1. How often are network standards reviewed? 2. What category of UTP cabling is
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Question
1. How often are network standards reviewed?
2. What category of UTP cabling is the minimum for a telephone cable?
3. What category of cabling should be installed as a best practice for a telephone cable?
4. What is the problem with leaving abandoned cable in place in a building?
5. Why must the twisting in the individual wires be maintained in a UTP cable?
6. How many wires does a gigabit cable use?
7. Is the labeling standard commonly used or not used?
8. Grounding should be attached to what in the building?
9. Horizontal cabling connects what areas to each other?
10. What is a plenum rated cable?
11. What is a riser tube used for?
12. What is the code for plenum rated horizontal cable?
13. How many wires in a UTP cable does Fast Ethernet use?
14. How many inches should separate UTP cable from 120 volt electrical cable?
15. What is the reason for grounding jumpers on each connection in ladder rack?
16. Why should overfilling of a riser tube be avoided?
17. Is the grounding of equipment a safety or a performance concern?
18. What are the current recognized horizontal cabling categories?
19. May an existing Category 5 cable be used to make network connections?
20. In the example used here what does the firestop material consist of?
21. In what circumstances will poorly installed cabling still function?
22. Why should the outer cover on a UTP cable be maintained in place?
23. Does cable labeling impact network performance?
24. May CM cable be used in the plenum space?
25. Why should a plastic riser tube not be used?
Explanation / Answer
There are a lot of different network standards that the majority of computers use. There are standards for both physical hardware and for signaling. For example, IEEE 802.11g is a wireless networking standard. It includes specifications for the type of radio that is used, how strong the signal can be amplified, a standard set of encryption schemes, etc.
Another standard is Ethernet, also known as IEEE 802.3. This is a standard for hardwired networks. When people talk about Cat 5 cable, this is usually what they mean. It defines what types of wiring can be used, transmission power requirements, connector styles, etc.
There are also protocols. TCP/IP is basically the protocol that runs the internet and most LANs that exist today. When people talk about IP addresses, subnet masks, default gateways, etc. those usually pertain to this. Note that TCP/IP is a protocol that is used in conjunction with things like 802.11g or Ethernet.
There's something called the OSI model, which defines the different "layers" of a network. I've only mentioned mentioned some of them, but there are 7 all together and standards exist for technologies on all of those levels. You can read about the OSI model here
Because networking evolved over severeal decades, many different cabling solutions have been used. But today, virtually all VDV copper cabling in the US has moved to unshielded twisted pair (UTP) as specified in the EIA/TIA 568 standard (ISO/IEC 11801 worldwide) because it has been inexpensive, may already be in place, is familiar to installers and is simple to install. (The cost and simplicity of installation has changed a bit, however, with Cat 5e/6/6A, see below.) Some users, mostly outside the US, use shielded twisted pair (STP) with shields over each pair in the cable or screened twisted pair (ScTP) with an overall shield around all the pairs. These cables can provide higher performance but require more care in installation.
UTP cable has been a standard cable for telephone systems for almost a century, where it is generally used for analog phone systems (POTS or plain old telephone service.) These cables are generally large multipair cables with pair-count configurations of 25, 50, 100, 200 pairs or more.
UTP
Most UTP cable used in structured cabling systems today is comprised of four pairs of carefully twisted pairs of solid copper wire, insulated with carefully chosen material to provide high bandwidth, low attenuation and crosstalk. Cables permanently installed in premises cabling systems use solid wire for higher performance but patchcords generally use stranded wire for greater flexibility and ruggedness when handled.
UTP cable works so well because it is used with transmitters that work on "balanced transmission" as shown below. They transmit equal but opposite signals on each wire of the pair so each wire has only half the amplitude of the final signal. The electrical and magnetic fields of each wire are opposite and cancel out eachother, producing low electromagnetic emissions. Likewise, electromagnetic pickup is the same on both wires so they cancel out. The twists on the pair of wires mixes the emissions from the electrical signals so they cancel out.
balanced transmission
Twisted Pair Trivia: The two wires are referred to as "tip" and "ring" - but why? Does it have something to do with the ringer on a phone? No! It refers to the connection on a old phone plug from manual switchboards. The white/stripe wire was connected to the "tip" of the plug and the solid wire to the "ring" connector behind it!
The applications seem to be performing alright, and there are no viruses or unexpected packets in the system. There are no Trojans on the server, and no one is downloading gigabytes of music to their iPod. You are stumped. But did you think of going to the communications room and checking the server's patch cable?
It is easy to forget that cables are the arterial systems of our networks. They can get clogged by too much data, and occasionally they can become degraded or corroded, forcing network managers to perform the equivalent of a triple bypass to get things running smoothly again.
Maintaining a healthy cabling system is crucial to the performance of the network, but how do you measure the health of your infrastructure?
Cabling: the basic structures
There are three main parts to most cabling structures: the core backbone cabling infrastructure is usually a vertical cabling system (running between floors) the structured cabling runs to the desk (normally horizontally along each floor) and the third part, the patch cabinet, is where computers on the local area network are connected to each other and hooked to incoming wide area network connections.
Patch cabinets are where things can go wrong, because cables are being pulled and replaced all the time.
Kelvyn Dale, managing director at network consultancy and cabling firm Q2 Communications, says, "When there is a problem, it tends to be the patch cords. The cables that you see in buildings that get pulled through risers, and so on, are solid, single-core copper, but patch cords are stranded, with strands of copper in each of the wires in the cord, so they tend to break more easily."
But just because it stays put when installed, backbone and structured cabling is not invulnerable. Even external cabling designed to run between buildings has unique vulnerabilities. Some suppliers have introduced anti-rat cables to stop data-hungry rodents doing their worst, for example. And Dale has seen other cabling that has given out after sitting in water-flooded ducts for months on end.
"We often find that electrical contractors pull the cables around as they would with electrical cable, and that is wrong," he says.
Cables have a certain bend radius beyond which they are not meant to flex. To see why, bend a thin piece of copper backwards and forwards and see what happens to it.
Cables get trodden on and bent backwards, all of which can degrade the information-carrying capabilities of the wire. Even having cable ties tied too tightly can cause problems.
Mapping and tracking cabling
When the experts do it, they do it properly. Mobile network operator T-Mobile is working with supplier Computacenter Services to lay new cable at T-Mobile's corporate campus and 14 switching centres - and there is a lot of cable.
The campus roll-out covers 48,000 outlets on the site and involves enough cabling to stretch from London to Moscow. Computacenter is currently working on upgrading T-Mobile's 14 switching offices, which handle voice and data services to customers.
"We have a complete strategy document that covers the way that cables are laid in buildings," says Tony Alger, manager for central and data products at T-Mobile. Alger says that such missives come from the engineering and planning department. "We have colour codes detailing what carries what service."
Cables carrying customer data, for example, use a different colour from those carrying support data or telephone voice call data. "If you drop something down into the void and it breaks through the protective coating and hits the cable, then, depending on what colour it is, you know how important it is to get things fixed," Alger says.
The void is the area of the datacentre where structured cabling runs and rarely gets changed. Experts carry out best practice everywhere, including here, but some amateur installers do not bother colour coding or documenting patch cabinets, where the environment changes frequently. That can quickly turn it into a cable installer's worst nightmare.
"When you get into the cabinet and you find the 'bowl of spaghetti' syndrome, that takes a long time to do current state analysis," says Computacenter's IT facilities solution unit director Neil Silverstein.
Sometimes, network teams will simply add another cord of any colour for expediency when carrying out a change on the network, and before long they will begin looking for another cabinet because their current one is full.
Often, they could recover 50% of a cabinet's capacity by pulling redundant cables, says Silverstein - if only they knew which was which.
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