Net. 1: Ch 4 Physical Flashcards
Home Integrated Service Routers
ISR - Another name for consumer routers that combine switch/router/firewall/and wireless access point (WAP)
3 Physical Media Forms
Copper
Fiber Optic
Wireless / Radio
Physical Encoding Method
converting stream of bits into predefined code
2 Physical Encoding Methods
Manchester Encoding
Non Return-to-Zero
Manchester Encoding
0 is represented by a high to low voltage change, 1 is represented by a low to high voltage change.
Used in older Ethernet/RFID/ Near Field Devices
Non Return-to-Zero Encoding
encoding that uses states “zero” and “one”, which has no neutral or rest position: 0’s and 1’s can be identified/assigned by different voltage levels.
signaling method
method of representing bits on a media
asynchronous method
signals are transmitted without associate clock signals; require start/stop flags.
synchronous method
signal sent along with clock signal which occurs at evenly spaced intervals (called bit time).
modulation
method of transmitting data by modifying wave characteristics
Frequency Modulation
FM: carrier frequency varies in accordance with signal.
Amplitude Modulation
AM: amplitude of carrier frequency varies in accordance with signal.
Pulse Coded Modulation
PCM: analog signal converted to digital signal by sampling signal’s amplitutde and expressing the different amplitudes as a binary #.
bandwidth
capacity of a medium to carry data: measured in bits per second
Bit Amount Prefixes
Kilo-10^3: Thousands Mega-10^6: Millions Giga: 10^9: Billions Tera: 10^12 Trillions Peta: 10^15 Quaddrillions Exa: 10^18: Quintillion Zetta: 10^21: Sextillion Yotta: 10^24: Septillion.
Factors Affecting Bandwidth
- Properties of physical media.
2. Technologies chosen for signaling methods and detecting network signals.
throughput
measure of the transfer of bits across a media over a given period of time.
latency
amount of time for data to travel from one point to another.
Factors Affecting Throughput
- Amount of Traffic
- Type of Traffic.
- Latency created by number of network devices between source and destination.
goodput
measure of usable data transferred over a given period of time.
signal attenuation
degradation of a signal over distance.
2 Interference Types
- ElectroMagnetic Interference (EMI)
2. Crosstalk
crosstalk
disturbance created by electric/magnetic fields from one wire, interacting on another wire.
Ways to Limit Interference
- Select cable type most suited to environment.
- Design cable infrastructure to avoid sources of interference.
- Use proper cabling / handling techniques.
