02 - Cabling and Topology Flashcards
Network Topology
The way that cables and other pieces of hardware connect to one another
Bus Topology
- used a single cable that connected all computers in a line
- data went out on whole bus
- needed termination at each end to prevent signal reflection
- a break removed the termination and causes signal reflection
Ring Topology
- connected all computers on a network with a ring of cable
- data moved in a circle from one computer to the next in the same direction
- no termination needed
- a break will break the circuit, stopping data flow
Star Topology
- all computers connect to a central box
- offered fault tolerance, if there was a break the other computers could still communicate
Physical topology
How the cables physically look
logical topology
how the signals travel electronically (signalling topology)
Hybrid Topology
Any form of networking that combines a physical topology with a signaling topology
Topology used today
Star-Bus
Mesh Topology
wireless network, every computer connects to every other computer via two or more routes
Partially Meshed Topology
at least two machines have redundant connections
Fully Meshed Topology
Every computer connects directly to every other computer
Coaxial Cable
- central conductor (usually copper)
- surrounded by an insulating material
- surrounded by a braided metal shield
- surrounded by a jacket
- center wire and braided metal shield share the same axis
- shields data transmissions from interference
EMI
Electromagnetic Interference
- can shut down a network because it is easily misinterpreted as a signal by devices like NICs
Coaxial connectors
- BNC - bayonet style
- F-type (screw on connector)
RG-59
- coaxial cable primarily used for cable television
- 75 ohms
- f-type connector
RG-6
- used for networking
- 75 ohms
- f-type connector
RG-58
- older cable
- 50 ohms
- BNC connector
Why use twisted pair?
- wire is twisted to prevent crosstalk
- the more twists per foot, the less crosstalk
STP
Shielded Twisted Pair
- shielding protects from EMI
Why use STP over UTP?
use STP in high EMI environments
Cat Ratings
- indicates the highest frequency the cable can handle
- rated in megahertz (MHz)
CAT 3
- 16 MHz
- 16 Mbps
CAT 5
- 100 MHz
- 100 Mbps
CAT 5e
- 100 MHz
- 1 Gbps
- most common today
CAT 6
- 250 MHz
- 10 Gbps
CAT 6a
- 500 MHz
- 10 Gbps
CAT 7
- 600 MHz
- 10+ Gbps
RJ-11
- telephone wires
- 2 pairs UTP
RJ-45
- network wires
- 4 pairs
Fiber-optic benefits
- not effected by EMI
- long-distance transmissions
Fiber-optic Cable
- core - the glass fiber
- cladding - makes the light reflect down the core
- buffer - gives wire strength
- insulating jacket
How are fiber-optic cables meausred?
- core/cladding size
- in micrometers
Duplex Cable
two pairs of fiber-optic wires fused together, one for sending and one for recieving
MMF Cable
Multimode Fiber
- uses LEDs as light source
- 850 nanometer wavelength
SMF Cable
Singlemode Fiber
- uses lasers as light source
- prevents modal distortion
- 1310 or 1550 nanometer wavelength
Modal Distortion
signals sent at the same time don’t arrive at the same time because the path differ slightly in length
Fiber Optic Connectors
- ST - (snap and twist)
- SC - (stick and click)
- LC - duplex (little connector)
- MT-RJ - duplex
DB-9 connector
- serial 9-pin
- 56 kbps
DB-25 connector
- parallel 25-pin
- 2 Mbps
Cable and Fire Ratings
PVC - no protection from smoke and fumes
Riser - for vertical runs, some protection
Plenum - more protection than riser
