Power Over Ethernet

It seems that everywhere we look these days, we are being told that this will finally be the year of convergence and asked why did we not adopt it sooner.

What is convergence?

Convergence is about different applications or product coming together under one umbrella. We can see in a wider context that  is happening in small steps.  For instance, we now have PDAs functioning as phones, e-mail and intelligent data storage devices.  At the other extreme Google, which was once only an on-line search engine, now offers wide ranging programmes including e-mail, desktop information management software and photo editing software.

So while devices and programmes are continuing to evolve and integrate what were once ‘alien’ functions,  where does this leave the humble network, which began its life in military applications? Well, it’s catching up. Convergence of voice and data applications has allowed questions to be asked concerning areas of the network. For example, “can we have a network which carries power and data?” “Can we reduce our installation costs and timeframe?” “Can we attach and power that IP Phone through one cable?”

The answer today is a resounding “yes”.

As recently as the early 80’s office networks consisted of installing a dedicated telephone system and a separate IT network on the basis that this approach was secure, reliable and the only way as the two systems could not be operated over one network. Consequently timeframes and installation costs were high because the IT systems and the telephony systems required different suppliers and installers.

These days, however, we expect more from our IT and telephony solutions. We want the latest document sharing and video conferencing capabilities, cheap call routing or VPN networks. We want IP phones so that we can work from home whilst having a DDI number that is our office extension, because we actually are dialling out via the office.

However, one problem still prevails.  How do you power devices around the home or office which are connected to the network?  Traditionally, two cables have been used, one to provide the power and one to carry the data. However, in this enlightened and environmentally-friendly age, this is no longer the best practice.  Convergence by Power over Ethernet (PoE) provides an effective solution from an environmental, installation and cost of deployment perspective.

Several applications spring to mind, which would benefit  from Power Over Ethernet capabilities, including:

1 – Wireless access points mounted near the ceiling or out of the way places.

2 – Real-time or motion activated CCTV cameras which are network based.

3 – IP based telephone solutions.

What Happens In The VOIP Age When The Mains Fails?

However what happens if the power fluctuates or even fails? Do we even have the right to expect 24x7x365 power?  It certainly cannot be guaranteed.   There are many external factors that play a part in bringing power down to earth? At the top of the list of threats is the potential for the national grid to fail - we’ve already seen this happen three times across the world.  Closer to home we rely on our fellow man not dig the cable up, or even worst case scenario, instigate an act of terrorism by attacking a power pylon.

In order to protect your business, you really have to start at the power level first of all because mains power can be so unreliable, especially when you start to consider how unreliable mains power can be.  For instance mains power is only 99.9% reliable and this equates to 9hours on average of no mains power being available. This situation can occur at any time of day or week.

Several UPS solutions exist today which provide advantages regardless of whether the UPS is rack mounted or stand alone.  A good UPS solution, whilst also providing credible power backup, will also incorporate a good software package that enables remote monitoring of power fluctuations and user selected events via the network. An advanced solution should come with software which allows you to remotely power on and off a selected group of sockets, thereby avoiding unnecessary delay in sending an engineer let alone the financial cost. 

What Next?

Power over Ethernet devices have irrevocably revolutionised the world of power. Pre-PoE the only choice for powering network connected DC devices was via the traditional black, bulky transformers, which still clutter so many offices. Nowadays, however, Midspan solutions will connect DC devices to the network and provide them with power via one simple cable.

The UPS’ network cards and proxy agents (embedded Web server, SNMP compatibility) provide users with a wide range of remote UPS management functions including configuring shutdowns, programming actions to respond to events, predicting the time before total battery discharge when there is a power failure, generating alarms, and integration into network management systems such as HP Openview.   The software automatically recognises the Midspan and UPS’, sends alarms and critical messages to the administrator and enables equipment or the individual supply to each RJ-45 port to be turned on or off remotely.

The extended applications for Power Over Ethernet are almost endless:  RFID Tag readers, security access controls, smoke detectors, thermostats. Perhaps in the distant future we’ll also find a component of the ATM powered by it. The market for POE applications is going to be huge and the latest IEE standard 802.3AF is enabling the market to move forward.

IEE 802.3AF incorporates a number of safeguards because it intelligently searches for POE-enabled terminals before providing power to every connected device, so reducing the potential for damaging non-powered devices. 

How to protect 24x7x365 applications

Applications need to be protected to the right degree. For instance, certain applications will be best supported for only 10-20 minutes while other applications need to be kept going for a number of hours. Therefore its vital that the UPS solutions you choose covers all your requirements or at least allows additional battery backup power to be added in the future should your business requirement change.

When considering how to protect applications you need to consider the degree of convergence they enable.   For example would a powered hub or Midspan be better for your network?  What are the maintenance implications of a Line Interactive UPS versus an ON-Line UPS? These questions need to be carefully considered with any decision being weighted against the cost of the solution as well as the benefits they provide. These issues should always be reviewed in line with the aims of the organisation and each department within it.

Departmental requirements play an important part because they may have local network closets or racks which, if switched off, cause a local or even distant part of the network to stop working. Network surveys are vital in preventing the miss able being missed and coming back to haunt the IT manager.  A market leading manufacturer will provide you with technical assistance that allows you to carry out the survey or offer a site survey, allowing you to make an informed decision on power over Ethernet and UPS protection.

Which UPS technology?

The internationally recognised standards IEC 62040-3 and ENV 50091-3 clearly distinguish the following three types of UPS topologies, the three technologies are shown below –

ü       Passive Standby formerly called off-line               

ü       Line-Interactive also known as active standby

ü       Double Conversion formerly called on-line

For the purpose of business critical applications which cover telecommunication and network applications it is not generally considered good practice to use passive standby UPS solutions because they do not provide a real of form of isolation from the upstream distribution system. In addition they provide no real voltage or frequency regulation which can damage sensitive IT hardware causing increased software errors and hardware downtime.

Line Interactive UPS solutions however that provide density optimised solutions are a good place to start.  Market leading product ranges cover a range of power ratings and, at the higher power rating, include a 16amp output socket that will allow the connection of a rack 12 way strip to the UPS. This configuration is shown in the diagram below –

For the critical parts of the network it would be beneficial to consider on-line UPS technology as this provides a good bullet proof vest against mains borne disturbances like low voltage and spikes. In addition it also provides a bypass, which allows the UPS to be maintained without taking down the network.  The following block diagram of an on-line UPS illustrates the three paths which are available for powering the load. In general terms though an on-line UPS is made up of the following :-

n an input rectifier/charger that rectifies the AC-input supply voltage used to charge

a battery as well as support an inverter;

n a battery supplying backup energy in the event of a utility power outage;

n an inverter that supplies power with a consistently high level of quality (frequency, voltage, etc. within tight tolerances);

n a static switch (static bypass) capable of transferring the load to bypass power without a break in the supply of power, thus enabling "downgraded" operation of the load (i.e. not supplied with quality power via the inverter).

Attention to detail is vital in preventing the installation of incorrect equipment that either has to be replaced, or worse, lived with!  A good UPS will be accompanied by excellent XTML or direct power management software. In addition, any credible Midspan solution will be capable of being monitored by power management software. However it does not stop there.  It is vital that maintenance is also considered as it will affect the life time ownership costs of the solution. Even though maintenance is often covered by a different budget or department, the important question is do you take the risk and not have a maintenance contract or do you purchase one. Several levels of cover exist, fundamentally though the question is risk management and if you suddenly need cover will an ‘any time’ response be suitable, typically the answer is no. Its always advisable to purchase maintenance from the original equipment manufacturer or manufacturer approved partner because they will have the latest technical update information on the product.

Is convergence here to stay? The answer is most certainly yes. Should Midspan and UPS solutions be researched? The answer is most certainly yes.  Converged networks carrying power are here to stay and by all accounts will become a 40 million port per annum business within 3 years.