Unit 2: Physical Layer Flashcards
(22 cards)
What is the role of the physical layer in the OSI model?
The physical layer is responsible for the actual transmission of raw bits over a physical medium.
It defines the electrical, mechanical, and procedural aspects for activating, maintaining, and deactivating the physical link.
Why is the physical layer important in networking?
It ensures that data in the form of electrical or optical signals is properly transmitted and received, providing a foundation for higher-layer functions.
What are the types of physical transmission media?
They are broadly classified into:
* Guided media (e.g., twisted pair, coaxial cable, optical fiber)
* Unguided media (e.g., radio waves, microwaves, infrared)
What is the difference between guided and unguided transmission media?
Guided media use physical paths like cables for signal transmission, while unguided media transmit signals through the air using wireless technologies.
Why is twisted pair cable commonly used?
Twisted pair cables are inexpensive, easy to install, and sufficient for many networking needs. Twisting reduces electromagnetic interference (EMI).
What is the difference between UTP and STP cables?
UTP (Unshielded Twisted Pair) lacks shielding and is more susceptible to EMI, while STP (Shielded Twisted Pair) has an extra shield to reduce interference.
What is a coaxial cable?
A coaxial cable consists of a central conductor, insulating layer, metallic shield, and outer jacket. It offers better shielding than twisted pair and is used in broadband systems.
Why is optical fiber considered superior for long-distance transmission?
Optical fiber provides high bandwidth, low signal attenuation, and is immune to electromagnetic interference, making it ideal for long-distance communication.
What is the principle of optical fiber communication?
It uses the principle of total internal reflection to transmit light pulses representing data over long distances.
What are the types of optical fibers?
They include:
* Single-mode fiber: for long-distance, high-speed transmission
* Multi-mode fiber: for shorter distances, with multiple light paths
What is an RJ45 connector?
RJ45 is an 8-pin connector commonly used to terminate twisted pair Ethernet cables and connect them to networking devices.
What is bit transmission in the context of the physical layer?
Bit transmission refers to sending individual bits of data as electrical or optical signals across a communication channel.
What is bandwidth in physical media?
Bandwidth is the range of frequencies a transmission medium can carry. Higher bandwidth allows more data to be transmitted per unit time.
What is frequency division multiplexing (FDM)?
FDM divides the bandwidth of a communication channel into multiple frequency bands, each carrying a separate signal simultaneously.
Why is FDM used?
FDM allows multiple signals to be transmitted simultaneously over a single medium without interference, increasing channel utilization.
What is time division multiplexing (TDM)?
TDM divides the time on a communication channel into time slots and allocates each slot to a signal in a round-robin fashion.
What is the difference between FDM and TDM?
FDM uses separate frequencies for each signal simultaneously, while TDM allocates different time slots to each signal sequentially.
What is attenuation in transmission media?
Attenuation is the gradual loss of signal strength over distance. It is a key factor limiting transmission range.
What is noise in physical transmission?
Noise refers to unwanted electrical signals that interfere with the transmitted signal, possibly corrupting the data.
What are repeaters and why are they used?
Repeaters are devices used to regenerate weak signals in a network to extend transmission distance and reduce signal degradation.
What is propagation delay?
Propagation delay is the time it takes for a signal to travel from sender to receiver over a medium. It depends on the distance and signal speed.
Why is synchronization important in bit-level transmission?
Synchronization ensures that the sender and receiver agree on bit timing, preventing misinterpretation of data.
