WO1997034440A1

WO1997034440A1 - Method and apparatus for communicating engineering orderwire information over synchronous communications network

Info

Publication number: WO1997034440A1
Application number: PCT/GB1997/000597
Authority: WO
Inventors: Christopher David Murton; Stephen Ian Roberts; Edward Mark Switalski
Original assignee: Northern Telecom Limited; SWITALSKA, Joanna, Theresa
Priority date: 1996-03-13
Filing date: 1997-03-05
Publication date: 1997-09-18
Also published as: CN1128561C; GB9605260D0; EP0951796A1; AU2100097A; CN1213483A

Abstract

A synchronous digital communications network comprises a plurality of node devices (301, 302, 304, 305) linked by a plurality of link devices, which communicate by means of an optical aggregate. An engineering orderwire facility is provided between node devices, the facility comprising a plurality of data terminals (306), which can be connected directly to individual node devices for communicating across the optical aggregate. The data terminals perform packetization, de-packetization and compression of engineering orderwire data, and operate over an OSI protocol stack.

Description

METHOD AND APPARATUS FOR COMMUNICATING ENGINEERING ORDERWIRE INFORMATION OVER SYNCHRONOUS COMMUNICATIONS

NETWORK

Field of the Invention

The present invention relates to digital communications networks, and particularly although not exclusively, to transmission of engineering data between network elements of a synchronous digital communications network.

Background to the Invention

In synchronous digital communications networks, such as synchronous digital hierarchy (SDH) networks operated in accordance with International Telecommunication Union Recommendations ITU-T G.70X¹ , or the North American Synchronous Optical Network System (SONET), such networks comprise a plurality of network elements comprising node devices connected by a plurality of link devices. Examples of link devices include long distance optical fiber communications links and optical regenerators connecting the plurality of node devices, such as multiplexers and interface equipment. The node devices may be separated from each other by long distances, of the order of tens to hundreds of kilometers. In order to construct such synchronous digital communications networks, and to perform maintenance operations on existing such synchronous communications networks, one or more craft or engineer personnel need to be present at each end of a link. The personnel at different ends of a link may be geographically separated by a large distance and need to communicate with each other in order to transfer instructions and engineering information during the course of installing the network elements. Since the svnchronous network may be installed in remote geographical regions where basic communications infrastructure is not yet in place, there is a problem in engineers communications with each other during commissioning or maintenance of synchronous digital communications network equipment. Normal service communications across the network may not be possible, since the network may be still under construction or under maintenance. As the equipment needs to be installed indoors, and often in an electrically shielded environment, the use of mobile telephone communications is precluded.

For earlier conventional types of communications network, for example the plain old telephone system (POTS) operating Plesiochronous Digital Hierarchy (PDH) methods, the traditional way of providing engineering information between network elements is to use a facility known as an engineering orderwire (EOW). A conventional engineering orderwire comprises a point to point telephone system which is built into conventional transmission system. The engineering orderwire has a capacity of 64 kbit s, and is capable of carrying voice data.

Referring to Fig. 1 herein, there is illustrated schematically a section of a prior art plesiochronous network, comprising first and second node devices, NE1 , NE2 connected by an optical link 100. To implement the engineering orderwire facility, each network element is provided with a respective engineering orderwire hardware card, 101 , 102 respectively into which may be plugged a conventional telephone handset 103, 104. The conventional engineering orderwire is fine for non-synchronous communications network, but has severe limitations when applied to synchronous digital communications networks.

Firstly, communications networks comprise node devices manufactured by a number of different manufacturers. Implementing the engineering orderwire system involves providing a specific dedicated hardware card fitted to the node device at which it is required to communicate. The dedicated hardware is specific to proprietary node device equipment of different manufacturers, and is not standardized internationally.

Secondly, the conventional engineering orderwire has developed to work on a single point to single point basis. Implementation of engineering orderwire communications between for example three node devices in a network is complicated and expensive, requiring dedicated hardware cards at each of the three node devices, which each may be of different proprietary manufacture. The engineering orderwire cards may not be compatible with one another, and significant effort is required to ensure compatibility between engineering orderwire card equipment at the ends of each of the links. Whilst point to point communication is adequate for plesiochronous networks, synchronous networks may be configured in a number of different ways, including point to point, ring, and hub configurations. A synchronous digital network can adopt a complex topology which leads to complexities in implementing the conventional engineering orderwire. For example in a topology consisting of a number of inter¬ connected ring structures, as illustrated schematically in Fig. 2 herein, communicating between a first node device 200, and a second node device 203, using conventional engineering orderwire apparatus involves creating three individual point to point engineering orderwire communications between respective node devices 200, 201 ; 201 , 202; and 202, 203. Each node device requires its own dedicated engineering orderwire hardware, and the engineering orderwire hardware need to be made compatible with each other to be connected together, where the node devices comprises proprietary equipment made by different manufacturers. Individual point to point connections would need to be individually linked together to provide the necessary communication facility between node device 200 and node device 203. The conventional engineering orderwire system becomes impractical for commission and maintenance of synchronous digital communications networks having ring or hub topologies.

Recognizing that general provision for orderwire facilities would be required in synchronous transmission systems, dedicated orderwire channels designated E1 , E2, each of a single byte have been reserved in the 72 byte section overhead area of the known STM-1 frame of the International Telecommunications Union SDH Recommendations. However, the dedicated orderwire channels using the E1 , E2 bytes have the limitations that the E1/E2 channels are primarily aimed at 64 kbit/s data transfer on a point to point basis. Whilst this may allow for engineering orderwire communications for a series of network elements connected along a line, there are still connectivity problems in ring networks and hub networks and other complex topologies, which the proposed E1/E2 byte orderwire facility does not solve

Specific methods and embodiments according the present invention aim to address some of the above problems.

Summary of the Invention

According to one aspect of the present invention, in a digital communications network comprising a plurality of node devices linked by a plurality of link devices, said communications network having an operation and maintenance channel for transmittal of operation and maintenance information between said node devices, there is provided a method of communicating engineering orderwire data between first and second said node devices comprising the steps of:

inputting engineering orderwire data signals into said first node device;

transmitting said engineering orderwire data to said second node device over said operation and maintenance channel; and

receiving said engineering orderwire data over said operation and maintenance channel at said second node device.

Preferably, said step of inputting said engineering orderwire data to said first node device comprises inputting said engineering orderwire data into a local area network port of said first node device.

The method may be implemented by connecting a conventional Ethernet port of a conventional personal computer or lap top computer to a corresponding Ethernet port of a network element of a synchronous digital communications network. Preferably, the method comprises the step of outputting said engineering orderwire data from a local area network port of said second node device.

Preferably, the method further comprises the step of packetizing said engineering orderwire data into a series of packet data signals, each comprising a data payload signal and a packet protocol overhead signal, wherein said packetized signals are respectively input and output from said first and second node devices.

Preferably a said packet protocol header comprises an address signal specifying an address of a receiving data terminal connected with a said node device.

Preferably, said engineering orderwire data is packetized in accordance with a protocol which does not require packet reception acknowledgment.

Preferably, said input engineering orderwire data is packetized in accordance with an Open System Interconnect (OSI) protocol method,

Said method may comprise the step of compressing said engineering orderwire data.

Preferably, said step of compression comprises compressing said engineering orderwire data in accordance with a Groupe Systeme Mobile data compression algorithm.

Said method may comprise the step of decompressing said engineering orderwire data.

Said communications network preferably comprises a synchronous digital hierarchy (SDH) network. Said operation and maintenance channel may comprise an embedded control channel as specified in International Telecommunications Union Recommendation G.784 of January 1994. This has an advantage that the data communications channel in synchronous digital hierarchy networks is already standardized and equipment from a range of different manufacturers are compatible with each other and reliably operate with each other.

Said communications network may comprise an American National Standards Institute synchronous optical network (SONET) network.

Preferably, said operation and maintenance channel comprises a synchronous digital hierarchy data communications channel carried within bytes D1 to D12 of a synchronous transfer mode (STM) data frame. This enables communications to be made in accordance with the present invention, in addition to the E1 , E2 orderwire channels in a synchronous digital hierarchy STM-1 frame. Further as the Data Communications Channel in synchronous digital hierarchy uses routing to forward packetized data, the point to point connectivity problem associated with conventional electronic orderwire is avoided.

According to a second aspect of the present invention, there is provided in a communications network comprising a plurality of node devices and at least one link device, said node devices adapted to communicate with each other via said link device over an operations and maintenance channel, an engineering orderwire apparatus comprising:

data terminal means operating to generate engineering orderwire data signals;

data packetization means for converting said engineering orderwire data signals into a series of data packet signals; and a multiplexer means for multiplexing said packetized data into said operations and maintenance channel of said communications network.

A said data terminal may comprise a device selected from the set; personal computer; laptop computer; palm top computer; personal organizer; application specific computer.

Preferably, said packetization means comprises: a processor; and a data storage medium, said data storage medium storing control signals for operating said processor to convert said engineering orderwire signals into said series of data packets.

Preferably, said multiplexer comprises a local area network port capable of receiving data signals, and said multiplexer operates to multiplex said packetized data signals received via said local area network port into said operation and maintenance channel.

According to a third aspect of the present invention, in a communcations network comprising a plurality of node devices and at least one link device said node devices adapted to communicate with each other via said link device over an operations and maintenance channel, there is provided an engineering orderwire apparatus comprising:

a demultiplexer means for de-multiplexing packetized data signals carried on said operations and maintenance channel of said communications network;

a de-packetizing means for converting a series of data packet signals each comprising a data payload signal and a protocol header signal into an engineering orderwire data; and a data terminal means capable of receiving said engineering orderwire data signals and of outputting engineering orderwire data corresponding to said engineering orderwire data signals.

Preferably, said de-packetizing means comprises: a processor; and a data storage medium, said data storage medium storing control signals operating said processor to convert said series of packetized signals into said engineering orderwire data signals corresponding to said engineering orderwire data.

A said data terminal may comprise a device selected from the set; personal computer; laptop computer; palm top computer; personal organizer, application specific computer.

Preferably, said demultiplexer comprises a local area network port and said data demultiplexer operates to de-multiplex said packetized data and present said packetized data at said local area network port.

The invention includes communications network comprising a plurality of node devices linked by a plurality of link devices, first and second said node devices being capable of communicating with each other over at least one said link device, wherein at a said first node device is provided:

a first multiplexer means capable of communicating over an operation and maintenance channel of said network;

a first local area network port capable of receiving input engineering orderwire data signals, said first local area network port connected to communicate with said first multiplexer;

a first data packetization means for packetizing an engineering orderwire signal representing engineering orderwire data and connected to communicate with said first local area network port; a first data de-packetization means for de-packetizing received packetized engineering orderwire data signals representing engineering orderwire data; and

at said second said node device is provided:

a second multiplexer means capable of communicating over an operation and maintenance channel of said network;

a second local area network port capable of receiving input engineering orderwire data signals, said second local area network port connected to communicate with said second multiplexer;

a second data packetization means for packetizing an engineering orderwire data signal representing engineering orderwire data and connected to communicate with said second local area network port; and

a second data de-packetization means for de-packetizing received packetized engineering orderwire data signals representing engineering orderwire data, said data de-packetization means connected to communicate with said second local area network port;

wherein, said first and second node devices communicate engineering orderwire data with each other by inputting said engineering orderwire data into a said packetization means, packetizing said engineering orderwire data by a said packetization means, inputing said engineering orderwire data into a said local area network port, multiplexing said engineering orderwire data by a said multiplexer, transmitting said engineering orderwire data between said first and second multiplexers, outputting said engineering orderwire data through a said local area network port and de-packetizing said engineering orderwire data by a said de-packetization means. Preferably, said operation and maintenance channel comprises a synchronous digital hierarchy data communications channel carried within bytes D1 to D12 of a synchronous transfer mode (STM) data frame. Said operation and maintenance channel may be carried in bytes D1 to D3, D4 and D12.

The invention includes a communications network comprising a plurality of node devices linked by a plurality of link devices, wherein;

a first said node device comprises:

a first multiplexer means capable of accessing an operation and maintenance channel;

a first local area network port;

a first interface for communicating between said first multiplexer means and said first local area network port; and

a first terminal apparatus connected to said first local area network port; and

a second said node device comprises:

a second multiplexer means capable of accessing said operation and maintenance channel;

a second local area network port;

a second interface for communicating between said second multiplexer means and said second local area network ports; and

a second terminal apparatus connected to said second local area network port; wherein, said first terminal operates to input engineering orderwire data to said operation and maintenance channel via said first local area network port, said first interface and said first multiplexer; said first multiplexer transmits said engineering orderwire data to said second multiplexer; said second multiplexer outputs said engineering orderwire data to said second local area network port via said second interface; and said second terminal apparatus receives said engineering orderwire data from said second local area network port.

The apparatus may include a keyboard and associated interface means for inputting data from the keyboard for communication to the network element.

The apparatus may be connected separately from the network to a network element that supports OSI protocols in an OSI data communications network.

The apparatus may be connected separately from the network to an SDH network element that supports OSI protocols in an SDH network.

The invention includes an apparatus, having means for communication separately from the network with a network element in an OSI data communications network, said communications implementing OSI protocol; means for transducing speech to outgoing audio signals and received audio signals to sound; and a means for converting outgoing audio signals to packets of data for transmission via said OSI protocols over the network and for converting data packets received from the network via said OSI protocols to received audio signals.

The OSI protocols may permit a human operative to communication through the network with any other network element, eg another such apparatus. The apparatus may allow speech communications between operatives. Since another instance of the apparatus would be identified by its network address in the OSI digital communications network it does not matter where in the network it is located.

Communication with the network element may, for example via a RS232C port or via a LAN port. It is common for the network element to already have a

LAN port for communication with UNIX based workstations and/or a management center. A preferred form of the apparatus conveniently includes a LAN port for the communication with the network element.

The invention includes a method of communication separately from the network with a network element in an OSI data communications network, said communication implementing OSI protocols; the method including transducing speech to outgoing audio signals and transducing received audio signals to sound; wherein outgoing audio signals are converted to packets of data for transmission via said OSI protocols over the network, and wherein data packets received from the network via said OSI protocols are converted to received audio signals.

The means for transducing may comprise a telephone hand set or head set.

In one preferred form, the apparatus is in the form of a handset.

At the site of the network element, it is conventional for the operative to communicate with the element, usually via an RS232C port, using a computer, usually a laptop he/she carries. The laptop may be used where a mobile terminal is used, carried from network element to network element. In a convenient alternative form, the apparatus may include an application specific computer, providing both communication via for example a LAN port using the OSI protocols and providing the conventional functions via an RS232C port. The application specific computer may be used where a permanent terminal installation is provided at a network element. The application specific computer may be configured in a custom made housing including a keypad and telephone handset. The means for transducing may comprise a telephone handset or headset.

The invention extends to the apparatus in combination with a network element that supports OSI protocols in a an OSI data communications network.

The invention also extends to the apparatus in combination with an SDH network element that supports OSI protocols in an SDH network.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Fig. 3 illustrates schematically a synchronous digital communications network comprising a tiered communications ring structure, operating in accordance with a specific method of the present invention and utilizing specific apparatus according to the present invention;

Fig. 4 illustrates schematically one example of a conventional synchronous digital multiplexer/demultiplexer network element comprising the network of Fig. 3;

Fig. 5 illustrates schematically another example of a conventional muliplexer/demultiplexer comprising a network element of the network of Fig. 3;

Fig. 6 illustrates schematically a layout of apparatus according to a specific embodiment of the present invention, comprising first and second network elements and first and second data terminals, for communicating in the network of Fig. 3; Fig. 7 illustrates schematically an architecture of a specific data terminal according to one specific embodiment of the present invention;

Fig. 8 illustrates schematically a functional overview of the data terminal of Fig. 7;

Fig. 9 illustrates schematically an overview of elements comprising a synchronous digital communications multiplexer/demultiplexer network element of the network of Fig. 3 comprising apparatus of a specific embodiment of the present invention;

Fig. 10 illustrates schematically a frame of data signals according to a synchronous transfer mode (STM) transmission mode operating in the network of Fig. 3 herein;

Fig. 11 illustrates schematically in further detail, a section overhead portion of the data frame signal of Fig. 10;

Fig. 12 illustrates schematically a protocol stack comprising a specific method according to the present invention utilized for communication across the communications network of Fig. 3;

Fig. 13 illustrates schematically one example of a method of transmitting engineering data in the communications network of Fig. 3 according to a specific method of the present invention;

Fig. 14 illustrates schematically one example of a method for receiving engineering data and processing the received engineering data according to a specific method of the present invention operating in the communications network of Fig.3; Fig. 15 illustrates schematically an example of a portion of a synchronous digital communications network in which communication of engineering orderwire data between first and second synchronous digital network elements, and over a wide area network is implemented, according to a further specific method of the present invention;

Fig. 16 illustrates an example of data processing steps for connection of a data terminal to a network element, and for transmission of engineering orderwire data onto a synchronous digital communications network.

Fig. 17 illustrates an overview of an example of connection and routing protocols for connection and routing of engineering orderwire data in a synchronous digital communications network;

Fig. 18 illustrates schematically a further example of a synchronous digital communications network according to a further specific embodiment of the present invention; and

Fig. 19 illustrates a relationship between an American National Standards Institute synchronous optical network data frame signal, and a synchronous digital hierarchy synchronous transfer mode data frame signal.

Detailed Description of the Best Mode for Carrying Out the Invention

There will now be described by way of example the best mode contemplated by the inventors for carrying out the invention. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent however, to one skilled in the art, that the present invention may be practiced without using these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention. Referring to Fig. 3 of the accompanying drawings, there is shown schematically a synchronous telecommunications network comprising a plurality of network node devices (NE) connected together by a plurality of digital communications link element devices. One or more network controllers 300 control the operation and maintenance of the network elements through passage of operation and maintenance signals between network elements, for use internally by the network elements. The operation and maintenance signals are transmitted over an operations and maintenance channel. The network operates in a synchronous transfer mode (STM) for communications of data. The node devices may comprise multiplexers which are capable of multiplexing a plurality of relatively low data rate signals into higher data rate signals and repeater devices for amplifying signals along the links. In the network shown in Fig. 3, a first tier of node devices 301 , 302 are separated from each other geographically by large distances, of the order 40 to 90 kilometers, and are connected by long distance optical fiber communications links in a ring arrangement 303. The first tier network element comprise a plurality of multiplexer apparatus 301 connected together by the optical fiber communications links, there being provided a plurality of optical repeater devices 302 between the first tier multiplexers 302 forming the ring. At a second tier of the network, there are provided a plurality of second tier multiplexers 304 which communicate with the first tier multiplexers 301. The second tier multiplexers groom communications data from further synchronous transfer mode (STM) rings of connected third tier multiplexers 305, at a third tier of the network, passing this data to the first tier multiplexers 301. The third tier multiplexers 305 which may comprise for example add-drop multiplexers, may have a remote interface, for connecting to a public switched telephone network (PSTN). Connected to various of the node devices at the third tier of the network are a plurality of data terminals in the form of application specific computers having telephone handsets 306, personal computers 307, laptop computers, palm top computers, or personal organizers. At the first tier of the network, are connected one or more routers 308. Data terminals are connected to the first tier node devices 301 via one or more of the routers 308. Referring to Fig. 4 of the accompanying drawings, there is illustrated schematically a first example of a prior art node device comprising a synchronous multiplexer/demultiplexer 400 as defined in the International Telecommunication Union Synchronous Digital Hierarchy (ITU-T SDH) Recommendations¹. The synchronous multiplexer 400 can accept a wide range of input digital data signals having a wide range of bit rates, from 1.5 Mbit/s to 240 Mbit/s. These input signals may be input through electrical or optical interfaces on a tributary side 401 of the device. On a line side 402 of the multiplexer (otherwise called the synchronous optical aggregate) optical signals may be transmitted at various transmission frame rates corresponding to synchronous transmission mode (STM), transmission rates STM-1 of 155.52 Mbit/s, STM-4 at 622.08 Mbit/s, STM- 16 at 2,488.32 Mbit/s, and STM-64 at 9,953.28 Mbit/s in accordance with ITU-T recommendation G.70X. Thus, the multiplexer 400 inputs and outputs electrical and/or optical signals on its tributary interfaces, which are multiplexed together into optical signals transmitted along optical fibers in the synchronous optical aggregate.

Referring to Fig. 5 herein, there is shown another form of prior art multiplexer/demultiplexer 500 which may comprise a node device of the network of Fig. 3 herein. The second prior art multiplexer/demultiplexer 500 comprises a set of tributary input/outputs 501 operating at data rates of 2 Mbit/s through a remote interface 502 of the device on a tributary side; a set of circuit connections 503 on the tributary side of the device, and a synchronous optical aggregate 504, comprising optical fibers carrying transmission channels at STM-1 , STM-4, STM- 16 and STM-64 data rates. The optical fibers comprise the optical aggregates for the communications links between node devices.

In the best mode described herein, a plurality of personnel may communicate with each other using a plurality of data terminals which can be connected to or disconnected from corresponding respective network element and may be portable about the network. As will be described hereinafter, each data terminal has a corresponding respective address, which identifies it, and which is independent of the topology and layout of the network. Two or more engineering personnel each using a respective data terminal, may communicate engineering orderwire data over optical channels of the network by connecting their data terminal apparatus directly to a local area network port of the network elements. In this specification, the term engineering orderwire is used to describe data communicated between service, engineering or craft personnel located at different node devices of the network. Depending upon the type of data terminal used, engineering orderwire data such as voice signals, facsimile or e-mail signals, graphics data, or low resolution video data may be communicated between data terminals. A new network element can be introduced anywhere in the network, and by connecting the data terminal to the new network element, the data terminal will be able to communicate with one or more other data terminals connected to any other network elements of the network.

Referring to Fig. 6 herein, there is illustrated first and second node devices

600, 601 respectively of the network of Fig. 3, to each of which is connected a corresponding respective data terminal 602, 603, comprising in this example a laptop personal computer. When installing, commissioning or maintaining the network, communication of engineering data needs to be made by craft personnel located at the first and second node devices 600, 601 , for installing or maintaining the network elements. The craft personnel require communication with each other, in order to set up connections between the first and second network elements, and the other network elements of the synchronous network. The first and second node devices 600, 601 may be situated indoors in a radio frequency shielded environment, which precludes the use of wireless communications between the first and second node devices, which may be geographically spaced apart by several tens of kilometers. According to the best mode of the invention described herein, the first and second data terminals 602, 603 connected to first and second node devices 600, 601 are used to provide electronic orderwire functionality across the synchronous digital network 300 in conjunction with an existing operation and maintenance channel between the node devices. Conventionally, such operation and maintenance channels are used to transmit operation and maintenance data for internal operation of node devices.

In the best mode described herein, engineering data is transmitted along the operation and maintenance channel and co-exists with the normal operation and maintenance data transmitted along the operation and maintenance channel.

Referring to Fig. 7 herein, there is illustrated schematically one embodiment of the first data terminal 602. The second data terminal 603 may be similarly configured The data terminal 602 comprises a processor 700; a data storage memory 701; an input/output port 702 operating on a conventional protocol, eg the known Ethernet protocol or the known RS232 Bus protocol; a visual display unit, a keyboard for entry of data, and optionally a pointing device eg a track ball device for inputting data, (visual display unit, keyboard and pointing device not shown in Fig. 7); an audio port 704, for connection of a telephone handset, or for providing voice communication via a microphone and speaker 705, 706, a disc drive data storage device 707, a CD-Rom drive data storage device 708, an analogue to digital converter, and a digital to analogue converter. The keyboard, visual display unit, processor, memory and input/output port operate in accordance with a known operating system, for example Microsoft Windows Version 3.11 , in an operating system layer of the data terminal. Stored in the memory 701 or disk drive 711 are sets of control instructions configured to implement packetization and transport algorithms for packetization of data prior to transmission over the output port 702; control instructions configured to implement de-packetization algorithms for de-packetization of data received over the input port 702; control instructions configured to implement compression algorithms for compression of signals entered via either the keyboard, audio port 704, or via another input port, for example disc drive terminal 702, or for compressing data signals pre-stored in the memory 701 prior to packetization; control instructions configured to implement decompression algorithms for decompression of signals resulting from the de-packetization algorithms; and control instructions for conversion of analogue voice signals to digital voice signals and for conversion of digital voice signals back to analogue voice signals. The compression, decompression, packetization and de-packetization control signals reside in a communications and transport layer of the data terminal. The digital to analogue and analogue to digital conversion instructions may comprise part of an operating layer of the data terminal or may reside in the communications and transport layer. The control instructions are stored in the memory 701 or on hard disc 707, or CD-Rom 708 in the form of electronic signals or electronically , optically or magnetically readable signals.

Referring to Fig. 8 herein, there is shown the data terminal of Figs. 6 and 7 in functional overview. Engineering orderwire data is either stored in a hard disc memory of the data terminal, input via a disc drive on for example a floppy disc, input via keyboard 800, or input via a telephone handset 306. When the data terminal acts as transmitter, the input engineering orderwire data is compressed by compression module 709 operating a compression algorithm, for example a conventional Groupe Systeme Mobile (GSM) compression algorithm, resulting in a compressed data rate of the order 1 to 2 Kbytes/s. In the case of audio data input through the telephone handset 306, analogue voice signals are digitized by the analogue to digital converter 802 prior to compression by the compression module 709. Data entered from the keypad, hard disc drive, floppy disc drive or other means is compressed directly by the compression module 709. The compressed data is input to packetization module 707, operating an open system inter-connect OSI packetization protocol. The compressed packetized engineering orderwire data is transmitted via the output port 702 operating a conventional protocol for example a known Ethernet protocol or RS232C protocol.

Acting as receiver, the data terminal receives packetized data through the input port 702 and feeds the received packetized data into de-packetization module 708 which de-packetizes incoming open system inter-connect OSI packetized signals. The packetization and de-packetization modules 707, 708 are implemented by operating the processor 700 in accordance with known commercially available software, or known freely available shareware stored in memory 701 or a disc drive 711. The de-packetization module 708 transmits de- packetized, but still compressed received engineering orderwire data signals to decompression module 710, which decompresses the engineering orderwire data in accordance with known GSM decompression protocols. The compression module 709 and decompression module 710 may be implemented by operation of the processor 700 in accordance with stored control signals in the form of commercially available software implementing GSM compression and decompression algorithms. The decompressed engineering orderwire data is routed either to the telephone handset 306, via digital to analogue converter 803 in the case of voice signal data, or to the visual display unit 801 in the case of text, e-mail or facsimile data, or directly to the hard disc of the data terminal.

Referring to Fig. 9 herein, there is illustrated schematically elements of a synchronous digital communications multiplexer/demultiplexer network element capable of operating in accordance with synchronous digital hierarchy (SDH) protocols, including synchronous optical network (SONET) protocols. The network element comprises first and second optical transmission paths 900, 901 , for carrying optical signals at STM or SONET data rates; a multiplexer/demultiplexer and optical drive 902, connecting the optical transmission paths 900, 901 with a plurality of 2 Mbit/s electrical or optical tributary transmission paths 903. The multiplexer/demultiplexer and optical drive 902 connects with a Data Communications Channel (DCC) 903 carried in the STM or SONET data frame signals. The DCC driver 903 is capable of inputting and outputting signals into and from a data communications channel of a multiplexed signal carried by the multiplexer/demultiplexer and optical drive unit 902. Access to the data communications channel is available to the data terminal through the DCC driver 903 via a known interface 904 to a local area network port 905 having a physical access terminal present on the casing or housing of the network element. Operation of the data terminal and network element in accordance with specific methods and processes according to the best mode of the present invention will now be described. Referring to Fig. 10 herein, there is shown a frame of data according to a known synchronous transfer mode (STM) data frame signal. The frame as shown in Fig. 10 is shown schematically, and physically comprises a set of digital signals arranged in bytes of data. The STM frame structure comprises a data payload section 1000 in which communications data is carried, and a section overhead 1001 which carries information concerning routing of the frame, error performance monitoring, remote error indication, remote failure indications, a signal label indicating a type of virtual connection payload, a remote defect indicator, and other house keeping information required for transmission of the frames and for operation and maintenance of network elements. An STM-1 frame can be considered as a 270 column x 9 row structure, where each column represents a column of bytes of data. The section overhead 1001 comprises a regenerator section overhead 1002 of 27 bytes and a multiplex section overhead 1003 of 45 bytes. A first row R1 of the frame comprises 9 bytes of section overhead, followed by 261 bytes of data payload signal. For transmission and reception, the frame as shown in Fig. 10 is read sequentially left to right and from top to bottom by a transmitter or multiplexer apparatus. Thus, row 1 is transmitted first comprising a 9 byte section overhead header followed 261 bytes of payload data followed by row 2 comprising 9 bytes of section overhead header followed by 261 bytes of payload, until the whole 9 rows of the frame have been transmitted. The data payload area comprises 2,349 bytes, and the section overhead area comprises 72 bytes. A further protocol header, the AU pointer area comprises 9 bytes.

Referring to Fig. 11 herein, there is illustrated schematically in greater detail the section overhead of the STM-1 frame shown in Fig. 10. In the section overhead bytes, there are shown bytes E1 , and E2, which are the bytes specified in prior art ITU-T Recommendations, for carrying orderwire data as described previously in the background section of this document. Bytes D1 to D12, are allocated according to prior art ITU-T Recommendation G.784 of January 1994¹ as a data communications channel (DCC) for carrying operation and maintenance data, used for internal configuration and maintenance of network elements. Bytes D1 to D3 provide a 192 kbit/s channel and bytes D4 to D12 provide a 576 kbit/s channel. Bytes D1 to D3, in the regenerator section overhead are accessible by all synchronous digital hierarchy network elements, whereas bytes D4 to D12 in the multiplex overhead, not being part of the regenerator section overhead, are not accessible at regenerator. Bytes D1 to D3 are allocated for network element use, whereas bytes D4 to D12 can be used as a wide area general purpose communication channel to support telecommunications network management functions including non-synchronous digital hierarchy applications. The management functions foreseen in ITU-T Recommendation G.784 contemplate use of the data communications channel (DCC) as an embedded control channel (ECC) for remote maintenance and operation of network elements from a centralized network controller for example, such as shown schematically in Fig. 3 herein. Conventionally such a centralized network controller 300 may comprise a workstation, for example a UNIX based workstation such as a Hewlett Packard 9000 Series Workstation, capable of downloading network management information to control elements within the network elements. Thus, the data intended to be transmitted via the embedded control channel in accordance with known ITU-T G784 protocol, is essentially data for internal operation of the network elements. Thus, the end user of data transmitted through the embedded control channel, carried physically over the data communications channel is intended by ITU-T Recommendation G784 to be internal facilities within the network elements.

According to the best mode herein, engineering orderwire data is transmitted in bytes D1 to D12 of the section overhead of the STM frame, and may co-exist with operation and maintenance data transmitted over this channel.

Referring again to Fig. 9 herein, in the best mode described herein, there is provided a route for accessing the data communications channel and the embedded control channel through the DCC driver 903, interface 904 and local area network port 905, presented at an external output connector ie an Ethernet or RS232C port connector on a casing or housing of a network element. Thus, the data terminal may access electronically, through a local area network port of a network element the optical embedded control channel, which is distributed optically throughout the network. Thus, when setting up new network elements, where only the optical connections are in place in the best mode herein, craft or engineer personnel may transmit data through the optical network by electronic connection of a data terminal an Ethernet or RS232C local area network port connector, without having to implement exchange apparatus tailored to the newly installed network element. In comparison the known E1 , E2 orderwire channels suggested in the prior art, these remain optical and cannot be accessed electronically at the network element without installation of significant additional exchangeequipment.

Access to the embedded control channel carried on bytes D1 to D12 of the data communications channel is made through the data terminals by packetizing voice or other engineering orderwire data in accordance with ISO protocols as described with reference to Fig.12 herein. Low bit rate audio, text, or other data input or generated by first data terminal 602 is packetized in accordance with ISO transport protocols 8072, 8074, 8602 and network protocols ISO 8348, ISO 8473 and ISO 9542, prior to being transmitted over a local area network data link operating ISO 8802-2/8802-3 protocols, and is input into the local area network port 905 of first node device 600. The engineering orderwire data, having being compressed and packetized and fed into the network element in the form of electronic signals, is converted within the network element, through the interface 904 and DCC driver 903 into an optical multiplexed STM or SONET frame signal to be transmitted optically over the optical aggregate 900, 901 to second node device 601. Although the optical data communications channel has adequate bandwidth for transmission of normal voice signals at 64 kbit/s, or low data rate text or graphics, the primary purpose of the embedded control channel carried in the DCC is for carrying operations and maintenance data between network elements. Therefore, in order for the presence engineering orderwire data to impact as little as possible on the main function of the embedded control channel in an operating network preferably, the proportion of bandwidth occupied by engineering orderwire data is made as small as possible by compression of the data prior to entry into the data communications channel. The engineering orderwire data is received by decompression on exit from the data communications channel. It has been found experimentally that GSM compression algorithms provide adequate compression in the best mode herein.

However, where the communications network is being newly installed and is not yet fully operational, compression and decompression need not necessarily be applied to all types of engineering orderwire data since operation and maintenance data traffic over the DCC may be small or none-existent, and the DCC is capable of carrying uncompressed 64 Kbit/s voice data. Where video data is required to be transmitted, data compression may be necessary.

At the receiving network element, second node device 601 , the optical multiplexed STM frame signals carrying the embedded control channel are received, and the information carried on the embedded control channel is separated from the STM frame by second DCC driver 903 of the second node device. The data contained on the Data Communications Channel is interfaced to second local area network port 905 of second network element 601 , to provide an electronic signal at the second local area network port of second node device 601. The engineering orderwire data is present at the second local area network port 905 of second node device 601 and is input into second data terminal 603 also operating local area network data link protocol ISO 8802-2/8802-3, network protocol ISO 8348, ISO 8473 and ISO 9542 and transport protocols ISO 8072/8703/8602, resulting in de-packetized, decompressed engineering orderwire data at the second data terminal 603.

Accessing the data communications channel via the local area network port and interface provides a way of accessing the optical channel between first and second network elements, which is otherwise inaccessible without significant additional equipment connected to the network element. Further, as the OSI protocol is self routing, provided the data terminals are at places on the network which are visible to a network controller apparatus, then the data terminals may be able to communicate with each other using the OSI protocol, irrespective of network topology.

Referring to Figs. 13 and 14 herein, there will now be described a method of communication of engineering orderwire data between first and second data terminals over the synchronous digital communications network. For a data terminal transmitting engineering orderwire data, for example the first data terminal, in step 1300, a user inputs engineering data, for example voice data, text, graphics etc into the data terminal. In the case of a telephone handset at the data terminal, this step may include speaking into the telephone, or in the case of a personal computer, laptop computer or personal organizer this step may comprise entering data via a keypad. In step 1301 , the user inputs an address of a receiving data terminal the second data terminal, with which the user wishes to communicate. In step 1302, sending the data terminal compresses the engineering orderwire data in the best mode herein in accordance with a GSM compression algorithm. In step 1303, the data terminal packetizes the engineering orderwire data prior to inputting the packetized data into the local area network port of the network element to which the first data terminal is connected, in step 1304. The compressed packetized data is input to the local area network in the form of electronic signals over a prior art Ethernet or RS232C connector. In step 1305, the network element receives the compressed packetized engineering orderwire data electronic signals and interfaces these to the data communications channel driver 903. The data communications channel driver inputs the data into the data communications channel in the optical multiplex transmitted by the optical driver and multiplexer 902. The multiplexer and optical driver 902 transmit optical STM or SONET data frames containing the data communications channel, in bytes D1 to D12 in the case of a synchronous digital hierarchy network, in step 1306. Referring to Fig. 14 herein, in step 1400 a network element to which the second data terminal is connected receives the STM or SONET frame signal over the synchronous optical aggregate which is de-multiplexed in step 1401 to recover the data communications channel. The DCC driver of the receiving network element passes an output signal corresponding to the embedded control channel to the local area network port of the receiving network element, via interface 904 of the receiving network element in step 1402. The receiving network element converts the received data communications channel optical signal into data in the form of electronic signals which are accessible at the local area network port 905 of the receiving network element, such that the signal carried by the data communications channel is output at the local area network of the receiving network element in step 1402. The second data terminal receives the signal from the local area network port of the receiving network element and de-packetizes the signal in step 1403 to recover compressed engineering orderwire data signals. The data terminal applies decompression to recover the transmitted engineering orderwire data in steps 1404 and 1405. In step 1406, the data terminal displays or otherwise makes available the engineering data, eg as a voice signal, or stores the engineering data.

There will now be described with reference to Figs. 15 to 17 herein, an example of a specific method according to the present invention whereby first and second data terminals are located within a synchronous digital communications network, and information carried in the embedded control channel is routed between first and second data terminals. Referring to Fig. 15 herein, there is shown schematically a portion of a synchronous digital communications network, in which a first data terminal 1500 is connected to a synchronous digital communications wide area network 1501 via a router 1502, for example a prior art router manufactured by CISCO Systems. Geographically separated from the first router 1502 over the wide area network is a second router 1503 having a local area network connection 1504. The second router 1503 communicates with a synchronous digital hierarchy network element 1505, which is itself is in communication with a further synchronous digital hierarchy network element 1506 via an optical link 1507 across the synchronous digital network. Third and fourth data terminals 1508, 1509 are connected to the local area network 1504 and to the further network element 1506 respectively. All network elements and routers support International Standards Organization (ISO) open system interconnect (OSI) protocols. In accordance with OSI protocols the data terminals can be referred to as end systems (ES), and the network elements eg routers and multiplexers are referred to as intermediate systems (IS).

Referring to Fig. 16 herein, in step 1600 on connecting first data terminal 1500 to a local area network port of a network element anywhere in the synchronous network, for example to the router 1502, the first data terminal, operating in accordance with a connection algorithm, repeatedly and periodically announces itself over the local area network to the network element to which it is connected. The first router 1502 in Fig. 15, specifies a unique code, supplied to the network element in the form of electronic digital data signals over the local area network.

The code supplied by the first data terminal has the following format:

00 - 08 - C8 88 - 06 - 71

Manufacturer Unique Code

The code comprises a 12 hexadecimal digit sequence, in which the first 6 digits specify the type of the data terminal equipment, ie the manufacturer of the data terminal equipment, and the second 6 digits specify a serial number of the data terminal. In step 1601 the first data terminal announces itself to its local area network using a known End System to Intermediate System (ES-IS) protocol. Regular and automatic announcement of the end system may occur for example every 30 to 90 seconds. Referring to Fig. 17, the first data terminal

1700 constitutes an end system for communication, and the network elements

1701 to 1703 each constitute intermediate systems (IS) as shown conceptually in Fig. 17. Communications between an end system and an intermediate system (ES-IS Communications) are made using known protocol ISO/IEC9542, whereas communications between intermediate systems (IS-IS Communications) are made using known protocol ISO 10589. In step 1602, the network element propagates the identification code of the first data terminal throughout the network to other intermediate systems using the known intermediate system to intermediate system (IS-IS) protocol ISO 10589. Each network element has a fixed geographical location and the network controller stores a location area code for each network element. Thus, when a data terminal is connected to a local area network part of a network element, the location address is added to the code identifying the data terminal. This information is propagated throughout the network by the network element, such that each other network element receives information that the first data terminal is connected to the network element in a specified location. The code data propagated throughout the network is represented schematically below:

49 0000 00 - 80 - C8 88 - 06 - 71

Area Code Manufacturer Code Unique Code

where the first 6 digits represent the area code of the network element to which the first data terminal is attached. All network elements in the optical rings receive this information. Thus, whilst the first data terminal only receives information conceming the network element to which it is attached, all network elements managed by the network controller each have information concerning the location and unique codes of all individual data terminals connected to the network. Similarly, second and third data terminals 1507, 1508 connected at other locations to other network elements respectively each perform an equivalent operation, announcing their individual unique codes to the corresponding network elements to which they are connected. Each corresponding respective network element signals to all other network elements in the network the location and data terminal identification of their corresponding respective connected data terminals. As with the first data terminal, the second and third data terminals only receive information concerning the network element to which they are attached, whereas each of the network elements receives information concerning all data terminals and the locations of the corresponding network elements to which they are attached. Thus, the intermediate systems have knowledge of all the end systems. A user of the first data terminal wishing to communicate with a user of the second and/or third data terminals, types into the keyboard of his or her data terminal the data terminal identification codes corresponding to each data terminal with which he or she wishes to communicate. The network elements, having a knowledge of the location of the network element to which those data terminals are connected, may then route communications to the corresponding respective network elements using IS-IS protocol ISO 10589. The sending data terminal generates compressed packetized data resulting in connectionless network layer protocol (CLNP) packets which are submitted to the local area network of the network element connected to the sending data terminal. The network element connected to the sending data terminal (the intermediate system) picks up the CLNP packet and forwards it to its destination, ie the network element connected to the second and third data terminals, using an optimum path, in step 1605. Construction of the CLNP packets corresponds to the transport protocols in Fig. 12 herein. The CLNP packets are forwarded from intermediate system to intermediate system across the synchronous digital communications network to the destination network elements specified in the address code of the addressed data terminals typed in at the first data terminal. The network elements in the intermediate system operate on a store and forward basis for transmitting the CLNP packets across the network, and communicate amongst themselves using the IS-IS protocols to determine the optimum route for sending the STM or SONET frame signals, carrying the engineering orderwire data in the data communications channel through the network. Use of the IES protocol for routing the engineering orderwire data throughout the system may have an advantage that the intermediate system to end system (IS-ES) protocol is self healing in the sense that if any optical link or network element is malfunctioning, the IS-ES protocols will configure transmission such as to transmit the STM or SONET frame signals by a different route around the network, thereby resulting in a robust means in the form of the data communications channel, for transmitting engineering orderwire data. In step 1606, the network element receiving the CLNP packets demultiplexes the data communications channel and passes the packetized data signals to the data terminal over the local area network port of that network element as hereinbefore described with reference to Figs. 10 to 15 hereinabove.

Referring to Fig. 18 herein, there is illustrated a further specific embodiment synchronous digital communications network comprising a local area network hub 1800 and connected router 1801 in a first area; a first synchronous digital communications ring 1802 operating synchronous transfer mode STM-16 data frame signals in a second area, and a second synchronous digital transmission ring operating STM-4 data frame signals in a third area. Each network element has an address 49+0000. Routers 1801 , 1804, 1805 in the first, second and third areas respectively each have a unique area address in addition to their address 49+0000. For example first router 1801 has an address

49+0000 39826 +21200001

second router 1804 has an address

49+0000 39826 +21200002

and third router 1805 has an address

49+0000 39826 +21200003

A data terminal 1806 in the first area connected to the first router 1801 by local area network hub 1800 and OSI local area network link 1807 has packetized engineering orderwire data transmitted from the first data terminal routed by the router 1801 to the second and third routers 1804, 1805 according to an address typed in at the data terminal 1806 by a user. First and second telephone handsets 1808, 1809 comprising end data terminals connected to respective network elements 1810, 1811 in the first and second rings received packetized operation and maintenance channel signals carried over the data communication channel (embedded control channel) of the network, and routed to the respective second and third telephones 1808, 1809 by virtue of their connection to network elements 1810, 1811 connected to the second and third routers 1804, 1805. In this example, a plurality of network elements have a common area address, the area address for the second area being

39826+210000

and the area address for the third area being

39826+2100003

Whilst the best mode described herein has been described with reference to an STM-1 frame, a data communications channel of a SONET frame signal may be accessed via a local area network port of a network element in another specific embodiment and specific method according to the present invention. Referring to Fig. 19 herein, there is a comparison of a SONET STS-1 frame and an SDH STM-1 frame. In the SONET STS-1 frame, a 3 byte section overhead of the STS-1 frame is provided. Three STS-1 SONET frames are multiplexed into a STS-3 frame, comprising a 3 x 3 column section overhead. The 3 x 3 column SONET section overhead comprises data communications channel bytes, which may be transmitted over the synchronous digital network in the same way, as the STM-1 frame hereinbefore described. The SONET protocol header carries a data communications channel in an optical frame signal, which can be accessed at a node device, as in the best mode described herein. An SDH network is an arbitrary mesh of SDH network network elements. The network may be connected to other SDH networks (not shown) by routers which also support OSI protocols. When one of the elements needs changing or servicing it is visited by an operative who may carry a laptop computer provided with an RS232 port and a LAN port by which it may be connected to the network element. The laptop may be used conventionally via the RS232 port to interrogate the network element in order, for example, to investigate its inventory.

Software is provided in the laptop computer data terminal to implement the lower four layers of the OSI protocol as indicated in Fig. 12. This enable data to be input to and received from the transport layer, through the network layer, the LAN data link layer and the LAN port physical layer. Connecting the LAN port of the laptop thus enables data communication over the network with another suitably equipped and connected laptop. As the other laptop is identified over the OSI digital communications network by its OSI address, it does not matter where in the network it is physically located.

The laptop is provided with means to transduce speech to outgoing audio signals and to transduce received audio signals to sound. The laptop may be provided with an internal microphone and speakers, or headset. On top of the lower four layers of the OSI protocol stack, a conventional arrangement of hardware and software is provided to convert outgoing audio signals to data and data to received audio signals. The outgoing audio signals are converted to data packets for transmission over the network. Data packets received over the network are converted to audio signals and transduced to sound.

In some applications it may not be desirable to use a laptop to interrogate the network element. For that, or other reasons, it may be preferred to provide speech communication independently of a laptop computer. In such cases the apparatus may be implemented as a handset including a keypad for entering address information, a conventional arrangement of hardware and software to convert outgoing audio signals to data and data to received audio signals, hardware and software providing the lower four layers of the OSI protocols and a LAN port for connection to the network element References

[1] International Telecommunications Union ITU-T Recommendation

G.70X, available from ITU Sales and Marketing Service, Place de Nations, CH- 1211 Geneva 20, Switzerland, E-Mail Sales@itu.com.

[2] American National Standards Institute (ANSI) T1X1 Committee,

New York Headquarters, 13^th Floor, 11 West 42^nd Street, New York, NY 10036, USA.

Abbreviations

ANSI American National Standards Institute

CLNP Connectionless Network Layer Protocol

DCC Data Communications Channel

ECC Embedded Control Channel

EOW Engineering Orderwire

ES-IS End System to Intermediate System

GSM Groupe Systeme Mobile

IS Intermediate System

IS-ES Intermediate System to End System

IS-IS Intermediate System to Intermediate System

ISO International Standards Organization

ITU International Telecommunications Union

NE Network Element

OSI Open System Interconnection

PDH Plesiochronous Digital Hierarchy

POTS Plain Old Telephone System

PSTN Public Switched Telephone Network

SDH Synchronous Digital Hierarchy

SONET Synchronous Optical Network System

STM Synchronous Transfer Mode

VDU Visual Display Unit

Claims

Claims:

1. In a digital communications network comprising a plurality of node devices (301 , 304, 305) linked by a plurality of link devices, said communications network having an operation and maintenance channel for transmittal of operation and maintenance information between said node devices, a method of communicating engineering orderwire data between first and second said node devices characterized by comprising the steps of:

inputting engineering orderwire data signals into said first node device;

transmitting (1306) said engineering orderwire data to said second node device over said operation and maintenance channel; and

receiving (1400) said engineering orderwire data over said operation and maintenance channel at said second node device.

2. A method as claimed in claim 1 , characterized in that said step of inputting said engineering orderwire data to said first node device comprises inputting said engineering orderwire data (1300) into a local area network port of said first node device.

3. A method as claimed in claim 1 or 2, characterized by comprising the step of outputting (1402) said engineering orderwire data from a local area network port of said second node device.

4. A method as claimed in any one of claims 1 to 3 characterized by further comprising the step of:

packetizing (1303) said engineering orderwire data into a series of packet data signals, each comprising a data payload signal and a packet protocol overhead signal, wherein said packetized signals are respectively input and output from said first and second node devices.

5. A method as claimed in claim 4, characterized in that said packet protocol header comprises an address signal specifying an address of a receiving data terminal connected with a said node device.

6. A method as claimed in claim 4 or 5, characterized by comprising the step of:

packetizing said engineering orderwire data in accordance with a protocol which does not require packet reception acknowledgment.

7. A method as claimed in any one of the preceding claims, characterized by comprising packetizing said input engineering orderwire data in accordance with an Open System Interconnect (OSI) protocol method,

8. A method as claimed in any one of the preceding claims, characterized by further comprising the step of compressing (1302) said engineering orderwire data.

9. A method as claimed in claim 8, characterized in that said step of compression comprises compressing said engineering orderwire data in accordance with a Groupe Systeme Mobile data compression algorithm.

10. A method as claimed in claim 8 or 9, characterized by further comprising the step of decompressing (1404) said engineering orderwire data.

11. A method as claimed in any one of the preceding claims, wherein said communications network comprises a synchronous digital hierarchy (SDH) network.

12. A method as claimed in claim 11 , characterized in that said operation and maintenance channel comprises an embedded control channel as specified in International Telecommunications Union Recommendation G.784 of January 1994.

13. A method as claimed in anyone of claims 1 to 10, wherein said communications network comprises an American National Standards Institute synchronous optical network (SONET) network.

14. A method as claimed in any one of claims 1 to 13, characterized in that said operation and maintenance channel comprises a synchronous digital hierarchy data communications channel carried within bytes D1 to D12 of a synchronous transfer mode (STM) data frame.

15. In a communications network comprising a plurality of node devices (301 , 302, 304, 305) and at least one link device, said node devices adapted to communicate with each other via said link device over an operations and maintenance channel, an engineering orderwire apparatus characterized by comprising:

data terminal means (306) operating to generate engineering orderwire data signals;

data packetization means for converting said engineering orderwire data signals into a series of data packet signals; and

a multiplexer means (902) for multiplexing said packetized data into said operations and maintenance channel of said communications network.

16. An engineering orderwire apparatus as claimed in claim 15, characterized in that a said data terminal comprises a device selected from the set;

personal computer; laptop computer;

palm top computer;

personal organizer;

an application specific computer.

17. An engineering orderwire apparatus as claimed in claim 15, characterized in that said packetization means comprises:

a processor (700); and

a data storage medium (701 , 711 , 712),

said data storage medium storing control signals for operating said processor to convert said engineering orderwire signals into said series of data packets.

18. An engineering orderwire apparatus as claimed in claim 15, characterized in that said multiplexer comprises a local area network port capable of receiving data signals, and said multiplexer operates to multiplex said packetized data signals received via said local area network port into said operation and maintenance channel.

19. In a communications network comprising a plurality of node devices (301 , 302, 304, 305) and at least one link device said node devices adapted to communicate with each other via said link device over an operations and maintenance channel; an engineering orderwire apparatus characterized by comprising: a demultiplexer means (902) for de-multiplexing packetized data signals carried on said operations and maintenance channel of said communications network;

a de-packetizing means (708) for converting a series of data packet signals each comprising a data payload signal and a protocol header signal into an engineering orderwire data; and

a data terminal means capable of receiving said engineering orderwire data signals and of outputting engineering orderwire data corresponding to said engineering orderwire data signals.

20. An engineering orderwire apparatus as claimed in claim 19, wherein said de-packetizing means comprises:

a processor (700); and

a data storage medium (701 , 711 , 712),

said data storage medium storing control signals operating said processor to convert said series of packetized signals into said engineering orderwire data signals corresponding to said engineering orderwire data.

21. An engineering orderwire apparatus as claimed in claim 19, wherein a said data terminal comprises a device selected from the set;

personal computer;

laptop computer;

palm top computer; personal organizer;

an application specific computer.

22. An engineering orderwire apparatus as claimed in claim 19, wherein said demultiplexer comprises a local area network port (905) and said data demultiplexer operates to de-multiplex said packetized data and present said packetized data at said local area network port.

23. A communications network comprising a plurality of node devices

(301 , 302, 304, 305) linked by a plurality of link devices, first and second said node devices being capable of communicating with each other over at least one said link device, characterized in that at a said first node device there is provided:

a first multiplexer means (902) capable of communicating over an operation and maintenance channel of said network;

a first local area network port (905) capable of receiving input engineering orderwire data signals, said first local area network port connected to communicate with said first multiplexer;

a first data packetization means (707) for packetizing an engineering orderwire signal representing engineering orderwire data and connected to communicate with said first local area network port;

a first data de-packetization means (708) for de-packetizing received packetized engineering orderwire data signals representing engineering orderwire data; and

at said second said node device is provided: a second multiplexer means capable of communicating over an operation and maintenance channel of said network;

wherein, said first and second node devices communicate engineering orderwire data with each other by inputting said engineering orderwire data into a said packetization means, packetizing said engineering orderwire data by a said packetization means, inputing said engineering orderwire data into a said local area network port, multiplexing said engineering orderwire data by a said multiplexer, transmitting said engineering orderwire data between said first and second multiplexers, outputting said engineering orderwire data through a said local area network port and de-packetizing said engineering orderwire data by a said de-packetization means.

24. A communications network as claimed in claim 23, characterized in that said operation and maintenance channel comprises a synchronous digital hierarchy data communications channel carried in bytes D1 to D12 of a synchronous transfer mode (STM) data frame.

25. A communications network comprising a plurality of node devices (301 , 302, 304, 305) linked by a plurality of link devices, characterized in that;

a first said node device comprises:

a first multiplexer means (902) capable of accessing an operation and maintenance channel;

a first local area network port (905);

a first interface (904) for communicating between said first multiplexer means and said first local area network port; and

a first terminal apparatus connected to said first local area network port; and

a second said node device comprises:

a second local area network port;

a second terminal apparatus connected to said second local area network port;

wherein, said first terminal operates to input engineering orderwire data to said operation and maintenance channel via said first local area network port, said first interface and said first multiplexer; said first multiplexer transmits said engineering orderwire data to said second multiplexer; said second multiplexer outputs said engineering orderwire data to said second local area network port via said second interface; and said second terminal apparatus receives said engineering orderwire data from said second local area network port.

26. Apparatus, having means for communication separately from the network with a network element in an OSI data communications network, characterized by said communication implementing OSI protocols; means for transducing speech to outgoing audio signals and received audio signals to sound; and means for converting outgoing audio signals to packets of data for transmission via said OSI protocols over the network and for converting data packets received from the network via said OSI protocols to received audio signals.

27. Apparatus as claimed in claim 26, wherein the means for transducing comprises a telephone hand set or head set.

28. Apparatus as claimed in claim 26 or 27, including a keyboard and associated interface means for inputting data from the keyboard for communication to the network element.

29. Apparatus as claimed in any preceding claim, connected separately from the network to a network element that supports OSI protocols in an OSI data communications network.

30. Apparatus as claimed in any of claims 26 to 28, connected separately from the network to an SDH network element that supports OSI protocols in an SDH network.

31. A method of communication separately from the network with a network element in an OSI data communications network, characterized by said communication implementing OSI protocols; the method including transducing speech to outgoing audio signals and transducing received audio signals to sound; wherein outgoing audio signals are converted to packets of data for transmission via said OSI protocols over the network, and wherein data packets received from the network via said OSI protocols are converted to received audio signals.