Chapter 4 Flashcards
What is the bandwidth rating
This is the number of bits per second that can be transmitted across a medium.
What is Encoding
The method used to represent bits on a medium.
different network standards use different patterns of electrical or light pulses to represent a series of bits on the medium
What is attenuation
This is the process of signal weakening to the point that the receiving device can no longer accurately read the information
What is a cable segment
This is the length of cable between any two network devices (such as a NIC and a switch). Passive (unpowered) devices such as a wall jack are considered a part of the total cable segment length.
What is electromagnetic interference (EMI)
a disturbance to the operation of an electronic cirucuit or its data, caused by devices that emit an electromagnetic field.
What is Radio Frequency Interference (RFI)
Similar to EMI, but RFI is usually interference caused by strong broadcast sources (such as a nearby tv or radio station)
What is crosstalk
This is interference one wire generates on another wire when both wires are in a bundle.
Which media is susceptible to electronic eavesdropping
Copper wire.
Fiber optic carries light instead of electricity and is therfore not susceptible to this kind of eavesdropping.
Cable grade is an inportant factor when deploying network media.
Cables ran between a false ceiling and the true celing must be ___ rated
UTP cabling is marked as one of two types, what are they?
Only one of the two types can only be used in building risers or in cable trays, which is it?
plenum
Communication Cable Rise (CMR), or Communication Cable Plenum (CMP)
CMR Communication Cable Riser
Give a brief background of Coaxial Cable
once the predominant form of network cabling
Inexpensive and easy to instal
started to phase out in the early 1990’s
Still used primarily in connecting a cable modem to the wall outlet your cable tv/internet provider installs
What are the two types of Twisted-Pair cables
What is the reason for the twists
The types are unshielded and shielded
The twists are necessary to improve resistance to corsstalk from wires and EMI from outside sources
What type of cabling do most networks use
How many wires does it consist of
Unshielded twisted pair
4 pairs of insulted wires
What is the purpose of the shielding in shileded twisted-pair cable?
to reduce cross-talk and interference
What are RJ - 45 connectors
STP and UTP use registered jack 45 (RJ-45)
Most commonly used in patch cables, which are used to connect computers to hubs, switches, and RJ-45 wall jacks
What is patch cable
short cable for connecting a computer to an RJ-45 wall jack or connecting a patch-panel port to a switch or hub
Can be made with inexpensive tools, two RJ-45 plugs and a length of TP cable
What are patch panels
Used to terminate long runs of cable from where the computers are to the wiring closet (where the switches and hubs are)
What are distribution racks
hold network equipment such as routers and switches, plus patch panels and rack mounted servers
Also called 19” racks because the upright rails are 19” apart
What is structured cabling
specifies how cabling should be organized, regardless of the media type or network architecture
Define work area
where workstations and other user devices are located
faceplates and wall jacks are installed in the work area
What is horizontal wiring
This runs from the work area’s wall jack to the telecommunication closet
Wiring from the wall jack to the patch panel should be no longer than 90 meters
What is a telecommunications closet
TC provides connectivity to computer equipment in the nearby work area
Typical equipment includes patch panels to terminate horizontal wiring runs, hubs and switches
A TC that houses the cabling and devices for work area computers is referred to as an intermediate distribution frame (IDF)
What is an equipment room
this houses servers, routers, switches, and other major network equipment and serves as a connection point for backbone cabling
What is a main distribution frame?
This is the name for an equipment room that’s the connection point betweein Intermediate Distribution Frames
What is an intermediate distribution frame (IDF)
This is a Telecommunications Closet that houses cabling and devices for work area computers
What is the main cross-connect for the entire network or it might serve as the connecting point for backbone cabling between buildings
The main distribution frame
Each building has it’s own
What does backbone cabling interconnect
IDFs and MDFs
it runs between floors or wings of a building and between buildings
frequently fiber-optic cable but can also be UTP if the distance between TCs is less than 90 meters
What is an entrance facillity
This is the location of the cabling and equipment that connects a corporate network to a third-party telecommunications provider
This can also serve as an equipment room and the main cross-connect for all backbone cabling
Where a connection to a WAN is made
What is the Demarcation point
point where corporate LAN equipment ends and a third-party provider’s equipment and cabling begins
What are the two kinds of patch cables and what is the difference between then
Straight through cables which have the same wiring standards on both ends
Crossover cables have a 568A standard on one end and a 568B standard on the other end
What are medium dependent interface (MDI) devices or MDI crossed (MDI-X) devices
- MDI devices transmit on pins 1 and 2 and receive on pins 3 and 6
- PC NICs and routers are examples
- MDI - X devices receive on pins 1 and 2 and transmit on pins 3 and 6
- Hubs and switches are examples
Why two transmit and two receive wires?
One pair is for receive and one pair is for transmit. They are positive and negative to mitigate interference (crosstalk and noise)
What is the composition of a fiber-optic cable
slender cylinder of glass fiber called the core surrounded by a concentric layer of glass called the cladding
fiber is then jacketed in a thin transparent plastic material called the buffer
What is a single-mode fiber (SMF)
Incldues a single, small-diameter fiber at the core (8microns)
Generally works with laser-based emitters
Spans the longest distances
Used in higher-bandwidth applications
What is Multimode fiber (MMF)
Larger diameter fiber at the core (50 and 62.5 microns)
Costs less than SMF
Works with lower-power light emitting diodes (LEDs)
Spans shorter distances
describe a Transceiver/access point (AP)
a transmitter/receiver device that must be installed to translate between wired and wireless networks
includes an antenna and a transmitter to send and receive wireless traffic but also connects to the wired side of the network
shuttles traffic back and forth between a network’s wired and wireless sides
What form do signals take in Wireless LAN transmission
waves in the Electromagnetic (EM) spectrum
The frequency of the wave forms used for communication is measured in cycles per second, usually expressed as hertz (Hz)
Lower-frequency transmissions can carry less data more slowly over longer disntaces, and higher-frequency transmissions can carry more data faster over shorter distances
What are the most common frequencies for wireless data communication
Radio - 10 KHz to 300 MHz
Microwave - 300 MHz to 300 GHz
Infared - 300 GHz to 400 THz (terahertz)
What are the four primary technologies that wireless LANs make use of for transmitting and receiving data?
Infrared
Laser
Narrowband (single-frequency) radio
Spread-spectrum radio
What are infrared (IR) signals
- These are infrared light beems to send signals between pairs of devices
- Works well for LAN applications due to high bandwidth
- Four main kinds of infrared LANs
- Line-of-sight networks - require an unobstrcuted view between transmitter and receiver
- Reflective wireless networks - broadcast signals from optical transceivers near devices to a central hub
- Scatter infrared networks - bounch tranmsissions off walls and ceilings to deliver signals
- Broadband optical telepoint networks - provide broadband services
How do narrowband radio LAN technologies work?
use low-powered, two-way radio communication
receiver and transmitter must be tuned to the same frequency
No line of sight, just a mximum range (around 70m or 230ft)
Walls or other solid objects can block signals
interference from other radio sources is possible
How does Spread-Spectrum LAN technology work
uses multiple frequencies simultaneously, improving reliability and reducing susceptibility to interferecnce (also makes eavesdropping more difficult)
Two main kinds of spread-spectrum communications
Frequency hopping - switches data between multiple frequencies at regular intervals
Direct-sequence modulation - breaks data into fixed-size segments called chips and transmits the data on several different frequencies at the same time
