Data Link Layer

Question 1

Ethernet

Answer 1

A protocol used to send data across individual links

Question 2

CSMA/CD
Carrier sense multiple access with collision detection

Answer 2

Used to determine when the communication channels are clear and when a device is free to transmit data

Question 3

Mac address

Answer 3

A globally unique identifier attached to an individual network frame.

48 bits
6 groups of hexadecimal numbers

Question 4

Hexadecimal

Answer 4

A way to represent numbers using 16 digits

Question 5

Octet

Answer 5

Any number that can be represented by 8 bits.

Question 6

Organizational unique identifier
OUI

Answer 6

The first 3 octet of a MAC address.

Question 7

Unicast

Answer 7

Meant for just one receiving address

Question 8

Multicast

Answer 8

Set to all devices on a local network segment. Will be accepted and discarded by each device.

Question 9

Broadcast

Answer 9

Sent to every single device on a LAN (local area network)

Question 10

Data packet

Answer 10

Term that represents any single set of binary data being sent across a network link

Question 11

Ethernet frame
(Data packets for a ethernet)

Answer 11

A highly structured collection of information presented in a specific order.

Question 12

Preamble
(8bytes/64bits)

Answer 12

Split into 2 sections. First 7 is a series of alternating zeros and ones, buffer between frames, sync clocks used to regulate the speed ar which they send data. Second is SFD.

Question 13

Start Frame Demiliter
SFD

Answer 13

This signals to receiving devices that the preamble is over and that the actual frame contents will now follow

Question 14

Destination MAC address

Answer 14

The hardware address of the intended recipient

Question 15

Ether-type field
(2bytes)

Answer 15

Describes protocol of the contents of the frame

Question 16

VLAN header
(4bytes)

Answer 16

Indication of a VLAN frame. An Ether-type field follows after this.

Question 17

Virtual LAN
(VLAN)

Answer 17

A technique that let’s you have multiple LANs operating on the same physical equipment.

Can only be delivered out of a switch interface configured to relay that specific tag.

Question 18

Payload
(46-1500bytes)

Answer 18

The actual data being transported which is everything that isn’t a header

Question 19

Frame check sequence
(FCS)

Answer 19

A 4 byte (or 32 bit) number that represents a checksum value for the entire frame

Question 20

Checksum Value

Answer 20

Is calculated by performing a CRC against the frame.

Question 21

Cyclical redundancy check
(CRC)

Answer 21

A mathematical transformation that uses polynomial division to create a number that represents a larger set of data. Must match the checksum number.