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full-duplex

 
 
oraclepz@gmail.com
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      03-04-2005
Which of the following statements about full-duplex Ethernet operation
are true? (Choose two.)

1. Full duplex is supported on shared media.
2. In full duplex, only one station may transmit at a time.
3.Full duplex is preferred over half duplex in link establishment
negotiation.
4. All implementations of Ethernet can support both half duplex and
full duplex.
5. Two methods of achieving a full duplex are auto-negotiation and
administrative configuration.

5 it is one answer, do you know second answer?

 
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Andrei Ivanov
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      03-04-2005
http://www.velocityreviews.com/forums/(E-Mail Removed) <(E-Mail Removed)> wrote:
> 3.Full duplex is preferred over half duplex in link establishment
> negotiation.


This sounds correct too. If both devices are configured to auto-
negotiate connection parameters, they will try full-duplex first,
and if it won't work, will fail down to half-duplex.

--
andrei
 
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Toby
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      03-04-2005

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
> Which of the following statements about full-duplex Ethernet operation
> are true? (Choose two.)
>
> 1. Full duplex is supported on shared media.
> 2. In full duplex, only one station may transmit at a time.
> 3.Full duplex is preferred over half duplex in link establishment
> negotiation.
> 4. All implementations of Ethernet can support both half duplex and
> full duplex.
> 5. Two methods of achieving a full duplex are auto-negotiation and
> administrative configuration.
>
> 5 it is one answer, do you know second answer?
>

The answer is 3 & 5

1 - Full duplex is only available when only 2 devices can talk on a network
segment at the same time and each device has a seperate transmit/recieve
path so FALSE..

2 - Transmit and recieve are on a seperate pair of wires so both can transit
simultaneously. so FALSE

3 - Full duplex increases bandwidth see 2 above so TRUE

4 - See 1 above so FALSE, i.e. hubs and older types of Ethernet, thinnet,
thicknet and certain other devices.

5 - If full duplex available to both, devices can negotiate by default or be
set in config so TRUE

This question though would better be suited to

alt.certification.cisco and not in this newsgroup.

Toby


 
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Hansang Bae
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      03-05-2005


(E-Mail Removed) wrote:
> Which of the following statements about full-duplex Ethernet operation
> are true? (Choose two.)


Better suited to alt.certification.cisco

> 3.Full duplex is preferred over half duplex in link establishment
> negotiation.


This is true for copper based Ethernet. The rule says to use the
*highest* common denominator.


> 4. All implementations of Ethernet can support both half duplex and
> full duplex.


not really. Older 10Mbps only NICs cannot handle FD. Some can but
it's not universal.

> 5. Two methods of achieving a full duplex are auto-negotiation and
> administrative configuration.


Ture.


--

hsb


"Somehow I imagined this experience would be more rewarding" Calvin
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anybody43@hotmail.com
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      03-06-2005
Hi,

Andrei is pretty close however maybe this is closer.

There is a pre link-up announcement phase
during which a device configured for Auto will
announce it's capabilities.

Before bringing the link up each end listens
for anouncements for a while.

A device that has sent announcements
of its capabilities and has received announcements
of its neighbours capabilities chooses the
'best' common capability in order of

100-FD -> 100-HD -> 10-FD -> 10-HD

If there are NO received announcements
then the device does HD. (And I guess detects
speed - see later)

Hard coded devices DO NOT SEND announcements.

The announcements are sent out of band using
something apparently called Fast Link Pulses.
I would assume that these are not propagated through repeaters. [or,
clearly, switches or routers)

Speed detection is done seperately if required. For
some reason you **NEVER** get a speed mis-match.

If you want to know more search
comp.dcom.lans.ethernet for the required
keywords and Rich Seifert. I have not read his book
but it seems a safe assumption that it
will discuss all of this correctly and in sufficent
detail for any network admin purpose.

 
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Walter Roberson
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      03-06-2005
In article <(E-Mail Removed) .com>,
<(E-Mail Removed)> wrote:
:Speed detection is done seperately if required. For
:some reason you **NEVER** get a speed mis-match.

Well, sometimes you do. I've seen it happen on a Bay LattisSwitch
28xxx -- a device we retired a number of years ago but still have
hanging around. More modernly, it happens with our all our
100 Mb SX <-> copper media convertors (which are mostly MiLan.)
--
"This was a Golden Age, a time of high adventure, rich living and
hard dying... but nobody thought so." -- Alfred Bester, TSMD
 
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Hansang Bae
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      03-06-2005
(E-Mail Removed) wrote:
[snip]
> Speed detection is done seperately if required. For
> some reason you NEVER get a speed mis-match.


Because it uses parallel detection. 10Base-T's signalling is
sufficiently different from 100Base-T signalling. So if FLP is not
heard, it listens for the signalling (e.g. NLP for 10Base-T) and uses
the info to determine the speed.


> If you want to know more search
> comp.dcom.lans.ethernet for the required
> keywords and Rich Seifert. I have not read his book
> but it seems a safe assumption that it
> will discuss all of this correctly and in sufficent
> detail for any network admin purpose.


More than sufficient!

--

hsb


"Somehow I imagined this experience would be more rewarding" Calvin
**************************ROT13 MY ADDRESS*************************
Due to the volume of email that I receive, I may not not be able to
reply to emails sent to my account. Please post a followup instead.
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anybody43@hotmail.com
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      03-08-2005
Thanks, yes I was too strong on that.
I was thinking of correctly functioning standards
compliant kit. I do very little hands on at the
moment and have not seen a speed mis-match
for years.

Are Media convertors catered for in the standards or
are they a hack?

I have nothing against hacks by the way, however is
is just as well to know when you are dealing with them.

 
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Hansang Bae
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      03-10-2005
(E-Mail Removed) wrote:

> Thanks, yes I was too strong on that.
> I was thinking of correctly functioning standards
> compliant kit. I do very little hands on at the
> moment and have not seen a speed mis-match
> for years.
>
> Are Media convertors catered for in the standards or
> are they a hack?
>
> I have nothing against hacks by the way, however is
> is just as well to know when you are dealing with them.



Not a hack at all but a limitation of auto-negotiation. AN signals
work over copper but not fiber. So there is no way to make a device
that's supposed to connect fiber to copper work with AN.

--

hsb


"Somehow I imagined this experience would be more rewarding" Calvin
**************************ROT13 MY ADDRESS*************************
Due to the volume of email that I receive, I may not not be able to
reply to emails sent to my account. Please post a followup instead.
************************************************** ******************
 
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anybody43@hotmail.com
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      03-10-2005
It is many moons since I saw a 10 or 100 fiber link.

OH yes! 10 and 100 fiber are completely incompatible.
Different wavelengths IIRC.

Thanks.

 
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