Chapter 2 Flashcards
The general topic of how on one computer, two adjacent layers in a networking architectural model work together, with the lower layer providing services to the higher layer.
Adjacent-layer interaction
A series of LAN standards defined by the IEEE, originally invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation.
Ethernet
Institute of Electrical and Electronics Engineers. A professional organization that develops communications and network standard, among other activities.
IEEE
A local-area network (LAN) that physically transmits bits using cables, often the wires inside cables. A term for local-area networks that use cables, emphasizing the fact that the LAN transmits data using wires (in cables) instead of wireless radio waves.
wired LAN
A local-area network (LAN) that physically transmits bits using radio waves. The name “wireless” compares these LANs to more traditional “wired” LANs, which are LANs that use cables (which often have copper wires inside).
Wireless LAN
A term referring to an Ethernet data link header and trailer, plus the data encapsulated between the header and trailer.
Ethernet Frame
The 10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling (Categories 3, 4, or 5): One pair transmits data and the other receives data. It is covered under the IEEE 802.3 specification and has a distance limit of approximately 100m (328 feet) per segment.
10BASE-T
A name for the IEEE Fast Ethernet standard that uses two-pair copper cabling, a speed of 100 Mbps, and a maximum cable length of 100 meters.
100BASE-T
A name for the IEEE Gigabit Ethernet standard that uses four-pair copper cabling, a speed of 1000 Mbps (1 Gbps), and a maximum cable length of 100 meters.
1000BASE-T
The common name for all the IEEE standards that send data at 100 megabits per second.
Fast Ethernet
The common name for all the IEEE standards that send data at 1 gigabit per second.
Gigabit Ethernet
A generic term for any physical link between two Ethernet nodes, no matter what type of cabling is used.
Ethernet link
A popular type of cabling connector used for Ethernet cabling. It is similar to the RJ-11 connector used for telephone wiring in homes in the United States. This connector allows the connection of eight wires.
RJ-45
A generic term for the opening on the side of any Ethernet node, typically in an Ethernet NIC or LAN switch, into which an Ethernet cable can be connected.
Ethernet port
A computer card, sometimes an expansion card and sometimes integrated into the motherboard of the computer, that provides the electronics and other functions to connect to a computer network.
Network Interface Card (NIC)
In Ethernet, a cable that connects the wire on pin 1 on one end of the cable to pin 1 on the other end of the cable, pin 2 on one end to pin 2 on the other end, and so on.
Straight through cable
An Ethernet cable that swaps the pair used for transmission on one device to a pair used for receiving on the device on the opposite end of the cable. In 10BASE-T and 100BASE-TX networks, this cable swaps the pair at pins 1, 2 to pins 3, 6 on the other end of the cable, and the pair at pins 3, 6 to pins 1, 2 as well.
Crossover cable
A 48-bit (6-byte) binary number, usually written as a 12-digit hexadecimal number, used to identify Ethernet nodes in an Ethernet network. Ethernet frame headers list a destination and source address field, used by the Ethernet devices to deliver Ethernet frames to the correct destination.
Ethernet address
A standardized data link layer address that is required for every device that connects to a LAN. Ethernet MAC addresses are 6 bytes long and are controlled by the IEEE. Also known as a hardware address and a physical address.
MAC address
Generally, any address in networking that represents a single device or interface, instead of a group of addresses (as would be represented by a multicast or broadcast address).
Unicast address
Generally, any address that represents all devices, and can be used to send one message to all devices. In Ethernet, the MAC address of all binary 1s, or FFFF.FFFF.FFFF in hex.
Broadcast address
A field in many data link trailers used as part of the error detection process.
Frame Check Sequence (FCS)
Family of LAN standards that define the physical and data link layers.
Ethernet
What devices are used to connect LANs to WANs
Routers
Layer two device that has physical ports for Ethernet cables to be connected to in a LAN
Ethernet switch
Does Ethernet define wireless technology?
No
Wireless LANs use _____ waves to send bits from one port to the next.
radio
What device do LANs rely on to connect wireless devices to the wired LAN?
Access Point (AP)
Most SOHO networks use a single device labeled as a _____ _____ that does the function of an AP, switch, and router.
wireless router
_____ _____ cabling sends light over a glass fibers in the center of the cable and typically allows for longer cabling distance between nodes.
Fiber optic
In the LAN for a small office, some user devices connect to a LAN using a cable, while others connect using wireless technology (and no cable). Which of the following is true regarding the use of Ethernet in this LAN?
a. Only devices that use cables are using Ethernet
b. Only devices that use wireless are using Ethernet
c. Both the devices using cables and those using wireless are using Ethernet
d. None of the devices are using Ethernet
a. Only devices that use cables are using Ethernet
What Ethernet standard defines Gigabit Ethernet over UTP cabling?
1000Base-T
Which of the following is true about Ethernet crossover cables for Fast Ethernet?
a. Pins 1 and 2 are reversed on the other end of the cable
b. Pins 1 and 2 on one end of the cable connect to pins 3 and 6 on the other end of the cable
c. Pins 1 and 2 on one end of the cable connect to pins 3 and 4 on the other end of the cable
d. The cable can be up to 1000 meters long to cross over between buildings
e. None of these answers is correct
b. Pins 1 and 2 on one end of the cable connect to pins 3 and 6 on the other end of the cable
Each answer lists two types of devices used in a 100BASE-T network. If these devices were connected with UTP Ethernet cables, which pairs of devices would require a straight-through cable? (Choose three answers.)
a. PC and router
b. PC and switch
c. Hub and switch
d. Router and hub
e. Wireless access point (Ethernet port) and switch
b. PC and switch
d. Router and hub
e. Wireless access point (Ethernet port) and switch
Which of the following is true about the CSMA/CD algorithm?
a. The algorithm never allows collisions to occur
b. Collisions can happen, but the algorithm defines how the computers should notice a collision and how to recover
c. The algorithm works with only two devices on the same Ethernet
d. None of the answers are correct
b. Collisions can happen, but the algorithm defines how the computers should notice a collision and how to recover
Which of the following is true about the Ethernet FCS field?
a. Ethernet uses FCS for error recovery
b. It is 2 bytes long
c. It resides in the Ethernet trailer, not the Ethernet header
d. It is used for encryption
c. It resides in the Ethernet trailer, not the Ethernet header
Which of the following are true about the format of Ethernet addresses? (Choose three answers.)
a. Each manufacturer puts a unique OUI code into the first 2 bytes of the address
b. Each manufacturer puts a unique OUI code into the first 3 bytes of the address
c. Each manufacturer puts a unique OUI code into the first half of the address.
d. The part of the address that holds this manufacturer’s code is called the MAC
e. The part of the address that holds this manufacturer’s code is called the OUI
f. The part of the address that holds this manufacturer’s code has no specific name
b. Each manufacturer puts a unique OUI code into the first 3 bytes of the address
c. Each manufacturer puts a unique OUI code into the first half of the address.
e. The part of the address that holds this manufacturer’s code is called the OUI
Which of the following terms describe Ethernet addresses that can be used to send one frame that is delivered to multiple devices on the LAN? (Choose two answers.)
a. Burned-in address
b. Unicast address
c. Broadcast address
d. Multicast address
c. Broadcast address
d. Multicast address
What is the maximum cabling distance for a 10 Mbps (10BASE-T) Ethernet cable?
100 meters (328 feet)
What is the maximum cabling distance for a 100 Mbps (100BASE-T) Ethernet cable?
100 meters (328 feet)
What is the maximum cabling distance for a 1000 Mbps (1000BASE-LX) Ethernet (fiber-optic) cable?
5000 meters (16,404 feet)
What is the common name used to describe Gigabit Ethernet Cabling that uses copper wire?
1000BASE-T
What is the common name used to describe Gigabit Ethernet Cabling that uses fiber-optic cable?
1000BASE-LX
What is the common name used to describe 10 Gigabit Ethernet Cabling that uses copper wire?
10GBASE-T
What is the term used to describe when the transmitting node changes the electrical signal over time, while the other node, the receiver, using the same rules, interprets those changes as either 0s or 1s.
Encoding scheme
In a UTP cable, the twisting of the wires helps prevent ______, which interferes with electrical signals in nearby wires.
Electromagnetic Interference (EMI)
EMI between wire pairs is called _____.
crosstalk
How many pairs of wires do the 10BASE-T and 100BASE-T standards require?
two
How many pairs of wires does the 1000BASE-T standards require?
four
The RJ-45 connector has eight physical locations into which the eight wires in the cable can be inserted. What are these locations called?
Pin positions
The RJ-45 connector is slightly wider, but otherwise similar, to the _____ connectors commonly used for telephone cables in homes in North America.
RJ-11
An enhanced small form-factor pluggable (SFP+) transceiver can run at what speed?
10 Gbps
How large are MAC addresses?
6 bytes (48 bits)
Most computers list MAC addresses as _____ digit hexadecimal numbers.
12
Before a manufacturer can build Ethernet products it must ask the IEEE to assign a universally unique 3 byte code. What is this called?
Organizationally Unique Identifier (OUI)
In addition to unicast addresses, Ethernet also uses _____ addresses. These addresses are used to identify more than one LAN interface card.
group
Frames sent to a _____ Ethernet address will be copied and forwarded to a subset of the devices on the LAN that volunteers to receive frames sent to this specific type of address.
multicast
Through FCS, if an error is discovered in the Ethernet frame, what does FCS do to that frame?
Discards it
The type of logic used when a device must wait to send if it is currently receiving a frame; in other words, it cannot send and receive at the same time.
Half duplex
The type of logic used when a device does not have to wait before sending; it can send and receive at the same time.
Full duplex
LAN hubs are considered to be a layer _____ device.
1
A LAN switch operates as a layer _____ device, meaning that it looks at the data-link header and trailer
2
What is the main issue created by using hubs
collisions
Nodes that use half-duplex logic use a relatively well known algorithm that takes care of obvious cases of preventing collisions but also cases of unfortunate timing. What is this algorithm called?
Carrier Sense Multiple Access with Collision Detection (CSMA/CD).
CSMA/CD allows the sender to listen when sending a message to see if a collision occurs. If a collision occurs, all sending nodes do what?
Send a jamming signal
Independently chooses random time to retransmit
Although most modern LANs do not often use hubs, some hubs still exist in enterprise networks. Because of this, each NIC and switch port has a _____ setting.
Duplex
For all links between PCs and switches, or between switches, use _____ duplex.
Full
For any link connected to a LAN hub, the connected LAN switch and NIC port should use _____ duplex.
Half
In a typical enterprise LAN, each floor has an Ethernet LAN switch and a wireless LAN AP. To allow communication between floors, each per-floor switch connects to one _____ _____ switch. In this type of setup, each floor communicate with each other and the data would first flow through this device.
centralized distribution
What two devices typically transmit on pins 3 and 6
Hubs and switches
How many bits is the vendor assigned portion of a MAC address?
24
