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Wireless QOTD for April 6th

Discussion in 'Wireless' started by tripwire45, Apr 6, 2004.

?

RTS/CTS is a protocol that is used to reduce the number of collisions on a WLAN. Of the choices bel

  1. A. Off

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  2. B. On

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  3. C. On with Threshold

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  4. D. On with Polling

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  1. tripwire45
    Honorary Member

    tripwire45 Zettabyte Poster

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    Answer later.
     
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  2. mattwest

    mattwest Megabyte Poster

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    I'd say C at a guess.

    So it only uses RTS/CTS when the data being sent is over a particular size or length?

    :eek:

    ?
     
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  3. Nelix
    Honorary Member

    Nelix Gigabyte Poster

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    Probably wrong but I choose A
     
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  4. SimonV

    SimonV Petabyte Poster Administrator

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    I'm going for A, just did a little research and most of the things I've read "suggest" is to monitor the wireless LAN for collisions. If you find a large number of collisions and the users are relatively far apart and likely out of range, then try enabling RTS/CTS.

    But I cant find anything that says this is the default for the access points as the above could apply to the wireless NIC's.

    EDIT: I just found it, Answer C "On with Threshold
     
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  5. tripwire45
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    tripwire45 Zettabyte Poster

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    Hey. Three of you replied but only two of you voted. C'mon...step up to the plate and take a swing (I'm American...I talk in baseball metaphors). Besides...just because someone "thinks" they have the right answer doesn't necessarily make it so. :wink:
     
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  6. mattwest

    mattwest Megabyte Poster

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    I voted, and i'm sticking with C!

    (the suspense is killing me!)

    :lol:
     
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  7. flex22

    flex22 Gigabyte Poster

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    I'm saying B.

    My reason is that this is the default.And I'm thinking that you'd set the threshold setting yourself.

    Unless a threshold figure is set by default.But the standard threshold may be different in different environments and setups.

    So how would they come up with a default threshold.Maybe all WLAN environments are similar, therefore a standard threshold could be agreed and set as the default.

    I'll stop ranting now..........

    Answer B
     
  8. SimonV

    SimonV Petabyte Poster Administrator

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    Make sure you Vote guys, it makes looking at the figures easier. :thumbleft
     
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  9. flex22

    flex22 Gigabyte Poster

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    I did vote, but it's dissapeared.

    Strange, I definitely saw B wiht one vote afterwards.

    Nevermind I'll do it again :!:
     
  10. tripwire45
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    tripwire45 Zettabyte Poster

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    Hmmm. It's getting late (at least according to forum time). I wonder how much longer I should wait before springing the answer on you???
     
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  11. tripwire45
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    tripwire45 Zettabyte Poster

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    Here it is. The correct answer is A. RTS/CTS is Off by default. The reason is that it can create a heck of a lot of overhead on the WLAN. Usually, if you're going to use it, you'll use the On with Threshold setting. The idea is to use it only if you're experiencing an unusual amount of collisions on the WLAN. WLANs have to use CSMA/CA rather than CSMA/CD as does Ethernet because WLANs can't "hear" a collision. When a Wireless station sends a data packet, it expects to receive an ACK from the receiving station. If the ACK is missing, the sending station assumes there's been a collision and resends the data.

    When there are an unusual amount of collisions, the recommendation is to use RTS/CTS first as a diagnostic tool. The idea is that larger packets are more vulnerable to collision and WLAN packets are larger than 802.3 Ethernet packets. On with Threshold means that the network admin can set the size of the packet at which RTS/CTS will be triggered to operate. The admin can set this at a fairly small size then adjust it while observing network behavior. When network throughput seems optimized, then the size adjustment threshold is set appropriately. RTS/CTS can then be used effectively despite the fact that it adds to network overhead and limits throughput. By using it to reduce collisions, it actually functions to increase throughput.

    More than you ever wanted to know?
     
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  12. SimonV

    SimonV Petabyte Poster Administrator

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    Good question Trip and an even better explanation.
     
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  13. flex22

    flex22 Gigabyte Poster

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    Darn it, you'll never believe me but I almost put A.My thinking about not knowing what setting a default should be almost led me to the conclusion that it's off, until the admins sets its limit.
    Instead I went with on until the admins ets its limit, either decrease or increase.
    Ahh well, I'd have loved to have got one over these clever fellows.

    Good explanation Trip, yes brill, good work.
    :afro :iagree
     
  14. tripwire45
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    tripwire45 Zettabyte Poster

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    Thanks. Actually, a lot of options are turned off by default (such as MS security settings) :eek: so that could have been a clue. Still, so much about WLANs are atypical compared to wired networks that it's tough to use the usual standards or reasoning. I'll get prepared and try out another one tomorrow. Well done, lads. Good participation.
     
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  15. mattwest

    mattwest Megabyte Poster

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    Damn got it worng! But at least i learnt something!

    Keep the questions coming, great explanation by the way!

    Matt
     
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