a
multiple conductor cable 66 to an address selector DIP switch 68 which is
used to provide each slave switch 48 with a unique address on the network
10". This, of course, is a technique well known in the art and forms no
point of novelty within the present invention per se.
Each slave switch 48 is provided with a local/computer control switch 70 by
which each slave switch 48 can be used to force connection to LAN1 12,
LAN2 14 or a "neutral" (i.e., unconnected to either LAN) position. Note
that for simplicity the multiconductor transceiver cable is shown as a
single thick line and with flow described in only one direction, whereas
the flow in some conductors therein is actually in the opposite direction.
When switch 70 is in the "SLAVE" position, which is the default position,
the slave switch 48 responds to signals on control line 40 originating the
SMC 30. Each CPU 54 within a slave switch 48 is connected by line 72 to
control the position of an analog switch 74 in a manner well known in the
art. Each analog switch 74 has a single input 76 to which a multiple
interfacing transceiver cable (i.e., line 32) from the associated device
is connected. Each analog switch 74 has three positions. In a first
position, the input 76 is connected to an output 78 to which the multiple
conductor cable previously indicated as line 36 is connected so as to
connect the associated device to the transceiver 18 of LAN1 12. In similar
fashion, in a second position, the input 76 of analog switch 74 is
connected to a second output 80 to which the multiple conductor cable
previously indicated as line 38 is connected which, in turn, connects to
the transceiver 18 of LAN2 14. In a third position, the input 76 of the
analog switch 74 is not connected to either output 78, 80. This is the
"neutral" position previously mentioned and completely disconnects the
associated computing device from the network 10". The CPU 54 of each slave
switch 48 is connected to drive three LEDs. LEDs 62 and 64 are red and
green, respectively, and function in the same manner as the LEDs 62, 64
associated with the master switch 50. LED 82, in the preferred embodiment,
is yellow and indicates that the slave switch 48 is in the neutral
position.
Having thus described the basic changes to the network 10" of the present
invention which make the objectives thereof possible, the details of
additional equipment employed and the manner of monitoring the network's
health will now be described.
Turning first to FIG. 6, a proposed Network Status Monitor (NSM) 84 is
shown as might be employed with the present invention to allow service
personnel to have a central location for determining the health of the
network. Such a monitor is only suggested and is not necessary to the
successful implementation of the present invention, of course, as the
various components thereof could be disposed at various other locations if
desired. | | |
