Introduction to Networking > 8. Data Link Layer > Flashcards

8. Data Link Layer Flashcards

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1
Q

What is data link layer responsible of?

A
  1. Communications between end-device network interface cards
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2
Q

What does Data Link Layer allows to access? ( 2 )

A
  1. Allows upper layer protocols to access the physical layer media and encapsulates Layer 3 packets ( Network Layer ) into Layer 2 frames
  2. Performs error detection and rejects corrupts frames
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3
Q

List out the 2 sublayers of Data Link Layer

A
  1. Logical Link Control ( LLC )
  2. Media Access Control ( MAC )
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4
Q

What stardards are specific to Ethernet, WLAN, WPAN ( Bluetooth )

A
  1. IEEE 802 LAN/MAN
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5
Q

What is Logical Link Control ( LLC ) responsible of?

A
  1. Communicates between the networking software at the upper layers and the device hardware at the lower layers
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6
Q

What is Media Access Control ( MAC ) responsible of?

A
  1. For data encapsulation and media access control
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7
Q

What basic layer 2 functions does router performs? ( 4 )

A
  1. Accepts a frame from the network medium
  2. De-encapsulates the frame to expose the encapsulated packet
  3. Re-encapsulates the packet into a new frame
  4. Forwards the new frame on the medium of the next network segment
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8
Q

What will packet experience when exchanging between nodes ?

A
  1. Numerous data link layers and media transitions
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9
Q

List out the 4 organizations for engineering organizations that define data link layer protocol

A
  1. Institute for Enlectrical and Electronic Engineers ( IEEE )
  2. International Telecommuncations Union ( ITU )
  3. International Organizations for Standardization ( ISO )
  4. American National Standards Institute ( ANSI )
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10
Q

What is a topology ?

A
  1. The arrangement and relationship of the network devices and the interconnections between them
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11
Q

List out the 2 types of topologies when describing networks

A
  1. Physical Topology
    • Shows physical connections and how devices are interconnected
  2. Logical Topology
    • Identifies the virtual connections between devices using device interfaces and IP addressing schemas
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12
Q

List out the 3 common physical WAN topologies

A
  1. Point-to-point
  2. Hub and Spoke
  3. Mesh
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13
Q

What is the simplest most common WAN topology?

A
  1. Point-to-point
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14
Q

What WAN topology consists permanet link between 2 endpoints

A
  1. Point-to-point
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15
Q

What WAN topology is similar to a star topology where a central site interconnects branch sites through point-to-point links

A
  1. Hub and spoke
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16
Q

What WAN topology provides high availability but requires every end system to be connected to every other end system?

A
  1. Mesh
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17
Q

How does point-to-point topology connects?

A
  1. Directy connect 2 nodes
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18
Q

Can the nodes share the media with other hosts in point-to-point topology?

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A
  1. No
  • Because all frames on the media can only travel to or from 2 nodes
  • Point-to-point protoocols can be very simple
19
Q

What topology that end devices usually connected to on LAN network?

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A
  1. Star Topology
  2. Extended Star Topology
20
Q

What are 2 additional topology for early ethernet and legacy token ring technologies?

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A
  1. Bus Topology
  2. Ring Topology
21
Q

What is the term Half-Duplex Communication does? What is it used for?

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A
  1. Only allows one device to send or reveive at a time on a shared medium
  2. Used on WLAN and legacy bus topologies with Ethernet hubs
22
Q

What is the term Full-Duplex Communication does? What is it used for?

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A
  1. Allows both devices to simulteneously transmit and revceive on a shared medium
  2. Ethernet switches operate in full-duplex mode
23
Q

List out 2 methods for Access Control Methods

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A
  1. Contention-based access
  2. Controlled access
24
Q

List out 2 examples that uses contention-based access

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A
  1. Carrier sense multiple access with collision detection ( CSMA / CD ) as used on legacy bus-topology Ethernet
  2. Carrier sense multiple access with collision avoidance ( CSMA/CA ) as used on Wireless LAN
25
What does controlled access determine?
1. Deterministic access where each node has its own time on the medium
26
Where does controlled access used?
1. Used on legacy networks such as Token Ring and ARCNET
27
Where does CSMA/CD used?
1. Ethernet LANs
28
What duplex does CSMA/CD operates at?
1. Half-duplex mode * One devices sends or receives at a time
29
What does CSMA/CD do?
1. Uses a collision detection process to govern when a device can send and what happens if multiple device send at a same time
30
List out the 3 process for CSMA/CD Collision Detection Process
1. Devices transmitting simultaneously will return in a signal collision on the shared media 2. Devices detect the collision. 3. Devices wait at a random period of the time and retransmit data.
31
What does CSMA/CA used in?
1. IEEE 802.11 WLANs ( Wifi )
32
What duplex mode does CSMA/CA uses?
1. Operates in Half-duplex mode where only one device sends or receives at a time
33
What does CSMA/CA do?
1. Uses a collision avoidance process to govern when a device can send and what happens if multiple devices send at the same time
34
List out 2 process for CSMA/CA Collision Avoidance
1. When transmitting, devices also include the time duration needed for the transmission 2. Other devices on the shared medium receive the time duration information and know how long the medium will be unavailable
35
List out the 3 parts for the Data Link Frame
1. Header 2. Data 3. Trailer
36
Will the fields of the header and trailer differ according to data link layer protocol?
1. Yes
37
What does the amount of control information carried with in the frame depends on? ( 2 )
1. Access control information 2. Logical Topology
38
What does header have in data link frame? ( 4 )
1. Frame Start - Identifies beginning of frame 2. Addressing - Indicates source and destination nodes 3. Type - Identifies encapsulated Layer 3 protocol 4. Control - Identifies the flow control services
39
What does trailer have in data link frame? ( 2 )
1. Error Detection - Used for determine transmission errors 2. Frame Stop - Identifies beginning and end of frame
40
List out 5 protocols used in data link layer
1. Ethernet 2. 802.11 Wireless 3. Point-to-point ( PPP ) 4. High-Level Data Link Control ( HDLC ) 5. Frame-Relay * Each protocol performs media access control for specified logical topologies
41
What does Layer 2 Addresses also known as?
1. Physical Address
42
Where does Layer 2 Addresses continained in?
1. Frame Header
43
What are the usage of Layer 2 Addresses?
1. Used only for local delivery of a frame on the link
44
When does Layer 2 Addresses updated
1. Updated by each device that forwards the frame
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