Final Exam

Question 1

What is meant by edge computing?

Answer 1

Edge computing is a distributed computing paradigm which brings computer data storage closer to the location where it is needed. Computation is largely or completely performed on distributed device nodes. Edge computing pushes applications, data and computing power (services) away from centralized points to locations closer to the user.

Question 2

Why is edge computing important for the Internet of Things?

Answer 2

Data generated by IoT devices is processed by the cloud; however, physical distance between these devices and the cloud can cause latency. Edge computing allows some application processing to be performed by a small edge server positioned between to the cloud and the user. Usually located closer to the user. Removes some of the work load from the cloud and the users device causing a low latency communication.

Question 3

What are some challenges with edge computing?

Answer 3

• Finding optimal locations and how to power the servers required
• Security (both cyber and physical)
• How to provide maintenance to the servers

Question 4

What year was Bluetooth version 1 released?

Answer 4

1999

Question 5

What is the name of the organization that founded Bluetooth, currently owns the Bluetooth Trademark, controls Bluetooth research and development, and licenses marketing?

Answer 5

Bluetooth Special Interest Group (SIG)

Question 6

What ways can you avoid interference with Wi-Fi

Answer 6

• Time Division Multiplexing (TDM)

- use 5Ghz Wi-Fi

Question 7

Which frequency-shift keying filter algorithm does Bluetooth use.

Answer 7

• Gaussian filter

- Differential filter

Question 8

Internet Protocol Stack

Answer 8

Application, Transport, Network, Link , Physical

Question 9

Why do you think that spectrum sharing between Wi-Fi and DSRC on the 5.9 GHz band would be a bad thing?

Answer 9

Disruption of communication. Latency due to increased network traffic on the same band. Decreased reliability due to packet loss and miscommunication.

Question 10

What are some security concerns with 5G?

Answer 10

• A much larger network, meaning a larger field of potential threats
• Creation of new services that will cause a need for new security solutions.
• The threat of automotive cyber attacks will rise as autonomous vehicles become more widespread.

Question 11

What is ARQ?

Answer 11

Automatic repeat request (ARQ) is a protocol for error control in data transmission. When the receiver detects an error in a packet, it automatically requests the transmitter to resend the packet. This process is repeated until the packet is error free or the error continues beyond a predetermined number of transmissions.

Question 12

Protocol examples for transport layer?

Answer 12

TCP/UDP

Question 13

Protocol examples for application layer?

Answer 13

DNS, HTTP, SMTP, FTP

Question 14

The application layer is responsible for?

Answer 14

supporting network applications

Question 15

What is the transport layer responsible for?

Answer 15

routing of datagrams from source to destination

Question 16

Example protocol for the network layer:?

Answer 16

IP

Question 17

What is the link layer responsible for?

Answer 17

Data transfer between neighboring network elements

ethernet, Wi-Fi 802.11

Question 18

What is the physical layer?

Answer 18

Actual ‘bits on the wire’

Question 19

What layers are in the OSI reference model?

Answer 19

Application, Presentation, Session, Transport, Network, Link , and Physical.

Question 20

What is the stop and wait protocol for the transport layer and how does it work?

Answer 20

It ensures that information is not lost due to dropped packets and that packets are received in the correct order. It is the simplest automatic repeat-request (ARQ) mechanism. A stop-and-wait ARQ sender sends one frame at a time; it is a special case of the general sliding window protocol with transmit and receive window sizes equal to one and greater than one respectively. After sending each frame, the sender doesn’t send any further frames until it receives an acknowledgement (ACK) signal. After receiving a valid frame, the receiver sends an ACK. If the ACK does not reach the sender before a certain time, known as the timeout, the sender sends the same frame again. The timeout countdown is reset after each frame transmission.

Question 21

What is the Go-Back-N protocol for the transport layer and how does it work?

Answer 21

• It is an example of a pipelined protocol.
• The sender can have up to N unacked packets in pipeline
• receiver only sends cumulative ack
• sender has timer for oldest unacked packet
• when timer expires, retransmit all unacked packets

Question 22

How does selective repeat work for the transport layer and how does it work?

Answer 22

• It is an example of a pipelined protocol
• receiver individually acknowledges all correctly received pkts
• sender only resends pkts for which ACK not received

Question 23

What is the RTS/CTS protocol?

Answer 23

(Request to Send / Clear to Send) is the optional mechanism used by the 802.11 wireless networking protocol to reduce frame collisions introduced by the hidden node problem.

Question 24

What are some challenges of using Radio Frequency under water rather than using Sound?

Answer 24

• Propagate at long distances through conductive sea water only at extra low frequencies (30-300Hz)
• large antennae and high transmission power
• Hidden terminal problem

Question 25

What are some applications for using Underwater Acoustic Sensor Networks? (UWASN)

Answer 25

• Ocean Sampling Networks
• Pollution Monitoring and other environmental monitoring (chemical, biological)
• Disaster Prevention
• Monitoring of ocean currents and winds
• Detecting climate change
• Assisted Navigation
• Mine Reconnaissance

Question 26

What is contained in the Ethernet header?

Answer 26

Preamble, Start of frame, Source address, destination address, length/type

Question 27

What is contained in the 802.11 header?

Answer 27

frame control, duration, source add, destination add, router add, seq control.