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Key points

  • Cable-Sense system can dynamically monitor networks, cable by cable
  • The developers made use of the inherent properties of twisted-pair cables
  • It can be retrofitted to cabling installations using proprietary software
  • This is said to reduce the cost of maintaining and running a network

Managing large computer networks can be fraught with difficulty. Often, as they grow in complexity, paper records become incomplete or disappear and even electronic records can go out of date, writes David Wilson.

As a result, computer network managers are challenged to know precisely what hardware is in their networks, where it is located, whether the relevant ports are patched out and which of them are redundant. In a typical enterprise, the answers to these questions may be, at best, found on an out-of-date spreadsheet or through an expensive and time-consuming audit of the cabling network.

Recognising the need to produce a simpler, more cost-effective automated solution to the issue, Prof Tony Peyton from Manchester University’s School of Electrical and Electronic Engineering (EEE) and John Kelly from the network IT industry have now developed a management system that can dynamically monitor the network, cable by cable, end to end.

Thanks in part to a major investment from Manchester technology investment specialist MTI Partners, the management system is now commercially available through university spin-out company Cable-Sense.

According to Peyton, what makes the Cable-Sense system unique and sets it apart from other network monitoring systems is that it can effectively ’interrogate’ the integrated physical layer of a network that conveys data at the electrical and mechanical level, typically on a set of twisted pairs.

That is unlike alternative competitive systems that simply monitor the data transferred across the network and, as such, do not provide the user with any indication of whether any faults might be down to software or hardware errors.

Kelly and Peyton realised they could develop such a system when they discovered they could make use of the inherent electrical properties of the unshielded twisted-pair cables that are used to connect computer systems in local-area networks. These cables comprise a set of eight cables twisted together in four pairs to cancel out electromagnetic interference from external sources and to minimise the crosstalk between them.

The engineers appreciated that they could take advantage of the inherent electromagnetic coupling between each combination of the two twisted pairs within such cables to provide an additional communications channel that could be used for diagnostic purposes.

What is more, they also discovered that a signal that did propagate along a twisted pair cable in such a ’pair-to-pair coupling’ could also propagate reliably over long distances without altering the transmission of data signals within the twisted pairs themselves owing to the ordered geometry of the cables.

In addition, the two Cable-Sense founders discovered that the diagnostic electromagnetic signals could be non-invasively coupled to, and extracted from, the twisted-pair network cables using simple clips that could be attached onto the outside of the cable at any point in the network, without requiring the connectors in the network to be modified. Therefore, the Cable-Sense system could be easily retrofitted to an existing network a key advantage given the huge amount of already installed network cable.

When an alternating voltage of small fixed amplitude is applied across the plates of the clip, an electromagnetic field is created that propagates down the pair-to-pair channel. The signal is then detected by another clip that is serving as a receiver, either at the other end of the cable or next to the transmitter.

According to Peyton, because the voltage applied across the cable is in the tens of millivolts range, the electromagnetic field generated appears as just a slight increase in common-mode noise on the network, with the result that it has no effect on the normal operation of the network at all.

The clips used to non-invasively couple to the twisted-pair cables are connected to a front-end board containing a transceiver, an amplifier and a switch. The front-end board can be positioned behind the patch panel of a communications rack that connects a network’s computers to each other and to outside lines.

Each one of the front-end boards, which can apply and receive swept signals to and from each one of 24 cables, is then connected in a hierarchical fashion to a rack-mounted scanner controller.

The scanner controller is responsible for performing the computationally intensive calculations that can extract the relevant data from the reflected signals to determine the state of the network. The board is essentially a multi-channel vector network analyser that produces and then characterises both the amplitude and phase properties of the signals on the network. In addition, however, it also switches the relevant ports on the front-end scanner boards, as well as multiplexing data signals to and from them.

To determine the status of the network, the scanner controller board incrementally generates a range of frequencies between 1MHz and 150MHz that are fed to the transmitters.

Then, software running on the board captures the spectral response of the network, calculating the amplitude and phase properties of the reflected signals over all the frequency ranges. An inverse Fourier transform performed on this spectral data creates time domain reflectometry plots where the response of the system to the impulses propagating through can be interpreted.

’Any discontinuities in the cable such as terminations or intermediate connectors cause some of the transmitted signal to be reflected back towards the source,’ said Peyton.

The new system from Cable-Sense can effectively ’interrogate’ the physical layer of a network

’Because the resulting reflected pulses that are measured are displayed or plotted as a function of time, the signals can then be used to deduce the length of the cable and hence whether any additional equipment has been added to, or removed from, the system,’ he added. ’The type of reflection that is observed can also be used to determine specifically what sort of equipment is connected to the end of the cable as well.’

To ensure that the system is scaleable, multiple scanner controllers can be connected to a site master controller that processes data from all the scanner controllers and passes the processed data to web-based software. None of the hardware requires space at the front of the rack, and all the hardware can be powered from a single mains electrical socket in a rack.

The system can be retrofitted to existing cabling installations using Cable-Sense’s proprietary software for network cable monitoring, scanning and mapping.

According to Cable-Sense, this reduces the cost of maintaining and running a network, including the cost and complexity of moves, making additions and changes, fault identification and diagnosis, inventory management and capital expenditure through the identification and reuse of redundant equipment and capacity.

’Due to its automated approach, expensively trained specialist operators are not required to operate or maintain the system,’ said Peyton. ’The vendor-independent system works in background mode, monitoring and recording the status of the network, alerting users only when a specific fault is found.’

The software that supports the scanner board is a web application that can be hosted anywhere. Data is sent to and from a user’s site in real time and stored in an SQL database.

The software has modules for alarm and alert reporting; visualisation of the network; moves, adds and changes; asset tracking and analysis; reporting; installation planning; and application programming interfaces for large networks and data centres.

Automated system could reduce complexity of monitoring computer networks

Key points

  • Cable-Sense system can dynamically monitor networks, cable by cable
  • The developers made use of the inherent properties of twisted-pair cables
  • It can be retrofitted to cabling installations using proprietary software
  • This is said to reduce the cost of maintaining and running a network

Managing large computer networks can be fraught with difficulty. Often, as they grow in complexity, paper records become incomplete or disappear and even electronic records can go out of date, writes David Wilson.

As a result, computer network managers are challenged to know precisely what hardware is in their networks, where it is located, whether the relevant ports are patched out and which of them are redundant. In a typical enterprise, the answers to these questions may be, at best, found on an out-of-date spreadsheet or through an expensive and time-consuming audit of the cabling network.

Recognising the need to produce a simpler, more cost-effective automated solution to the issue, Prof Tony Peyton from Manchester University’s School of Electrical and Electronic Engineering (EEE) and John Kelly from the network IT industry have now developed a management system that can dynamically monitor the network, cable by cable, end to end.

Thanks in part to a major investment from Manchester technology investment specialist MTI Partners, the management system is now commercially available through university spin-out company Cable-Sense.

According to Peyton, what makes the Cable-Sense system unique and sets it apart from other network monitoring systems is that it can effectively ’interrogate’ the integrated physical layer of a network that conveys data at the electrical and mechanical level, typically on a set of twisted pairs.

That is unlike alternative competitive systems that simply monitor the data transferred across the network and, as such, do not provide the user with any indication of whether any faults might be down to software or hardware errors.

Kelly and Peyton realised they could develop such a system when they discovered they could make use of the inherent electrical properties of the unshielded twisted-pair cables that are used to connect computer systems in local-area networks. These cables comprise a set of eight cables twisted together in four pairs to cancel out electromagnetic interference from external sources and to minimise the crosstalk between them.

The engineers appreciated that they could take advantage of the inherent electromagnetic coupling between each combination of the two twisted pairs within such cables to provide an additional communications channel that could be used for diagnostic purposes.

What is more, they also discovered that a signal that did propagate along a twisted pair cable in such a ’pair-to-pair coupling’ could also propagate reliably over long distances without altering the transmission of data signals within the twisted pairs themselves owing to the ordered geometry of the cables.

In addition, the two Cable-Sense founders discovered that the diagnostic electromagnetic signals could be non-invasively coupled to, and extracted from, the twisted-pair network cables using simple clips that could be attached onto the outside of the cable at any point in the network, without requiring the connectors in the network to be modified. Therefore, the Cable-Sense system could be easily retrofitted to an existing network a key advantage given the huge amount of already installed network cable.

When an alternating voltage of small fixed amplitude is applied across the plates of the clip, an electromagnetic field is created that propagates down the pair-to-pair channel. The signal is then detected by another clip that is serving as a receiver, either at the other end of the cable or next to the transmitter.

According to Peyton, because the voltage applied across the cable is in the tens of millivolts range, the electromagnetic field generated appears as just a slight increase in common-mode noise on the network, with the result that it has no effect on the normal operation of the network at all.

The clips used to non-invasively couple to the twisted-pair cables are connected to a front-end board containing a transceiver, an amplifier and a switch. The front-end board can be positioned behind the patch panel of a communications rack that connects a network’s computers to each other and to outside lines.

Each one of the front-end boards, which can apply and receive swept signals to and from each one of 24 cables, is then connected in a hierarchical fashion to a rack-mounted scanner controller.

The scanner controller is responsible for performing the computationally intensive calculations that can extract the relevant data from the reflected signals to determine the state of the network. The board is essentially a multi-channel vector network analyser that produces and then characterises both the amplitude and phase properties of the signals on the network. In addition, however, it also switches the relevant ports on the front-end scanner boards, as well as multiplexing data signals to and from them.

To determine the status of the network, the scanner controller board incrementally generates a range of frequencies between 1MHz and 150MHz that are fed to the transmitters.

Then, software running on the board captures the spectral response of the network, calculating the amplitude and phase properties of the reflected signals over all the frequency ranges. An inverse Fourier transform performed on this spectral data creates time domain reflectometry plots where the response of the system to the impulses propagating through can be interpreted.

’Any discontinuities in the cable such as terminations or intermediate connectors cause some of the transmitted signal to be reflected back towards the source,’ said Peyton.

The new system from Cable-Sense can effectively ’interrogate’ the physical layer of a network

’Because the resulting reflected pulses that are measured are displayed or plotted as a function of time, the signals can then be used to deduce the length of the cable and hence whether any additional equipment has been added to, or removed from, the system,’ he added. ’The type of reflection that is observed can also be used to determine specifically what sort of equipment is connected to the end of the cable as well.’

To ensure that the system is scaleable, multiple scanner controllers can be connected to a site master controller that processes data from all the scanner controllers and passes the processed data to web-based software. None of the hardware requires space at the front of the rack, and all the hardware can be powered from a single mains electrical socket in a rack.

The system can be retrofitted to existing cabling installations using Cable-Sense’s proprietary software for network cable monitoring, scanning and mapping.

According to Cable-Sense, this reduces the cost of maintaining and running a network, including the cost and complexity of moves, making additions and changes, fault identification and diagnosis, inventory management and capital expenditure through the identification and reuse of redundant equipment and capacity.

’Due to its automated approach, expensively trained specialist operators are not required to operate or maintain the system,’ said Peyton. ’The vendor-independent system works in background mode, monitoring and recording the status of the network, alerting users only when a specific fault is found.’

The software that supports the scanner board is a web application that can be hosted anywhere. Data is sent to and from a user’s site in real time and stored in an SQL database.

The software has modules for alarm and alert reporting; visualisation of the network; moves, adds and changes; asset tracking and analysis; reporting; installation planning; and application programming interfaces for large networks and data centres.

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