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Exam 2 Flashcards

1
Q

What does the Physical Layer provide?

A

Provides the means to transport the bits that make up a data link layer frame across the network media.

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2
Q

What are the components of a wireless access point?

A

Wireless antennas
Several Ethernet Switchports
An internet port

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3
Q

What is a NIC and a WLAN NIC?

A

A NIC is a network interface card, which connects a device to a network. NICS are for wired, WLAN NIC is a NIC that connects to a network wirelessly.

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4
Q

Explain the process of encapsulation the physical layer performs.

A

The OSI physical layer handles the transmission of data link layer frames by encoding them into signals for network media. It receives complete frames, encodes them into signals, and sends them over the physical medium, representing the bits in each frame.

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5
Q

What are the three basic forms of media?

A

Copper cable
Fiber
Wireless

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6
Q

What does the physical layer consist of?

A

Circuitry
Media
Connectors

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7
Q

What are the organizations that are responsible for physical layer standards?

A

International Organization for Standardization (ISO)
Telecommunications Industry Association/Electronic Industries Association (TIA/EIA)
International Telecommunication Union (ITU)
American National Standards Institute (ANSI)
Institute of Electrical and Electronics Engineers (IEEE)
FCC and ETSI

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8
Q

The four areas these organizations define and govern of the Physical layer standards?

A

Hardware, media, encoding, and signaling

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9
Q

What are the three fundamental functions of the Physical layer?

A

Physical components, Encoding, Signaling

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10
Q

How are the bits of the frame transmitted by the physical layer?

A

One bit at a time. The destination node physical layer retrieves these individual signals from the media, restores them to their bit representation and passes the bits up to the data link layer as a complete frame.

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11
Q

What is a signaling method?

A

Shows how the bit values 1’s and 0’s will be represented on a physical medium

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12
Q

How do we represent digital information across a medium?

A

Encoding

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13
Q

How do we measure bandwidth?

A

Bandwidth is measured in bits per second which is the capacity in which a medium can carry data.

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14
Q

Which medium uses Manchester encoding?

A

10Mbps Ethernet such as 10BASE-T Ethernet. Used in older Ethernet Standards.

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15
Q

What determines the practical bandwidth of a network?

A

The properties of the physical media and the technologies chosen for signaling and detecting network signals.

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16
Q

What are the three measures for bandwidth quality?

A

Latency, Throughput, Goodput

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17
Q

What type of connector is commonly used in copper cabling?

A

RJ45

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17
Q

What is the difference between throughput and goodput?

A

Throughput- The measure of the transfer of bits across the media over a given period of time
Goodput- *The measure of usable data transferred over a given period of time
Goodput = Throughput - traffic overhead (Practical Bandwidth)

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18
Q

What are the properties of UTP cabling?

A

UTP is the most common networking media.
The outer jacket protects the copper wires from physical damage.
Twisted pairs protect the signal from interference.
Color-coded

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18
Q

What is done to the pairs of wires to minimize signal degradation due to electronic noise?

A

Cancellation and variation of twists.
Wires are twisted together in opposite polarities to cancel out EMI/ RFI frequencies
Wires are twisted at different feet, helps reduce crosstalk

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19
Q

What is crosstalk? What is used to limit crosstalk?

A

Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal on a adjacent wire. Opposing wire pairs twisted together.

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20
Q

What are the other methods listed to limit the susceptibility of copper cables to electronic noise?

A

Shielding combines the effects of EMI and RFI and wire twisting.

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21
Q

What are some of the elements defined by the TIA/EIA 568A standard?

A

Type
Length
Connector
Termination
Testing

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21
Q

What changes in the twist from one pair of wires to the next pair to improve the limitation of crosstalk?

A

Opposing wire pairs twisted together.

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22
Q

What are the three types of Ethernet cables?

A

Straight Through
Cross Over
Rollover

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23
Q

What is a straight-through used for?

A

Host to network device such as a hub or switch.

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24
Q

What is a crossover used for and when would I possibly need it?

A

Used to interconnect similar devices. Host to host, switch to switch, router to router.

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25
Q

What is a rollover used for?

A

Connecting a computer’s serial port to the console port of a router (with an adapter)

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26
Q

What are the other two types of copper cabling besides UTP?

A

Shielded Twisted Pair (STP)
Coaxial Cable

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27
Q

What type of materials can be used for fiber optic cabling?

A

Glass or Plastic
Led

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28
Q

What is the encoding method for fiber optic?

A

Light Pulses

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29
Q

`What is meant when I say fiber is used as a ‘light pipe’?

A

Uses light to encode bits of information to be sent across thin strands of glass

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30
Q

What areas usually implement fiber optic cabling?

A

Business
Home
Long Range
Ocean

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31
Q

Are two cables needed to transmit and receive light signals? Why?

A

Not anymore. Until recently, light could only travel in one direction. Now, different wavelengths can be used

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32
Q

What are the two types of fiber optic cables?

A

Single Mode (SMF) and MultiMode (MMF)

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32
Q

What is the major concerns/limitations for wireless signals?

A
  • Limited coverage area
  • Interference
  • Security
  • Shared medium
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33
Q

How do wireless media carry electromagnetic signals?

A

Radio wave or microwave frequencies

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34
Q

What are the 4 standards for wireless networks?

A
  • Wi-Fi (IEEE 802.11)
  • Bluetooth (802.15)
  • WiMAX (802:16)
  • Zigbee
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35
Q

What are the 4 areas physical layer standards are applied for wireless media?

A

Data-to-radio signal encoding
Frequency and power of transmission
Signal reception and decoding requirements
Antenna Design and Construction

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36
Q

What are the two network devices necessary to implement a wireless network?

A

WAP
WNIC

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37
Q

What is the purpose of encoding?

A

represents data bits by using voltages light electromagnetic waves
as they are placed onto the physical media.

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38
Q

What are the 2 basic services the Data Link layer provides?

A

framing allows the upper layers to access the media
media access control (MAC) and error detection

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39
Q

List and define the 4 specific terms associated with the Data Link layer.

A

Frame - The Data Link layer PDU
Node - notation for network devices connected to a common medium
Media/medium - way to transfer between two nodes
Network - Two nodes on a medium

40
Q

What happens to the frame as it moves from source to destination?

A

It changes based on the medium used

41
Q

What is Media Access Control (MAC) and what does it do?

A

regulates the placement of data frames onto the media
Provides data link addressing.
The technique used for getting the frame on and off media

42
Q

What can the control information tell you?

A

Which are talking?
Stops and Starts
Errors
Who’s Next?

43
Q

List and define the 3 elements of a Data Link Layer Frame.

A

Data - The packet from the Network layer
Header - Contains control information, such addressing, and is located at the beginning of the PDU
Trailer - Contains control information added to the end of the PDU

44
Q

What is the most common physical device that is used for the Data Link Layer?

A

NIC

44
Q

List and define the 5 typical field types of an ethernet frame.

A

Start and stop indicator fields
Naming or addressing fields
Type field
Quality
Data field

45
Q

Describe the two sublayers of the Data Link Layer.

A

The upper sublayer defines the software processes that provide services to the Network layer protocols.

The lower sublayer defines the media access processes performed by the hardware.

46
Q

What are the two functions of the Logical Link Control?

A

Frames the network layer packet
Identifies the network layer protocol

47
Q

What are the two functions of the Media Access Control sublayer?

A

Addresses the frame
Marks the beginning and ending of each frame

48
Q

What analogy is made with the media access control?

A

Traffic rules that regulate the entrance of motor vehicles onto a roadway

49
Q

What are the 4 organizations that define the Data Link standards?

A

International Organization for Standardization (ISO)
Institute of Electrical and Electronics Engineers (IEEE)
American National Standards Institute (ANSI)
International Telecommunication Union (ITU)

50
Q

What are two examples of controlled media access?

A

Token Ring
FDDI

50
Q

What are two examples of contention-based media access?

A

ethernet
wireless

51
Q

What does the method that media access control uses depend on?

A

Media sharing - If and how the nodes share the media
Topology - How the connection between the nodes appears to the Data Link layer

52
Q

Why can controlled media access be inefficient?

A

Because a device has to wait for its turn before it can use the medium

53
Q

What is CSMA?

A

Carrier Sense Multiple access

54
Q

What is a data collision?

A

When two devices transmit at the same time

55
Q

What is CSMA/CD?

A

Carrier Sense Multiple access with Collision Detection

56
Q

What is CSMA/CA?

A

Carrier Sense Multiple Access with Collision Avoidance

56
Q

Half-Duplex

A

Devices can both transmit and receive on the media but cannot do so simultaneously

57
Q

Full-Duplex

A

Both devices can transmit and receive on the media at the same time.

58
Q

physical topology

A

Arrangement of the nodes and the physical connections between them

59
Q

logical topology

A

the way a network transfers frames from one node to the next

60
Q

What logical and physical topologies are typically used in networks?

A

Point-to-Point
Multi-Access
Ring

60
Q

What are the three types of media access control can be used in a multi-access topology?

A

CSMA/CD, CSMA/CA, or token passing

61
Q

Which type of topology is used to determine the media access control?

A

Logical point-to-point topology

62
Q

How does a data flow in a ring network?

A

From node to node until it reaches the destination.

62
Q

Which part the network (WAN/LAN) is the data link address used in delivering?

A

LAN

63
Q

What is the difference between Data Link Address and Logical Address?

A

Data Link address only defines the machine it is not logically assigned

64
Q

Explain the Frame Check Sequence (FCS)

A

The Frame Check Sequence (FCS) is an error-checking mechanism used in network communication. It ensures data integrity during transmission.

The FCS doesn’t correct errors but efficiently detects them, ensuring data accuracy.

65
Q

How is the data link address expressed?

A

48 bit
Hexadecimal

65
Q

What is error detection?

A

Accomplished by placing a logical or mathematical summary of the bits that comprise the frame in the trailer

65
Q

Do all Data Link protocols support using the FCS to determine errors?

A

No

66
Q

What is the standard used for wireless LANs?

A

802.11

66
Q

Does a point-to-point link need a data link address?

A

No it only has one place to go

67
Q

What is the data link address?

A

MAC Address

68
Q

What services are supported by 802.11?

A

Authentication, association (connectivity to a wireless device), and privacy (encryption)

68
Q

How does the data link layer prepare packets for transmission?

A

The data link layer prepares a packet for transport across the local media by encapsulating it with a header and a trailer to create a frame.

69
Q

Describe the features of a logical ring topology.

A

In a logical ring topology, each node in turn receives a frame. If the frame is not
addressed to a node, the frame is passed to the next node. If there is no data being
transmitted, a signal (known as a token) can be placed on the media. A node can place
a frame on the media only when it has the token. This is a controlled media access control
technique called token passing.

70
Q

Name five layer 2 protocols.

A

Ethernet
PPP
High-Level Data Link Control (HDLC)
Frame Relay
ATM

71
Q

If a node receives a frame and the calculated CRC does not match the CRC in the FCS, what action will the node take?

A

The node drops the frame. The CRC provides error detection, not error correction, so B is incorrect. C is incorrect because the frame is not forwarded. The interface is not disabled, so D is incorrect

72
Q

Which protocols are typically used in WANs for media access?

A

PPP and HDLC are designed as WAN protocols.

73
Q

What are the contents of the data field in a frame?
A. 64 bytes
B. The network layer PDU
C. The Layer 2 source address
D. The data directly from the application that generated the data

A

B. The network layer PDU is encapsulated in the frame. The number of bytes in the
payload is variable, so A is incorrect. C is incorrect because the Layer 2 source address is in the address field of the frame header. The data from the application undergoes encapsulation before being passed down to the data link layer, so D is incorrect.

74
Q

Which of the following is a characteristic of contention-based MAC?
A. Used on nonshared media.
B. Nodes compete for the use of the medium.
C. Leaves MAC to the upper layer.
D. Each node has a specific time to use the medium

A

B. Nodes compete for the media. Option A is incorrect because contention-based is
used on shared media. C is incorrect because one of the primary purposes of Layer 2 is
MAC. D is incorrect because taking turns is a function of controlled access.

75
Q

What are the IEEE802.3 data encapsulation components?

A

Ethernet, MAC Sublayer

76
Q

What is the minimum and maximum size of the ethernet frame field?

A

64 - 1518

77
Q

Frames less than the minimum are called? Greater than the maximum?

A

collision fragment/runt frame

jumbo/baby giant frames

78
Q

What does an Ethernet MAC address consist of (bits and type)?

A

48-bit hexadecimal

79
Q

Know the different methods for denoting a MAC hexadecimal address (‘H’, 0x…)

A

0x, subscript 16, hex number followed by H

80
Q

Know the different components of a MAC address (OUI and Vendor assigned) and where they are located.

A

Block ID= Vendor Assigned and is the first 6 characters.
Device ID= Remaining 6 characters.

81
Q

What address (MAC) is used to perform broadcast message? Multicast? Unicast?

A

Unicast - represent a single LAN, A frame will be sent to a single device. Will use the Destination MAC

Multicast - represent a group of devices in a LAN. A frame will be sent to a group of devices on the LAN. Will use the have a value of “1” in the least significant bit of the first octet. (01:00:0C:CC:CC:CC)01:00:5E|then whatever for the last half.

Broadcast - Represents all devices on the LAN. Will use the broadcast address (FFFF.FFFF.FFFF)

82
Q

What does the frame in the data link layer encapsulate?

A

Frame Header - Contains Source and Destination Addresses of the frame.

Payload - Contains Segment, then data inside that.

Trailer - contains FCS

82
Q

Know how a frame is processed.

A

Its like an onion. Peel back the layers

82
Q

What is a ‘burned-in address’?

A

A nick-name for MAC address since they are given at the manufacturer.

83
Q

What is Address Resolution Protocol?

A

Method for finding a host’s hardware address (MAC) when only its network layer address (IP) is known. Address of target host if on local network; addresses of a router if host is not on local network.

83
Q

What is Neighborhood Discovery?

A

​​The process that a source host uses to determine the destination MAC address associated with an IPv6 address is known as Neighbor Discovery (ND).

84
Q

Understanding how a switch works, forwards, and builds a MAC address table.

A

Builds: By inspecting incoming layer 2 frames and recording the source MAC address found in the frame header. The discovered and recorded MAC address is then associated with the port used to receive the frame.

85
Q

What happens if a frame is received that is not included in a switches MAC address table?

A

flooded out all Ethernet switch ports except the incoming port

85
Q

What is the two memory buffering methods on switches?

A

A) Port-based Memory Buffering (used by cheaper switches). In port-based memory buffering, frames are stored in queues that are linked to specific incoming and outgoing ports. In port-based memory buffering frames are stored in queues that are linked to specific incoming ports. A frame is transmitted to the outgoing port only when all the frames ahead of it in the queue have been successfully transmitted. It is possible for a single frame to delay the transmission of all the frames in memory because of a busy destination port. This delay occurs even if the other frames could be transmitted to open destination ports.

B) Shared Memory Buffering. Shared memory buffering deposits all frames into a common memory buffer that all the ports on the switch share. Shared memory buffering deposits all frames into a common memory buffer which all the ports on the switch share. the amount of buffer memory required by a port is dynamically allocated. The frames in the buffer are linked dynamically to the destination port. this allows the packet to be received on one port and than transmitted on another port, without moving it to a different queue. Shared memory is more sophisticated and more $$$.

85
Q

What are the two variants of cut-through switching?

A

A) Fast-forward switching (fastest but with most errors - Good in stable environments). Fast-forward switching offers the lowest level of latency. Fast-forward switching immediately forwards a packet after reading the destination address. Because fast-forward switching starts forwarding before the entire packet has been received, there may be times when packets are relayed with errors.

B) Fragment-free switching. In fragment-free switching, the switch stores the first 64 bytes of the frame before forwarding. Fragment-free switching can be viewed as a compromise between the store-and-forward switching and fast-forward switching. The reason fragment-free switching stores only the first 64 bytes of the frame is that most network errors and collisions occur during the first 64 bytes.

85
Q

What is auto-negotiation in speed and duplex settings?

A

Autonegotiation is an optional function found on most Ethernet switches and NICs. It enables two devices to automatically negotiate the best speed and duplex capabilities.

86
Q

What is store-and-forward switching?

A

This frame forwarding method receives the entire frame and computes the CRC (Cycle Redundancy Check—Error Checking). If the CRC is valid, the switch looks up the destination address, which determines the outgoing interface. Then the frame is forwarded out of the correct port. (looking for transmission errors)

87
Q

Know and describe the two types of duplex settings used for communications on Ethernet networks.

A

Half and Full Duplex

88
Q

What is auto-MDIX?

A

When enabled, the switch automatically detects the type of cable attached to the port and configures the interfaces accordingly

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