Chapter 4 - The Current Ethernet Specifications Flashcards
broadcast domain refers to the set of all devices on a network segment that hear all the broadcasts sent on that segment.
collision event a situation where each device’s digital signals interfere with another on the wire—occurs and forces the devices to retransmit later.
The term collision domain is an Ethernet term that refers to a particular network scenario wherein one device sends a packet out on a network segment and thereby forces every other device on that same physical network segment to pay attention to it.
Ethernet is a contention media-access method that allows all hosts on a network to share the same bandwidth of a link.
Ethernet uses both Data Link and Physical layer specifications,
Ethernet networking uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) , a media access control method that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium.
CSMA/CD was created to overcome the problem of those collisions that occur when packets are transmitted simultaneously from different hosts.
Only bridges, switches, and routers, but not hubs, can effectively prevent a transmission from propagating throughout the entire network.
And following are the effects of having a CSMA/CD network that has sustained heavy collisions:
Delay
Low throughput
Congestion
Backoff on an 802.3 network is the retransmission delay that’s enforced when a collision occurs. When a collision occurs, a host will resume transmission after the forced time delay has expired. After this backoff delay period has expired, all stations have equal priority to transmit data.
Broadband allows us to send multiple frequencies of different signals down the same wire at the same time (called frequency-division multiplexing) and to send both analog and digital signals.
full-duplex Ethernet uses two pairs of wires at the same time instead of one measly wire pair like half duplex employs. Plus, full duplex uses a point-to-point connection between the transmitter of the sending device and the receiver of the receiving device (in most cases the switch).
Full-duplex Ethernet can be used in many situations; here are some examples:
With a connection from a switch to a host
With a connection from a switch to a switch
With a connection from a host to a host using a crossover cable
You can run full duplex with just about any device except a hub.
There are no collisions in full-duplex mode. A dedicated switch port is required for each full-duplex host. The host network card and the switch port must be capable of operating in full-duplex mode.
Remember that half-duplex Ethernet shares a collision domain and provides a lower effective throughput than full-duplex Ethernet, which typically has a private collision domain and a higher effective throughput.
On an Ethernet switched network, what address does one host computer use to communicate with another?
- IP address
- MAC address
- Street address
- HUB address
. B. On an Ethernet network, the MAC address (hardware address) is used for one host to communicate with another.
Which of the following can run full duplex and achieve 200 Mbps with Cat 5e cable?
- 100BaseF
- 100BaseTX
- 1000BaseF
- 1000BaseT
B. 100BaseTX uses CAT 5e and can run 200 Mbps when using full duplex.
How many devices in a collision domain have to listen when a single host talks?
- 2
- 3
- 1
- All
D. When one device sends a packet out on a network segment, all other devices on the same physical network segment must wait and let it be transmitted.
If you are using a cable medium called 10Base2, what does this mean?
- That you are running Ethernet over HDMI
- That you are running Ethernet over fiber
- That you are running Ethernet over thicknet
- That you are bundling multiple connections
- That you are really old and using thinnet coax for your LAN medium
E. 10Base2 was one of the very first Ethernet network physical mediums and is a thinnet coax.
What network access control method helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium?
- TCP/IP
- CSMA/CD
- HTTPS
- TFTP
B. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) helps packets that are transmitted simultaneously from different hosts share bandwidth evenly. Option B is the correct answer. You might think that CSMA/CA would be the correct answer, but always think in terms of what is the best answer out of all the options, and only B is correct. The exam will never have cut-and-dry answers.
What is the maximum distance of 10GBaseSR?
- 100 meters (328 feet)
- 302 meters (990 feet)
- 305 meters (1,000 feet)
- 1,593 km (990 miles)
B. A 10GBaseSR cable can have a maximum distance of 990 feet (302 meters).
How many wire pairs are used with half duplex?
- Two
- One
- Four
- None of the above
B. With half duplex, you are using only one wire pair at a time, with a digital signal either transmitting or receiving.
