CCNA > M1.6 Data Link Layer > Flashcards

M1.6 Data Link Layer Flashcards

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1
Q

What layer prepares network data for the physical network

A

The Data Link layer.

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2
Q

What is the primary responsibility of the Data Link layer

A

It handles network interface card to network interface card communications.

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3
Q

How does the Data Link layer help upper layers

A

It enables upper layers to access the media.

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4
Q

What does the Data Link layer encapsulate Layer 3 packets into

A

It encapsulates them into Layer 2 frames.

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5
Q

What does the Data Link layer do with frames

A

It exchanges frames between endpoints over the network media.

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6
Q

What is the Data Link layer’s function for error handling

A

It performs error detection and rejects any corrupt frame.

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7
Q

What are the two sublayers of the IEEE 802 LAN/MAN data link layer

A

Logical Link Control LLC and Media Access Control MAC.

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8
Q

Which Data Link sublayer is defined by the IEEE 802.2 standard

A

The Logical Link Control LLC sublayer.

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9
Q

What does the LLC sublayer communicate between

A

It communicates between upper-layer software and lower-layer hardware.

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10
Q

What information does the LLC sublayer place in a frame

A

It identifies which network layer protocol is being used for the frame.

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11
Q

Which Data Link sublayer is responsible for data encapsulation

A

The Media Access Control MAC sublayer.

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12
Q

Which Data Link sublayer provides addressing for the Layer 2 frame

A

The Media Access Control MAC sublayer.

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13
Q

What MAC sublayer function provides synchronization between nodes

A

Frame delimiting.

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14
Q

What MAC sublayer function includes a trailer to detect transmission errors

A

Error detection.

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15
Q

What is the first Layer 2 function a router performs at each hop

A

It accepts a frame from a medium.

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16
Q

What is the second Layer 2 function a router performs at each hop

A

It de-encapsulates the frame.

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17
Q

What is the third Layer 2 function a router performs at each hop

A

It re-encapsulates the packet into a new frame.

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18
Q

What is the fourth Layer 2 function a router performs at each hop

A

It forwards the new frame to the medium of the next segment.

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19
Q

Name the 4 engineering organization that define network access layer standards

A
  • IEEE
  • ITU
  • ISO
  • ANSI
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20
Q

What does a physical topology identify

A

It identifies physical connections and how devices are interconnected.

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21
Q

What does a logical topology refer to

A

It refers to the way a network transfers frames from one node to the next.

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22
Q

Which layer sees the logical topology of a network

A

The Data Link layer sees the logical topology.

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23
Q

What is the simplest and most common physical WAN topology

A

Point-to-Point.

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24
Q

What WAN topology uses a central site to interconnect branch sites

A

Hub and Spoke.

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25
What WAN topology provides high availability by interconnecting every end system
Mesh.
26
What is a variation or combination of any network topologies called
A hybrid topology.
27
How many nodes are directly connected in a physical point-to-point topology
Two nodes.
28
Are logical data link protocols simple or complex in a point-to-point topology
They can be very simple.
29
Does adding intermediary physical devices always change the logical topology
No the logical point-to-point connection can remain the same.
30
What modern LAN topology connects end devices to a central intermediary device
A Star topology.
31
What topology extends a star topology by interconnecting multiple switches
An Extended Star topology.
32
What legacy LAN topology chained all end systems to each other
A Bus topology.
33
What legacy LAN topology connected end systems to their respective neighbors
A Ring topology.
34
What is communication where both devices can transmit and receive but not simultaneously
Half-duplex communication.
35
What is communication where both devices can transmit and receive simultaneously
Full-duplex communication.
36
What is it called when two interconnected interfaces have different duplex modes
A duplex mismatch.
37
What is the default operational mode for Ethernet switches
Full-duplex mode.
38
What access control method involves nodes competing for use of the medium
Contention-based access.
39
What contention-based method is used on legacy bus-topology Ethernet LANs
Carrier sense multiple access with collision detection CSMA/CD.
40
What access control method gives each node its own time to use the medium
Controlled access.
41
What are examples of a controlled access method
Legacy Token Ring. Legacy ARCNET
42
What is the first step in the CSMA/CD process
A NIC checks if the medium has a carrier signal.
43
What happens in CSMA/CD if two devices transmit at the same time
A collision occurs.
44
Why do modern full-duplex Ethernet LANs not require an access method
Because devices can send and receive simultaneously without collisions.
45
What is an Ethernet hub also known as
A multiport repeater.
46
What does an Ethernet hub do with bits received on a port
It regenerates and sends them out all other ports.
47
How does a destination NIC handle a frame addressed to it
It accepts and copies in the entire frame.
48
How do other NICs handle a frame not addressed to them
They ignore the frame.
49
Which IEEE 802.11 protocol uses CSMA/CA
Wireless LANs use CSMA/CA.
50
How does CSMA/CA attempt to avoid collisions
By waiting before transmitting.
51
What information does a device transmitting via CSMA/CA include in its frame
The time duration needed for the transmission.
52
What do other wireless devices do with the transmission duration information
They know how long the medium will be unavailable.
53
What does a receiver return after a wireless device sends an 802.11 frame
An acknowledgment.
54
Do contention-based systems scale well under heavy media use
No they do not scale well.
55
What are the three basic parts of a data link frame
Header Data and Trailer.
56
What part of the Ethernet frame contains the encapsulated Layer 3 packet
The Data part.
57
Which layer is unique for appending a trailer to its encapsulation
The Data Link layer.
58
What generic frame field identifies the beginning and end of a frame
Frame start and stop indicator flags.
59
What generic frame field indicates the source and destination nodes
The Addressing field.
60
What generic frame field identifies the Layer 3 protocol in the data field
The Type field.
61
What generic Data Link frame field identifies special flow control services like QoS
The Control field.
62
What generic frame field contains the frame payload
The Data field.
63
What trailer field is used to determine if the frame arrived without error
The Error Detection field.
64
What is the purpose of the Frame Check Sequence FCS field
To determine if the frame experienced transmission errors.
65
What does CRC stand for
Cyclic Redundancy Check.
66
What are device addresses at the Data Link layer called
Physical addresses.
67
Is a Layer 2 physical address hierarchical or flat
A Layer 2 address is flat.
68
Is a Layer 3 logical address hierarchical or flat
A Layer 3 address is hierarchical.
69
Where are Layer 2 addresses used
They are only used to connect devices on the same shared media.
70
On the first network segment from host to R1 what is the source Layer 2 address
The source host's Layer 2 address.
71
On the first network segment from host to R1 what is the destination Layer 2 address
The Layer 2 address of router R1.
72
On the segment from router R1 to router R2 what is the source Layer 2 address
The Layer 2 address of router R1.
73
On the segment from router R1 to router R2 what is the destination Layer 2 address
The Layer 2 address of router R2.
74
On the final segment from router R2 to the server what is the source Layer 2 address
The Layer 2 address of router R2.
75
On the final segment from router R2 to the server what is the destination Layer 2 address
The destination server's Layer 2 address.
76
Which Layer 2 protocol is commonly used by wired LANs
Ethernet.
77
Which Layer 2 protocol is specified by the IEEE 802.11 standard
Wireless.
78
Name a traditional WAN protocol used for point-to-point topologies
Point-to-Point Protocol PPP.
79
What modern protocol is replacing traditional Layer 2 WAN protocols like HDLC and PPP
Ethernet.
80
What is a node in computer networks ?
a device that can receive, create, store, or forward data along a communications path. A node can be either an end device such as a laptop or mobile phone, or an intermediary device such as an Ethernet switch
81
What is the function of the Logical Link Control (LLC) sublayer ?
- Communicates between upper-layer networking software and lower-layer device hardware - Identifying the network protocol used
82
What are the two primary responsabilities of MAC sublayer ?
- Data encapsulation - Media Access Control
83
Which data link sublayer is typically implemented in hardware and is responsible for data link layer addressing ?
MAC sublayer
84
Which LAN topology often uses coax cables ?
Bus topology
85
Ethernet switches operate in ____ mode by default
Full-duplex
86
What is a multiaccess network ?
A network that can have two or more end devices attempting to access the network simultaneously
87
What are the two basic access control methods for shared media ?
1.Contention based access 1.2 Collision detection 1.3 Collision Avoidance 2.Controlled access
88
In ___ networks, all nodes operate in half-duplex and compete for the use of the medium
Contention -based
89
What is the contention-based access method used on legacy bus-topology Ethernet LANs?
Carrier sense multiple access with collision detection (CSMA/CD)
90
What is the contention-based access methods used on Wireless LANs (WLANS) ?
Carrier sense multiple access with collision avoidance (CSMA/CA)
91
In the CSMA/CD process, how does a NIC detect a collision ?
By comparing the data it transmitted with the data it received, or by recognizing and abnormally high signal amplitude
92
Name the order of the frame fields of the Data Link Layer
- Frame start - Addressing - Type - Control - Data - Error detection - Frame stop
93
List the ayer 2 and Layer 3 address fields in the correct order
Destination NIC Source NIC Source IP Destination IP
94
Name the organizations that define the open standard protocols that apply to the network access layer
- IEEE - ITU - ISO - ANSI
95
What is contained in the header of Data Link ?
Frame start Addressing Type Control
96
What is contained in the Data ?
Data
97
What is contained in the trailer of Data Link ?
Error detection Frame Stop
98
Which access control method is deterministic ?
Controlled access
99
What type of communication rule would best describe CSMA/CD ?
Access method
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