IT-113 Structured Cabling Chapter 1 Introduction to Data Cabling
Objectives • Define the basic communication system.• List the components of the data communication process. • Identify the various signals of data transfer. • Describe how the electrical characteristics of the transmission media affect data transmission.
Basics of Cabling • Golden rules of cabling• Importance of reliable cabling• Legacy of proprietary cabling• Increasing cabling demands for higher speeds• Cable design and materials• Communications media• Limitations of cabling• Future of cabling
Golden Rules of Cabling • Networks never get smaller• Build one system for voice and data• Install more than you need• Use structured-cabling standards• Quality counts; cabling and components• Don’t scrimp on installation costs• Plan for higher speed technologies – 5 yrs• Documentation is a must!!
Importance of Reliable Cabling • 10 % total network cost is cabling • Life span upwards of 16 years • 70 % of al network problems due to cabling and component technique problems
Importance of Reliable Cabling – 2 • Cabling is the foundation of any network • Cost of poor cabling – Intermittent problems– Slow access time– PC’s locking up • Is cabling to blame – YES!!!
Importance of Reliable Cabling – 3 • Is cabling to blame – YES!!! • Why?? – Substandard components– Poor installation techniques • How?? – Drop-rate magnification– 1% drop in Ethernet packets relates to 80% drop in throughput – Wiring problems drop packets
Legacy of Proprietary Cabling Systems • Vendor specific• No standards existed in the 1980’s• Different equipment/connections – Wang– IBM twinax– Twisted Pair – digital phone systems– Thinnet and thicknet– RS-232 forms– Coaxial cable • Thing of the past, but stil exists in some areas
Legacy of Proprietary Cabling Systems • Anixter Cables Performance Levels describe performance only • Organizations involved – ANSI– TIA– EIA • Comprehensive standards set – ANSI/TIA/EIA-568-1991– ANSI/TIA/EIA-568-A in 1995– ANSI/TIA/EIA-568-B in 2001
Cabling and the Need for Speed • 10 Mbps – Ethernet• 16 Mbps – Token ring• 100 Mbps – FDDI, & Fast Ethernet• 155 Mbps – ATM• 655 Mbps – ATM• 1000 Mbps – Gigabit Ethernet• 2.5 Gbps – ATM• 10 Gbps – 10G Ethernet
Cabling and the Need for Speed WHY ?? • Application size and data transfer rates have increased • Applications are more complex and require more bandwidth to operate • Performance demands on cabling must be able to keep up with these new requirements
Types of Communication Media • Twisted Pair – UTP • Most common today• 100 ohm Ω ± 15%, 24 AWG, four-pair cable – STP • Standard set by IBM Type 1A cable• Al the cable pairs are shielded from EMI• Performance considerations – Shield must be continuous– All components must be shielded– Shield must be grounded at both ends IAW TIA/EIA-607
Types of Communication Media • Twisted Pair – ScTP • Hybrid of STP• 100 ohm Ω , 24 AWG, four-pair cable• Foil shield surrounds al the pairs and a drain wire provided for bonding • Individual pairs not shielded• Must use special RJ-45 plugs and jacks• Used in area with high EMI levels
UTP STP ScTP
Types of Communication Media • Fiber optic cable• Advantages – Greater transmission distances– Higher bandwidth capability– Not affected by EMI– No crosstalk– More secure • Dark fiber – spare fiber cables “Not Lit-up”
Types of Communication Media • Single-mode fiber – Used as a backbone cable– One light source only– Long distance communications • Multimode fiber – Used with ATM, FDDI and 10Base-FL applications– Al ows more than one path through the fiber– Types • Step index• Graded index
Fiber-Optic Cable Single-mode fiber Multimode fiber Dual Fiber Cable
Types of Communication Media • Coaxial – Used primarily for TV and video distribution now – Difficult to run and terminate– Better protection against EMI than UTP– Higher bandwidth than UTP also
Coaxial Cable
Cable Design • Questions to be answered• What types of cable in ceiling?• Cable markings?• Untwist a twisted pair cable?• Shielded or unshielded?• Single-mode or multimode fiber?• NEC ratings on fire safety requirements? – Table 1.2
Cable Design cont.
Cable Design cont. • Plenum – Space between false ceiling and structural ceiling– Requires a cable rated for this type of space • Riser – Vertical shaft between two floors– TOWERING INFERNO !!! / chimney effect– Must be fire-stopped on each floor • General purpose – Horizontal cable – wiring closet to wal outlet– Patch cables • Limited use – Single and duplex residences only
Cable Design cont. • Cable jackets – Normal y polyvinyl chloride (PVC) jacket– Cat 1-3 PVC jacket and insulation– Cat 4 and higher – jacket only, insulation uses other materials such as HALAR, KYNAR, and FEP – Slitting cord– Jacket color – no standard
Cable Design cont. Cat 5e cutaway diagram
Cable Design cont. • Cable Markings – Example – 000750 FT 4/24 (UL) c(UL) CMP/MMP VERIFIED (UL) CAT 5e SUPERIOR ESSEX COBRA 2313H – FT – footage indicator– 4/24 – four pair, 24 AWG– (UL), c(UL) – underwriters laboratories listed– CMP/MMP – plenum rating– VERIFIED (UL) CAT 5e – certifies to standard– SUPERIOR ESSEX – manufacturer– COBRA – cable brand– 2313 – Julian date of manufacture – H – manufacturing plant
Cable Design cont. • Common Abbreviations – NFPA – National Fire Protection Association– NEC – National Electrical Code– UL – Underwriters Laboratories– CSA – Canadian Standards Association– PCC – Premises Communication Cord
Cable Design cont. • Wire insulation – Excellent dielectric for high frequency signals – Fluorinated ethylene-propylene (FEP), polytetraflourethylene (PTFE/TFE) – plenum rated – High density polyethylene (HDPE) – non- plenum rated
Cable Design cont. • Wire Insulation colors – Colors are standardized– US color code based on 10 colors– Tip and ring combinations • Tip – white/colored stripe or band • Ring – unique color – 25 possible pair combinations– Table1.3, 1.4
Cable Design cont. • Twists – Cancels out unwanted EMI on pairs • Crosstalk and other effects – Do not untwist more than ½ inch at any connector – 2 to 12 or > twists per foot • Wire gauge – AWG– 22-26 range– Table 1.5
Cable Design cont. • Solid versus stranded conductor – Solid has better electrical properties • Used as horizontal cabling – Stranded • More flexible • 20% more attenuation due to skin effect • Normal y used as patch cables • Some networks set up with stranded conductors – Require different connectors– Punch-down blocks require solid conductor
Cable Design cont. • Cable Length – Attenuation is a problem • Propagation delay • Delay skew – Cable length vs. conductor length • Twists make the four pairs have different lengths • Example – Cat 5e cable -139 ft cable length– Pair 1-2 145 ft – Pair 3-6 143 ft – Pair 4-5 141 ft – Pair 7-8 142 ft
Data Communications 101 • Bandwidth – Maximum frequency for data transmission • Frequency – Expressed in Hz • Data Rate – Maximum data transmitted in one second – Bps • Table 1.6
Data Communications 101 cont.
LAN Throughput vs. Operating Frequency
What are dB’s • Tenfold logarithmic ratio of power output to power input • 10*log(P1/P2) – power output• 3 db – 50 % change in signal power• Table 1.7• 20*log(P1/P2) – voltage output• 6 db – 50 % change in signal voltage• Table 1.8
Speed Bumps • Attenuation – The lose of signal as it moves away • Noise – The additional unwanted signals from outside sources • Other – EMI, RFI, Static
ATTENTUATION • Loss of signal• Conductor resistance• Mutual capacitance• Impedance• Return loss
Noise • Resistance unbalance• Capacitance unbalance• Crosstalk• Twist requirement
Crosstalk • Near-End (NEXT) – same end as source– 20-30 meters • Far End (FEXT) – End opposite the source • Equal-Level Far-End (ELFEXT) – End of cable pairs opposite source
Crosstalk cont. • Pair-to Pair • Power-Sum
Other Hindrances • External Interference• Attenuation-to Crosstalk Ratio (ACR) – Also cal ed signal-to-noise ratio (SNR)– Calculated value– Difference between crosstalk and attenuation • Propagation Delay – Nominal Velocity of Propagation (NVP)– Normally 60-90 % speed of light • Delay Skew
• ACR • Delay Skew
SUMMARY • Complete Unit 1-1 Lab• Homework Week 1 – Research the fol owing cable types • Cat 3, Cat 5e, Cat 6, Cat 7• Create a table with the fol owing specifications for each cable type • Impedance, Attenuation, NEXT, FEXT, Pair-to-pair crosstalk, Power-sum crosstalk, Data rate, Operating frequency, Twist ratios, and cost – Answer the questions on the handout.