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Wireless QOTD for May 31st

Discussion in 'Wireless' started by tripwire45, May 31, 2004.

  1. tripwire45
    Honorary Member

    tripwire45 Zettabyte Poster

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    Peter is a network administrator for a company that has just rolled out a WLAN in the research department. Research users have a need to roam the department and a WLAN solution gives them more mobility than the Ethernet set up they used to have. The IT staff is all fairly new to WiFi but the company has decided to train their in-house staff rather than call in a consulting firm to set up and configure their WLAN. The IT staff is very familiar with wired networks and has a good track record at supporting the network thus far. Soon after setting up the Engineering WLAN, users started complaining that the network seems to run slower than expected. The network uses the 802.11g standard which is expected to be slower than the 100 Mbp/sec Ethernet the users have been used to. What is the most likely cause of the user’s complaints.

    A. The users are just having trouble adjusting to shifting from 100 Mbp/sec Ethernet speeds to 56 Mbp/sec 802.11g network speeds.
    B. The IT staff did not conduct a proper site survey prior to setting up the WLAN. Due to their inexperience with wireless networks, they placed the access points too far apart resulting in reduced network throughput.
    C. Due to the IT staff’s inexperience, they accidentally placed some 802.11b access points in the department. As signals pass through the 11.b APs, the network speed is reduced from 56 Mbp/sec to 11 Mbp/sec and the users experience a significant drop in throughput due to this.
    D. While Ethernet depends on CSMA/CD for collision handling, WLANs use CSMA/CA which has a much higher overhead. This results in a reduction of network throughput since CSMA/CA must send additional signals onto the network rather than “listening” for collisions passively like an Ethernet network would do.

    Answer later.
     
    Certifications: A+ and Network+
  2. punkboy101
    Honorary Member

    punkboy101 Back from the wilderness

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    I'm gonna go for A. I've got the feeling I'm wrong tho.
     
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  3. Greebo

    Greebo Byte Poster

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    My choice is C :)
     
  4. AJ

    AJ Administrator Administrator

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    I'm with Greebo on this one C
     
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  5. nugget
    Honorary Member

    nugget Junior toady

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    I'll take C on this one too.
     
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  6. tripwire45
    Honorary Member

    tripwire45 Zettabyte Poster

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    Hi gang. Correct answer is actually D. This was a tough one as all of the explanations have a certain amount of merit. D is the most likely explanation assuming that, even though the IT folks are inexperienced with WLANs, they set everything up right. The key here is that they are familiar with Ethernet but not so much with WLANs.

    Ethernet uses CSMA/CD which has a certain amount of network overhead attached but usually that's about 30% cost to bandwidth. CSMA/CA which is used by WLANs has a much higher bandwidth cost; generally 50 to 70%. If you were used to Ethernet contention methods and suddenly switched to a WLAN only system...you might notice a significant drop in throughput, even on a good day. More tomorrow.
     
    Certifications: A+ and Network+

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