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| Acibrix 2002-09-01, 2:14 pm |
| I came across this question and don't understand it.
Which of the following are not ture of standard half-duplex ethernet circuitry?
a) IT's alternate one way communication
b)the recieve (Rx) is wired directly to the transmit (tx) of the remote station.
c) The receiver (tx) is wired directly to the receive (rx) of the remote station.
d) Collisions are not possible.
e) Both stations can tranmit simultaneously
What you guys think the answer truely is?
thanks | |
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| The answer is (a).
Half-duplex is communications in one direction at a time - either TX or RX.
Full-duplex is two way communications - - TX & RX at the same time. This is only possible with 4 wire media such as UTP.
HTH
Hippo
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| superuserX 2002-09-01, 7:32 pm |
| Hippo chose the true answer. The question asks for the false one.
For full-duplex communications to occur both NIC cards have to support it and you have to go through a switch, not a hub. That is where the rx wired to the tx comes in. The switch creates a temporary circuit between the 2 NIC cards. The receive of each card is "wired" to the transmit of the other card, allowing each machine to transmit and receive at the same time without risk of collisions.
Except for A the other answers describe full-duplex. If all the conditions for full-duplex are not met you are using half-duplex. | |
| Acibrix 2002-09-02, 1:21 pm |
| So do you think the answer is D? | |
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| No. The answer is definitely (a).
(d) is not correct. Collisions WILL occur on a half-duplex ethernet medium. This is a feature, and is a result of more than one ethernet attached device attempting to transmit at the same time. Another protocol, CSMA/CD (Carrier Sense, Multiple Access/Collision Detection) takes care of this feature. Devices listen for carrier on the medium and then transmit their frame; if two devices do this at exactly the same time, CSMA/CD recognises that a collision has occurred and requests that both deivces back off and re-transmit after a random time.
Hippo
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| kris108 2002-09-03, 1:56 pm |
| Options B through E appear to describe Full duplex thereby falling squarely under the category of "not true for half-duplex circuitry".
A would be the only option I would NOT click on. | |
| pepe le pew 2002-09-03, 7:11 pm |
| My pick would be D & E. Reasoning for D is:
quote:
Collisions WILL occur on a half-duplex ethernet medium. This is a feature, and is a result of more than one ethernet attached device attempting to transmit at the same time.
For E is both stations should not transmit at both directions simultaneously, because it will not be half-duplex mode anymore, but rather in full duplex mode. Half Duplex transmits data one direction at a time.
I think both D & E would be a classification of a full-duplex ethernet. | |
| pepe le pew 2002-09-03, 7:12 pm |
| Follow-up:
The question was asking for a "NOT TRUE" answer, this was what SuperuserX was trying to point out.
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| shahandiza 2002-09-04, 12:38 am |
| D and E
rgds,
--ditto | |
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| I stand corrected by others here.
Indeed , if I had read the question properly I could have given the correct answer.
Sorry for any confusion.
Hippo
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| Dkelly 2002-09-05, 7:01 am |
| D is the answer, because E - both systems can transmit simultaneously - that is how collisions happen! | |
| ANDRONDA 2002-09-05, 10:15 am |
| HELLO GUYS
You have gotten yourselves way confused because of the double negatives here.
The best way to answer this is to take each statement and determine its validity irrespective of the question.
So let’s do that:
a) It’s alternate one-way communication This is a TRUE STATEMENT.
b) The receive (Rx) is wired directly to the transmit (tx) of the remote station. This is a FALSE STATEMENT. This statement describes FULL DUPLEX configuration.
c) The receiver (tx) is wired directly to the receive (rx) of the remote station. Also a FALSE STATEMENT for the same reasons, see above.
d) Collisions are not possible. A big time FALSE STATEMENT. Collisions are most assuredly possible. Half duplex Ethernet uses CMSA/CD to manage this.
e) Both stations can transmit simultaneously. Another big time FALSE STATEMENT. It is alternate one-way.
So now ask the question:
Which of the following are not true of standard half-duplex Ethernet circuitry?
The correct answer is BCDE.
I have seen the converse of this one asked, “Which of the following is true of standard half-duplex Ethernet circuitry?” with the same answers and the correct one would be A in that case. | |
| superuserX 2002-09-06, 5:32 am |
| quote:
Originally posted by Acibrix
So do you think the answer is D?
I think the answer is B,C,D,E for the reasons I stated above. |
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