READ Free Dumps For CISCO- 100-105
| Question ID 14441 | Which three statements are true about the operation of a full-duplex Ethernet network?
(Choose three.)
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| Option A | There are no collisions in full-duplex mode.
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| Option B | A dedicated switch port is required for each full-duplex node.
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| Option C | Ethernet hub ports are preconfigured for full-duplex mode.
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| Option D | In a full-duplex environment, the host network card must check for the availability of the network media before transmitting.
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| Option E | The host network card and the switch port must be capable of operating in full-duplex mode.
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| Correct Answer | A,B,E |
Explanation Explanation: Half-duplex Ethernet is defined in the original 802.3 Ethernet and Cisco says you only use one wire pair with a digital signal running in both directions on the wire. It also uses the CSMA/CD protocol to help prevent collisions and to permit retransmitting if a collision does occur. If a hub is attached to a switch, it must operate in half-duplex mode because the end stations must be able to detect collisions. Half-duplex Ethernettypically 10BaseTis only about 30 to 40 percent efficient as Cisco sees it, because a large 10BaseT network will usually only give you 3- to 4Mbpsat most. Full-duplex Ethernet uses two pairs of wires, instead of one wire pair like half duplex. Also, full duplex uses a point-to-point connection between the transmitter of the transmitting device and the receiver of the receiving device, which means that with full-duplex data transfer, you get a faster data transfer compared to half duplex. And because the transmitted data is sent on a different set of wires than the received data, no collisions occur. The reason you dont need to worry about collisions is because now Full-duplex Ethernet is like a freeway with multiple lanes instead of the single-lane road provided by half duplex. Full-duplex Ethernet is supposed to offer 100 percent efficiency in both directions; this means you can get 20Mbps with a 10Mbps Ethernet running full duplex, or 200Mbps for FastEthernet.
| Question ID 14442 | Which two statements describe the operation of the CSMA/CD access method? (Choose
two.)
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| Option A | In a CSMA/CD collision domain, multiple stations can successfully transmit data simultaneously.
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| Option B | In a CSMA/CD collision domain, stations must wait until the media is not in use before transmitting.
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| Option C | The use of hubs to enlarge the size of collision domains is one way to improve the operation of the CSMA/CD access method.
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| Option D | After a collision, the station that detected the collision has first priority to resend the lost data.
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| Option E | After a collision, all stations run a random backoff algorithm. When the backoff delay period has expired, all stations have equal priority to transmit data.
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| Option F | After a collision, all stations involved run an identical backoff algorithm and then synchronize with each other prior to transmitting data.
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| Correct Answer | B,E |
Explanation Explanation: Ethernet networking uses Carrier Sense Multiple Access with Collision Detect (CSMA/CD), a protocol 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 nodes. And trust me, good collision management is crucial, because when a node transmits in a CSMA/CD network, all the other nodes on the network receive and examine that transmission. Only bridges and routers can effectively prevent a transmission from propagating throughout the entire network! So, how does the CSMA/CD protocol work? Like this: when a host wants to transmit over the network, it first checks for the presence of a digital signal on the wire. If all is clear (no other host is transmitting), the host will then proceed with its transmission. But it doesnt stop there. The transmitting host constantly monitors the wire to make sure no other hosts begin transmitting. If the host detects another signal on the wire, it sends out an extended jam signal that causes all nodes on the segment to stop sending data (think, busy signal). The nodes respond to that jam signal by waiting a while before attempting to transmit again. Backoff algorithms determine when the colliding stations can retransmit. If collisions keep occurring after 15 tries, the nodes attempting to transmit will then time out.