Unit 1 Review
The Golden Rules of Data Cabling * Networks don’t get small or less complicated * Build a cabling system that can do voice and data * Installing more cable will benefit in the long run, along with extra outlets * Higher quality cabling and cabling components matters a lot for long term use * Plan for higher speed technologies that may be coming out in the near future * Document all installation that is happening in case you have to go for notes later
The importance of Reliable Cabling * Data cabling is less than ten percent of the network infrastructure * The lifespan of cabling can last up to sixteen years * Nearly seventy percent of network problems occur because of poor cabling techniques * Poor cabling can cause the network to run at a much slower speed, not meeting the minimum requirements for a proper install.
Twisted Pair Wiring * The most economically and widely installed cabling today is twisted pair wiring. * Unshielded twisted-pair (UTP) has been used for many years for telephone systems * A typical UTP cable is covered by an insulation material with good dielectric properties; being electrically nonconductive, it must also have certain properties that allow good signal propagation. * Shielded twist-pair (STP) * Classified as data cabling made popular by IBM. * Some cabling uses a woven copper shield wrapped in a foil shield. * STP cable is 22 AWG and has a nominal impedance of 150 ohms * The shield must be electrically continuous along the whole link * All components in the link must be shielded * Screened Twisted-Pair (ScTP) * A recognized cable type in the ANSI/TIA-568-C standard is screened twisted-pair cabling and a hybrid of STP and UTP cable. * Contains four pairs of unshielded 24 AWG, 100 ohm wire surrounded by a foil shield or wrapper and a drain wire for grounding purposes. * the foil shield is less susceptible to noise * Used in the environments that have abnormally high ambient electromagnetic interferences such as: * Industrial work places, hospitals, airports, and government or military communication centers. * Screened Shielded Twisted-Pair (S/STP or S/FTP) * Also known as screened fully shielded twist-pair * Contains four individually shielded pairs of 24 AWG, 100 ohm wire surrounded by an outer metal shielding * Offers the best protection from interface from external sources * Eliminates alien crosstalk allowing the greatest potential for higher speeds
Color Codes for Four-Pair UTP Cable Pair Number | Tip Color | Ring Color | 1 | White/Blue | Blue | 2 | White/Orange | Orange | 3 | White/Green | Green | 4 | White/Brown | Brown |

Cables are rated in hertz rather than bits per second
Network Engineers are more concerned with how much data can be pushed through a cable than with the frequency at which that data is traveling.
Data Rate is defined as the number of bits per second that move through a transmission medium. * Older LAN technologies have a one-to-one relationship with the transmission frequency
For gigabit Ethernet to work over category 5e, 6, and 6A, all four pairs must be used
Decibels and Power * Referring to power, decibels are calculated in this fashion: dB=10xlog10(P1/P2) * P1 indicated the measured power * P2 is the reference power * The measure power level on the opposite side of the cable is 0.5 watts
Types of Crosstalk * Near-End Crosstalk (NEXT) * Crosstalk is detected in the same end of the cable that generated the signal * Far-End Crosstalk (FEXT) * Similar to NEXT except that it is detected at the opposite end of the cable from where the signal was sent * Equal-Level Far-End Crosstalk (ELFEXT) * The crosstalk coupling pairs measured at the end of the cable opposite to the end of the signal source, taking into account signal loss * Pair-to-Pair Crosstalk * For both near-end and far end crosstalk; used for measuring crosstalk * Power-Sum Crosstalk * Applies to both NEXT and FEXT and must be taken into consideration for cables that will support technologies using more than one wire pair at a time * Alien Crosstalk (AXT) * Occurs when the signal being carried in one cable interferes with the signal being carried in another cable. * Attenuation-to-Crosswalk Ratio (ACR) * An indication of how much larger the received signal is when compared to the NEXT on the same pair