Exploring the TCP/IP Link Layer

Question 1

To connect a switch to a LAN, you must use some sort of media. The most common LAN media is Ethernet. Ethernet is not just a type of cable or protocol. It is a network standard published by the Institute of Electrical and Electronics Engineers

Answer 1

Institute of Electrical and Electronics Engineers (IEEE)

Question 2

Specifies a transmission speed of 1000 Megabits per second (Mbps) or 1 Gigabit per second (Gbps)

Answer 2

1000

Question 3

Refers to baseband signaling (which means that only Ethernet signals are carried on the medium)

Answer 3

BASE

Question 4

Represents twisted-pair cabling

Answer 4

T

Question 5

Type of wiring in which two conductors are twisted together for the purposes of canceling electromagnetic interference (EMI) from external sources.

Answer 5

Twisted-pair cabling

Question 6

Copper cabling for short and medium-length distances because of its low cost, when compared to fiber-optic or coaxial cable.

Answer 6

unshielded twisted-pair (UTP)

Question 7

Capable of transmitting data at speeds of up to 100 Mbps

Answer 7

Category 5

Question 8

Used in networks running at speeds of up to 1000 Mbps (1 Gbps)

Answer 8

Category 5e

Question 9

Comprises four pairs of 24-gauge copper wires, which can transmit data at speeds of up to 10 Gbps

Answer 9

Category 6

Question 10

Used in networks running at speeds of up to 10 Gbps

Answer 10

Category 6a

Question 11

Used in networks running at speeds of up to 10 Gbps

Answer 11

Category 7

Question 12

Used in networks running at speeds of up to 40 Gbps

Answer 12

Category 8

Question 13

Describes systems which pass electric power along with data on Ethernet cabling.

Answer 13

Power over Ethernet (PoE)

Question 14

Cables are primarily used for connecting electrically unlike devices.

Answer 14

Straight-through cables

Question 15

Used for connecting electrically like devices.

Answer 15

Crossover cables

Question 16

Enabled on an interface, the interface automatically detects the required cable connection type (straight through or crossover) and configures the connection appropriately.

Answer 16

medium-dependent interface crossover (auto-MDIX)

Question 17

A flexible, transparent fiber that is made of very pure glass (silica) and is not much larger than a human hair. It acts as a waveguide, or “light pipe,” to transmit light between the two ends of the fiber.

Answer 17

optical fiber

Question 18

Is used for shorter distances at a lower bit rate than SMF

Answer 18

MMF (Multi-Mode Fiber)

Question 19

For long-distance communications,

Answer 19

SMF (Single-Mode Fiber)

Question 20

Is for enterprise equipment and is commonly used on small form-factor pluggable (SFP) modules.

Answer 20

Local connector (LC)

Question 21

Is for enterprise equipment.

Answer 21

Subscriber connector (SC)

Question 22

Is for patch panels (for their durability)

Answer 22

Straight tip (ST)

Question 23

Is for patch panels and is used by service providers.

Answer 23

Fiber-optic connector (FC)

Question 24

Connector is a two-fiber connector (transmit and receive), has a form factor and is used for enterprise equipment.

Answer 24

Mechanical Transfer Registered Jack (MT-RJ)

Question 25

This field consists of 8 bytes of alternating 1s and 0s that are used to synchronize the signals of the communicating computers.

Answer 25

Preamble

Question 26

The DA field contains the MAC address of the network interface card (NIC) on the local network to which the frame is being sent.

Answer 26

Destination Address (DA)

Question 27

The SA field contains the MAC address of the NIC of the sending computer.

Answer 27

Source Address (SA)

Question 28

This field contains a code that identifies the network layer protocol.

Answer 28

Type

Question 29

This field contains the network layer data. If the data is shorter than the minimum length of 46 bytes, a string of extraneous bits is used to pad the field. This field is also known as “data and padding”.

Answer 29

Payload

Question 30

The frame check sequence (FCS) field includes a checking mechanism to ensure that the frame of data has been transmitted without corruption. The checking mechanism that is being used is the cyclic redundancy check (CRC).

Answer 30

FCS (frame check sequence)

Question 31

Communication in which a frame is sent from one host and is addressed to one specific destination. In a unicast transmission, there is only one sender and one receiver. Unicast transmission is the predominant form of transmission on LANs and within the Internet.

Answer 31

Unicast

Question 32

Communication in which a frame is sent from one address to all other addresses. In this case, there is only one sender, but the information is sent to all the connected receivers. Broadcast transmission is used for sending the same message to all devices on the LAN.

Answer 32

Broadcast

Question 33

Communication in which information is sent to a specific group of devices or clients. Unlike broadcast transmission, in multicast transmission, clients must be members of a multicast group to receive the information.

Answer 33

Multicast

Question 34

The OUI identifies the manufacturer of the NIC. The IEEE regulates the assignment of OUI numbers. Within the OUI, there are 2 bits that have meaning only when used in the destination address field:

Answer 34

24-bit OUI

Question 35

When the least significant bit in the first octet of the MAC address is 1, it indicates to the receiving interface that the frame is destined for all (broadcast) or a group of (multicast) end stations on the LAN segment. This bit is referred to as the Individual/Group (I/G) address bit.

Answer 35

Broadcast or multicast bit

Question 36

The second least significant bit of the first octet of the MAC address is referred as a universally or locally (U/L) administered address bit. Normally, the combination of the OUI and a 24-bit station address is universally unique. However, if the address is modified locally, this bit should be set to 1.

Answer 36

Locally administered address bit

Question 37

This portion uniquely identifies the Ethernet hardware.

Answer 37

24-bit, vendor-assigned, end-station address

Question 38

The MAC address table is stored in the

Answer 38

content-addressable memory (CAM)

Question 39

The switch examines the destination MAC address and if it is unicast, performs one of the following actions depending whether the MAC address is present in the MAC address table: - No: Forwards the frame out all ports except the incoming port (referred to as unknown unicast). - Yes: Forwards the frame out of the port from which that MAC address was learned previously.

Answer 39

Unicast frames forwarding

Question 40

The switch examines the destination MAC address and if it is broadcast or multicast, forwards the frame out all ports except the incoming port (unless using Internet Group Management Protocol (IGMP) with multicast, in which case it will only send the frame to specific ports).

Answer 40

Broadcast or multicast frames forwarding