Annex C12 Physical Layer Flashcards
Physical Layer
The purpose of this layer is to encode the binary digits that represent data link layer frames into signals and to transmit and receive these signals across the physical media, whether it is copper wires, optical fiber, or wireless, that connect network devices
Where in the OSI model does troubleshooting begin?
Physical layer
Bandwidth
Theoretical capacity of media to transmit data. Measured in Kbps or Mbps. Actual data rate over a given media is never as much as the max capacity
Throughput
The amount of data that is actually transmitted over the media. Throughput will always be less than the advertised bandwidth
Goodput
Goodput is a term used to describe the amount of useable data left after all of the protocol overhead traffic from the OSI layers have been removed.
Goodput = Throughput - Overhead
Straight Through Cable
Terminated with both sides using the same pin out.
This cable is used to connect unlike devices together. Unlike devices are devices that operate at different levels of the OSI model
Crossover Cable
Cable terminated with one end using the 586A standard and the other end using the 586B standard. A crossover cable is used to connect like devices together
Rollover Cable
Cisco proprietary pinout that is used to console into a router or a switch IOT configure it
Single Mode Fiber Optic Cabling
Cable used for long haul, high bandwidth data networks. Can have segments as long as 80 km. Normally, plan for up to 3 Km. Another advantage is that there is no danger of cross talk of EI because the signal is transmitted as pulses of light. Uses lasers on either side of the fiber to push pulses of light
Multimode Fiber Optic Cabling
Much shorter range that SMF because it relies upon diodes (LEDS) to transmit pulses of light. It can carry the same amount of bandwidth that SMF can, just not as far
Wireless Access Point
Device that terminates wireless signals from users and connects them to an existing copper or fiber infrastructure.
Wireless Network Interface Card (NIC) Adapter
Provides wireless connectivity to each host allowing them to connect o WAPs
Purpose of different signaling modes
Non Return to Zero (NRZ): Voltage level on the medium during a bit time represents either a 1 or 0. A higher voltage is 1, and a low voltage is 0. This scheme is very susceptible to residual charges. Sufficient only for short distance signaling such as within computers
Manchester Encoding: Signaling method that looks for a change in a voltage in the middle of a bit time. The mmid cell transition makes this scheme self clocking which makes it less susceptible to attenuation.
Code Groups: special method of encoding data. Code groups become more important at high data speeds, where networks become more error prone. A code group is a symbol that is predefined small group of bits that represent a larger group of data bits.
Purpose of bit time
Time it takes for a NIC at OSI layer 2 to generate one bit of data and send it out to the media as a signal
