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Network Cables Online, LLC

FAQs

What type of cable should we be installing?


Cat 5 and Cat 5E 
The basic Cat 5 system used to be the only real choice, but developments in Ethernet technology led to the introduction of 'Enhanced Category 5' or Cat 5E. Both systems are capable of transmission rates up to 100MHz, but the test parameters for Cat 5 assumed that data signals would only use two of the four pairs (one pair for transmitting and one pair for receiving) and crosstalk measurements were only taken between each pair combination. With Gigabit Ethernet however, all four pairs can be used to transmit simultaneously, and so the cross talk on each pair has to be measured for the combined effects of the other three pairs. 

Cat 6 
At last! the standard for Cat 6 has been approved for publication by the EIA (TIA/EIA-568-B.2-1). Category 6 is capable of transmission frequencies up to 250Mhz and has a positive power sum attenuation to crosstalk ratio upto 200MHz using improved cables and RJ45 connectors. The problem that manufacturers have, is that to meet the Cat 6 specification, requires the use of cables and connectors which are designed to work together as a 'tuned' system. This means that if you install a Cat 6 system the manufacturer will only guarantee performance if all of the components including the patch leads are from their Cat 6 product range. In fact, by mixing Cat 6 components from different manufacturers you could end up with a system with worse performance characteristics than a conventional Cat 5e system. That said, it is worth noting that Cat 6 systems are backwards compatible with Cat 5/5e cabling and when mixed with these lower bandwidth systems the performance criteria of the lower specification will still be met. 

Testing Cat 6 cables can be a frustrating process, apart from taking longer because the tester has to scan frequency steps up to 200MHz instead of 100MHz, the fine line between pass and fail is accentuated it seems by the slightest kink and twist. The most significant factor when testing a Cat 6 system can be return loss failures due to the test leads themselves. All connectors have a life cycle and with the average RJ45 connector this is around one or two thousand insertions, so test leads should be replaced after every 1000 tests or so. OK, not a problem but at around $200 per set this cost will have to be considered when pricing jobs. 

Fluke seem to have a solution to this problem with their DSP-LIA101S Permanent Link Adapters. The connector at the end of the leads are interchangeable and replaceable with connectors from different manufacturers to ensure compatibility with the system under test. Although a good idea, the adapters are over $500 and a new pair of "Personality Modules" cost over $100. Surely the test plugs should now be considered as 'consumables' and the price lowered to reflect this.

Cat 7 
This is proposed to be a 600MHz system using a shielded cable with individually screened pairs and a new type of connector. The cable and connectors are slightly bigger than Cat 5e and installation time can be increased because of the complexity of the termination. There are two main draw backs with installing this type of cabling, the first is the additional cost involved, and the second is that almost all networking hardware uses RJ45 jacks. To connect to the cabling system, you have to use Cat 7 to Cat 5e patch leads, and because any system is only as good as its weakest link, your speed is back down to 100MHz. Ratification of the Cat 7 standard could be two years away by which time fibre might be a cheaper alternative. 

Shielded or Unshielded 
This is a subject that has been debated and argued over for a long time, and as yet, there are still no definite answers. Most countries in Europe, and in particular Germany, argue that apart from protecting data signals against high frequency noise from outside sources, shielded cable also protects the humans against the possibility of having their brains fried due to the effects of high frequency emissions from the cable itself. Other countries, such as the UK, US and Canada, aren't particularly bothered by this because nothing has been proved, and after all, millions of people wander around with mobile phones pressed against the side of their heads with no apparent side effects, er... yet. My advice would be to install unshielded cable unless the customer insists on a shielded system. 

Shielded cables and components are more expensive and are more time consuming to terminate, you should also bear in mind that a shielded cable that isn't properly grounded has worse performance characteristics than an unshielded cable. If a shielded cable isn't grounded at all, the screen can act like an antenna and induce all manner of noise on to the data signal. 

Low Smoke Zero Halogen 
In public buildings, such as airports, shops and hospitals, then the cable should be Low Smoke Zero Halogen (LS0H or LSZH). 


Some questions we have received via email

How can I tell if a cable is a crossover or straight through?
Q. I currently have 2 PCs, one running windows xp and one running windows 98 which I would like to network together using the XP machine as the host. I have 2 rj45 ethernet cards and a 10 metre cat 5e twisted pair cable.
Is there any way to tell if I have the right cable as my computers aren’t communicating and I have tried every other troubleshooting resource, and the only conclusion I can come to is that my cable is not a crossover type.
Any advice would be GREATLY appreciated! 

A. If you hold both of the RJ45 connectors side by side and look at them from the bottom (ie. the clip is away from you) you can make out which colour is connected to which pin. The pins you are interested in are (from left to right) 1 & 2 and 3 & 6. If they are the same either end then it is a straight through cable, if pin 1 (usually orange/white, but not necessarily) is connected to pin 3 at the other end and 2 is connected to pin 6 (and vice versa) then you have a crossover cable. The 'crossed pair' image is actually the correct wiring for a crossover cable and above it is the correct wiring for a straight through cable. 
If you have a straight through cable then it won't work without a hub, if pins 1 & 2 and 3 & 6 are crossed over then the problem lies with the way the network is setup.

Cat 5 crossover cable?
Q. I have been looking at your site and it was very helpful.
I'm trying to connect two computers with a cat 5 crossover cable. The cable that I received in the mail was crossed correctly, but it was also crossed at 4 &5. My question is will this cable work by just joining PC to PC without any hubs or anything else. I bought the cable from an individual.

A. If you are using it for 10BaseT or 100BaseT Ethernet then the wiring should be 1 to 3, & 2 to 6
Pins 4 & 5 aren't used on 10/100BaseT Ethernet systems so it should be OK. If you are planning to use Gigabit Ethernet or Token Ring then it won't work.

Cable length limits?
Q. I know that cables have restrictions on distance, but I really would like to know why those limits are for each cable. E.g. Why is Cat X cable limited to 100m, and thinnet 185M etc. I have just accepted these values but have been asked why and I do not know a technical enough answer as I have never been a cabler. I could not find this on your site and was hoping it might be added or if you could email me back with why. Thanks.

A. The length limits are not for the particular cables as such, they are for the type of data signal that they carry.

Let me try and explain!

Thinnet (RG58 coax) was used for 10Base2 Ethernet, at 10Mbps on RG58 coax Ethernet can reliably operate upto a distance of 185m. The native cabling environment of the AS400 is Twinax and the standard operating speed is only 1Mbps. At this speed it has a maximum distance of 1800m, however, if Cat 5 forms part or all of the link the distance can drop to between 36m and 364m.

So for a proprietary network such as Thinnet, the distance is set at the maximum length that the signal will work reliably at a given speed over a given type of cable. So far so good!

Now, when we talk about Cat 5, 5e, 6 etc. these are cabling 'Standards' which define a method of connecting all types of networking protocols, over a cabling system that uses a common media, common connectors and a common topology. So the length limit was arbitrarily set for the worst case scenario. 10BaseT may well work on Cat 5 for 150m but ATM, AS400, Token Ring etc. may not, and because a structured cabling system has to work for all networking methods, a limit had to be set.

I don't think I have explained this very well but I hope you get idea. Incidentally, I have heard talk of the length limit being dropped from the standards as it is the overall Attenuation to Crosstalk Ratio which determines a cables ability to transmit a signal successfully, and not the length of the cable. If anyone can elaborate on this point please let me know.

Low cost cable testers?
Q. Is there a low cost unit that will test all of the tests you talk about?
ACR, Time Domain Reflectrometry (TDR), Near End cross Talk, Power Sum Near End Cross Talk, Far End Cross Talk (FEXT), or can you give me a list of units to buy? and is there a way to test with a meter? if so how?

A. Thanks for your email. Unfortunately there is no low cost unit that will test all the parameters required to certify a cable to Cat 5e/6 standards. In my opinion, the best cable testers on the market are the Fluke DSP 4000 and the MicroTest OmniScanner. If you only need to test a few cables or if this is a one off job you may be able to hire one for a week or two relatively cheaply. Or check NetworkCablesOnline.com for other testers.

Another point is that if you are an IT manager and responsible for a sites network, the Fluke would be the better option as it can also perform some Ethernet tests as well, things like traffic monitoring and I think it also monitors collisions.


Network Topologies?
Q. what are some advantages and disadvantages about star, ring, and bus topologies?

A. In answer to your question regarding Network Topologies I hope the following helps.

Bus Topology
Advantages - Simple to implement, all machines are 'daisy chained' which makes wiring as easy as stringing coax cable from one computer to the next and so on.
Disadvantages - Not very versatile when machines have to be moved, as rewiring part of the network is necessary. Not very fault tolerant, on some systems (10Base2) if one part of the bus is disconnected the whole segment of the network goes down. Not suitable for voice.

Ring Topology
Advantages - Fairly simple to wire. Quite fault tolerant, with a Token Ring network if the main ring is disconnected anywhere, the ring uses a loop back system to maintain ring integrity.
Disadvantages - It is only really used with Token Ring networks these days and it uses Type 1 cable, this is very bulky and is not really suitable for running voice. Again, moves and additions mean rewiring and re-routing cables.

Star Topology
Advantages - These days most buildings are cabled using a star topology with Cat 5e or Cat 6 cable. This gives the network a centralized wiring point which makes connecting and disconnecting machines as simple as plugging and unplugging an RJ45 connector in to a hub or switch (Ethernet, Token Ring and any other type of network or service that is required). It can also be used for voice, data, video and any low voltage application.
Disadvantages - Requires a centralized wiring point, which can be just a cabinet on the wall for small installations, or a dedicated air conditioned room with racks and cabinets in large office accommodation. On large installations the sheer bulk of cable coming back to the wiring closet can be difficult to control and keep tidy.


Cabling problems?
Q. We have a small Pier to Pier network setup with 13 systems and one printer connected to 2 eight port hubs. We are having all kinds of instability with the network. A station might see all the other stations on the network but they can't see him or visa-versa. Sometimes it will appear and other times not.
When we made the cables for the stations, we used cat 5 cable (4prs) with the following wiring: 
Pin 1 wht/org, Pin 2 org/wht, Pin 3 wht/grn, Pin 4 grn/wht, Pin 5 wht/blu, Pin 6 blu/wht, Pin 7 wht/brn, Pin 8 brn/wht.

We tested them using a TBase cable tester, and they passed just fine. Looking at your diagram for correct wiring, it looks like you have some colored wires in different locations, but it is still pin for pin. Is there a reason why ours would be causing our problems?

A. Regarding your question on RJ45 pinouts, I would say that you are probably experiencing crosstalk problems.

The reason is this, Ethernet uses pins 1 & 2 and 3 & 6 on 10/100BaseT networks (I know it's a funny way to do it but thats how it is!). One pair is used for transmit and the other pair for receive, so pins 1 & 2 at one end will connect to pins 3 & 6 on the other end and vice versa. In the correct wiring configuration each signal path (transmit or receive) is on its own twisted pair of wires, the twists help to eliminate crosstalk. With your wiring, pins 3 & 6 are split between the green and blue pairs making them susceptible to crosstalk (or noise), this also gets worse when using higher speeds (100BaseT or Gigabit Ethernet).

The reason your tester didn't pick it up is because it only tests for continuity, shorts, crossed pairs etc. (not split pairs) you would have to use a scanner (like the Fluke DSP4000 or MicroTest OmniScanner) to find a split pair.


Three questions regarding fibre optics?
Q. How can a beam of light possibly carry information?
A. The one's and zero's of the binary data are converted to light pulses and sent down the fibre at very high frequencies.

Q. For every pulse of light that is sent down a fibre optic cable there is some light which is lost because it is beyond critical angle and cannot be reflected. If part of this mode is lost then doesn't that mean the data is sent as incomplete? How can the computer make sense of an incomplete signal? Could you explain this situation.
A. The data is sent as a stream of bits and so the amount of light that is lost merely reduces the strength of the signal. The pulses of light that reach the other end will have lost some of their strength but they will still be large enough to reassemble into bytes of information. Multi-mode transmission simply means that the light travelling down the fibre will take multiple paths, it does not mean that each mode is transmitting different data. Each pulse of light comprises all modes.

Q. Finally, I know that the time between transmitting each pulse must be enough so that the first pulse completely arrives at the receiver before the second pulse does. What happens if two pulses do crossover one another? Do they mix to create a different pulse, does the PC say transfer error, or the screen freezes etc.?
A. The pulses all travel at the same speed so it is not possible for one to overtake another. The main reasons for errors in a fibre system are too much attenuation (reduction in signal strength), and reflections or backscatter at poor connections which if large enough will interfere with the signal.


Cabling in residential homes?
Q. The company I work for is interested in installing network cabling for residential homes in the construction phase (as the home
is being built) well I am supposed to make some brochure about this and I have no idea where to even start. Some of the things I now I need (text information) are: why is it going to benefit the consumer and builder, what are the perks of having network cable, and why is it easier and a more efficient way to connect to the internet. I am not asking you for the answers but I would like to know if you can suggest any web sites that I may find information about the questions I asked above.
Thank you for your time

A. This is a big question!

First of all, we are in the 'Information Age' and more and more households are using the internet and have more than one computer. Because of this, home networking is becoming commonplace and it is a more efficient method of connecting two or three computers to the internet over one phone line or DSL (Digital Subscriber Line).

The main benefits of installing the cabling during construction are the cost and ease of implementation. Cable is fairly inexpensive and installing it during the building work is far easier than trying to do it once the property is finished and decorated. I get a lot of email from people all over the world who are cabling their houses to connect PC's together, and hiding cables in wall cavities or chasing out and re-plastering is not an easy task for them, unlike most office environments where this is not such an issue.

Another point worth raising is that residential cabling is not just for connecting PC's together. 'Smart Houses' also use intelligent devices such as alarm systems, refrigerators and heating/air conditioning systems all of which can be networked to a controlling PC or accessed via the Internet when you are away from home. OK, you may be asking why would we need to? but it is starting to happen. And, of course, the cabling system can also be used for telephones, which makes adding an extension phone as simple as plugging it in at the nearest cabling outlet and patching it through at the panel.


Two jacks per cable?
Q. Our offices are moving into an existing building which was wired by the previous owners, or a contractor for them, and their wiring is one I have never seen before. Each wall outlet has two data jack which are "sharing" a single UTP cable, 2 pairs to the left jack and the other two pairs to the right jack. What problems are we likely to encounter with this setup? Our normal wiring method is one jack one cable.....

A. It sounds like costs were an issue when this building was cabled, but if it is configured for Ethernet (using pins 1, 2, 3 & 6) it should be OK for 10BaseT. I wouldn't like to speculate on whether it will run at higher speeds because that is dependent on the quality of the installation and the amount of network traffic.

If the installation was originally wired for Token Ring then it will use pins 3, 4, 5 & 6 which will not work with Ethernet.
Crosstalk could be an issue if the pairs have been split between outlets and/or between pins on the jack, (pins 1 & 2 should be a pair and 3 & 6 should be a pair).

I hope this helps, and although it is possible that you will have no problems, I would strongly advise a rewire. This is because it will be easier at this time to carry out the work and, as you move to higher speeds in the future this wiring configuration will undoubtedly start to cause problems.


Whats the difference between stranded and solid cabling?
Q. I just found your web site and i thought that it was very informative, but i could not find any thing on the difference between stranded and solid cabling, could you tell me what the difference between them is? (I think stranded is used as patch leads and solid is used as a connector between the patch panel and the wall outlet).
A. You are correct, stranded cable is used for patch leads because it is more flexible than solid copper. The solid cable is used in the fixed part of the installation, ie. the cable between the patch cabinet and the wall outlets. Solid cable has better performance characteristics than stranded and it is cheaper to make.

Q. Thank you for your help, it was very useful. One other thing you could help me with, is the way that the solid and stranded cable are wired up different? because i know that you can get RJ45 plugs for solid and stranded cable (i know how to wire up stranded cable to a RJ45 plug), if so then how is the solid cable wired up to the RJ45 plug.
A. The colour codes are the same for solid and stranded cables, the difference is in the IDC (insulation displacement connector) in the RJ45 plug. Because the cores are different the contacts have to be slightly different to ensure a good contact is made.

Ethernet over ICS Cabling?
Q. I have this small question: Our company currently uses a Token Ring LAN however we want to change to Ethernet.
Do you know if we can use the ICS cabling (in the wall) with Ethernet? 


A. In answer to your question, yes ICS can be used for Ethernet by using ICS/Ethernet baluns. These baluns look like IBM Data Connectors with an RJ45 socket on the back and should be readily available from your Networking supplier. 

There are however, a few things to bear in mind. The first is that all the baluns should be matched (buy them all from the same supplier) failure to do this can bring the whole network to a grinding halt (I know, I had this problem at a major distribution centre several years ago). The next thing to realise is that ICS only has 2 pairs so it will never run Gigabit Ethernet (Gigabit needs 4 pairs) even though the Type 1 cable is good for about 300MHz if installed correctly.


Token ring crossover cable?
Q. Please, help me, I normally make token ring cables for our network, the order of the cables is as follows:
At both ends of the plugs are the same:
orange white / orange /green white / blue / blue white / green / brown white / brown

My question is: one of the techs wants a twist token ring cable, what would be the order of the cables?????
Please, respond or if you need more info, let me know,
your prompt response, will be greatly appreciated.

A. With a normal Type 1 or Type 6 Token Ring cable the colours are Red, Green, Orange, Black as there are only two pairs used. I assume your are using a Cat 5 cable which means that only the middle 4 wires are actually connected these will be your Green/White, Blue, Blue/White and Green on pins 3, 4, 5, & 6. These pairs on a Cat 5 cable are the greens on pins 3 & 6, and the
blues on pins 4 & 5, therefore to make a cross over cable you have to connect them as follows:

Pin 3 (Green/White) to Pin 4 (Blue)
Pin 4 (Blue) to Pin 3 (Green/White)
Pin 5 (Blue/White) to Pin 6 (Green)
Pin 6 (Green) to Pin 5 (Blue/White)

So at one end you will have the greens straddling the blues and at the other end the blues will be straddling the greens, there is no need to the change the oranges and browns because they're not used. If this doesn't work it will be because the send and receive pairs are the wrong way round, so just try the other combination of connecting the solid colours together (ie. Blue to Green) and the whites together (ie. Blue/White to Green/White), but it should work as described above.

Is this cable something to do with a Token Ring fibre link?, if so, you will have to make sure you use it at the correct end of the link, but thats a whole other story!


What type of network installation? 
Q. Hi, regarding a network installation here in Malaysia, nearly all installation are LAN and WAN architecture and they widely use the 10/100 Mbps ethernet adapter. Since the emergence of Data Storage Network, Network Attached Storage, VoIP and many more types of network offered by different network vendors, could there be other types of networks that are implemented now, which look to have a better potential in the future. It seems that the transferring rate has always been the issue here.
What type of network installation at this present moment is in high demand?
I am waiting for your reply, for this could help me a lot with my proposals.
Thanks

A. For campus size installations the main concern will be available bandwidth between the different buildings and the servers or storage devices. If the distances are under about 220m then a standard 50/125 fibre will easily accommodate Gigabit Ethernet, more than this distance would require the added expense of single mode fibres. It would probably be a good idea to install single mode 'Dark Fibres' (fibres that are not terminated) alongside the multi modes anyway, this will future proof the installation to a certain
extent with out adding too much to the costs. Talk of 'Terabit Ethernet' has started to filter through, but this will have to be over single mode fibres using laser technology, if you already have the fibres in place ready to be terminated, then that is as much as you can do at this time.

The copper cabling should be at least Cat 5e or Cat 6, and should be tested to ensure that it fully complies with the relevant standards.

I think a major issue in years to come will be the quality of the installation, as we try to squeeze more and more bandwidth out of existing cabling systems then bad workmanship will start to show up. Make sure the cable routes have plenty of space and the cabinets are not congested. The planning at this stage and the installation of the copper cabling itself should not be taken lightly.

With a WAN, you are very much at the mercy of the telecoms company, and can only implement what they have to offer, in any wide area network this is always going to be the 'bottleneck' of the network.

I hope this helps with your proposal.


Pricing for a cabling installation?
Q. I am doing some research and am looking for information on pricing for a cable installation. For instance do you have a flat rate per drop installing Cat 5 or fiber or do you charge per feet? Also what is the going rate for this type of installation including wall plates and cable. Any information you can give me on this would be very helpful in my research!

A. It is normal to price a job on a per drop basis but this is subject to the numerous other factors involved. These include the difficulty of the installation (ie. is there a false floor or ceiling or will it all have to be trunked out!), and the type of cable and connectors that have been specified (some systems are more expensive than others). 

I think the overriding factor is usually down to the amount of man/hours involved, once a price has been worked out for this and the material costs and profit have been added, the total can then be divided by the number of outlets to give a price per drop.

The same goes for a fibre installation although the cost of materials is higher than copper.


Fibre cable testing?
Q. Could you please tell me what is used for fibre cable testing?

A. An OTDR (Optical Time Domain Reflectrometer) is commonly used to test fibre cables although for data networks it is easier these days to use a fibre certification tool.

OTDR results can be difficult to interpret and involve some mathematics, fibre certification tools simply tell what networks the fibre is good for, for example 10Base-X and 1000-BaseSX etc .

For basic testing a simple light source and power meter can be used but this only gives a dB loss reading and does not test for maximum bandwidth or distance.

I hope this answers some of your questions.


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