Cable Testing Solutions

CABLE TESTING

ACR
The first thing to understand about testing data cables is the ACR, this stands for Attenuation to Crosstalk Ratio. The pink area in the graph is the attenuation, this can be caused by several things as will be explained below, and the blue area is the crosstalk. Attenuation is the reduction in signal strength over the length of the cable and frequency range, the crosstalk is the external noise that is introduced into the cable. So, if the two areas meet, the data signal will be lost because the crosstalk noise will be at the same level as the attenuated signal.

ACR is the most important result when testing a link because it represents the overall performance of the cable.

So what causes the signal to attenuate?, and where does the crosstalk come from?
Below are of some of the terms used in high performance cable testing, and a description of what they mean.

Length
The length of a cable is one of the more obvious causes of attenuation because the longer it is, the more resistance it has, and therefore less of the signal will get through. To measure the length, a cable tester uses Time Domain Reflectometry (TDR). A pulse is sent down the cable and when it reaches the far end it reflects back, by measuring the time it takes to travel down the cable and back again, the tester can determine how long the cable is. To do this, the tester also needs to know how fast the pulsed signal is travelling, this is called the Nominal Velocity of Propagation (NVP) and is expressed as a percentage of the speed of light. The NVP is usually somewhere between 60% and 90% of the speed of light, with most Cat 5E cables being around 70%. Due to the twists in the cable, the measured length will be greater than the physical length, so if a run looks like it might be over 80m it would be wise to check it before it is tied up and terminated.



Wire Map
This test is to ensure that the two ends have been terminated pin for pin, i.e. that pin 1 at the patch panel goes to pin 1 at the outlet, pin 2 goes to pin 2 etc. etc. The wire map also checks for continuity, shorts, crossed pairs, reversed pairs and split pairs. A Split pair is probably the only thing that requires an explanation here, as they are undetectable with a simple continuity tester, this is because pin for pin they seem to be correct. As explained on the Cabling Basics page, balanced line operation requires that the signal is transmitted over a pair of wires that are twisted together, with a 'split pair' the signal would be split between two different pairs.


Return Loss
When a cable is manufactured there are slight imperfections in the copper. These imperfections all contribute to the Structural Return Loss (SRL) measurement because each one causes an impedance mismatch which adds to the cables attenuation.


DC loop resistance
This is simply the resistance between the two conductors of a twisted pair which is looped back at the far end. The primary purpose of this test is to make sure that there are no high resistance connections in the link.


Attenuation
This is the decrease in signal strength (expressed as negative dB) from one end of a cable to the other. The main causes of attenuation are impedance,
temperature, skin effect and dielectric loss. Impedance is the combination of resistance, inductance and capacitance in a cable, it is measured in Ohms and opposes the flow of current. Skin effect is phenomena which happens at high frequencies where the signal tries to escape from the confines of the copper and into the air. The signal travels along the outer 'skin' of the copper which effectively reduces the cross sectional area of the cable and therefore increases its resistance.



NEXT
This stands for Near End cross Talk, and it occurs because alternating current flow produces an electromagnetic field around the cable, this field then induces a current flow in adjacent cables. The strength of this field increases with the frequency of the signal, and because the speed of data transmissions is ever increasing, NEXT is a big problem.

The name 'Cross Talk' comes from the telecommunications industry, you may have heard a faint conversation in the background while on the phone yourself, this is caused by the electromagnetic effect between adjacent telephone wires. In the transmission of data, cross talk is at its highest level in the RJ45 connection as it enters the cable, or at the 'Near End'. The term 'Near End' is slightly confusing because data can travel in both directions, and the NEXT test is carried out in both directions automatically by the tester, so the NEXT result is relative to the end of the cable that it was carried out on.
The twists in a cable help to cancel out the effects of NEXT and the more twists there are, the better the cancellation, however, the twists also increase attenuation, so there is a trade off between NEXT cancellation and attenuation. The twist rates in data cables are optimised for the best overall performance, the twist rates are also varied for each pair within the cable to help combat crosstalk.


PSNEXT
This stands for Power Sum Near End Cross Talk and is actually just a calculation. When a tester carries out the NEXT test it measures the cross talk on each pair as affected by each of the other three pairs individually, PSNEXT is simply the addition of the three NEXT results for each pair. So this is the combined effect that a pair would be subject to when used in a network that supports a four pair transmissions method, e.g.. Gigabit Ethernet.

FEXT, ELFEXT and PSELFEXT
Basically, Far End Cross Talk (FEXT) is like NEXT but it is measured at the far end (well that seems logical!). However, on its own FEXT doesn't mean much because the length of the cable determines how much the signal is attenuated before it can affect the pairs at the far end. To compensate for this, and to provide a more meaningful result, the attenuation is subtracted from the FEXT test and the result is then called Equal Level Far End Cross Talk (ELFEXT).
And of course, no test parameter these days would be complete without adding the results together for each pair and calling it a Power Sum measurement, so now we have Power Sum Equal Level Far End Cross Talk or PSELFEXT for short.

Delay
This is the propagation delay or the time it takes for the signal to travel from one end of the cable to the other, it is not very important on it own because it value is directly proportional to the length of the cable. What is important is the relationship between the delays on each of the four pairs. This brings us nicely on to .........................

Delay Skew
Now this is important, Delay Skew is the difference between the fastest and slowest pairs. Some networks use a four pair transmission method, this means that the signal is split into four, sent down the four pairs in the cable and re-combined at the far end. It is essential that the signals reach the far end at near enough the same time, otherwise the signal will not be re-combined correctly.

FUSION SPLICING

FUSION SPLICING

Fusion Splicing

There are several reasons for splicing a fiber cable, these include:

To join two fibers due to a breakage.

To connect some of the cores straight through a patch cabinet.

To extend a cable run.

To reduce losses, a fusion splice has much lower losses than two connectorized cables joined through a coupler.

Or to attach a pre-terminated pigtail.

A Pigtail is a short length of fiber with a factory fitted and polished connector. In the past these were used in preference to field terminations because of the complexities at the time of manually terminating optical fibers. These days pigtails are mainly used where the environment isn't suitable for manual terminations or where speed is a factor.

As with all fiber termination methods, safety is very important so first some safety tips.

* Always work in a clean and tidy area.

* Fiber offcuts are hard to see and can easily penetrate the skin especially if they get into your clothes, so care must be taken to ensure the safe disposal of all offcuts. Dispose of fiber scraps immediately using a suitable container and do not throw into a waste paper bin. * Because of the dangers of ingesting a fiber, do not eat or drink in the termination area.

* Fusion splicers use an electric arc to fuse the fibers together so they should never be used in an environment where flammable gases or liquids are present.* Never look into the end of a live fiber connector. Holding some multimode fibers up to a piece of paper may prove the presence of light and therefore prove that it is live, but it doesn't prove that it isn't live! Some laser powered equipment use light which is outside of the visible spectrum, so err on the side of caution.


Overview

A fusion splice is a way of joining two fiber cores by melting the ends together using an electric arc. A splicing machine is used because an extremely high degree of accuracy is needed, the machine first has to align the cores and then apply the exact amount of heat to melt the ends before pressing them together. Splicing can be carried out using a mechanical splice but these only hold the fiber ends together, precisely aligned but not permanently joined.

There are four basic steps to fusion splicing 1 - Strip back all coatings down to the bare fibers and clean using isopropyl alcohol. 2 - Cleave the fibers using a precision cleaving tool and put the heat shrink tube on to one of the ends. 3 - Fuse the fibers together in the fusion splicer. 4 - Put the heat shrink protector on the fiber joint.

Fusion Splicing Method

Stripping

Strip back the external sheathing of the cable using a rotary stripping tool.Cut back the aramid strength member using ceramic or kevlar scissors. Strip the primary buffer from the fiber using fiber strippers not ordinary wire strippers. Do this a small section at a time to prevent the fiber breaking, about 10mm (3/8 in) on each cut is fine until you get used to it. Strip back about 35mm (1.5 in).

Clean the bare fiber with a lint free wipe and isopropyl alcohol, it will "squeak" when it is clean.

Cleaving

The cleaver first scores the fiber and then pulls the fiber apart to make a clean break. It is important that the the ends are smooth and perpendicular to get a good joint, this is why a hand held cleaver will not do. Cleavers vary from manufacturer to manufacturer and you should read the instructions for the one you are using. Basically the operation consists of putting the fiber into the groove and clamping, then close the lid and press the lever. Easy eh! Good cleaving tools can cost between $800 to $3000

The Fusion Process

Once the fiber ends are prepared they are placed in the fusion splicer. Press the button and the machine takes care of the rest of the fusion process automatically. First the two fibers are aligned, you can see this on the photo where a much magnified image shows the two fiber ends. The display also shows how well the cleaver does its job of producing a perfect 90 degree cut. If you watch very carefully in the video you can see the X and Y alignment that takes place. The splicer aligns the fibers on one axis and then from another camera angle set at at 90 degrees, it aligns the other axis. This high precision alignment is critical for a low loss joint, any mismatch of the fiber cores will significantly reduce the propagation of light through the joint. Bearing in mind that we are dealing with two very small glass rods of only 125 microns in diameter, it brings it home as to how extremely accurate these machines are.

Once the fibers are aligned the splicer fires an electric arc between the two ends which melts them immediately and pushes them together, or fuses them into one piece of fiber. The fusion splicer then tests for dB loss and tensile strength before giving the "OK" beeps for you to remove the splice from the machine.

Protection

The splicer in the video has a built in heat shrink oven, so when the fiber is taken out of the machine the protective tube is slid into place and the whole assembly is put into the oven to shrink the tube on to the splice. The protective tube gives physical protection to the splice and further protection is provided by placing the splice into a splice tray.

Once all of the fibers have been joined the whole tray is then fixed into a splice box which protects the cable joint as a whole and the cable clamps are then tightened to prevent any external forces from pulling on the splices.

Fusion splicers are expensive and can cost between about $5,000 to over $30,000, so you need to be doing a lot of splicing to justify the initial outlay but, for a low loss and relatively fast connection it is the only tool for the job.

Fiber Optic - Cold Cure Termination

Cold Cure Termination

There are several different methods of terminating fiber cables including heat-cured, cold cured, pre-injected epoxy, UV adhesives and crimped termination's. There are also environmental conditions to take into consideration, but for the purpose of this tutorial we will discuss the cold cure method as it is the most widely used system and probably the easiest to learn. It is also preferable on site as it doesn't require a power source for ovens and fusion splicers.

As with all fiber termination methods, safety is very important so first some safety tips.

* Always work in a clean and tidy area.

* Fiber offcuts are hard to see and can easily penetrate the skin especially if they get into your clothes, so care must be taken to ensure the safe disposal of all offcuts. Dispose of fiber scraps immediately using a suitable container and do not throw into a waste paper bin.

* Because of the dangers of ingesting a fiber, do not eat or drink in the termination area.

* Observe manufacturers recommendations when using solvent based adhesives.

* Never look into the end of a live fiber connector. Holding some multimode fibers up to a piece of paper may prove the presence of light and therefore prove that it is live, but it doesn't prove that it isn't live! Some laser powered equipment use light which is outside of the visible spectrum, so err on the side of caution.

On to the lesson . . . . . .


The Connector

	There are three parts to a fiber connector (four if you count the dust cap) they are: The connector housing, the connector body and the strain relief boot. The body contains the ferrule which aligns the fiber perfectly for mating with another
connector, it's a precision engineered component. The housing contains the fiber body and provides the latching mechanism. The strain relief boot prevents the fiber from bending past the critical point at which it can break.

Preparation

Fill the syringe with adhesive ready to use. Strip back the external sheathing of the cable using a rotary stripping tool. Cut back the aramid strength member using ceramic or kevlar scissors. Slide the strain relief boot onto the fiber to be terminated. Strip the primary buffer from the fiber using fiber strippers not ordinary wire strippers.
Do this a small section at a time to prevent the fiber breaking, about 10mm (3/8 in) on each cut is fine until you get used to it. Strip back about 30mm (1.25 in).

"Sticking" on the connector!

Inject the adhesive into the connector body until a small bead appears at the end of the ferrule. Clean the bare fiber with a lint free wipe and isopropyl alcohol, it will "squeak" when it is clean. Apply the primer to the bare fiber either with the brush supplied or by dipping it into the bottle. Push the fiber in to the connector body in one smooth action until you feel the buffer reach the back of the ferrule.

The chemical reaction between the adhesive and the primer happens almost instantly so don't stop while inserting the fiber otherwise it will stick before it is fully home.

Cleaving

The purpose of cleaving the fiber is to ensure that it breaks cleanly at 90 degrees, although you may think that because it is ground down to the ferrule and then polished it wouldn't make any difference if it were just snapped off! It makes a big difference. If the fiber shatters or splinters down past the ferrule then no amount of polishing will turn it into a good connection. A hand held scribe or pen cleaver is adequate for this job, unlike fusion splicing where a perfectly cleaved end is essential for a good connection.

Lightly scribe the fiber as close to the ferrule as possible and use a slight tug to break the fiber end away. Dispose of the fiber offcut immediately in the hazardous debris container.

Polishing

The first step in polishing is to take the fiber down to the ferrule, for this we use about a 9 micron lapping film. Hold the connector in one hand and rub the nub of fiber down to the ferrule with the lapping film. When it is close enough you will feel it get smoother. Step two. Insert the connector into the polishing puck, this keeps it perpendicular to the polishing surface. Place a sheet of 2 micron lapping film on a suitable flat surface.

Hold the connector and puck, and place it on the polishing surface. Then move it in a figure of 8 pattern about 30 times using slight pressure. The end is now polished and can be inspected with the microscope. Some people recommend 3 or 4 stages of polishing but we find that we get just as good results from just these two grades of abrasives.

Visual Check

Using the illuminated microscope check that the polished end is OK. Things to look out for are excessive scratches or remnants of the epoxy adhesive. You can now fit the housing and dust cap. Testing Once both ends are terminated the fiber can be tested. Fiber testing used to involve a bulky OTDR (Optical Time Domain Reflectometer) operated by a geek with a degree in optical physics, but these days a simple hand held light source and power meter can be used. To give it a full test you can also use a fiber certification tools which simply tells you what systems the fiber is good for. These simple to use (but quite expensive) instruments will give a print out of all test parameters and losses as well as the communications media it will work on.

FIBER OPTIC Introduction

Fiber Optic Introduction

The installation and termination of optical fibers used to be regarded as somewhat of a 'Black Art' but with standardization and easier terminating techniques this is no longer true. A basic knowledge of the subject, together with a quick lesson and some practice can get you started in fibre optics, but to really understand the subject and gain full in-depth knowledge will require some formal training. There are lots of Fibre Optic training companies offering recognised qualifications and a quick search on the net should find one in your area. If you are in the UK, Optical Technology Training Ltd offer several different courses to choose from including a City & Guilds qualification. There are also hundreds of books on fibre optics and a search on the Barnes and Noble web site will find nearly 600 titles. Without reviewing them all it is difficult to know what to recommend, but two of the best sellers in this category seem to follow on quite nicely from this page without getting too involved with mathematics. The two books are the Introduction to Fibre-Optics by John Crisp and Understanding Fiber Optics, Third Edition by Jeff Hecht. Right, lets get on with the lesson First a bit history In 1870, John Tyndall demonstrated that light follows the curve of a stream of water pouring from a container, it was this simple principle that led to the study and development of applications for this phenomenon. John Logie Baird patented a method of transmitting light in a glass rod for use in an early colour TV, but the optical losses inherent in the materials at the time made it impractical to use. In the 1950's more research and development into the transmission of visible images through optical fibres led to some success in the medical world, as they began using them in remote illumination and viewing instruments. In 1966 Charles Kao and George Hockham proposed the transmission of information over glass fibre, and they also realised that to make it a practical proposition, much lower losses in the cables were essential. This was the driving force behind the developments to improve the optical losses in fibre manufacturing, and today optical losses are significantly lower than the original target set out by Charles Kao and George Hockham. The advantages of using fibre optics Because of the Low loss, high bandwidth properties of fiber cable they can be used over greater distances than copper cables, in data networks this can be as much as 2km without the use of repeaters. Their light weight and small size also make them ideal for applications where running copper cables would be impractical, and by using multiplexors one fibre could replace hundreds of copper cables. This is pretty impressive for a tiny glass filament, but the real benefits in the data industry are its immunity to Electro Magnetic Interference (EMI), and the fact that glass is not an electrical conductor. Because fibre is non-conductive, it can be used where electrical isolation is needed, for instance between buildings where copper cables would require cross bonding to eliminate differences in earth potentials. Fibres also pose no threat in dangerous environments such as chemical plants where a spark could trigger an explosion. Last but not least is the security aspect, it is very, very difficult to tap into a fibre cable to read the data signals. Fibre construction There are many different types of fiber cable, but for the purposes of this explanation we will deal with one of the most common types, 62.5/125 micron loose tube. The numbers represent the diameters of the fibre core and cladding, these are measured in microns which are millionths of a metre. Loose tube fibre cable can be indoor or outdoor, or both, the outdoor cables usually have the tube filled with gel to act as a moisture barrier which stops the ingress of water. The number of cores in one cable can be anywhere from 4 to 144 Over the years a variety of core sizes have been produced but these days there are only three main sizes that are used in data communications, these are 50/125, 62.5/125 and 8.3/125. The 50/125 and 62.5/125 micron multi-mode cables are the most widely used in data networks, although recently the 62.5 has become the more popular choice. This is rather unfortunate, because the 50/125 has been found to be the better option for Gigabit Ethernet applications. The 8.3/125 micron is a single mode cable which until now hasn't been widely used in data networking, this was due to the high cost of single mode hardware. Things are beginning to change because the length limits for Gigabit Ethernet over 62.5/125 fibre has been reduced to around 220m, and now, using 8.3/125 may be the only choice for some campus size networks. Hopefully, this shift to single mode may start to bring the costs down. What's the difference between single-mode and multi-mode? With copper cables larger size means less resistance and therefore more current, but with fibre the opposite is true. To explain this we first need to understand how the light propagates within the fibre core. Light propagation Light travels along a fiber cable by a process called 'Total Internal Reflection' (TIR), this is made possible by using two types of glass which have different refractive indexes. The inner core has a high refractive index and the outer cladding has a low index. This is the same principle as the reflection you see when you look into a pond. The water in the pond has a higher refractive index than the air, and if you look at it from a shallow angle you will see a reflection of the surrounding area, however, if you look straight down at the water you can see the bottom of the pond. At some specific angle between these two view points the light stops reflecting off the surface of the water and passes through the air/water interface allowing you to see the bottom of the pond. In multi-mode fibres, as the name suggests, there are multiple modes of propagation for the rays of light. These range from low order modes which take the most direct route straight down the middle, to high order modes which take the longest route as they bounce from one side to the other all the way down the fibre.
		This has the effect of scattering the signal because the rays from one pulse of light, arrive at the far end at different times, this is known as Intermodal Dispersion (sometimes referred to as Differential Mode Delay, DMD). To ease the problem, graded index fibres were developed. Unlike the examples above which have a definite barrier between core and cladding, these have a high refractive index at the centre which gradually reduces to a low refractive index at the circumference. This slows down the lower order modes allowing the rays to arrive at the far end closer together, thereby reducing intermodal dispersion and improving the shape of the signal.

How TOKEN RING Works

Unlike Ethernet, Token Ring uses a ring topology whereby the data is sent from one machine to the next and so on around the ring until it ends up back where it started. It also uses a token passing protocol which means that a machine can only use the network when it has control of the Token, this ensures that there are no collisions because only one machine can use the network at any given time.

The Basics
Here is an animated GIF that shows the basic operation of a Token Ring, and below is an explanation of what is going on.

Although 16Mbps is the standard ring speed these days (and Fast Token Ring is being developed) we will consider a 4Mbps Token Ring in this tutorial to explain the basic concepts.

Hit 'Refresh' on your browser to start the animation from the beginning

At the start, a free Token is circulating on the ring, this is a data frame which to all intents and purposes is an empty vessel for transporting data. To use the network, a machine first has to capture the free Token and replace the data with its own message.

In the example above, machine 1 wants to send some data to machine 4, so it first has to capture the free Token. It then writes its data and the recipient's address onto the Token (represented by the yellow flashing screen).

The packet of data is then sent to machine 2 who reads the address, realizes it is not its own, so passes it on to machine 3. Machine 3 does the same and passes the Token on to machine 4.

This time it is the correct address and so number 4 reads the message (represented by the yellow flashing screen). It cannot, however, release a free Token on to the ring, it must first send the message back to number 1 with an acknowledgement to say that it has received the data (represented by the purple flashing screen).

The receipt is then sent to machine 5 who checks the address, realizes that it is not its own and so forwards it on to the next machine in the ring, number 6.

Machine 6 does the same and forwards the data to number 1, who sent the original message.

Machine 1 recognizes the address, reads the acknowledgement from number 4 (represented by the purple flashing screen) and then releases the free Token back on to the ring ready for the next machine to use.

That's the basics of Token Ring and it shows how data is sent, received and acknowledged, but Token Ring also has a built in management and recovery system which makes it very fault tolerant. Below is a brief outline of Token Ring's self maintenance system.
 

Token Ring Self Maintenance
When a Token Ring network starts up, the machines all take part in a negotiation to decide who will control the ring, or become the 'Active Monitor' to give it its proper title. This is won by the machine with the highest MAC address who is participating in the contention procedure, and all other machines become 'Standby Monitors'.

The job of the Active Monitor is to make sure that none of the machines are causing problems on the network, and to re-establish the ring after a break or an error has occurred. The Active Monitor performs Ring Polling every seven seconds and ring purges when there appears to be a problem. The ring polling allows all machines on the network to find out who is participating in the ring and to learn the address of their Nearest Active Upstream Neighbour (NAUN). Ring purges reset the ring after an interruption or loss of data is reported.

Each machine knows the address of its Nearest Active Upstream Neighbour. This is an important function in a Token Ring as it updates the information required to re-establish itself when machines enter or leave the ring.

When a machine enters the ring it performs a lobe test to verify that its own connection is working properly, if it passes, it sends a voltage to the hub which operates a relay to insert it into the ring.

If a problem occurs anywhere on the ring, the machine that is immediately after the fault will cease to receive signals. If this situation continues for a short period of time it initiates a recovery procedure which assumes that its NAUN is at fault, the outcome of this procedure either removes its neighbour from the ring or it removes itself.
 

Token Ring Operation using a Hub

A Token Ring hub simply changes the topology from a physical ring to a star wired ring. The Token still circulates around the network and is still controlled in the same manner, however, using a hub or a switch greatly improves reliability because the hub can automatically bypass any ports that are disconnected or have a cabling fault.

Further advancements have been made in recent years with regard to Token Ring technology, such as early Token release and Token Ring switching but as this site is primarily concerned with cabling issues we will not go into any more detail here.

How Ethernet Works

Ethernet was developed in the late 1970's by the Xerox Corporation at their Palo Alto Research Centre in California. It has been estimated that over 70% of the worlds networks use the Ethernet protocol, so with this in mind it would seem only sensible to discuss how it works. If you would like to buy books on this subject, have a look at the Computers section of Barnes and Nobles online book store.

OK, lets begin the lesson. Ethernet uses a protocol called CSMA/CD, this stands for Carrier Sense, Multiple Access with Collision Detection. To understand what this means lets separate the three parts.

Carrier Sense - When a device connected to an Ethernet network wants to send data it first checks to make sure it has a carrier on which to send its data (usually a piece of copper cable connected to a hub or another machine).

Multiple Access - This means that all machines on the network are free to use the network whenever they like so long as no one else is transmitting.

Collision Detection - A means of ensuring that when two machines start to transmit data simultaneously, that the resultant corrupted data is discarded, and re-transmissions are generated at differing time intervals.

Here are some animated GIF's to help explain basic Ethernet operation, below each one is a description of what is happening.
If you want to start an animation from the beginning hit your browsers refresh button.

The Basic Ethernet Bus

This is a coax based Ethernet network where all machines are daisy chained using RG58 coaxial cable (sometime referred to as Thin Ethernet or Thin-net).

Machine 2 wants to send a message to machine 4, but first it 'listens' to make sure no one else is using the network.

If it is all clear it starts to transmit its data on to the network (represented by the yellow flashing screens). Each packet of data contains the destination address, the senders address, and of course the data to be transmitted.

The signal moves down the cable and is received by every machine on the network but because it is only addressed to number 4, the other machines ignore it.

Machine 4 then sends a message back to number 2 acknowledging receipt of the data (represented by the purple flashing screens).

But what happens when two machines try to transmit at the same time? …… a collision occurs, and each machine has to 'back off' for a random period of time before re-trying.

For the sake of simplicity I have omitted the acknowledgement transmissions from the rest of the animation's on this page.

Collisions

This animation starts with machine 2 and machine 5 both trying to transmit simultaneously.

The resulting collision destroys both signals and each machine knows this has happened because they do not 'hear' their own transmission within a given period of time (this time period is the propagation delay and is equivalent to the time it takes for a signal to travel to the furthest part of the network and back again).

Both machines then wait for a random period of time before re-trying. On small networks this all happens so quickly that it is virtually unnoticeable, however, as more and more machines are added to a network the number of collisions rises dramatically and eventually results in slow network response. Time to buy a switch!!!

The exact number of machines that a single Ethernet segment can handle depends upon the applications being used, but it is generally considered that between 40 and 70 users are the limit before network speed is compromised.

Using a Hub

An Ethernet hub changes the topology from a 'bus' to a 'star wired bus', here's how it works.

Again, machine 1 is transmitting data to machine 4, but this time the signal travels in and out of the hub to each of the other machines.

As you can see, it is still possible for collisions to occur but hubs have the advantage of centralised wiring, and they can automatically bypass any ports that are disconnected or have a cabling fault. This makes the network much more fault tolerant than a coax based system where disconnecting a single connection will bring the whole network down.

Using a Switch

To overcome the problem of collisions and other effects on network speed, a switch is used.

With a switch, machines can transmit simultaneously, in this case 1 & 5 first, and then 2 & 4. As you can see, the switch reads the destination addresses and 'switches' the signals directly to the recipients without broadcasting to all of the machines on the network.

This 'point to point' switching alleviates the problems associated with collisions and considerably improves network speed.

In the real world however, one or more of these machines will be servers, and as most network traffic is between the clients and a server a serious bottle neck can occur. The answer to this problem is to make server connections faster than the clients. The normal solution is to have the client machines on 100Mbs ports and the servers on 1000Mbs ports (Gigabit Ethernet). This ten to one ratio is usually adequate because not all of the clients will need to access the servers at the same time.

FAULT Findings on Structured Cabling Systems

First the Basics
I've lost track of the number of times I've been on a customers site and found that they have re-used the old Cat 3 and Cat 4 patch leads simply because they didn't have any Cat 5 leads at the time. These leads almost never get changed because it hasn't made any noticeable difference to the operation of the network. Years later of course, things start to go wrong and the old leads aren't even suspected because "they've not been a problem in the past".

By all means use old leads on voice systems but never use them on data networks.

It is like throwing a load of rocks into a smooth running stream, the data will probably still get through at first but when you increase 'the flow', they will start to impede the throughput.


If the problem only affects one PC, take that PC to the patch cabinet and plug it directly into the hub. This may seem like an obvious thing to try but it has to be said as it proves whether the fault is actually a cabling problem or not. You should use a known good port on the hub and a known good patch lead, if the machine works then the problem is either the original hub port, the patch lead, the drop lead or the fixed cabling. From here it is easy to eliminate each part of the link, but it must be carried out methodically, one component at a time. Another point worth mentioning is that a patch lead that works fine in a Token Ring network may not work in an Ethernet network, this is because they use different pins on the RJ45 plug. Token Ring uses pins 3, 4, 5 & 6 whereas 10BaseT Ethernet uses 1, 2, 3 & 6, so any cable with a fault on pins 1 & 2 will work for Token Ring but not for Ethernet. Although a Cat 5/5E tester can be very expensive, you can buy a simple continuity tester for under $100 which will test for shorts, opens and crossed pairs, this will not prove your cabling is up to standard but they are quick and easy for finding faulty Cat 5 patch leads.

Another thing to watch out for is the wiring configuration, there are actually two different schemes allowed under the 568A standard. These are called 258A (or T568B), and 258B (or T568A). Pin for pin they are the same but with the orange and blue pairs swapped over, so as long as you have the same type of jack at each end, no problem. However, if you have 258A on one end, and 258B on the other then you have a crossed pair.

Check the time of day!
The time of day may indicate another cause of network problems. If the problem only occurs at a certain time, it maybe that the network is slowing due to an increase in traffic say at 9:00am or 5:00pm. If, for instance, the drawing office starts at 9:00am and twenty draughtsmen are all trying to pull large drawing files from a server which is on the general network, this will impact the rest of the company's business. Likewise at 5:00pm when they are all saving their work back to the server the sudden increase in traffic may cause so many collisions that the network to grinds to a halt. A process of elimination is easy to implement and if this is the cause, it is time to put the drawing office and the CAD server on to its own hub or switch.

Electrically 'noisy' environments
Another common cause is electromagnetic interference from electric motors and sources of high frequency radio waves. The more obvious things to look for are cable routes that pass too close to lift motors, arc and spot welders, heavy plant machinery which use large electric motors, and fluorescent light fittings. All of these things, if situated close to the data cabling, could induce spikes into the network. Take a walk around the building and make a note of all possible causes, and then try to eliminate them one at a time.

What next?
Eliminating possible causes one at a time is the ideal, but sometimes the problem occurs so infrequently that it is almost impossible to track down, and specialist equipment and engineers have to be employed. 'Network Sniffers' and mains monitors can be hired from companies such as Livingston Hire, and if you are confident that you can correctly interpret the results, do it yourself. If not, well its the end of the line and time to call in the specialists.

To summarize, the following considerations should be taken into account:

1. Low grade patch leads and/or drop leads.

2. Time of day.

3. Increase in network traffic from other sources.

4. Electromagnetic interference.


If you need more in-depth information on any IT related subject check out the wealth of knowledge at www.SearchNetworking.com. They have news, advice and tips on all aspects of computer networking, and is a valuable source of help for network managers and administrators .

Ethernet
Most of the points mentioned above should find Ethernet problems, however, there are a couple of things that should be taken into consideration when dealing with Gigabit Ethernet.

Although Gigabit Ethernet was designed to run on 100MHz cable, problems may arise with older Cat 5 systems. The more stringent Cat 5E standards take into consideration that Gigabit Ethernet uses a four pair transmission method, but this was not part of the test parameters with Cat 5. If you are trying to run Gigabit Ethernet over standard Cat 5 cabling, then the whole system should be tested to confirm that it meets the new Cat 5E standard.

It used to be said that multimode fibre was good for 2km, but recently it has been found that for Gigabit Ethernet applications the length limit is right down to around 220m over 62.5/125 fibre. The only way to prove if a fibre is good enough for Gigabit Ethernet is to use a certification tool. These are fairly expensive test instruments, but you should be able to hire one from a specialist hire company. The results give a clear 'pass or fail' for different applications, but bear in mind that one dirty connector can affect the results considerably.

Token Ring
Type 1 cable was designed for Token Ring and is a very robust system, however, some of the data connector termination's I've seen leave a lot to be desired. It is possible to re-terminate these connectors, so if you have some that are looking decidedly worn or broken, get them fixed. Because of their large size, data connectors tend to get knocked and bumped and this can be the cause of a lot of problems. Also remember that Type 1 is a shielded system which has to be grounded properly at the patch cabinet, ground continuity should also be carried right through to the PC. Failure to ensure proper grounding can cause a multitude of problems.

The data connector was designed to 'loop back' when unplugged to ensure that if the main ring cabling is interrupted the network will stay up. If you look into the end of a data connector you will see two gold strips one behind the other These 'short circuit' the transmit and receive pairs when the connector is unplugged, and loops the signal back the other way thereby maintaining ring integrity. This very clever piece of design does have a slight draw back in that a disconnection on the main ring path can go unnoticed because the data connector is doing its job. This means that if you have a fault on the ring and it is already working on loop back, you will only know when a second fault occurs. In theory, if your Token Ring is working perfectly and the ring is complete, you should be able to disconnect the main ring path anywhere without disrupting the network. If, on the other hand, your Token Ring is already running on loop back due to a fault that you are not aware of, disconnecting the main ring will effectively split the network in half.
 

AS400 cabling
AS400e series have three new features which are designed to speed up throughput to 5250 devices, unfortunately some Twinax hardware will not support them.

Split Mode
When operating in Split mode, the AS400 poles its ports two at a time, i.e. 0 & 4, 1 & 5, etc., this only causes a problem when eight port multiplexors are used as they will be trying to multiplex and de-multiplex both simultaneous signals. To overcome this, two four port mux's should be used, or the Split mode feature turned off.

Optimized Mode
In optimized mode no overheads are added to the data frame which under normal conditions works fine, however some star hubs and mux's need the additional information to work correctly. The solutions are to either buy new hubs and mux's, or again turn off the Optimized mode feature on the AS400.

Express Mode
This is simply the AS400 running at 2Mbs instead of 1Mbs, and again some hubs and mux's can't handle this speed. The solution?, same as above really, buy new hubs or switch off the Express mode feature.

Length limits
The maximum distance for Twinax cable on each port of the Work Station Controller is 1800m, this limit is reduced to 1458m when running in Express mode. It is also a little known fact that there is a minimum length limit of 25 feet or about 8m on all types of cable used to transmit 5250 signals. This distance is the length of the signal itself, and if the cable is less than this, the signal can become corrupted by its own reflections before it has finished transmitting.

When using IBM Type 1 cabling, the limits are the same as Twinax operation (1800m) but this reduced to 1312m when running in Express mode.

For UTP installations the distances vary according to whether Twinax is used on part of the installation. The limits range from a maximum of 364m when only a few metres of Twinax has been used between the Work Station Controller and the hub, down to a minimum of only 36m where more than 1600m of Twinax has been used. For further information visit the IBM networking web site.

Where fibre is used between mux's or converters, the maximum limit is 2400m, again this may be reduced if the AS400 is running in Express mode.

5250 Star hubs
Some active star hubs can introduce delays into the system, if these delays are close to the limits for 5250 operation, it can affect the reliability and performance of the network. Passive star hubs don't cause delays, so if you are having intermittent problems with a particular line it might be worth trying a passive star in place of an active one. This is sometimes the case when a line of terminals has been working perfectly well on the old Twinax but problems start to arise when they are moved to the new structured cabling.

When running 5250 devices over a UTP structured cabling system problems can sometimes be due to mismatched baluns. Make sure all of the baluns on each line are from the same manufacturer, and that they are wired for the same pin-out configuration, some star hubs use pins 1 & 2 as the active pins and some use 4 & 5.

 

RS232
With RS232, transmit and receive are connected via pins 2 and 3 of the D type plugs with pin 7 (on 25 way) being the ground point. The other pins are used to control the flow of data, usually referred to as 'hard wired handshaking', the pin-out chart below shows what each pin is used for.

A device can be either a Data Terminal Equipment (DTE) or a Data Communications Equipment (DCE), this determines whether pin 2 is transmit and pin 3 receive or vice versa. Usually you will find that terminals are DTE and printers are DCE and the ports on the server board will be configured to communicate with one or the other. This makes a big difference if you start moving things around and inadvertently connect terminals or printers into the wrong ports.

25 pin	9 pin	Abbreviation	Description
1	N/A	GND	Shield Ground
2	3	TXD	Transmit Data
3	2	RXD	Receive Data
4	7	RTS	Request to Send
5	8	CTS	Clear to Send
6	6	DSR	Data Set Ready
7	5	GND	System Ground
8	1	CD	Carrier Detect
9	N/A	0	Reserved
10	N/A	0	Reserved
11	N/A	STF	Select Transmit Channel
12	N/A	SCD	Secondary Carrier Detect
13	N/A	SCTS	Secondary Clear to Send
14	N/A	STXD	Secondary Transmit Data
15	N/A	TCK	Transmission Signal Element Timing
16	N/A	SRXD	Secondary Receive Data
17	N/A	RCK	Receiver Signal Element Timing
18	N/A	LL	Local Loop Control
19	N/A	SRTS	Secondary Request to Send
20	4	DTR	Data Terminal Ready
21	N/A	RL	Remote Loop Control
22	9	RI	Ring Indicator
23	N/A	DSR	Data Signal Rate Selector
24	N/A	XCK	Transmit Signal Element Timing
25	N/A	TI	Test Indicator

Introduction to Structured Cabling

There are also lots of books on the subject of cabling and a selection of these can be found at the Barnes and Noble website in their Computers section, although my personal favourite is The Cabling Handbook 2nd Edition by John Vacca. It has over 1300 pages covering all aspects of network cabling and includes chapters on The Standards, Network Design, Wireless Communications, Fibre and Home Wiring, plus a whole lot more.

If you don't want to invest any money on training until you are seeing some financial results, then you can gain valuable experience by actually doing some work for an existing cabling company.

Here are some basic questions you may be asking yourself if you have never installed a structured cabling system before.

What are 'The standards' ?
There are three main cabling standards:

• EIA/TIA 568A - This is the American standard and was the first to be published (1991).
• ISO/IEC 11801 - The International standard for structured cabling systems.
• CENELEC EN 50173 - The European cabling standard (the British version is BS EN 50173).

The reason for having a 'Standard' is to define a method of connecting all types of vendors voice and data equipment, over a cabling system that uses a common media, common connectors and a common topology. This means that a building can be cabled for all its communications needs without the planner or architect ever having to know what type of equipment will be used.

It is advisable to get a copy of one of the cabling standards documents, although once you have read through it once and understood some of what it describes, it will probably be filed away and never opened again. If you have ever tried to read a standards document you will know that it is hard work. Trying to separate the useful information from all the technical jargon can be very time consuming and even then you may not find the answer to your question. The bad news is, the Cabling Standards are no different, they are full of cross references, formulas and tables all of which can be a very daunting prospect and can make the installation engineer think twice about installing the stuff.

Now for the good news, the standards are mostly concerned with the performance criteria of the components of a cabling system, and, as that is guaranteed by the manufacturers of the different cabling components, you don't have to worry about it. Great eh!

What type of cable do I install?
Please go to the Questions and Opinions page for my personal views on the subject.

What materials do I need?
Lets work on a hypothetical installation. It is for 30 double outlets, in one building, with an average run of about 30m. Each double outlet will be used for one PC and one telephone. A detailed breakdown of this list giving reasons for sizes and quantities is Here

 

• 1 x 27U, 600 x 600 cabinet.
• 3 x 32 way RJ45 patch panels.
• 6 x boxes of Cat 5e cable.
• 30 x double Cat 5e outlets and backboxes
• 30 x PBX master telephone adapters
• 30 x 1.5m patch leads
• 30 x 2m patch leads
• 30 x 3m fly leads.
• Trunking, cable ties and a method of labelling the system.

 

How do I install it?
Here are the basic do's and don'ts.

Although the maximum cable length for a Cat 5e/6/7 system is often reported to be 100m, this length is inclusive of patch and drop leads. Cable testers however, when set to perform a 'Basic Link' test, take this into account and you will find that the maximum length is set to either 90m or 94m depending on the standard you are testing to. Also, because the length is measured with a Cable Analyser it is not the physical length of the run but the copper length that is measured. The copper length is longer due to the twists in the cable pairs, so if a run looks like it might be over 85m it would be wise to check it before it is tied up and terminated.

Each outlet cable should be run directly back to the patch cabinet, that is one cable per outlet. A transition point or connection box is allowed if necessary, but in practice this can be more trouble than its worth.

Care should be taken when pulling cables in to ensure that they are not kinked or nicked.

Cable routes should be planned to avoid fluorescent light fittings and power cables (exceptions can be made in the case of optical fibre). They should not be run in the same conduit as power, or the same channel of a trunking system, and where they are run parallel to power they must be at least 60mm apart (BS7671-92) . Crossing power cables is allowed but it must be at right angles, and some form of bridge should be used.

A means of supporting the cables should be installed such as cable tray, catenary wire or cable tie fixings, tying cables to ceiling hangers is not permitted. Cables should be tied at a minimum of 500mm intervals on horizontal runs and more frequently on vertical runs, with no more than 48 cables in a loom. Cable ties should only be finger tight to avoid crushing the cables as this could affect the cables performance characteristics. Do not use cable tie guns or staple guns.

Cable trays should be used under false floors, if not, a suitable method of keeping the cable off the floor slab should be employed. This is because the lime in the concrete apparently reacts with the cables sheathing, and over time could damage the cable. I personally think the cable will have outlived its usefulness long before this could have any affect on the cables performance.

Care should be taken when pulling cables into trunking to avoid damage due to snagging. Trunking partitions should be used to separate the data cables from power, and bridges should be used where data cables have to cross the mains.

When terminating patch panels, cable looms should not exceed 48 cables. Each cable loom should then be tied in a tidy manner to a cable tray fitted the full length of the cabinet.

All terminating should be carried out according to the manufacturers instructions and guidelines, and the standards for generic cabling systems. The cable sheath should be stripped back no more than 13mm from the point of termination and the twist rates should be maintained.

Cable ties MUST be fitted to the individual RJ45 modules in the patch panels and outlets to support each cable.

When terminating outlets, care must be taken to avoid damaging the copper cores when stripping back the outer sheathing.

Excessive amounts of cable should not be left in the outlet backbox. Care should be taken when attaching the outlet faceplate not to kink, trap or strain the cable.

Cable tray should be fitted in cabinets housing structured cabling to keep cable looms secure and tidy, and to provide room for any additional cabling.

All cabinets must be earthed to the 16th edition IEEE wiring regulations (British regulations). Where shielded cable is used the earth should be clean and where two cabinets are linked with a copper backbone (shielded or unshielded) a minimum of 10mm² earth wire should also be installed to cross bond the cabinets.

 
Testing and documentation
All testing whether copper or fibre should begin with calibration of test equipment, and batteries should be fully charged before testing begins. Descriptions of the various test parameters can be found on the Cable Testing  page.

On all installations, and particularly on large jobs, two way radios or internal telephone lines should be used to ensure correct numbering of outlets and patch panels during testing.
 

What do they mean by Balanced line? How does it work?
Balanced line operation is a transmission method which helps to eliminate the effects of noise on the cable. In the first diagram a coaxial cable is transmitting a 4V signal, this is unbalanced as all of the 4V signal is carried by the centre core of the coax with respect to the grounded screen. If 1V of noise is introduced, it adds to the signal being transmitted making 5V, this could interfere with our data.

With a balanced line transmission our 4V signal is split into +2V and -2V on one twisted pair, so we still have 4V between the two. Now when we introduce the 1V of noise, the +2V becomes +3V, and the -2V becomes -1V, but the potential difference between the two is still 4V. The devices we put on the ends of the cable to make the line balanced are called baluns, this name is derived from the function of the devices of converting between balanced and unbalanced transmission modes.

These days, more and more equipment is being designed to operate on balanced lines without the need for baluns, but there are still a lot of older systems out there that still use these converters.

MHz? Mbps? Baud?
If you are confused about the different terms used in data communications this article written by Mark Barratt should help to clear things up.

Bandwidth is the difference between the highest and lowest frequencies which will propagate through an equipment or system. In many cases, the lower limit is DC, zero hertz, and so the bandwidth is the same as the upper frequency limit. The public telephone system constrains all signals to the range 300 Hz - 3 kHz. Its bandwidth is therefore 2.7kHz.

In the most obvious method of modulation (representing data electrically), two different voltages are used to represent a '1' and a '0'. The receiver expects a data bit at a certain time, and samples the input voltage to determine the value of the bit. This is called "amplitude shift keying" (ASK). The maximum frequency of the signal will depend upon the slew rate (the time taken to change from 0 to 1, or vice versa). The maximum slew rate is the upper frequency limit, and the slew rate, in turn, limits the maximum data rate.

Plainly, the bandwidth of such a system directly limits the data rate, but in theory it need not. Consider a protocol which uses "frequency shift keying" instead. Here, two different frequencies (both of them within the legal bandwidth) are used to represent 1 and 0. The maximum data rate is now the maximum speed at which you can shift between the two frequencies. This is still limited by the bandwidth, but not so directly - the resulting maximum data rate is higher. And what happens if you use more than two frequencies? You can then transmit more than one bit of information per signal transition, upping the data rate again without increasing the maximum frequency of the signal.

It is techniques such as these which have allowed the development of 56k modems. Using a combination of multiple-level amplitude, frequency and phase modulation, they manage to extract up to 56,000 bits per second of performance from the aforementioned 2.7 kHz bandwidth. To achieve this using plain 2-level ASK would require a bandwidth of hundreds of kilohertz.

"Baud rate", strictly, is a measure of "signal elements" per second, and is not a useful measure where the above signalling techniques are being used. Such systems are generally rated in "bits per second" bps. It is worth noting that manufacturers will claim the highest figure they can for this parameter, so that the figure will include bits which are part of the signalling protocol rather than the user's data, and may even incorporate an assumption about the compressibility of the data. It is rarely (if ever) valid to divide bps by 8 to arrive at bytes of data transmitted/expected per second.

Structured Cabling Overview

Structured Cabling is defined as building or campus telecommunications cabling infrastructure that consists of a number of standardized smaller elements (hence structured) called subsystems.

Structured cabling falls into the following six sub-systems:

Entrance Facilities is where the building interfaces with the outside world.
Equipment Rooms host equipment which serves the users inside the building.
Telecommunications Rooms are where various telecommunications and data equipment resides, connecting the backbone and horizontal cabling sub-systems.
Backbone Cabling as the name suggests carries the signals between the entrance facilities, equipment rooms and telecommunications rooms.
Horizontal Cabling is the wiring from telecommunications rooms to the individual outlets on the floor.
Work-Area Components connect end-user equipment to the outlets of the horizontal cabling system.
Structured cabling design and installation is governed by a set of standards that determine how to wire a data center, office or apartment building for data or voice communications, using Category 5 or Category 6 cable and modular sockets. These standards define how to lay the cabling in a star formation, such that all outlets terminate at a central patch panel (which is normally 19 inch rack-mounted), from where it can be determined exactly how these connections will be used. Each outlet can be 'patched' into a data network switch (normally also rack mounted alongside), or patched into a 'telecoms patch panel' which forms a bridge into a private branch exchange (PBX) telephone system, thus making the connection a voice port.

Lines patched as data ports into a network switch require simple straight-through patch cables at the other end to connect a computer. Voice patches to PBXs in most countries require an adapter at the remote end to translate the configuration on 8P8C modular connectors into the local standard telephone wall socket. In the U.S., no adapter is needed, as the 6P6C plug used with RJ11 telephone connections is physically compatible with the larger 8P8C socket and the wiring of the 8P8C is compatible with RJ11. In the UK, an adapter must be present at the remote end as the 6-pin BT socket is physically incompatible with 8P8C.

It is normal to see different colour patch cables used in the patch panel to help identify which type of connection is being carried, though the structured cabling standards do not require this, except in the demarcation wall field

Cabling standards demand that all eight connectors in Cat5/5e/6 cable are connected, resisting the tempation to 'double-up' or use one cable for both voice and data. This is generally a good thing as it means that they fully support features such as Power over Ethernet which require the so-far unused brown cables.

Structured Cabling Standards
The main structured cabling standards used in the USA and many other countries are:

A. TIA-526-7 “Measurement of Optical Power Loss of Installed Single-Mode Fiber Cable Plant “– OFSTP-7 - (February 2002)

B. TIA-526-14-A Optical Power Loss Measurements of Installed Multimode Fiber Cable Plant – OFSTP-14 - (August 1998)

C. ANSI/TIA/EIA-568-B.1 Commercial Building Telecommunications Cabling Standard Part 1: General Requirements: General Requirements, may 2001.

D. Adenda ANSI/TIA/EIA-568-B.1-1-2001, Addendum 1, Minimum Curve Radius for 4 pair UTP and ScTP cable, july, 2001.

E. TIA/EIA-568-B.1-2 Commercial Building Telecommunications Cabling Standard Part 1: General Requirements Addendum 2 – Grounding and Bonding Requirements for Screened Balanced Twisted-Pair Horizontal Cabling - (February 2003)

F. TIA/EIA-568-B.1-3 Commercial Building Telecommunications Cabling Standard Part 1: General Requirements Addendum 3 – Supportable Distances and Channel Attenuation for Optical Fiber Applications by Fiber Type - (February 2003)

G. TIA/EIA-568-B.1-4 Commercial Building Telecommunications Cabling Standard Part 1: General Requirements Addendum 4 – Recognition of Category 6 and 850 nm Laser Optimized 50/125 μm Multimode Optical Fiber Cabling - (February 2003)

H. TIA/EIA-568-B.1-5 Commercial Building Telecommunications Cabling Standard Part 1: General Requirements Addendum 5 – Telecommunications Cabling for Telecommunications Enclosures – (March 2004)

I. TIA/EIA-568-B.1-7 Commercial Building Telecommunications Cabling Standard Part 1: General Requirements Addendum 7 - Guidelines for Maintaining Polarity Using Array Connectors – (January 2006)

J. TIA/EIA-568-B.2 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components - (December 2003)

K. TIA/EIA-568-B.2-1 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 1 – Transmission Performance Specifications for 4-Pair 100 ohm Category 6 Cabling - (June 2002)

L. TIA/EIA-568-B.2-2 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 2 – Revision of Sub-clauses - (December 2001)

M. TIA/EIA-568-B.2-3 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 3 – Additional Considerations for Insertion Loss & Return Loss Pass/Fail Determination - (March 2002)

N. TIA/EIA-568-B.2-4 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 4 – Solderless Connection Reliability Requirements for Copper Connecting Hardware - (June 2002)

O. TIA/EIA-568-B.2-5 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 5 – Corrections to TIA/EIA-568-B.2 – (January 2003)

P. TIA/EIA-568-B.2-6 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 6 – Category 6 Related Component Test Procedures – (December 2003)

Q. TIA/EIA-568-B.2-11 Commercial Building Telecommunications Cabling Standard Part 2: Balanced Twisted-Pair Cabling Components – Addendum 11 - Specification of 4-Pair UTP and SCTP Cabling – (December 2005)

R. TIA/EIA-568-3 Optical Fiber Cabling Components Standard - (April 2002)

S. TIA/EIA-568-3.1 Optical Fiber Cabling Components Standard – Addendum 1 – Additional Transmission Performance Specifications for 50/125 μm Optical Fiber Cables – (April 2002)

T. TIA-569-B Commercial Building Standard for Telecommunications Pathways and Spaces - (October 2004)

U. TIA-598-C Optical Fiber Cable Color Coding - (January 2005)

V. TIA/EIA-606-A Administration Standard for Commercial Telecommunications Infrastructure - (May 2002)

W. J-STD-607-A Commercial Building Grounding (Earthing) and Bonding Requirements for Telecommunications - (October 2002)

X. TIA-758-A Customer-owned Outside Plant Telecommunications Infrastructure Standard – August 2004

European countries use another set of standards, the main one being ISO/IEC 11801.

 

Microsoft Certified Professional - MCP

Microsoft Certified Professional (MCP) refers to both an individual Microsoft certification and a broader professional certification program.

To be an MCP, candidates must complete any one exam within the program. The MCP program offers multiple certifications, based on different areas of technical expertise. To attain these certifications, a candidate must pass a series of exams within the program. Popular certifications are MCP, Microsoft Certified System Engineer (MCSE), Microsoft Certified Solution Developer (MCSD) and Microsoft Certified Database Administrator (MCDBA).[1]

Some employers require or prefer certain MCP certifications for specific jobs. MCP curriculum revolves around Microsoft's operating systems. Other vendors have their own certification programs such as the Sun Certified Professional program, the Red Hat Certification Program, the Oracle Certification Program, the Cisco Career Certifications program, the Ubuntu Certified Professional program and the Apple Certification Program.

Each exam costs approximately US$125. Exams usually take between 2 and 3 hours to complete and consist of between 45 and 90 multiple choice, drag and drop, and solution building questions. In early 2006 Microsoft announced a return to simulated content within exams where students are required to perform certain common administrative tasks appropriate for the topic at hand.

In October 2005, Microsoft announced the restructuring of its certification by launching a three-tiered certification program.[2]

 

Certification Programs

Microsoft Certified Systems Engineer
Microsoft Certified Systems Engineer (or MCSE) is the best-known and premiere Microsoft certification. It qualifies an individual as being able to analyze the business requirements for information systems solutions, and design and implement the infrastructure required. As of 2007, the MCSE is available for two different product lines; Windows 2000 and Windows Server 2003, each of which requires a different set of exams.

For the MCSE 2003, candidates must pass six core design exams (Four networking exams, one client operating system and one design exam) and one elective exam, for a total of seven exams. For the MCSE 2000, a candidate needs to pass five Core Exams (Four operating system exams, one design exam) and two electives. For the MCSE NT 4.0 (which is no longer available to earn, though it is still recognized as a valid certification), a candidate needed to pass four Core Exams (Networking Essentials, Windows NT Workstation, Windows NT Server and Windows NT Server in the Enterprise) and two electives.

The topic of these exams include network security, computer networking infrastructure, Active Directory, Microsoft Exchange Server, Microsoft SQL Server, and other topics of both general networking interest as well as specific Microsoft products.

Perhaps due to controversies over the term Engineer, this qualification has also been pejoratively referred to as Minesweeper Consultant and Solitaire Expert.

Microsoft Certified Solution Developer
The Microsoft Certified Solution Developer (MCSD) certification is the highest level programming certification offered by Microsoft. To fulfill the requirements of the certification, a total of five exams (four core exams, one elective exam) must be passed. Some of the core exams are also requirements for the MCAD. Microsoft has declared that this certification will be focused towards the needs of developers using .NET Framework 1.0 and 1.1 versions. Developers using .NET Framework 2.0 and Microsoft Visual Studio 2005 are expected to consider undergoing Microsoft Certified Technology Specialist (MCTS) and Microsoft Certified Professional Developer (MCPD) certification.

Microsoft Certified Systems Administrator
The Microsoft Certified Systems Administrator (MCSA) certification certifies a user's knowledge in system administration of Microsoft Windows operating systems and is generally simpler than, but not a subset of, the MCSE. The Windows Server 2003 MCSA is achieved upon passing 2 networking system exams, a client operating system exam (generally Microsoft Windows XP), and an elective exam. The Windows Server 2000 MCSA title is granted after taking 3 core exams and one elective. Although the MCSA is not a subset of the MCSE, it is possible to gain an MCSA on the way to an MCSE without doing any exams that are extraneous to the MCSE.

Whereas the MCSE is supposed to certify a person's ability to "plan, design, and implement Microsoft Windows server solutions and architectures in medium- to large-sized companies", the MCSA certifies a holder's ability to "implement, manage, and maintain the typically complex computing environment of medium- to large-sized companies".

Like the MCSE, the MCSA is available as "MCSA on Windows 2000" and "MCSA on Windows 2003" as of 2005. There exist two specializations for both tracks: Messaging and Security.

As an alternative to the electives on the MCSA electives table, certifications or certification combinations may substitute for an MCSA elective. For example, CompTIA A+ and Network+ together or CompTIA A+ and Server+ together can be credited and substituted for an elective through a Microsoft and CompTIA partnership agreement. One may also substitute Security+ alone which counts for the elective and one of two exams for the "Security Specialization." Security+ counts for MCSA 2003 and MCSE 2003. This is just one cost effective way to earning an MCSA if candidates are already certified in other areas.

Microsoft Certified Database Administrator
The Microsoft Certified Database Administrator (MCDBA) credential is for database administrators, who implement and administer Microsoft SQL Server databases. The certification is appropriate for individuals who derive physical database designs, develop logical data models, create physical databases, create data services by using Transact-SQL, manage and maintain databases, configure and manage security, monitor and optimize databases, and install and configure SQL Server. This certification requires passing three core exams, and one elective exam. According to Microsoft, people who operate MSSQL 2005 should apply for other certifications such as the MCITP (Microsoft Certified IT Professional) or MCTS (Microsoft Certified Technology Specialist), rather than the MCDBA. Complete course lasts 250 hours.

Microsoft Certified Desktop Support Technician
The Microsoft Certified Desktop Support Technician (MCDST) is a lower-level credential that demonstrates a technician can competently support end users and troubleshoot desktop environments running on Microsoft Windows. MCDST candidates are required to pass two core exams. Elective exams are not required. Complete course lasts 50 hours.

Microsoft Office Specialist
The Microsoft Office Specialist (MOS), previously named Microsoft Office User Specialist (MOUS) is a certification for using the Microsoft Office suite of business applications. While listed under the MCP Certification Programs, it is not officially an MCP Certification. The MOS exams are managed by a third party company, Certiport.

It appears (January 2007) that a new set of qualifications will replace the MOS/MOUS certifications for Office 2007. The direct application specific skills are the “Microsoft Certified Application Specialist” (“MCAS”) for each Office 2007 Application. And, a new “Microsoft Certified Application Professional” (“MCAP”) based on how to complete more common business tasks. While these qualification exams will be managed by Certiport it appears other exam providers may also become involved.

Microsoft Certified Trainer
The Microsoft Certified Trainer (MCT) certification is for individuals who intend to train users wanting to obtain any of the other certifications. They must have some type of certification out of the Microsoft Course. For example, in Australia, many MCT's have a diploma or degree in teaching either primary school or secondary education. It is also a requirement by many training companies, especially Microsoft Gold Partners to have MCT's with a degree in teaching.

Microsoft Certified Professional
Anyone passing just one operating system based exam, can be certified as Microsoft Certified Professional (MCP)(270, 271, or 272). (Except for exam 70-058: Networking Essentials since it isn't a product exam).

Microsoft Certification Resources
There are several courses, Boot camps, and practice tests from different vendors offering preparation material for Microsoft certification exams. Bootcamps normally provide residential program that includes food and lodging. These courses are meant for busy professionals who do not have enough time for self preparation or wish to get trained by professional trainers. Microsoft Press provides several books towards Microsoft certification exams preparation. Books are normally the first place to explore Microsoft certification options, and preparation. Apart from Microsoft Press books, there are other reputed publishers like Sybex, and others. In addition to books, Microsoft Learning also offers courses for each of the exams.

Apart from books, there are several practice tests vendors that offer pre-certification exams. These mock exams almost mimic actual exams, and normally priced much less than the actual exam. Several user forums are available for certification preparation where most questions are answered by other forum users.

Experts and past candidates recommend not only reading more than one book, but spending a good amount of time practicing the concepts on computers on a test environment. After practicing and reading, it's also recommended to take sample exams before taking the Microsoft exam.

Microsoft New Generation of Certifications
Microsoft has released a new three-tiered certification hierarchy. It consist of three series and four credentials that introduce an entry-level Technology Series, a Professional Series comprised of an IT Professional and Professional Developer credentials and a new top-level Microsoft Certified Architect.

There exist three series:

Technology Series
Professional Series
Architect Series

Technology Series
The seven Microsoft Certified Professional Developer (MCPD) Technology Specialist (MCTS) certifications are:

Technology Specialist: .NET Framework 2.0 Web Applications
This certification requires that one pass the following examinations:

Exam 70-536: TS: Microsoft .NET Framework 2.0 - Application Development Foundation
Exam 70-528: TS: Microsoft .NET Framework 2.0 - Web-Based Client Development

Technology Specialist: .NET Framework 2.0 Windows Applications
This certification requires that one pass the following examinations:

Exam 70-536: TS: Microsoft .NET Framework 2.0 - Application Development Foundation
Exam 70-526: TS: Microsoft .NET Framework 2.0 - Windows-Based Client Development

Technology Specialist: .NET Framework 2.0 Distributed Applications
This certification requires that one pass the following examinations:

Exam 70-536: TS: Microsoft .NET Framework 2.0 - Application Development Foundation
Exam 70-529: TS: Microsoft .NET Framework 2.0 - Distributed Application Development

Technology Specialist: SQL Server 2005
This certification requires that one pass the following examination:

Exam 70-431: TS: Microsoft SQL Server 2005 - Implementation and Maintenance (http://www.microsoft.com/learning/mcp/mcts/sql/default.mspx)

Technology Specialist: SQL Server 2005 Business Intelligence
This certification requires that one pass the following examination:

Exam 70-445: TS: Microsoft SQL Server 2005 Business Intelligence - Implementation and Maintenance (http://www.microsoft.com/learning/mcp/mcts/bi/default.mspx)

Technology Specialist: BizTalk Server 2006
This certification requires that one pass the following examination:

Exam 70-235: TS: Developing Business Process and Integration Solutions Using Microsoft BizTalk Server (http://www.microsoft.com/learning/mcp/mcts/biztalk/default.mspx)

Technology Specialist: Live Communications Server 2005
This certification requires that one pass the following examination:

Exam 70-262 TS: Office Live Communications Server 2005-Implementing, Managing, and Troubleshooting (available early 2006) (http://www.microsoft.com/learning/mcp/mcts/livecomm/default.mspx)

Technology Specialist: Microsoft Windows Mobile 5.0 Applications
This certification requires that one pass the following examination:

Exam Exam 70-540: TS: Microsoft Windows Mobile 5.0 - Application Development (http://www.microsoft.com/learning/mcp/mcts/mobility/default.mspx)

Professional Series
These certifications are based around .NET 2.0, Visual Studio 2005 and SQL Server 2005.

Microsoft Certified Professional Developer (MCPD)

Professional Developer: Web Developer
This certification requires that one pass the following examinations:

Prerequisite: MCTS: .NET Framework 2.0 Web Applications
Exam 70-547: PRO: Designing and Developing Web Applications by Using the Microsoft .NET Framework

Professional Developer: Windows Developer
This certification requires that one pass the following examinations:

Prerequisite: MCTS: .NET Framework 2.0 Windows Applications
Exam 70–548: PRO: Designing and Developing Windows Applications by Using the Microsoft .NET Framework

Professional Developer: Enterprise Applications Developer
This certification requires that one pass the following examinations:

Prerequisite: MCTS: .NET Framework 2.0 Web Applications
Prerequisite: MCTS: .NET Framework 2.0 Windows Applications
Prerequisite: MCTS: .NET Framework 2.0 Distributed Applications
Exam 70–549: PRO: Designing and Developing Enterprise Applications by Using the Microsoft .NET Framework

Microsoft Certified IT Professional (MCITP)

IT Professional: Database Administrator

IT Professional: Database Developer
=====IT Professional: Business Intelligence Developer=====
MCITP : Enterprise Support Technician - current
MCITP : Consumer Support Technician - current
MCITP : Server Administrator - Feb 28th, 2008
MCITP : Enterprise Administrator - Feb 28th, 2008

 

Obsolete Certification

Microsoft Certified Professional + Internet
Microsoft Certified Professional + Internet (MCP+I) requires passing three exams: Windows NT 4.0 Server, TCP/IP for Windows NT 4.0 Server and Internet Information Server 4.0 (or IIS 3.0 + Index Server)

Microsoft Certified Professional + Site Builder
Microsoft Certified Professional + Site Builder (MCP+SB) requires passing three exams: Windows NT 4.0 Server, Microsoft Site Server 3.0 and Microsoft FrontPage 98 (originally FrontPage 97)

Data Center

Data Center

A data center is a facility used to house computer systems and associated components, such astelecommunications and storage systems. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (air conditioning, fire suppression, etc.), and special security devices.

History
Data centers have their roots in the huge computer rooms of the early ages of the computing industry. Early computer systems were complex to operate and maintain, and needed a special environment to keep working. A lot of cables were necessary to connect all the parts. Also, old computers required a lot of power, and had to be cooled to avoid overheating. Security was important; computers were expensive, and were often used for military purposes. For this reason, engineering practices were developed since the start of the computing industry. Basic design guidelines for controlling access to the computer room were devised. Elements such as standard racks to mount equipment, elevated floors, and cable trays (installed overhead or under the elevated floor) were introduced in this early age, and have modernized relatively little compared to the computer systems themselves.

During the boom of the microcomputer industry, and especially during the 1980s, computers started to be deployed everywhere, in many cases with little or no care about operating requirements. However, as IT operations started to grow in complexity, companies grew aware of the need to control IT resources. With the advent of client-server computing, during the decade of 1990, microcomputers (now called "servers") started to find their places on the old computer rooms. The availability of inexpensive networking equipment, coupled with new standards for network cabling, made it possible to use a hierarchical design which put the servers in a specific room inside the company. The use of the term "data center", as applied to specially design computer rooms, started to gain popular recognition about this time.

The boom of data centers came during the dot-com bubble. Companies needed fast Internet connectivity and non-stop operation to deploy systems and establish a presence on the Internet. Installing such equipment was not viable for many smaller companies. Many companies started building very large facilities, called "internet data centers", or IDCs, which provide businesses with a range of solutions for systems deployment and operation. New technologies and practices were designed to handle the scale and the operational requirements of such large scale operations. These practices eventually migrated towards the private data centers, and were largely adopted because of their practical results.

As of 2007, data center design, construction, and operation is a well-known discipline. Standard documents from accredited professional groups, such as the Telecommunications Industry Association, specify the requirements for data center design. Well-known operational metrics for data center availability can be used to evaluate the business impact of a disruption. There is still a lot of development being done in operation practice, and also in environmentally-friendly data center design.

Requirements for modern data centers
 
Racks of telecommunications equipment in part of a data center.IT operations are a crucial aspect of most organizational operations. One of the main concerns is business continuity; companies rely on its informations systems to run its operations. If a system becomes unavailable, company operations may be impaired or stopped completely. It is necessary to provide a reliable infrastructure for IT operations, in order to minimize any chance of disruption. Information security is also a concern, and for this reason a data center has to offer a secure environment which minimizes the chances of a security breach. A data center must therefore keep high standards for assuring the integrity and functionality of its hosted computer environment.

Data center classification
The TIA-942:Data Center Standards Overview describes the requirements for the data center infrastructure. Four tiers The simplest is a Tier 1 data center, which is basically a computer room, following basic guidelines for the installation of computer systems. The most stringent level is a Tier 4 data center, which is designed to host mission critical computer systems, with fully redundant subsystems and compartmentalized security zones controlled by biometric access controls methods.

Physical layout
 
A data center can occupy one room of a building, one or more floors, or an entire building. Most of the equipment is often in the form of servers racked up into 19 inch rack cabinets, which are usually placed in single rows forming corridors between them. This allows people access to the front and rear of each cabinet. Servers differ greatly in size from 1U servers to huge storage silos which occupy many tiles on the floor. Some equipment such as mainframe computers and storage devices are often as big as the racks themselves, and are placed alongside them.

The physical environment of the data center is usually under strict control:

Air conditioning is used to keep the room cool; it may also be used for humidity control. Generally, temperature is kept around 20-22 degrees Celsius (about 68-72 degrees Fahrenheit). The primary goal of data center air conditioning systems is to keep the server components at the board level within the manufacturer's specified temperature/humidity range. This is crucial since electronic equipment in a confined space generates much excess heat, and tends to malfunction if not adequately cooled. Air conditioning systems also help keep humidity within acceptable parameters. The humidity parameters are kept between 35% and 65% Relative Humidity. Too much humidity and water may begin to condense on internal components; too little and static electricity may damage components. ASHRAE recommends a temperature range of 20-25 °C and humidity range of 40 - 60% as optimal for data center conditions.[citation needed]
Backup power is catered for via one or more uninterruptible power supplies and/or diesel generators.
To prevent single points of failure, all elements of the electrical systems, including backup system, are typically fully duplicated, and critical servers are connected to both the "A-side" and "B-side" power feeds. This arrangement is often made to achieve N+1 Redundancy in the systems. Static switches are sometimes used to ensure instantaneous switchover from one supply to the other in the event of a power failure.
Data centers typically have raised flooring made up of 60 cm (2 ft) removable square tiles. These provide a plenum for air to circulate below the floor, as part of the air conditioning system, as well as providing space for power cabling. Data cabling is typically routed through overhead cable trays in modern data centers. Smaller/less expensive data centers without raised flooring may use anti-static tiles for a flooring surface.
Data centers often have elaborate fire prevention and fire extinguishing systems. Modern data centers tend to have two kinds of fire alarm systems; a first system designed to spot the slightest sign of particles being given off by hot components, so a potential fire can be investigated and extinguished locally before it takes hold (sometimes, just by turning smoldering equipment off), and a second system designed to take full-scale action if the fire takes hold. Fire prevention and detection systems are also typically zoned, and high-quality fire-doors and other physical fire-breaks used, so that even if a fire does break out it can be contained and extinguished within a small part of the facility.
Using conventional water sprinkler systems on operational electrical equipment can do just as much damage as a fire. Originally Halon gas, a halogenated organic compound that chemically stops combustion, was used to extinguish flames. However, the use of Halon has been banned by the Montreal Protocol because of the danger Halon poses the ozone layer. Unlike fire extinguishing agents that displace oxygen, Halon did not pose a great risk to people caught in the data center when it was discharged. More environmentally-friendly alternatives include Argonite and FM-200, and even systems based on mists of tiny particles of ultra-pure water. There are also systems available which can control the gas mixture of the air so as to lower the oxygen content below the level at which combustion can take place but still high enough to support human life (similar to very high altitudes).
Physical security also plays a large role with data centers. Physical access to the site is usually restricted to selected personnel. Video camera surveillance and permanent security guards are almost always present if the data center is large or contains sensitive information on any of the systems within.

Network infrastructure
 
An example of "rack mounted" servers.Communications in data centers today are most often based on networks running the IP protocol suite. Data centers contain a set of routers and switches that transport traffic between the servers and to the outside world. Redundancy of the Internet connection is often provided by using two or more upstream service providers (see Multihoming).

Some of the servers at the data center are used for running the basic Internet and intranet services needed by internal users in the organization: e-mail servers, proxy servers, DNS servers, etc.

Network security elements are also usually deployed: firewalls, VPN gateways, Intrusion detection systems, etc. Also common are monitoring systems for the network and some of the applications. Additional off site monitoring systems are also typical, in case of a failure of communications inside the data center.

Applications
 
The main purpose of a data center is running the applications that handle the core business and operational data of the organization. Such systems may be proprietary and developed internally by the organization, or bought from enterprise software vendors. Such common applications are ERP and CRM systems.

Often these applications will be composed of multiple hosts, each running a single component. Common components of such applications are databases, file servers, application servers, middleware and various others.

Data centers are also used for off site backups. Companies may subscribe to backup services provided by a data center. This is often used in conjunction with backup tapes. Backups can be taken of servers locally on to tapes., however tapes stored on site pose a security threat and are also susceptible to fire and flooding. Larger companies may also send their backups off site for added security. This can be done by backing up to a data center. Encrypted backups can be sent over the internet to data center where they can be stored securely.

 

 

Cisco Career Certifications Guide

Cisco Career Certifications are IT professional certifications for Cisco products. The tests are administered by Pearson VUE (Prometric previously administered the test; but as of 1 Aug 2007, no longer does). There are three levels of certification: Associate, Professional, and Expert.

 

Technician Certifications
The first stage of Cisco's certification system is the "Associate" level and begins with CCENT as an interim step to Associate level or directly with CCNA and CCDA certifications. The CCENT covers only basic networking knowledge, and does not get involved with the more technical aspects of the Cisco curriculum. The CCNA Discovery curriculum covers most of what is required to pass this exam.

Associate Certifications

Cisco Certified Network Associate (CCNA)
Candidates have the option of gaining the certification by passing two tests (INTRO and ICND), or one single test (CCNA); the two-test option has the advantage of allowing the candidate to focus on certain subjects.

The certification is valid for three years; at that time a CCNA holder must either

re-take the CCNA or ICND exam, or
take and pass an exam for one of the Professional (e.g., CCNP) or Specialist level certifications (excluding the sales specialist exams), or pass the CCIE written exam.
These exams are known by their corresponding numbers. When the curriculum of the exam changes the exam number also changes. The current exam number for CCNA is 640-802 (from 15 Aug 2007). The exam number for INTRO is 640-821 (Last day to test 11/6/07) and ICND the exam number is 640-811 (Last day to test 11/6/07). New ICND Part1 (640-822 ICND1) and ICND Part2 (640-816 ICND2) available from 15 Aug 2007. These exams are conducted by authorized test centers at a cost of $125 each for the INTRO or ICND exams and $150[1] for the full CCNA exam.

There is also the Cisco Networking Academy, which brings the CCNA and CCNP curricula into traditional educational institutions in over 150 countries.[2] Students enrolled in Cisco Networking Academy can request exam vouchers that allow them to take the retired exam for an extended period of time.[3]

Cisco Certified Design Associate (CCDA)
The CCDA certification indicates an apprentice knowledge of Cisco network design. Individuals who have earned a CCDA are capable of designing switched or routed networks consisting of LANs, WANs, and various dial services. While a CCNA certification is not required to take the CCDA exam, Cisco recommends being familiar with CCNA material.

Professional certifications

[ Cisco Certified Network Professional (CCNP)
The CCNP is considered proof of having the ability to work with medium-sized networks (between 100 and 500 end devices) and with technology such as QoS, broadband, VPNs, and security-minded features. To acquire a CCNP one must possess a CCNA certification first and then pass three or four tests, depending on the path one chooses. The four tests path requires the candidate to pass the following tests:

642-901 BSCI: Building Scalable Cisco Internetworks (BSCI)[4]
642-812 BCMSN: Building Cisco Multilayer Switched Networks (BCMSN)[5]
642-825 ISCW: Implementing Secure Converged Wide Area Networks (ISCW)[6]
642-845 ONT: Optimizing Converged Cisco Networks (ONT)[7]
The BSCI and BCMSN tests can be taken as one single composite test known as the 642-892 Composite[8] which covers subjects for Building Scalable Cisco Internetworks (BSCI) and Building Cisco Multilayer Switched Networks (BCMSN).

In order to retain the certification one must either re-certify or upgrade to a CCIE every three years. Additional resources and tools to aid in preparing for the certification are available on the CCNP Prep Center.[9]

Cisco Certified Design Professional (CCDP)
The CCDP certification is an advanced network design certification provided by Cisco Systems, Inc. Candidates for the certification are tested for advanced knowledge of Cisco devices and the way to interconnect them. This certification is considered a professional level certificate by Cisco Systems. (The CCNA and CCDA are prerequisites.)

Cisco Certified Internetwork Professional (CCIP)
The CCIP certification is a professional certification covering the end-to-end protocols used in large scale networks.

To attain this certification tests must be passed in the areas of routing, BGP, MPLS and Quality of service.

Cisco Certified Voice Professional (CCVP)
The CCVP is a certification covering all aspects of IP Telephony/VOIP networks and applications.

To attain this certification, five tests must be passed in the areas of Quality of service, Cisco VoIP, IP Telephony Troubleshooting, Cisco IP Telephony, and Gateway Gatekeeper.

Recertification
To recertify any Professional level certification, pass any 642 exam that is part of the professional level curriculum after August 18, 2006, or pass a current CCIE written exam.

Expert-level certifications: Cisco Certified Internetwork Expert
The expert-level certification is the Cisco Certified Internetwork Expert (CCIE). It is the highest level of professional certification that Cisco provides. There are 5 active CCIE tracks, as below. As of August 2, 2007 there are 15,062 people with active CCIE certifications.[10]

Cisco began its CCIE program in 1993[11] originally with a two day lab, later changing it to the one day format used today. Less than 3% of Cisco certified individuals attain CCIE certification, and on average will spend thousands of dollars and 18 months studying before passing.[12] Many candidates build mock-labs at home using old Cisco equipment, selling it again to other candidates after passing. Alternatively candidates may rent "rack time" online and practice lab scenarios on Cisco equipment hosted on the Internet for that purpose.

Cisco refers to the CCIE as the "most respected IT certification",[13] and from 2002 to 2005[14] it was voted as such in CertCities magazine. It has also been voted the most technically advanced IT certification by CertMag,[15] and is generally reported as the highest salaried certification in IT salary surveys.

The CCIE is comprised of a written exam and a "lab" exam (each in the specific area of the chosen track). The written exam is required to take the lab exam, and has a cost of $315[1] USD per attempt. Upon passing the written exam, the candidate is qualified to have a first attempt the lab exam for 18 months. If the first attempt is unsuccessful the candidate has 3 years from the date the written exam was passed to successfully complete the lab. If a candidate does not pass the CCIE lab in that time, they must pass the CCIE written exam again before making additional attempts at the CCIE lab exam. As many attempts can be made to pass the lab exam for up to 3 years after passing the written, so long as the first attempt is within 18 months. There is a minimum waiting time between attempts of one month.

The CCIE Lab is currently $1,400 USD[1] per attempt and are offered only at ten Cisco lab exam locations worldwide. The locations are Bangalore; Beijing; Brussels; Dubai; Hong Kong; Research Triangle Park, NC; San Jose, CA; São Paulo; Sydney; and Tokyo. In addition, according to a survey by Cisco the average cost to prepare for CCIE certification is $9,050 as of April 2006, spent mostly on practice equipment and self study material.[16] This is partially offset by the increased salary the certification commands, which a March 2007 Network World article estimates at 10% - 15% over similarly experienced engineers who do not have a CCIE.[17]

The lab is an 8-hour hands-on exam designed to demonstrate that the candidate not only knows the theory, but is also able to practice it. Many prospective CCIEs need multiple attempts to pass the lab exam.

There are no formal prerequisites for the CCIE exam, but Cisco recommends one has at least 3 - 5 years experience in networking before attempting to become a CCIE. CCIE was the first Cisco Certified qualification, and as such there were no other certifications that could be taken prior. The development of the associate and professional certifications was due to recognition of the fact that a CCIE is overkill for many networking personnel, and also for the vast majority of businesses who employ such people, and that certifications needed to be offered at lower levels. Despite the development of the lower certifications, Cisco has chosen not to make them formal requirements for the CCIE certification.

It is possible to hold multiple CCIE certifications. This is done by passing both the written and the lab exam in a particular track. As of September 19th, 2007 there are 1,240 individuals who hold multiple CCIE certifications. Of those, 189 hold three or more CCIE certifications.[18]

CCIE Routing & Switching
Routing and Switching is by far the most popular track, and covers a wide range of subjects, such as: LAN, WAN, Ethernet, TCP/IP, OSPF and BGP,IPv6 and many more.

CCIE Security
The Security track concentrates on network security and covers subjects such as ASA, IDS, IOS security, security and many others.

CCIE Service Provider
The Service Provider track focuses on networking in the service provider industry. Subjects include Optical networks, DSL, WAN switching, Voice over IP, Content Networking, Broadband Cable and Metro Ethernet.

CCIE Voice
The Voice track concentrates on voice solutions for the enterprise and includes subjects such as QoS, MGCP, Call Manager (Cisco's VoIP PBX), Cisco Unity (Cisco's Unified Messaging platform), Unity Express and IP Contact Center Express.

CCIE Storage Networking
The latest addition to the CCIE certification tracks is the CCIE Storage Networking track. As the name suggests, the Storage Networking track concentrates on storage networking topics, such as Fibre Channel, iSCSI, FCIP, Intra VSAN Routing and FICON.

 

The UNIX FreeBSD Version Released

 

FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4.4BSD operating systems. It runs on Intel x86 family (IA-32) PC compatible systems (including the Microsoft Xbox[1]), and also DEC Alpha, Sun UltraSPARC, IA-64, AMD64, PowerPC and NEC PC-98 architectures. Support for the ARM and MIPS architectures are under development.

FreeBSD is developed as a complete operating system. The kernel, device drivers and all of the userland utilities, such as the shell, are held in the same source code revision tracking tree (CVS). This model can be contrasted with Linux where the kernel, userland utilities and applications are developed separately and packaged together by other groups as Linux distributions.

As an operating system, FreeBSD is generally regarded as reliable and robust, and of the operating systems that accurately report uptime remotely,[2] FreeBSD is the most common free operating system listed in Netcraft's list[3] of the 50 web servers with the longest uptime. A long uptime also indicates that no crashes have occurred and that no kernel updates have been deemed necessary, as installing a new kernel requires a reboot and resets the uptime counter of the system.

 

History and development
Initial development of FreeBSD started in 1993, originating in the unofficial patchkit maintained by users of the 386BSD operating system. The first official release of FreeBSD was FreeBSD 1.0 in December 1993.

However, due to concerns about the legality of the BSD Net/2 release source code used in 386BSD and a consequent lawsuit between USL (then owner of the UNIX copyright) and Berkeley, FreeBSD ended up re-engineering much of the system using the 4.4BSD-Lite release from the University of California, Berkeley, with the FreeBSD 2.0 release in January 1995. The FreeBSD Handbook includes more information about the genesis of FreeBSD.

Perhaps FreeBSD 2.0's most notable advance was the revamp of the original Carnegie Mellon University Mach Virtual Memory system, which was optimized for performance under high loads, and the creation of the FreeBSD Ports system that made downloading, building and installing third party software very easy. FreeBSD powered extremely successful sites like Walnut Creek CDROM (a huge repository of software that broke several throughput records on the Internet), Hotmail, and Yahoo!.

FreeBSD 3.0 brought many changes: it switched to the ELF binary format, and initial support for SMP systems and the 64 bit Alpha platform were added.

Initially, FreeBSD employed the BSD Daemon as its logo, but in 2005 a competition for a new logo was arranged. On October 8, 2005, the competition finished and the design by Anton K. Gural was chosen as the new FreeBSD logo.[4] The BSD Daemon will remain as the FreeBSD Project mascot.

FreeBSD 5 development and changes
The latest and final FreeBSD release from the 5-STABLE branch is 5.5, and was released in May 2006. FreeBSD developers maintain (at least) two branches of simultaneous development. A -STABLE branch of FreeBSD is created for each major version number, from which releases are cut about once every 4-6 months. The latest 4-STABLE release of FreeBSD is 4.11, which is the last of the 4-STABLE branch releases. The first 5-STABLE release was 5.3 (5.0 through 5.2.1 were cut from -CURRENT). The first 6-STABLE release was 6.0. The development branch, -CURRENT, is now 7.0-CURRENT, which contains aggressive new kernel and userspace features. If a feature is sufficiently stable and mature, it is eventually backported ("MFC" - Merge from CURRENT in the FreeBSD developer slang) to the -STABLE branch. FreeBSD's development model is described in an in-depth article by Niklas Saers.[5]

The largest architectural change in FreeBSD 5 was a major change in the low-level kernel locking mechanisms to enable better symmetric multiprocessor (SMP) support, releasing much of the kernel from the MP lock, sometimes referred to as the Giant Lock. It is now possible for more than one process to execute in kernel mode at the same time.

Other major changes include an m:n threading solution called KSE which is now the default threading (pthreads) library, starting with 5.3 (the creation of the 5-STABLE branch). The terminology m:n, where m and n are small positive integers, implies that m userland threads correspond to n kernel threads. Many other new features are security related.

A project called "TrustedBSD" was launched by Robert Watson for the purpose of adding security lock-down frameworks functionality to the FreeBSD operating system (this is not related to "trusted computing"). An extensible mandatory access control framework (the TrustedBSD MAC Framework), filesystem Access Control Lists (ACLs), enhanced PAM support (OpenPAM) and the new UFS2 filesystem all came from TrustedBSD. Some of the TrustedBSD functionality has been integrated into the NetBSD and OpenBSD operating systems as well. This work was supported through sponsorship by DARPA.

FreeBSD 5 also significantly changed the block I/O layer with the introduction of the GEOM modular disk I/O request transformation framework, contributed by Poul-Henning Kamp. GEOM enables the simple creation of many kinds of functionality, such as mirroring (gmirror) and encryption (GBDE and GELI). This work was supported through sponsorship by DARPA.

The 5.4 and 5.5 releases of FreeBSD have confirmed the FreeBSD 5.x branch as a highly stable and well-performing release, albeit one with a long gestation period due to the large feature set.

FreeBSD 6
The FreeBSD 6 release series is the current -STABLE development series. FreeBSD 6.2 was released on January 15, 2007. These versions continue the work on SMP and threading optimization, as well as additional work in the area of advanced 802.11 functionality, TrustedBSD security event auditing, significant network stack performance enhancements, a fully preemptive kernel, and support for hardware performance counters (HWPMC). The primary accomplishments of these releases include removal of the Giant lock from VFS, addition of a better-performing optional libthr library with 1:1 threading and the addition of a Basic Security Module (BSM) audit implementation called OpenBSM, created by the TrustedBSD Project (based on the BSM implementation found in Apple's open source Darwin) and released under a BSD-style license.

FreeBSD 7
FreeBSD 7.0 is currently under development, the third beta having been released in November 2007. Features currently under development include: SCTP, network stack virtualization, UFS journaling, a port of Sun's ZFS file system, GCC4, support for the ARM and MIPS architectures and major updates relating to audio, USB and the scheduler. FreeBSD 7.0 is scheduled for release in December 2007.

FreeBSD 8
FreeBSD 8.0 is the bleeding edge development version (so called -CURRENT in FreeBSD parlance). It should feature superpages, dtrace, Xen and network stack virtualization. This version is currently in the early stages of development[6].

Linux compatibility
FreeBSD provides binary compatibility with several other Unix-like operating systems, including Linux. This permits Linux programs to be run, including some commercial applications distributed only in binary form. Applications which use the Linux compatibility layer include StarOffice, the Linux version of Firefox, Adobe Acrobat, RealPlayer, VMware, Oracle, Mathematica, Matlab, WordPerfect, Skype, Doom 3 and Quake 4[7]. There is said to be no noticeable performance penalty when running Linux binaries over native FreeBSD programs, and, in some cases, they may even perform better than the same binaries running on Linux[8]. However, the layer is not completely seamless and some Linux binaries are unusable on FreeBSD or possess limited functionality: this is often as the compatibility layer only supports the system calls available in the historical Linux kernel 2.4.2, work is ongoing to provide Linux 2.6 support.

License
FreeBSD is released under a variety of licenses. All of the kernel code and most newly created code is released under the two-clause BSD license, which allows everyone to use and redistribute FreeBSD as they wish. There are also parts under the GPL, LGPL, ISC, CDDL, and Beerware licenses, as well as three- and four-clause BSD licenses. In addition, some device drivers include a binary blob, such as the Atheros HAL.

Derivatives
A wide variety of products are directly or indirectly based on FreeBSD. These range from embedded devices, such as Juniper Networks routers, Ironport network security appliances, Nokia's firewall operating system, NetApp's OnTap GX, Panasas's and Isilon Systems's cluster storage operating systems, NetASQ security appliances, St Bernard iPrism web filtering appliances, to portions of other operating systems including Linux and the RTOS VxWorks. Darwin, the core of Apple's Mac OS X, borrows heavily from FreeBSD, including its virtual file system, network stack and components of its userspace. Apple continues to integrate new code from and contribute changes back to FreeBSD. The now-defunct OpenDarwin project, which was based on Apple's Darwin operating system, also included substantial FreeBSD code. In addition, there are a number of operating systems originally forked from or based on FreeBSD including PC-BSD and DesktopBSD, which include enhancements aimed at home users and workstations; the FreeSBIE and Frenzy live CD distributions; the m0n0wall and pfSense embedded firewalls; FreeNAS Free network attached storage ; and DragonFly BSD, a fork from FreeBSD 4.8 aiming for a different multiprocessor synchronization strategy than that chosen for FreeBSD 5 and development of some microkernel features.

TrustedBSD
The TrustedBSD project provides a set of trusted operating system extensions to FreeBSD. It was begun primarily by Robert Watson with the goal of implementing concepts from the Common Criteria for Information Technology Security Evaluation and the Orange Book. The project still continues, and many of its extensions have been integrated into FreeBSD.

The main focuses of the TrustedBSD project are access control lists (ACLs), security event auditing, extended file system attributes, fine-grained capabilities, and mandatory access controls (MAC). The project has also ported the NSA's FLASK/TE implementation from SELinux to FreeBSD. Other work includes the development of OpenBSM, an open source implementation of Sun's Basic Security Module (BSM) API and audit log file format, which supports an extensive security audit system. This was shipped as part of FreeBSD 6.2. Other infrastructure work in FreeBSD performed as part of the TrustedBSD Project has included SYN cookies, GEOM, and OpenPAM.

While most components of the TrustedBSD project are eventually folded into the main sources for FreeBSD, many features, once fully matured, find their way into other operating systems. For example, OpenPAM and UFS2 have been adopted by NetBSD, and the TrustedBSD MAC Framework and TrustedBSD Audit implementation have been adopted by Apple Computer for Mac OS X.

Governance structure
The FreeBSD Project is run by FreeBSD committers, or developers who have CVS commit access. Committers come in several flavours, including source committers (base operating system), doc committers (documentation and web site authors) and ports (third party application porting and infrastructure). Every two years, the FreeBSD committers elect a 9-member FreeBSD Core Team, who are responsible for overall project direction, setting and enforcing project rules, and approving new "commit bits", or the granting of CVS commit access. A number of responsibilities are officially assigned to other development teams by the FreeBSD Core Team, including responsibility for security advisories (the Security Officer Team), release engineering (the Release Engineering Team), and managing the ports collection (the Port Manager team). Developers may give up their commit rights to retire or for "safe-keeping" after a period of a year or more of inactivity, although commit rights will generally be restored on request (both of which have happened a moderate number of times in over 12 years of development). Under rare circumstances, commit rights may be removed by Core Team vote as a result of repeated violation of project rules and standards. The FreeBSD Project is unusual among open source projects in having developers who have worked with its source base for over 25 years, as a result of the involvement of a number of past University of California developers who worked on BSD at the CSRG.

Microsoft Windows Server 2008

Windows Server 2008 is the next server operating system from Microsoft. It is the successor to Windows Server 2003. Windows Server 2008 introduces most of the new features from Windows Vista to Windows Server. This is a similar relationship to that between Windows Server 2003 and Windows XP.

It was known as Windows Server Codename "Longhorn" until May 16, 2007, when Bill Gates announced its official title during his keynote address at WinHEC.[1]

Beta 1 was released on July 27, 2005. Beta 2 was announced and released on May 23, 2006 at WinHEC 2006, Beta 3 was released publicly on April 25, 2007[2] and Release Candidate 0 was released to the general public on September 24, 2007[3]. Windows Server 2008 will be released to manufacturing in the first quarter of 2008 with the official launch taking place on February 27, 2008.[4]

 

Windows Server 2008 is built from the same code base as Windows Vista Service Pack 1; therefore, it shares much of the same architecture and functionality. As the code base is common, it automatically benefits from most of the technical, security, management and administrative features new to Windows Vista such as the new improved rewritten networking stack (native IPv6, native wireless, speed and security improvements); improved image-based installation, deployment and recovery; improved diagnostics, monitoring, event logging and reporting tools; new security features such as Bitlocker and ASLR; improved Windows Firewall with secure default configuration; .NET Framework 3.0 technologies, specifically Windows Communication Foundation, Microsoft Message Queuing and Windows Workflow Foundation; and the core kernel, memory and file system improvements. Processors and memory devices are modelled as Plug and Play devices, to allow hot-plugging of these devices. This allows the system resources to be partitioned dynamically using Dynamic Hardware Partitioning; each partition having its own memory, processor and I/O host bridge devices independent of other partitions.[5]

Server Core
Perhaps the most notable new feature of Windows Server 2008 is a new variation of installation called Server Core. Server Core is a significantly scaled-back installation where no Windows Explorer shell is installed, and all configuration and maintenance is done entirely through command line interface windows, or by connecting to the machine remotely using Microsoft Management Console. Server Core also does not include the .NET Framework, Internet Explorer or many other features not related to core server features. A Server Core machine can be configured for several basic roles: Domain controller/Active Directory Domain Services, ADLDS (ADAM), DNS Server, DHCP Server, file server, print server, Windows Media Server, Terminal Services Easy Print, TS Remote Programs, and TS Gateway, IIS 7 web server and Windows Server Virtualization virtual server. This last role is projected to be available at most 180 days after release of Windows Server 2008.

Active Directory roles
Active Directory is expanded with identity, certificate and rights management services. Active Directory until Windows Server 2003 allowed network administrators to centrally manage connected computers, to set policies for groups of users, and to centrally deploy new applications to multiple computers. This role of Active Directory is being renamed as Active Directory Domain Services (ADDS).[6] A number of other additional services are being introduced, including Active Directory Federation Services (ADFS), Active Directory Lightweight Directory Services (ADLDS), (formerly Active Directory Application Mode, or ADAM), Active Directory Certificate Services (ADCS), and Active Directory Rights Management Services (ADRMS). Identity and certificate services allow administrators to manage user accounts and the digital certificates that allow them to access certain services and systems. Federation management services enable enterprises to share credentials with trusted partners and customers, allowing a consultant to use his company user name and password to log in on a client's network. Identity Integration Feature Pack is included as Active Directory Metadirectory Services. Each of these services represents a server role.

Terminal Services
Windows Server 2008 features major upgrades to Terminal Services. Terminal Services now supports Remote Desktop Protocol 6.0. The most notable improvement is the ability to share a single application over a Remote Desktop connection, instead of the entire desktop. This feature is called Terminal Services Remote Programs. Other features new to Terminal Services include Terminal Services Gateway and Terminal Services Web Access (full web interface). With Terminal Services Gateway, authorized computers are able to connect securely to a Terminal Server or Remote Desktop from the Internet using RDP via HTTPS without implementing a VPN session first. Additional ports do not need to be opened in the firewall, RDP is tunneled through HTTPS. Terminal Services Web Access enables administrators to provide access to the Terminal Services Sessions via a Web interface. TS Web Access comes with an adjustable Webpart for IIS and Sharepoint, which advertises the possible applications and connections to the user. Using TS Gateway and TS Remote Programs, the whole communication is via HTTP(S) and the remote applications appear transparent to the user as if they are running locally. Multiple applications run in the same session to ensure that there is no need for additional licenses per user. Terminal Services Easy Print does not require administrators to install any printer drivers on the server, but guarantees successful client printer redirection and availability of all printer UI and properties for use in remote sessions. Terminal Services sessions are created in parallel, instead of a serial operation - the new session model can initiate at least four sessions in parallel, or more if a server has more than four processors.

Windows PowerShell
 
Screenshot of a sample Windows PowerShell session.Main article: Windows PowerShell
Windows Server 2008 is the first Windows operating system that will ship with Windows PowerShell, Microsoft's new extensible command line shell and task-based scripting technology.[7] PowerShell is based on object-oriented programming and version 2.0 of the Microsoft .NET Framework and includes more than 120 system administration utilities, consistent syntax and naming conventions, and built-in capabilities to work with common management data such as the Windows Registry, certificate store, or Windows Management Instrumentation. PowerShell's scripting language was specifically designed for IT administration, and can be used in place of cmd.exe and Windows Script Host.

Self-healing NTFS
In previous Windows versions, if the operating system detected corruption in the file system of an NTFS volume, it marked the volume "dirty"; to correct errors on the volume, it had to be taken offline. With self-healing NTFS, an NTFS worker thread is spawned in the background which performs a localized fix-up of damaged data structures, with only the corrupted files/folders remaining unavailable without locking out the entire volume and needing the server to be taken down.[8]

Windows Server Virtualization
 
Windows Server Virtualization architectureMain article: Windows Server Virtualization
Windows Server Virtualization an implementation of operating system-level virtualization, forming a core part of Microsoft's virtualization strategy. This hypervisor virtualizes servers on an operating system's kernel layer. It can be thought of as partitioning a single physical server into multiple small computational partitions. Windows Server Virtualization will include the ability to act as a Xen virtualization hypervisor host allowing Xen-enabled guest operating systems to run virtualized. This will not be a part of Windows Server 2008 initially, and will ship within 180 days after it.[9] It will be available only on x64 versions of Windows Server 2008.

Windows System Resource Manager
Main article: Windows System Resource Manager
Windows System Resource Manager (WSRM) is being integrated into Windows Server 2008. It provides resource management and can be used to control how much resources a process or a user can use based on business priorities. Process Matching Criteria, which is defined by the name, type or owner of the process, enforces restrictions on the resource usage by a process that matches the criteria. CPU time, bandwidth that it can use, number of processors it can be run on, and memory allocated to a process can be restricted. Restrictions can be set to be imposed only on certain dates as well.

Server Manager
Server Manager is a new roles-based management tool for Windows Server 2008[10]. It is a combination of Manage Your Server and Security Configuration Wizard from Windows Server 2003. Server Manager is an improvement of the Configure my server dialog that launches by default on Windows Server 2003 machines. However, rather than serve only as a starting point to configuring new roles, Server Manager gathers together all of the operations users would want to conduct on the server, such as, getting a remote deployment method set up, adding more server roles etc and provides a consolidated, portal-like view about the status of each role.

Other features
Other new or enhanced features include:

Core OS improvements
Fully multi-componentized operating system.
Improved hot patching, a feature that allows non-kernel patches to occur without the need for a reboot.
Support for being booted from Extensible Firmware Interface (EFI)-compliant firmware on x86-64 systems.

Active Directory improvements
A new "Read-Only Domain Controller" operation mode in Active Directory, intended for use in branch office scenarios where a domain controller may reside in a low physical security environment. The RODC holds a non-writeable copy of Active Directory, and redirects all write attempts to a Full Domain Controller. It replicates all accounts except sensitive ones. In RODC mode, credentials are not cached by default. Moreover, only the Domain Controller running the PDC-Emulator needs to run Windows Server 2008. Also, local administrators can log on to the machine to perform maintenance tasks without requiring administrative rights on the domain.
Restartable Active Directory allows ADDS to be stopped and restarted from the Management Console or the command-line without rebooting the domain controller. This reduces downtime for offline operations and reduces overall DC servicing requirements with Server Core. ADDS is implemented as a Domain Controller Service in Windows Server 2008.

Policy related improvements
All of the Group Policy improvements from Windows Vista. Group Policy Management Console (GPMC) is built-in. The Group Policy objects are indexed for search, as well as can be commented on.[11]
Policy-based networking with Network Access Protection, improved branch management and enhanced end user collaboration. Policies can be created to ensure greater Quality of Service for certain applications or services that require prioritization of network bandwidth between client and server.
Granular password settings within a single domain - ability to implement different password policies for administrative accounts on a "group" and "user" basis, instead of a single set of password settings to the whole domain.

Disk management and file storage improvements
The ability to resize hard disk partitions without stopping the server, even the system partition.
Shadow Copy based block-level backup which supports optical media, network shares and Windows Recovery Environment.
DFS enhancements - SYSVOL on DFS-R, Read-only Folder Replication Member. There is also support for domain-based DFS namespaces that exceed the previous size recommendation of 5,000 folders with targets in a namespace. [12]
Several improvements to failover clusters (High-availability clusters).[13]
Internet Storage Naming Server (iSNS) enables central registration, deregistration and queries for iSCSI hard drives.

Protocol and cryptography improvements
Support for 128- and 256-bit AES encryption for the Kerberos authentication protocol.
New cryptography (CNG) API which supports elliptic curve cryptography and improved certificate management.
Secure Socket Tunneling Protocol, a new Microsoft proprietary VPN protocol.
AuthIP, a Microsoft proprietary extension of the IKE cryptographic protocol used in IPsec VPN networks.
Server Message Block 2.0 protocol in the new TCP/IP stack provides a number of communication enhancements, including greater performance when connecting to file shares over high-latency links and better security through the use of mutual authentication and message signing.

Improvements due to client-side (Windows Vista) enhancements
Searching Windows Server 2008 servers from Windows Vista clients delegates the query to the server, which uses the Windows Search technology to search and transfer the results back to the client.
In a networked environment with a print server running Windows Vista, clients can render print jobs locally before sending them to print servers to reduce the load on the server and increase its availability.
Event forwarding aggregates and forwards logs of subscribed Windows Vista client computers back to a central console. Event forwarding can be enabled on the client subscribers from the central server directly from the event management console.
Offline Files are cached locally so that they are available even if the server is not, with copies seamlessly updating when the client and server are reconnected.

Miscellaneous improvements
Windows Deployment Services replacing Automated Deployment Services and Remote Installation Services. Windows Deployment Services (WDS) support an enhanced multicast feature when deploying operating system images. [14]
Internet Information Services 7 - Increased security, xcopy-deployment, improved diagnostic tools, delegated administration.
An optional "Desktop Experience" component provides the same Windows Aero user interface as Windows Vista, both for local users, as well as remote users connecting through Remote Desktop.

Supported platforms
Most editions of Windows Server 2008 will be available in x64 (64-bit) and x86 (32-bit) versions. Windows Server 2008 for Itanium-based Systems will support IA-64 processors. The IA-64 version will be optimized for high workload scenarios like database servers and Line of Business (LOB) applications. As such it will not be optimized for use as a file server or media server. Microsoft has announced that Windows Server 2008 will be the last 32-bit Windows server operating system.[15]

Editions
Windows Server 2008 will be available in the editions listed below,[16] similar to Windows Server 2003.

Windows Server 2008 Standard Edition (x86 and x86-64)
Windows Server 2008 Enterprise Edition (x86 and x86-64)
Windows Server 2008 Datacenter Edition (x86 and x86-64)
Windows Web Server 2008 (x86 and x86-64)
Windows Storage Server 2008 (x86 and x86-64)
Windows Small Business Server 2008 (Codenamed "Cougar") (x86-64) for small businesses
Windows Essential Business Server 2008 (Codenamed "Centro") (x86-64) for medium-sized businesses [17]
Windows Server 2008 for Itanium-based Systems (IA-64)
Server Core is available in the Standard, Enterprise and Datacenter editions. It is not available in Web edition or in the Itanium edition. It is important to note that Server Core is simply a server role supported by some of the editions, and not a separate edition by itself. As of Beta 3, each edition has a separate evaluation DVD.