CSNETWK Physical Layer

Network interface cards

NICs: connects a device to a network

Copper cable

The signals are patterns of electrical pulses

Fiber-optic cable

The signals are patterns of light

Wireless

The signals are patterns of microwave transmissions.

Bandwidth

The capacity of a medium to carry data typically measured in kilobits per second (kb/s) or megabits per second (Mb/s)

Throughput

rate (bits/time unit) at which bits are being sent from sender to receiver

Attenuation

In copper cables, the longer the signal travels the more it deteriorates

Crosstalk

disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire

Electromagnetic interference and frequency interference

distorts and corrupts the data signals being carried by copper media

multipath propagation

radio signal reflects off objects ground, built environment, arriving at destination at slightly different times

Signal to noise ratio

SNR: larger SNR – easier to extract signal from noise

control plane

bit error rate

BER: the ratio of incorrectly received bits to the total number of transmitted bits

self learning

this is what switches do to figure out where to send the data to. this is done indpendently without outside help

hidden terminal problem

when two nodes out of each other’s range transmit to a common access point

multipath propagation

this is when echoes happen because of interferences in microwave