United States Patent [19]
`de Nijs et al.
`'
`
`llllllllllllllllllllllll|l|l||l|lllllllllllllllllllllllllllllllllllllllllll
`5,568,525
`Oct. 22, 1996
`
`[11] Patent Number:
`[45] Date of Patent:
`
`US005568525A
`
`[54] SYSTEM AND METHOD FOR CONNECTION
`OF MULTIPLE PROTOCOL TERMINALS
`
`[75] Inventors: Richard H. J. de Nijs; Charles L.
`Haymes; Dale T. Ulmer, all of Raleigh,
`N_C_
`
`[73] Assignee: International Business Machines
`Corporation, Armonk, NY.
`
`[21] Appl' N05 109,185
`[22] Filed:
`Aug 19, 1993
`
`[51] Int. Cl.6 ...................................................... .. HML 7/00
`[52] US. Cl. ........... ..
`375/356; 370/855; 370/8514
`[58] Field of Search ................................... .. 375/106, 107,
`375/108, 359; 370/1001, 103, 1052, 95_1,
`953, 85_1, 355, 85,12, 85_14
`
`[56]
`
`References Cited
`
`US‘ PATENT DOCUMENTS
`9/1987 Gagliardi 813.1. .............. .. 370/1001 X
`2/1989 Van Asselt ..... ..
`370/100.1 X
`9/1990 Stone et al. ..
`375/107 X
`4/1991 Shobs et al. .
`370/110.l
`7/1993 Dresher ............................. .. 375/108 X
`
`4,696,001
`4,805,169
`4,955,020
`5,012,470
`5,228,030
`
`OTHER PUBLICATIONS
`
`IBM, TDB, vol. 29, No. 9, Feb. 1987, pp. 3776-3778.
`IBM, TDB, Jul., 1986, pp. 892-900.
`
`Primary Examiner—Stephen Chin
`Assistant Examiner-Bryan E. Webster
`Attorney, Agent, or Fim1—Stephen T. Keohane
`
`ABSTRACT
`[57]
`A network port con?gurator device for automatically con
`?guring a system having network workstations and corre
`sponding network equipment of various physical protocols.
`The network port con?gurator comprises a plurality of input
`and output ports for receiving physical wiring to which the
`workstations and network equipment are attached. Detection
`circuitry attached to the input and output ports determine the
`physical protocol of the attached workstations and network
`equipment by determining a characteristic of the attached
`equipment. Examples of identifying characteristics include a
`characteristic impedance, a characteristic voltage, and a
`characteristic cable identi?cation of the workstation. Logic
`circuitry uses this information to Control a Circuit Switching
`mechanism that connects the input ports to the output ports.
`-
`
`20 Claims, 5 Drawing Sheets
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`D-Link-1011
`Page 1 (of 11)
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`U.S. Patent
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`Oct. 22, 1996
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`US. Patent
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`Oct. 22, 1996
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`Page 3 (of 11)
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`U.S. Patent
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`Oct. 22, 1996
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`U.S. Patent
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`Oct. 22, 1996
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`US. Patent
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`0a. 22, 1996
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`5,568,525
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`1
`SYSTEM AND METHOD FOR CONNECTION
`OF MULTIPLE PROTOCOL TERMINALS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to the interconnection of
`digital communications networks and, more particularly, to
`a system for automatically connecting a network worksta
`tion of a particular protocol type with network equipment of
`the same protocol type.
`2. Background and Prior Art
`Rapid changes in digital communications networks have
`generated a multiplicity of network types, many of which
`co-exist. For example, many times both host-centric and
`distributed communications networks are used within a
`business environment. Each type of network has a useful
`function necessary in many business environments.
`A host-centric communications network is one in which
`all information transferred between connected devices is
`managed by a central host processor unit. An example of a
`host-centric network is one comprising a mainframe from
`International Business Machines (IBM)® (such as a System/
`390®) having a plurality of display terminals (such as IBM
`3270 Information Display Systems) connected via a control
`unit (such as an IBM 3174 terminal controller).
`A distributed communications network is one in which
`information is transferred between devices attached to the
`network without the intervention of a central host processor.
`These distributed networks can be constructed from local
`area network technologies, such as Ethernet (as de?ned by
`the IEEE 802.3 standard) or token ring (IEEE 802.5 stan
`dard).
`The ad hoc development and deployment of the various
`types of networks in earlier years has resulted in non
`compatibility for interconnection. Each network type has its
`own protocols under which it operates and communicates
`with other networks of the same protocol type. For instance,
`a networking protocol may de?ne the manner in which the
`data is framed or in which errors are checked. Furthermore,
`a networking protocol normally de?nes the physical inter
`face, or the actual physical connectivity and medium used by
`the network. This physical interface de?nition is analogous
`to the physical layer of the seven-layer Open Systems
`Interface (OSI) reference model. Examples are the use of
`unshielded twisted pair, coaxial or ?ber optic cabling for the
`transmission of bit streams across the particular physical
`medium. Thus, a business having multiple networks, each of
`a unique protocol, many times has corresponding sets of
`wiring in its facility to accommodate them.
`Currently, as multiple networks are installed in facilities,
`the wiring and physical ports compatible with each type of
`network physical interface also are installed. That is, distinct
`sets of wiring media are routed throughout the facility to the
`points where the distinct network workstations (devices/
`terminals) and network equipment (such as hosts or host
`control units) are located.
`Common practice is to install the various sets of wiring
`media in a star con?guration from a wiring hub or termi
`nation point to the network workstations and to the network
`equipment in a point-to-point manner. This method of wiring
`also facilitates the management of the networks by provid
`ing a central management point as well as resolving the
`architectural considerations to provide spaces, such as wir
`ing closets, to house electrical wiring panels and commu
`nications equipment.
`
`10
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`25
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`35
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`2
`Contemporary installation of wiring media utilizes a
`single multiprotocol cable that is electrically compatible
`with several network types. For example, data-grade,
`shielded-twisted pair wiring is being used to transmit data
`conforming to the token ring, Ethernet lObaseT, and RS232
`serial protocols.
`The use of such a multiprotocol medium eliminates the
`need to wire facilities differently for each unique network. In
`addition, such a wiring system permits a device, equipped
`with one of many interfaces, connected to a nearby port
`wired with the single multiprotocol medium to communicate
`with the appropriate controller, concentrator, multiplexor, or
`hub connected at the other end to complete the network
`connection. Furthermore, the use of such multiprotocol
`medium permits a device to be moved to another office, for
`instance, no matter which physical interface the device has
`if the o?ice has a multiprotocol-wired port.
`An example of this is shown in FIG. 1A. The system 10
`comprises a wiring closet 12 for providing a centralized
`location for the network wiring to terminate, and two of?ces,
`Office 14 and O?ice 16, each having a wall port, Wall Port
`18 and Wall Port 20. O?ice 14 has a Terminal Workstation
`22 connected to Wall Port 18 while Office 16 has a Token
`Ring Workstation 24 connected to Wall Port 20.
`In Wiring Closet 12, a Patch Panel 26 connects Cabling 28
`from Wall Port 18 and Cabling 30 from Wall Port 20 to a
`Terminal Controller 32 and a Token Ring Multistation
`Access Unit (MAU) 34 via Cabling 36 and Cabling 38,
`respectively. Terminal Controller 32 and Token Ring MAU
`34 are respectively connected to their corresponding net
`works via Cabling 40 (to/from Mainframe) and Cabling 42
`(to and from token ring network).
`In the case where Cabling 28 and Cabling 30 are multi
`protocol wiring media, in this case, both supporting the
`token ring (for Token Ring Workstation 24) and synchro
`nous data link control (SDLC) (for Ternrinal Workstation
`22) physical medium protocols, Token Ring Workstation 24
`may be moved to O?ice 14 and connected to Wall Port 18
`as Cabling 28 supports the token ring physical protocol.
`Likewise, Terminal Workstation 22 may be moved to Office
`16 and connected to Wall Port 20. In .order for the network
`workstations to communicate with their respective net
`works, however, Cabling 36 and Cabling 38 must be
`swapped at Patch Panel 26, i.e., Cabling 36 must be discon
`nected from Patch Panel Port 46 and connected to Patch
`Panel Port 48 and vice versa with Cabling 38. This process
`is a manual one and requires that a technician, ?rst, ?nd the
`cable associated with the newly attached device, then dis
`connect the cable from its current point of attachment, and
`?nally, reconnect it to a designated port on equipment that
`is compatible with the device being attached.
`Other communications equipment, known as media cen
`ters or intelligent hubs (IHUBS), have been devised to
`replace patch panels in wiring closets so that the networks
`connected thereto can be remotely managed. Similarly, in
`this system, the terminals or other devices are connected to
`wall ports which are attached by various media, including
`multiprotocol media, to these hubs. Within the IHUBs,
`modules, or “blades”, for each individual protocol type
`supported (such as token ring or Ethernet networks) are
`installed. The workstations are connected to these blades. It
`is possible to remotely recon?gure such an IHUB by means
`of a network manager so that a workstation of one type, such
`as a token ring workstation, may be disconnected from its
`port and reconnected to another port, so long as the other
`port is connected to a token ring blade within the IHUB.
`
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`3
`However, a workstation of one type may not be moved to a
`port con?gured for another type of workstation. This is
`shown in FIG. 1B where Terminal Workstation 22 in Of?ce
`14 is connected to Terminal Controller Blade 32‘ in IHUB 50
`and Token Ring Workstation 24 in O?icc 16 is connected to
`Token Ring Blade 34' in IHUB 50. If Terminal Workstation
`22 and Token Ring Workstation 24 were to exchange o?ices,
`Terminal Workstation 22 moving to O?ice 16 and connect
`ing to Wall Port 20 and Token Ring Workstation 24 moving
`to Of?ce 14 and connecting to Wall Port 18, Cabling 28 and
`Cabling 30 would have to be manually exchanged. The
`IHUB 50 is only recon?gurable using Network Manager 52
`if the workstations are of the same protocol type and are
`connected to the same blade or dilferent blades (if an
`additional bridging blade were available and installed).
`Presently, there is no system or method of automatically
`connecting a network workstation with its corresponding
`network equipment based upon physical interface protocol
`of the network. There is a need for such a system as network
`workstations become more portable as laptop and palmtop
`personal computers become more proli?c in their use. This
`requirement is shown by the existence of these and other
`PCs having more than one network interface adapter
`installed therein.
`
`SUMMARY OF THE INVENTION
`
`A network port con?gurator device for automatically
`con?guring a system having network workstations and cor~
`responding network equipment of various physical proto
`cols. The network port con?gurator comprises a plurality of
`input and output ports for receiving physical wiring to which
`the workstations and network equipment are attached.
`Detection circuitry attached to the input and output ports
`determine the physical protocol of the attached workstations
`and network equipment by determining a characteristic of
`the attached equipment. Examples of an identifying charac
`teristic include a characteristic impedance, a characteristic
`voltage, and a characteristic cable identi?cation of the
`workstation. Logic circuitry uses this information to control
`a circuit switching mechanism that connects the input ports
`to the output ports.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`While the technical description concludes with claims
`particularly pointing out and distinctly claiming that which
`is regarded as the invention, details of a preferred embodi
`ment of the invention may be more readily ascertained from
`the following technical description when read in conjunction
`with the accompanying drawings, where:
`FIG. 1A is a block diagram illustrating a prior art instal
`lation of two types of networks in a facility.
`FIG. 1B is a block diagram illustrating a second prior art
`installation of two types of networks ina facility.
`FIG. 2 is a block diagram illustrating an installation, in a
`facility, of two types of networks using the network port
`con?gurator of the present invention.
`FIGS. 3A, 3B and 3C are diagrams illustrating the char
`acteristic impedance of a terminal workstation, a token ring
`workstation and an Ethernet workstation, respectively.
`FIG. 4 is a block diagram of the network con?gurator of
`the present invention.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`FIG. 2 illustrates a facility 50, similar to the facility shown
`in FIGS. 1A and 1B, but having the network port con?gu
`
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`rator 54 of the present invention installed therein. Facility 50
`comprises o?ices 14 and 16 having Terminal Workstation 22
`and Token Ring Workstation 24, respectively. Facility 50
`further has a Wiring Closet 52 connected to Of?ces 14 and
`16 via multiprotocol Cabling 28 and 30, respectively. Wiring
`Closet 52 has a Terminal Network Controller 32 for com
`municating with the Terminal Workstation 22 and a Token
`Ring Multistation Access Unit (MAU) 34 for communicat
`ing with the Token Ring Workstation 24. Terminal Network
`Controller 32 and Token Ring MAU 34 are connected to the
`Network Port Con?gurator 54 of the present invention via
`Cabling 36 and 38, respectively. Terminal Network Control
`ler 32 and Token Ring MAU 34 are connected to, respec
`tively, a mainframe and a token ring network via Cabling 40
`(to/from mainframe) and Cabling 42 (to/from token ring
`network).
`The Network Port Con?gurator 54 of the present inven
`tion automatically connects a network workstation (i.e.,
`Terminal Workstation 22 and Token Ring Workstation 24)
`with its corresponding network equipment (Terminal Net
`work Controller 32 and Token Ring MAU 34) based upon
`physical interface protocol of the network workstation and
`corresponding network equipment. For instance, where Ter~
`minal Workstation 22 is disconnected from Wall Port 18 and
`is moved to O?ice 16 and connected to Wall Port 20, the
`Network Port Con?gurator 54 senses that Terminal Work
`station 22 is connected at its Port 62 and automatically
`establishes a connection between Port 62 and Port 56. The
`Network Port Con?gurator 54 accomplishes this by detect
`ing and determining a characteristic of the attached network
`workstations at Ports 60, 62. Because each type of network
`workstation has a unique characteristic, the Network Port
`Con?gurator is able to determine which type of Workstation
`is attached thereto. Similarly, each type of network equip
`ment has a unique characteristic and, therefore, can be
`distinguished by the Network Port Con?gurator 54 from
`other types of network equipment. It is in this manner that
`the Network Port Con?gurator of the present invention is
`able to automatically recon?gure itself so that the network
`workstations are connected to their corresponding network
`equipment even where the network workstation is discon
`nected from its original location and reconnected elsewhere.
`This is accomplished without any manual intervention.
`The detectable unique characteristic of the various work
`stations can vary, depending upon the network protocol type.
`For example, the characteristic impedances of a token ring
`workstation, an Ethernet workstation and a terminal work
`station (a 3270-type terminal) are three distinct and detect
`able impedances. By detecting and determining the imped
`ance of the attached device (if it is one of these three types),
`the Network Port Con?gurator may determine which type it
`is in order to connect it to its corresponding network
`equipment.
`Schematic diagrams of the characteristic impedance of a
`token ring, a lObaseT Ethernet and a terminal workstation
`are shown in FIGS. 3A, 3B and 3C. As shown in FIG. 3A,
`the characteristic impedance of a terminal workstation, such
`as a 3270—type workstation, is indicated by Zu. Of a standard
`four-wire connector having wires R, G, O, and B, Connector
`51a uses only wires R and G. The impedance between these
`two wires is the transformer impedance of transformer T1.
`There is nothing connected to Wires 0 and B and, therefore,
`the impedance between the two wires is open. The overall
`characteristic impedance of the 3270-type terminal is Zu.
`FIG. 3B illustrates the characteristic impedance of a token
`ring workstation. The characteristic impedance of this work
`station is Zv. The Connector 51b of the token ring worksta
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`5
`tion uses all four wires R, G, O, and B and has transformers
`T2 and T3 connected therebetween. The token ring work
`station further has a Signal Circuit 53 connected between
`R/O and G/B. The overall characteristic impedance of the
`token ring workstation is Zv.
`FIG. 3C illustrates the characteristic impedance of an
`Ethernet l0baseT workstation. The characteristic impedance
`of this workstation is Zw. The Connector 51c of the Ethernet
`l0baseT workstation uses all four wires R, G, O, and B and
`has transformers T4 and T5 connected therebetween. As was
`noted above, the overall characteristic impedance of the
`Ethernet lObaseT workstation is Zw.
`Thus, as each of these workstations has a different char
`acteristic impedance which can be easily detected and
`determined, the Network Port Con?gurator of the present
`invention merely determines the characteristic impedance of
`the attached device in order to determine which particular
`device is attached to each particular port. Characteristic
`impedance is shown as but one example of a characteristic
`by which workstations may be distinguished. Other
`examples include characteristic voltage levels and cable
`identi?cations.
`FIG. 4 illustrates in detail one embodiment of the Net
`work Port Con?gurator 54 of the present invention. Network
`Port Con?gurator 54 comprises a plurality of Network Port
`Con?gurator (NPC) Ports 64, 66, NPC Ports 64 for being
`connected to I/O Ports 61 (for network equipment) and NPC
`Ports 66 for being connected to I/O Ports 63 (for network
`workstations). I/O Ports 61, 63 are connected to the Network
`Port Con?gurator 54 by multiprotocol cabling 57, 59. Con
`nected between NPC Ports 64, 66 via cabling 65, 67,
`respectively, is a Switch 68. Switch 68 can be any type of
`switch which is capable of switching any of the NPC Ports
`66 to any of the NPC Ports 64, such as a cross-bar switch.
`Switch 68 is responsive to control signals transmitted by
`Con?guration (Con?g.) Logic 70 and conveyed by cabling
`72. Con?g. Logic 70 is further connected to Detection
`Circuitry 74 via cabling 76. Both Con?g. Logic 70 and
`Detection Circuitry 74 are under the control of Program
`Control 78 via cabling 80. Detection Circuitry 74 is con
`nected to each of the NPC Ports 66 via cabling 82.
`In general, the Network Port Con?gurator 54 operates as
`follows. I/O Ports 63 are located in various o?ices through
`out a facility operating a number of different network
`protocols, such as token ring networks, Ethernet networks,
`and 3270-type networks. Connected to the I/O Ports 63 are
`network workstations for communicating on the various
`networks. Examples of such network workstations are token
`ring workstations, Ethernet workstations and 3270 termi
`nals. On the other side of the Network Port Con?gurator 54
`are connected the network equipment to I/O Ports 61.
`Examples of network equipment are a token ring multista
`tion access unit (MAU), an Ethernet concentrator, and a
`3174 terminal controller. The network workstations are
`connected to the corresponding network equipment through
`Switch 68. Con?g. Logic 70, which consists of logic cir
`cuitry and switch drivers, generates and transmits control
`signals to the Switch 68 for setting the Switch in the proper
`con?guration, i.e., so that network workstations communi
`cate with their respective and corresponding network equip
`ment. Con?g. Logic 70 generates these control signals based
`upon signals it receives from Detection Circuitry 74 and
`Program Control 78.
`Detection Circuitry 74, which is connected to each of
`NPC Ports 66, contains circuitry for detecting and deter—
`mining the particular characteristic of the network worksta
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`tions (such as characteristic impedance) connected to the I/O
`Ports 63. Based upon the characteristic of the respective
`network workstations (and further based upon the Program
`Control 78), the Detection Circuitry transmits signals to the
`Con?g. Logic 70 so that Switch 68 may be con?gured
`properly.
`Because the particular detected characteristic of each of
`the various types of network workstations is different from
`one another, the Detection Circuitry 74 can determine which
`type of network workstation is connected to the NPC Port
`66. The Detection Circuitry 74 forwards this information,
`i.e., which type of workstation is connected to which NPC
`Port 66, to Con?g. Logic 70. Through Program Control 78,
`Con?g. Logic 70 knows which types of network equipment
`are connected to which NPC Ports 64. By knowing which
`type of network workstation is attached to which NPC Port
`66, the Con?g. Logic 70 is able to transmit the proper
`control signals to Switch 68 so that the Switch 68 is properly
`con?gured, i.e., the network workstations are connected to
`their corresponding network equipment.
`Alternatively, Detection Circuitry 74 may be connected to
`NPC Ports 64, as shown by dashed lines 67a. (For clarity,
`only one dashed line 67a is shown. Not shown are the other
`dashed lines between the remaining NPC Ports 64 and the
`detection Circuit 74.) In this case, Detection Circuitry 74 is
`able to detect a characteristic of the attached network
`equipment, in addition to being able to detect a characteristic
`of the network workstations. Because the various types of
`network equipment have unique characteristics (as do the
`workstations), the Network Port Con?gurator of the present
`invention is able to distinguish them and automatically
`con?gure itself so that the network workstations are properly
`connected with their corresponding network equipment.
`Thus, it can be seen that the method and system of the
`present invention allows network workstations connected to
`the system to be disconnected, moved and reconnected to
`another port of the system and be automatically connected to
`its corresponding network equipment for communication.
`This is accomplished through the unique utilization of a
`detection circuit which detects a characteristic of the
`attached workstations, such as characteristic impedance, so
`that the system may determine the type of network. It is in
`this manner that the workstation may be automatically
`connected to its corresponding network equipment without
`manual intervention. While the invention has been particu
`larly shown and described with reference to preferred
`embodiments thereof, it will be understood by those skilled
`in the art that various other changes in form and detail may
`be made without departing from the spirit and scope of the
`invention.
`What is claimed is:
`1. For use with a plurality of network workstations and a
`plurality of network equipment, each workstation and each
`network equipment being a protocol type of a set of protocol
`55
`. types, a system for automatically connecting a workstation
`of a particular protocol type with a network equipment of the
`same protocol type, each workstation of a particular protocol
`type having a unique physical characteristic as compared to
`workstations of other protocol types, said system compris
`ing:
`a plurality of workstation ports for connecting to one or
`more workstations;
`a plurality of network equipment ports for connecting to
`one or more network equipment, at least one of said one
`or more network equipment being of the same protocol
`type as at least one of said one or more workstations;
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`means connected to said workstation ports for determin
`ing the protocol type of said set of protocol types of
`each of said workstations connected to said workstation
`ports by determining said unique physical characteris
`tic of said workstation, said protocol determining
`means generating an output indicative of each said
`protocol type; and
`means, connected between said workstation ports and said
`network equipment ports, for establishing connections
`between said workstation ports and said network equip
`ment pens, said establishing connections means being
`responsive to said protocol determining means output.
`2. The system de?ned in claim 1 wherein said unique
`physical characteristic is a characteristic impedance and said
`protocol determining means comprises an impedance detec
`tion means for detecting the characteristic impedance of said
`workstations.
`3. The system de?ned in claim 1 further comprising
`means connected to said network equipment ports for deter
`mining the protocol type of said network equipment, said
`network equipment protocol determining means generating
`an output indicative of said network equipment protocol and
`means, connected between said workstation ports and said
`network equipment ports, for establishing connections
`between said workstation ports and said network equipment
`ports, said establishing connections means being responsive
`to said network equipment protocol determining means
`output.
`4. The system de?ned in claim 3 wherein said unique
`physical characteristic is a characteristic impedance and said
`network equipment protocol type determining means com»
`prises a detection circuit for determining the characteristic
`impedance of said network equipment.
`5. The system de?ned in claim 1 wherein said connection
`establishing means is responsive to said protocol detemrin
`ing means output so that a workstation of a particular
`protocol type is connected with a network equipment of the
`same protocol type.
`6. For use with a system for con?guring networks, said
`networks comprising a plurality of network workstations
`and a plurality of network equipment, each workstation and
`each network equipment being a protocol type of a set of
`protocol types, a method for automatically connecting a
`workstation of a particular protocol type with a network
`equipment of the same protocol type, each workstation of a
`particular protocol type having a unique physical character
`istic as compared to workstations of other protocol types,
`said method comprising the steps of:
`determining the protocol type of said set of protocol types
`of a ?rst workstation by determining said unique physi
`cal characteristic of said workstation, said protocol
`determining means generating an output indicative of
`said protocol type; and
`establishing a connection, based upon said output,
`between said ?rst workstation and a network equipment
`having the same protocol type of said set of protocol
`types as said ?rst workstation.
`7. The method de?ned in claim 6 wherein said unique
`physical characteristic is a characteristic impedance and said
`protocol type determining step comprises the step of detect
`ing the characteristic impedance of said ?rst workstation.
`8. The method de?ned in claim 6 further comprising the
`steps of determining the protocol type of said network
`equipment, generating an output indicative of said network
`equipment protocol type and establishing connections
`between said workstation ports and said network equipment
`ports based upon said network equipment protocol type
`output.
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`9. The method de?ned in claim 8 wherein said unique
`physical characteristic is a characteristic impedance and said
`network equipment protocol type determining step com
`prises the step of determining the characteristic impedance
`of said network equipment.
`10. An automatically recon?gurable network comprising:
`a plurality of network workstations and a plurality of
`network equipment, each workstation and each net
`work equipment being a protocol type of a set of
`protocol types, each workstation of a particular proto
`col type having a unique physical characteristic as
`compared to workstations of other protocol types;
`means connected between said workstations and said
`network equipment for automatically connecting a
`workstation of a particular protocol type of said set of
`protocol types with a network equipment of the same
`protocol type of said set of protocol types comprising
`‘a plurality of workstation ports for connecting to one or
`more workstations, a plurality of network equipment
`ports for connecting to one or more network equip
`ment, at least one of said one or more network equip
`ment being of the same protocol type as at least one of
`said one or more workstations, means connected to said
`workstation ports for determining the protocol type of
`said one or more workstations by determining said
`unique physical characteristic of each said one or more
`workstations, said protocol determining means gener
`ating an output indicative of said protocol type, and
`means, connected between said workstation ports and
`said network equipment ports, for establishing connec
`tions between said workstation ports and said network
`equipment ports, said establishing connections means
`being responsive to said protocol determining means
`output.
`11. The network de?ned in claim 10 wherein said unique
`physical characteristic is a characteristic impedance and said
`protocol determining means comprises an impedance detec
`tion means for detecting the characteristic impedance of said
`workstations.
`12. The network de?ned in claim 10 f