Network Cables ITNW 1325, Chapter III, Part II. Coaxial Cable

Network Cables

ITNW 1325, Chapter III, Part II

Coaxial Cable

Coaxial Cable

Overview: Was the foundation of Ethernet networks in 1970s –

replaced by newer twisted pair and fiber cable Has a single or multiple copper strands at its center –

protected by PVC or Teflon insulation Protected and grounded via metallic shield (“braiding”) Protected from physical damage by a layer of dielectric

insulator (“sheath”) on the outside Allows relatively long segments and highly resistant to

noise – more expensive and less convenient to handle

Coaxial Cable

Overview (continued):

Coaxial Cable

Overview (continued): Defined by Radio Guide (RG) specifications – with few

most common types in use Classify the cores according to American Wire Gauge

(AWG) numbers – the smaller is the diameter, the larger is the AWG number

Differ by materials used for the core and for shielding, the core’s diameter, impedance, attenuation, data rates, and terminators used

Coaxial Cable

RG-6: Contains an 18 AWG conducting copper core with an

impedance of 75 ohms – thick and not flexible Used for delivering cable TV and Internet service over

long distances to residential areas – not used for LANs

Coaxial Cable

RG-6 (continued):

Coaxial Cable

RG-8 (“Thicknet”, “10Base5”): Contains an 10 AWG conducting copper core with an

impedance of 50 ohms – very thick and inconvenient Allowed throughput up 10 Mbps with a maximum

segment length of 500 m Used within first baseband (Ethernet) data networks

Coaxial Cable

RG-8 (continued):

Coaxial Cable

RG-58 (“Thinnet”, “10Base2 Cable”): Contains a 24 AWG conducting copper core with an

impedance of 50 ohms – thin and quite flexible Allowed throughput up 10 Mbps with a maximum

segment length of 185 m Entirely replaced the 10Base5 cable within baseband

data networks – popular in mid-80s and 90s

Coaxial Cable

RG-58 (continued):

Coaxial Cable

RG-59: Contains a 20 or 22 AWG conducting copper core with

an impedance of 75 ohms – thin and quite flexible Allowed throughput up 10 Mbps with a maximum

segment length of 185 m Used for delivering video signals for short distances Less expensive than RG-6 but suffers from attenuation

Coaxial Cable

RG-59 (continued):

Coaxial Cable Termination


Overview: Necessary to avoid bouncing of the signal off the cable’s

ends – accomplished by using connectors or special terminators with the same impedance as the cable used

Two common types – F-type and BNC

F-Connector: Suitable for cables with a solid metal core – becomes the

pin in the center of the connector (used in RG-6) Mounted on a cable by crimping or compression – both

male and female connectors are threaded and screw together like a nut and bolt assembly


F-Connector (continued):

Male Female


Bayonet Neill-Concelman (BNC) Connector: Mounted on a cable by crimping, compression, or

twisting – connects to another BNC connector via a turning and locking mechanism (“bayonet coupling”)

Male connector uses its own conducting pin – not the core of the cable like F-type ones

Commonly used with RG-59 cable


BNC Connector (continued):

Male Female


BNC Connector (continued):

Twisted Pair (TP) Cable

Twisted Pair Cable

Overview: Carries color-coded pairs of insulated copper wires Wires in each pair are twisted around each other – from

1 to 4200 pairs depending on the cable type Inexpensive, flexible, easy to install Twist ratio – the number of twists per meter –

measures resistance to crosstalk Higher twist ratio leads to lesser crosstalk but requires

more cable – increases attenuation and raises the cost

Twisted Pair Cable

Overview (continued): Uses a variety of twist ratios, pair numbers, copper

grades, shielding types, etc. The TIA/EIA 568 standard defines categories – CAT5,

CAT6, or CAT7 TP cable is needed for modern LANs Comes in two types – shielded and unshielded

Twisted Pair Cable

Shielded (STP): Shielding prevents external EM forces from distorting

the signal traveling in the wires Each pair in individually insulated and surrounded by

metallic shielding Grounded shielding enhances its protective effects Noise, shielding material, quality, and symmetry, and

grounding affect the protection provided

Twisted Pair Cable

Unshielded (UTP): Employs no shielding – contains insulated wire pairs

encased in a plastic sheath only Provides acceptable resistance to and less expensive

than STP – widely used on computer networks

Twisted Pair Cable

STP vs. UTP: Provide same levels of throughput – from 10 Mbps to

10Gbps – depending on quality and type STP is more expensive since uses more materials, is

less common, and required more expensive installation due to grounding

High-grade UTP is priced similarly to mid-grade STP

TIA/EIA Twisted Pair Categories


CAT3: Contains four wire pairs Provides 10 Mbps throughput and 16 MHz bandwidth Limits segment length to 100 m (330 ft) Widely used in VoIP networks

CAT4: Provides 10 Mbps throughput and 20 MHz bandwidth Carries better interference protection than CAT3

Both are replaced by newer UTP categories


CAT4 (continued):


CAT5: Contains four wire pairs Provides 100 Mbps throughput and 100 MHz bandwidth Limits the length of each segment to 100 m (330 ft) Connects to a NIC via an RJ-45 connector Uses 118 twists per meter (3 per inch) on average Was produced in large quantities – still widely available Inexpensive, effective, popular


CAT5 (continued):


CAT5e: A version of CAT 5 cable with high-quality copper Contains four wire pairs Has higher twist ratios Incorporates better cross-talk reduction methods Provides 350 MHz bandwidth Allows 350/100 m segments at 100/1000 Mbps Inexpensive – widely used within 1 Gbps networks


CAT5e (continued):


CAT6: Contains four wire pairs, each wrapped in foil insulation Additional insulation covers the bundle of four pairs Carries fire-resistant plastic sheath on the outside Resistant to crosstalk 250 MHz bandwidth provides up to 10 Gbps throughput Allows 100 m (300 ft) long or 37 m (120 ft) long

segments (for up to 1 Gbps or 10 Gbps, respectively) Uses newer GG-45 connectors Widely used in modern 1 Gbps networks


CAT6 (continued):


CAT6 (continued):


CAT6e: A higher-grade version of CAT6 cable Further reduces attenuation and crosstalk Allows longer segment lengths – up to 100 m at 10

Gbps Provides 550 MHz bandwidth Requires GG-45 connectors De Facto standard on modern networks


CAT6e (continued):


CAT7: Contains increased amount of shielding Larger, heavier, less flexible Has 600 MHz bandwidth Provides 10 Gbps throughput on up to 100 m (330 ft)

segment length, with large margin Requires GG-45 connectors De Facto standard on modern backbone networks

CAT7a: In theory – 1 GHz, 40/100 Gbps at up to 50/15 m Currently under development


CAT7 (continued):

TIA/EIA Twisted Pair CategoriesCost: PCI Express NIC, single RJ-45 connector: $30–40 CAT6 50 ft patch cable: $10–12 Troubleshooting implies replacing cable

Twisted Pair Termination


Overview: Proper termination is required on both ends Poor termination leads to a data loss or a noise TP cable is automatically terminated when RJ-45 and

GG-45 jacks are crimped onto it Two TIA/EIA standards exist for inserting the cable

into jacks – 568A and 568B Any of the two standard can be used – the same one

should be used on the entire network TP patch cable – sold in stores as premade, terminated,

tested, and packaged cable


Termination (overview):

Green Pair #3 – Transmit Orange Pair #2 – Transmit

Orange Pair #2 – Receive Green Pair #3 – Receive


Straight-Through: Implies same TIA/EIA standard used on both ends Wires aren’t twisted end-to-end Used for connecting a PC to a hub or a switch

Crossover: Implies using TIA/EIA 568A standard on one end and

TIA/EIA 568B standard on another end Used for connecting two workstations or two network

devices directly


Crossover (continued):

Making Twisted Pair Cables


Tools Needed: A wire cutter A wire stripper (removes the sheath) A crimping tool (fixes wires inside the connector) May come within same device

Steps: Make a clean cut at both ends of wire using wire cutter Remove one inch of the sheath off of one end or wire Make sure to not to damage insulation


Steps (continued): Separate the pairs and unwind each pair for up to ½ inch Align the wires on a flat surface according to colors and

positions Pull steadily across the unwound section of each wire

(“groom” wires) Slide wires into their positions in the RJ-45 plug Place the RJ-45 plug in the crimping tool and press

firmly avoiding any rotation Use tester to verify transmission over the wire made

Fiber Optic Cable

Fiber Optic CableLayered Structure: Inner core – glass or plastic fibers at the center that

carry laser pulses or an LED light used for data transmission

Cladding – a layer of plastic or glass around the fibers that reflects the light back to the core

Plastic buffer – an opaque layer that protects the cladding and the core and absorbs any light that escapes

Strands of Kevlar – a polymeric fiber that surrounds the plastic buffer and prevents stretching and damaging

Plastic sheath – providing the overall cable protection

Fiber Optic CableLayered Structure (continued):

Fiber Optic CableSingle-Mode Fiber (SMF): Uses narrow core – less than 10 microns in diameter Propagates light without reflections – causes no

dispersion and no significant energy loss Provides the highest bandwidth of all media and allows

the longest distance without requiring repeaters Allows 60 km (37 mi) long segments at 10 Gbps Good for connecting large networks together The most expensive networking medium Suitable for WANs

Fiber Optic CableSingle-Mode Fiber (continued):

Multi-Mode Fiber (MMF): Uses wider core – from 50 to 115 microns in diameter,

with 62.5 microns being most common size Multiple laser or LED pulses are sent over the fiber at

different angles Allows 300 m (910 ft) long segments at 10 Gbps, 550

m (1670 ft) at 1 Gbps, and 2 km (6060 ft) at 100 Mbps Used for connecting network devices to a backbone Suitable for both LANs and WANs

Fiber Optic Cable

SMF vs. MMF:

Fiber Optic Cable

MMF vs. Copper, Advantages: Allows longest distances without requiring repeaters Much more resistant to noise Very secure – tapping into light transmissions isn’t easy

MMF vs. Copper, Disadvantages: Installation and field repairs are much more complex for

MMF (requires special equipment) Much more expensive MMF is used to provide much higher throughput – not

anymore (CAT7 TP cable – up to 10 Gbps)

Fiber Optic Cable

Fiber Optic CableCharacteristics: Highest throughput – no resistance allows achieving 100

Gbps per channel and reduces errors Highest cost – most expensive medium, NICs, and hubs,

plus the highest installation costs – not practical for small networks

Best EMI and noise immunity – no current used Size and scalability – segment length is limited by

degradation of the signal (“optical loss”), with typical values from 150 to 40,000 meters (455 to 121,200 ft)

Imperfections at connection points affect segment length

Fiber Optic CableConnectors: Ten different types exist, with four being being most

common – Straight Tip (ST), Standard Connector (SC), Local Connector (LC), and Mechanical Transfer Registered Jack (MT-RJ)

All can be used for both SMF and MMF ST and SC are used on older networks LC and MT-RJ are smaller in size – allow higher

density at termination points, used in newer networks MT-RJ connector contains two strands of fiber in a short

protective tube (“ferrule”), allowing full-duplex mode

Fiber Optic CableConnectors (continued):

ST connector SC connector


LC connector MT-RJ connector


Fiber Optic CableCost: PCI Express NIC, single LC connector: $500–600 MMF 50 ft cable, LC connecter: $50 – 60 Troubleshooting implies using professional services Installation time and labor costs are much higher than

for TP cable

Homework Read the chapter and the summary section, then review

the key terms learned Answer the review questions and verify your answers

with the chapter or lecture slides Complete the case projects 3-1 and 3-3

Documents

Network Cables ITNW 1325, Chapter III, Part II. Coaxial Cable