TUTORIAL 2 - Network Media

Question 1

what is the criteria of choosing network media

Answer 1

1. bandwidth rating
2. max segment length
3. interference & eavesdropping susceptibility
4. cable grade
5. connection hardware

• ease of installation
• testability
• total cost

Question 2

bandwidth rating criteria

Answer 2

num of bits per sec that can be transmitted across medium

factor determining bandwidth is how bit signals represented on medium (called encoding)

when possible choose cabling category that’s compatible with the standard you want to implement now but will support growth & faster speeds

Question 3

max segment length criteria

Answer 3

max cable length between 2 network devices

each cable type can transport data only so far before its signals begin to weaken beyond what can be read by a receiving device (attenuation)

intermediate passive devices (Eg. wall jacks) are part of total segment length

Question 4

interference & eavesdropping susceptibility criteria

Answer 4

comes in form of electromagnetic interference (EMI) & radio frequency interference (RFI)

motors, transformers, fluorescent lights, or other sources of intense electrical activity can emit both EMI & RFI

RFI can also affect wireless networks if frequency in same range

Crosstalk - interference 1 wire generates on another when in bundle

copper wires susceptible to electronic eavesdropping

fiber-optic carry light signals so not susceptible to interference or eavesdropping

Question 5

cable grade criteria

Answer 5

building & fire codes include specific cabling requirements

cables ran between false ceiling

true ceiling (plenum) must be plenum-rated

UTP cabling marked as communication cable riser (CMR) or comm cable plenum (CMP)

CMR can only be used for building risers/cable trays

CMP suitable for use in plenum spaces

Question 6

connection hardware criteria

Answer 6

every type of cable has connectors that influence kinds of hardware cable can connect to

must make sure media selected can support network device

Question 7

the types of cables

Answer 7

coaxial
shielded twisted
unshielded twisted

Question 8

why must the twisted pair cable be twisted

Answer 8

consists of 1 or more pairs of insulated strands of copper wires twisted around 1 another & housed in outer jacket

twists necessary to improve resistance to crosstalk from wires & EMI from outside sources

more twists per unit length, better resistance to EMI & crosstalk

more expensive TP wisted more than less expensive

provides better pathway for higher bandwidth networks

tbh you won’t bother, just make sure its cat is high

Question 9

what is a shielded twisted pair cable made of

Answer 9

includes shielding to reduce crosstalk & interference

has wire braid inside sheath material/foil wrap

best to use in electrically noisy environments/very high-bandwidth apps

Question 10

what are the cable plant components in the twisted pair cables

Answer 10

RJ-45 connectors - STP & UTP uses registered jack 45

most commonly used in patch cables

used to connect computers to hubs, switches & RJ-45 wall jacks

Rj-45 jacks - what you plug an RJ-45 connector into when computer not near a switch/hub

usually placed behind wall plates when cables run inside walls

patch cable

short cable for connecting computer to RJ-45 wall jack or connecting a patch-panel port to switch/hub

can be made with inexpensive tols, 2 RJ-45 plugs & length of TP cable

patch panels

used to terminate long runs of cable from where computers are to wiring closet (where switches & hubs are)

distribution racks

hold network equipment

Eg. routers, switches, patch panels, rack-mounted servers etc.

AKA 19” racks as upright rails are 19” apart

Question 11

Why is there a need for 2 transmit & 2 receive wires?

Answer 11

1 wire pair used for transmit (labeled transmit+/transmit-) and 1 pair for receive (labeled receive+/receive-)

plus & minus symbols indicate that wires carry positive & negative signal

this differential signal mitigates effect of crosstalk & noise on cable

Question 12

fiber optic cables

Answer 12

immune to electrical interference

highly secure

electronic eavesdropping eliminated

composition

slender cylinder glass fiber called core surrounded by concentric layer of glass called cladding

fiber jacketed in thin transparent plastic material called buffer

each fiber-optic strand carries data in only 1 direction

network connections consist of 2 or more strands

fiber-optic cable used as backbone cabling often comes in bundles of 12 or more fiber strands

even only using 2 in backbone, running more is good idea so ready for future expansion

some testing shown that glass fibers can carry several terabits (1000 gigabits) per second

fiber-optic may 1 day replace copper for all types of network connections

Question 13

what are the types of fiber optic connectors

Answer 13

straight tip (ST)

straight connection (SC)

locking connection (LC)

mechanical transfer registered jack (MT-RJ)

fiber channel or ferrule connector (FC)

medium interface connector (MIC)

subminiature type A (SMA)

Question 14

installation of fiber optic cables

Answer 14

more difficult & time consuming than copper media installation

however advances in connector tech closing gap

connectors & test eq required for termination still more expensive than copper

many methods for terminating fiber-optic cables due to many connectors & cable types available

installation details beyond scope of this book

Question 15

what are the types of fiber optic cables

Answer 15

single-mode fiber (SMF)

includes single, small-diameter fiber at core

8 microns

generally works with laser-based emitters

longest dist

used in higher-bandwidth apps

multimode fiber (MMF)

larger diameter fiber at core

50 & 62.5 microns

cheaper than SMF

works with lower-power light emitting diodes (LEDs)

shorter dist

Question 16

what is structured cabling

Answer 16

specifies how cabling should be organized, regardless of media type or network architecture

large networks typically use most/all of these

work area

horizontal wiring

telecommunications closets

equipment rooms

backbone or vertical wiring

entrance facilities

Question 17

what are work areas

Answer 17

where workstations & other user devices located

faceplates & wall jacks installed in work area

patch cable connect computers & printers to wall

Question 18

what is horizontal wiring

Answer 18

runs from work area’s wall jack to telecomm closet

wiring from wall jack to patch panel should be no longer than 90 meters (plus 10m for patch cables)

Question 19

what is a telecommunications closet

Answer 19

TC provides connectivity to computer equipment in nearby work area

typical eq includes

patch panels to terminate horizontal wiring runs

hubs

switches

TC that hosues cabling & devices for work area computers referred as intermediate distribution frame (IDF)

Question 20

what is an equipment room

Answer 20

houses servers, routers, switches & other major network equipment

serves as connection point for backbone cabling

ea room that’s connection point between IDFs called main distribution frame (MDF)

MDF can be main cross-connect for entire network or serve as connecting point for backbone cabling between buildings

ea building has own MDF

Question 21

what is backbone cabling

Answer 21

interconnects IDFs & MDFs

runs between floors/wings of building & between buildings

frequently fiber-optic cable but can also be UTP if dist between TC is < 90m

Question 22

what is an entrance facility

Answer 22

location of cabling & equipment that connects a corporate network to 3rd party telecomm provider

can also serve as eq room & main cross-connect for all backbone cabling

where WAN connection made

demarcation point - point where corporate LAN eq ends & 3rd party provider’s equipment & cabling begins

Question 23

installation of unshielded twisted cables

Answer 23

cable termination - putting RJ-45 plugs on ends of cable/punching down wires into terminal blocks on jack/patch panel

tools needed
o wire cutters
o crimping tool
o cable tester
o punchdown tool
o cable stripper
o RJ-45 plugs/jacks

when making cable/terminating cable at a jack or patch panel

important to get colored wires arranged in correct order

2 standards: 568A & 568B

Question 24

differences between straight through and crossover cable

Answer 24

straight through:
same wiring standard on both ends

crossover:
use 568A standard on 1 side & 568B on other

crosses transmit & receives wires so that transmit on 1 end connects to receive on other

this type of cable often needed when you connect 2 devices of same type to 1 another

for 1000BaseT crossover cable, have to cross blue & brown pins as used in 1000BaseT

Question 25

what are some cable-testing equipment and what are they used for

Answer 25

common tools for testing & troubleshooting wired networks

cable certifier

basic cable tester

tone generator

time domain reflectometer (TDR)

multimeter

optical power meter (OPM)

Question 26

what is wireless networking

Answer 26

often used with wired to interconnect geographically dispersed LANs or groups of mobile users with wired servers & resources on wired LAN

AKA hybrid networks

AP or router usually connects to internet via wired connection to cable modem though clients through wireless

Question 27

what are some wireless networking benefits

Answer 27

create temp connections to wired networks

establishes backup/contingency connectivity for existing wired networks

extends network’s span beyond reach of wire-based or fiber-optic cabling

especially in older buildings where rewiring might be too ex

allows businesses to provide customers with wireless networking easily, offering service that gets customers in & keeps them

enables users to roam around a corporate/college campus with their machines

Question 28

what are the types of wireless networks

Answer 28

local area networks (LAN)

usually provides connectivity for mobile users or across areas that couldn’t otherwise be networked

extended LANs

usually used to increase LAN’s span beyond normal dist limitations

internet service

used to bring internet access to homes & businesses

mobile computing

users communicate by using wireless networking medium that enable them to move while remaining connected

Question 29

what are some wireless LAN components

Answer 29

network interface attaches to antenna & emitter instead of cable

transceiver/access point (AP) - transmitter /receiver device must be installed to translate between wired & wireless networks

includes antenna & transmitter to send & receive wireless traffic but also connects to wired side of network

shuttles traffic back & forth between network’s wired & wireless sides

Question 30

what is wireless LAN transmission

Answer 30

network interface attaches to antenna & emitter instead of cable

transceiver/access point (AP) - transmitter /receiver device must be installed to translate between wired & wireless networks

includes antenna & transmitter to send & receive wireless traffic but also connects to wired side of network

shuttles traffic back & forth between network’s wired & wireless sides

Question 31

what is infrared LAN tech and what kinds are there

Answer 31

use infrared light beams to send signals between devices

works well for LAN apps due to high bandwidth

4 main kinds

line-of-sight networks - require unobstructed view between transmitter & receiver

reflective wireless networks - broadcast signals from optical transceivers near devices to central hub

scatter infrared networks - bounce transmissions offwalls & ceilings to deliver signals

broadband optical telepoint networks - provide broadband services

Question 32

what is a laser-based LAN tech

Answer 32

also need clear line of sight between sender & receiver

subject to many same limitations as infrared

aren’t as susceptible to interference from visible light sources as infrared

Question 33

what is narrowband radio LAN tech

Answer 33

use low-powered, 2 way radio comm

receiver & transmitter must be tuned to same frequency to handle incoming/outgoing data

need no line of sight between sender & receiver as long as both stay within broadcast range

70m or 230 feet

depending on freq, walls or solid barriers can block signals

interference from other radio sources possible

Question 34

what is spread spectrum LAN tech

Answer 34

uses multiple freq simultaneously, improving reliability & reducing susceptibility to interference

also makes eavesdropping more difficult

2 main kinds

freq-hopping - switches data between multiple freq at regular intervals

direct-sequence modulation - breaks data into fixed-size segments called chips

transmits data on several diff freq at once

Question 35

what is the LAN media selection criteria

Answer 35

3 main media choices: UTP, fiber-optic & wireless

bandwidth - higher = more expensive & higher installation costs

if >40gbps, fiber-optic only choice

budget

typical UTP cable installation costs $100 to $200 per cable run

fiber-optic costs twice

wireless has no physical installation costs but need to install access points & verify connectivity

environmental considerations

how electrically noisy?

how important is data security?

more weight factor has, more likely fiber-optic/secured wireless is right choice

span

what dist must network span?
longer spans need fiber-optic or wireless to use between buildings

strategic placement of small switches/hubs give UTP surprising reach

existing cable plant

for upgrade, existing cable plant must be considered