Unit 2

Question 1

A hub is a Layer __ device that repeats the frame down every network cable connected to it.

Answer 1

1

Question 2

In the OSI model of computer networking, a ___ is the protocol data unit (PDU) at the Data Link Layer. A ___ is the result of the final layer of encapsulation. Once encapsulated, the data transmits over the Physical Layer (Layer 1).

Answer 2

frame

Question 3

Hubs are ___ ___ devices and are rarely used in today’s
networks.

Answer 3

half-duplex

Question 4

Half-duplex means a port can transmit data or receive data, but it cannot:

Answer 4

do both simultaneously

Question 5

A bridge is a layer __ device that can either be software or hardware based.

Answer 5

2

Question 6

___ are used to create a connection between two separate computer networks, or to divide one network into two.

Answer 6

Bridges

Question 7

While ___ always send every received frame out of every other port, bridges are able to make forwarding and/or filtering decisions.

Answer 7

hubs

Question 8

Bridges are able to make forwarding and/or filtering decisions. To forward traffic means that traffic originating on one port ___ sent out of the other port(s); to filter traffic means traffic originating on one port is ___ sent out of the other port(s).

Answer 8

IS
NOT

Question 9

Bridges are considered to be layer 2 devices because the forward/filter decision is made based on ___ addresses. A bridge learns which ___ addresses are connected to which port. Then, based on the destination ___ address in the frame, the bridge determines whether to forward the frame out of the other port(s) or to filter the frame from the other port(s).

Answer 9

MAC addresses

Question 10

Bridges are ___ ___ devices and are rarely used in today’s networks.

Answer 10

half-duplex

Question 11

A ___ is a much more intelligent version of a bridge.

Answer 11

switch

Question 12

Like a hub and a bridge, a switch physically connects devices together on a LAN. While bridges only had two or four ports, switches can have ___ of ports.

Answer 12

100s

Question 13

Switches are classified as layer ___ devices because they also make
forwarding/filtering decisions based on MAC addresses.

Answer 13

2

Question 14

Bridges are layer 2 devices because they also make forwarding/filtering decisions based on MAC addresses. However, switches have many benefits
over bridges, such as the ability to create ___ ___ and support full-duplex data transfer.

Answer 14

Virtual LANs (VLANs)

Question 15

___ ___ means the port can transmit and receive data at the same time. For these reasons, switches are used extensively in today’s networks.

Answer 15

Full Duplex

Question 16

A ___ connects different networks/LANs together. ___ are responsible for routing functions and logical addressing (IP addressing).

Answer 16

router

Question 17

A router makes its forwarding (routing) decision based on
IP addresses, so it is classified as a layer __ device.

Answer 17

3

Question 18

____ is the standard for bridging and management.

Answer 18

IEEE 802.1

Question 19

____ handles the architecture, security, management, and internetworking of local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs). It also designs and implements standards that regulate network management practices.

Answer 19

IEEE 802.1

Question 20

____ is the standard for Carrier Sense Multiple Access/Collision Detection (CSMA/CD).

Answer 20

IEEE 802.3

Question 21

____ is also the standard for defining Ethernet specifications. This standard specifies the physical media and working characteristics of Ethernet.

Answer 21

IEEE 802.3

Question 22

It defines a physical layer and a data link layer for media access control for a wired Ethernet connection.

Answer 22

IEEE 802.3

Question 23

___ ___ ___ ___ ___ ___ is a set of rules determining how network devices access network media. ___ also defines how devices should respond when two devices attempt to use a data channel simultaneously.

Answer 23

Carrier Sense Multiple Access/Collision Detection (CSMA/CD)

Question 24

___ ___ is an ongoing activity of a data station to detect whether another station is transmitting. Each machine on the network examines the cable before sending a data frame. If another machine is using the network, the node detects traffic and waits until the cable is free. If the node detects no traffic, the node sends its data frame.

Answer 24

Carrier Sense

Question 25

___ ___ occurs when all machines have equal access to the wire. If the line is free, an Ethernet node does not have to get approval to use the wire.

Answer 25

Multiple Access

Question 26

___ ___ comes into play once a collision has occurred.

Answer 26

Collision Detection

Question 27

A ____ is when two or more devices attempt to access the same media at the same time.

Answer 27

collision

Question 28

When this occurs, the data collides and becomes corrupted. When the collision is detected, both devices back off and wait a random amount of time before retrying. The idea is that the stations involved in the collision will wait different amounts of time before attempting to retransmit. This is an attempt avoid further collision. If another collision does occur, the random wait time intervals increase systematically. This is known as an ___ ___, further decreasing the probability of the two stations colliding again.

Answer 28

exponential backoff

Question 29

___ provides organizations and individuals the ability to remove media associated with connecting devices together, which can limit distance or devices.

Answer 29

WLAN

Question 30

However, WLAN or ____ allows versatility and the ability to connect to a network wirelessly through the walls, across the building, and with your neighbor.

Answer 30

Wi-Fi

Question 31

IEEE ___ standards are the standard most modern WLANs are based on.

Answer 31

802.11

Question 32

___ ___ ___ ___ is a wireless computer network that links two or more devices using a wireless distribution method within a limited area such as a home, school, computer laboratory, or office building.

Answer 32

Wireless Local Area Network (WLAN)

Question 33

As previously discussed in this book, wireless communication is one of the four types of ____ used for networking.

Answer 33

media

Question 34

___ is a network contention protocol that listens to a network in order to avoid collisions, unlike ____ which deals with network transmissions once a collision has been detected.

Answer 34

CSMA/CA
CSMA/CD

Question 35

CSMA/CA contributes to network traffic because, before any real data transmits, it has to ___ ___ ___ onto the network in order to listen for collision scenarios and to tell other devices not to broadcast.

Answer 35

broadcast a signal

Question 36

CSMA/CA used in WLANs same way CSMA/CD is used in wired Ethernet networks. Using a control message, CSMA/CA does not detect collisions but rather ___ ___.

Answer 36

avoids them

Question 37

____ is impractical for WLANs because of its nature of listening to determine if it can transmit packages. In addition, if a collision is detected, the end devices would have to wait a random amount of time before they can start retransmission.

Answer 37

CSMA/CD

Question 38

IEEE ____ is a set of specifications for implementing WLANs.

Answer 38

802.11

Question 39

IEEE 802.11 is the standard for…?

Answer 39

CSMA/CA

Question 40

This was the first standard developed for Wi-Fi. The ____ standard has a maximum raw data rate of 11Mbit/s and uses the same media access method defined in the original standard. ___ is a direct extension of the 1997 standard and appeared on the market in early 2000.

Answer 40

802.11b

Question 41

The ____ standard uses the same data link layer protocol and frame format as the original standard. It operates in the 5GHz band with a maximum net data rate of 54Mbit/s. In theory, ____ signals are absorbed more readily by walls and other solid objects in their path due to their smaller wavelength, and, as a result, cannot penetrate as far as those of 802.11b.

Answer 41

802.11a

Question 42

IEEE created a third modulation standard (____) in June 2003. This works in the 2.4GHz frequency band and uses the same transmission scheme as 802.11b. It operates at a maximum
physical layer bit rate of 54Mbit/s. ____ hardware is fully backward compatible with 802.11b hardware.

Answer 42

802.11g

Question 43

____ is an amendment that improves upon the previous 802.11 standards by adding multiple-input multiple-output antennas (MIMO). ____ operates on both the 2.4 GHz and the lesser-
used 5 GHz bands.

Answer 43

802.11n

Question 44

IEEE ____-2013 is an amendment to IEEE 802.11. It was published in December 2013, and it builds on 802.11n. Changes compared to 802.11n include wider channels (80 MHz or 160 MHz versus 40 MHz) in the 5 GHz band, more spatial streams (up to eight versus four), higher-order modulation (up to 256-QAM vs. 64-QAM), and the addition of Multi-user MIMO (MU-MIMO).

Answer 44

802.11ac

Question 45

In a nutshell, ____ is a hyped- up version of 802.11n (the current Wi-Fi standard your laptop and smartphone probably uses), offering link speeds ranging from 430 Mbps all the way through several Gbps.

Answer 45

802.11ac

Question 46

Bluetooth is a wireless networking protocol for short-range networks, used mostly for devices such as wireless keyboards, mice, and cell phones. Bluetooth devices operate in the 2.4-2.85 GHz
range.

Answer 46

IEEE 802.15.1 (Bluetooth)

Question 47

What are the two advantages of wireless networks?

Answer 47

Cost - One advantage of wireless networks is cost. It is very cost-effective to use wireless communications rather than running physical cables.

Mobility - Another advantage of wireless networks is mobility. Since you are not running physical cables, you are not constrained by the limitations of the cables and the logistics of cable placement.

Question 48

What are the disadvantages of wireless network?

Answer 48

Speed
Reliability
Security
Reduced Management Control