Why only 20-30 mbit/s on wifi when 95 mbit/s on ethernet?

Discussion in 'Mac OS X Server, Xserve, and Networking' started by frosse, Nov 8, 2010.

  1. frosse macrumors 6502a

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    Sep 23, 2007
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    Sweden
    #1
    When I connect my macbook pro with ethernet without a router straight to my wall I get approx. 95 mbit/s. However, when I connect an N router (2,4 ghz, 145 mbit/s) I only get about 20-30 mbit/s. The MBP is the only connected device and I'm sitting two feet away from the router.

    It should be a bit more atleast?
     
  2. mulo macrumors 68020

    mulo

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    #2
    you should add this to your signature "and have super fast internet"
    I envy your internet.

    in regards to the matter, all I can say is I have no problem going to 50mb/s on my AEBS.
     
  3. whooleytoo macrumors 603

    whooleytoo

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    #3
    Are there any 802.11g devices connected to the same Wifi network? If so, I don't think you get 802.11n speeds.
     
  4. fpnc macrumors 68000

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    Oct 30, 2002
    Location:
    San Diego, CA
    #4
    Ethernet is an efficient wired transfer protocol while WiFi is neither (sorry to be so obvious, but that's the reason). However, your observed 20-30mbps is a little low. Under good conditions and over a modest distance, you might expect twice that performance on a dedicated 802.11n network (a little more than that in a best-case, dead-simple configuration).

    Now, before someone comes in and claims that they're getting well over 200mbps on their 802.11n setup you need to understand the difference between link rate and real data throughput. Link rates (as reported in any number of WiFi utilities -- including Apple's own AirPort Utility) do NOT indicate true data throughput (i.e. observed data transfer in bit/bytes per second). WiFi link rates can be reported in the hundreds of millions of units but they're simply a "pie-in-the-sky" value which indicates the communication rate at which the WiFi driver believes that it can operate. However, you can use link rates to help diagnose problems, since generally speaking the higher the link rate the better your data transfer rate and your average data transfer rate will never exceed your link rate.

    If you are having problems with your WiFi (and it appears that you are) you need to check your setup for the latest firmware and software (and configured properly) and then look for sources of interference (additional base stations on the same channel, wireless phones, microwave ovens, etc.).
     
  5. mulo, Nov 8, 2010
    Last edited: Nov 8, 2010

    mulo macrumors 68020

    mulo

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    #5
    well actually I just ran at 20.7 mbyte/s or 165.6mbit/s. best of all, I have a screenshot to prove it! :D
    actually, even better, I just realized I'm slowed down by the (ancient) drive in my G5 that i'm transferring to :D

    option click on your wifi icon to show extensive details (as in the second screenshot)
    you wanna be looking at Channel and Transmit Rate
     

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  6. fpnc, Nov 8, 2010
    Last edited: Nov 8, 2010

    fpnc macrumors 68000

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    San Diego, CA
    #6
    That "Transmit Rate" as reported in the Mac OS X menu is a link rate, I've already covered that in my first post. Those other values in the topmost screen shot I can't comment on because I don't know what utility that is or even what it is trying to report (could it be the total routing bandwidth?).

    In any case, from a practical perspective, you aren't going to get WiFi data transfer rates significantly over 100mbps unless you are running commercial-grade routers and access points -- an AirPort or just about any other consumer-grade device won't offer that kind of performance (however, the latest consumer-grade equipment is getting somewhat better, so don't hold me exactly to that 100Mbps limit). If you doubt my word, then you should go over to a review site like smallnetbuilder.com ( http://www.smallnetbuilder.com/wireless ). Here you can see that when they tested the newest AirPort Extreme they got a maximum of 99.1Mbps (uplink, 5GHz, 40MHz channel width). However, the AVERAGE downlink throughput for all test cases was around 28Mbps which actually was about middle-of-the-road when compared to several other WiFi base stations (those ranged from 18Mbps to 35Mbps for the 802.11n 5GHz downlink tests).

    Link to full review and test results: http://www.smallnetbuilder.com/wire...ng-new-apple-airport-extreme-briefly-reviewed

    Here is the part of the test where they report the wireless performance: http://www.smallnetbuilder.com/wire...ort-extreme-briefly-reviewed?showall=&start=2

    By the way, smallnetbuilder has some excellent tutorials on WiFi setup and troubleshooting. It also has some good articles on the differences between link rates and theoretical bandwidth and real-world performance.
     
  7. mulo macrumors 68020

    mulo

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    #7
    I love how some people think they know so much, yet in reality they know nothing.

    as you failed to see I covered both data throughput and link speed.
     
  8. BertyBoy macrumors 6502

    Joined:
    Feb 1, 2009
    #8
    what you meant to say was "Look at me, I have no life. I made the effort to post screenshots of my network statistics". Well, nobody cares what throughput and link rate you get, none of your posts help the original poster.

    ps. the screenshots look photoshop'd to me.

    Can anyone recommend some wireless network diagnostic software that will show failed packets, etc. ??
     
  9. mulo macrumors 68020

    mulo

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    #9
    obviously no knowledge here either

    http://pingtest.net/
     
  10. fpnc macrumors 68000

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    San Diego, CA
    #10
    Have you even looked at the extensive test results on real-world WiFi data THROUGHPUT on smallnetbuilder.com? I'm also a little confused as to why that first test shows a bandwidth IN (average?) of only 353KBps (approx. 2.8Mbps). Are you reporting bandwidth from your ISP or memory-to-memory or disc-to-disc data transfers? If your results are for true wireless data throughput and on an Airport base station then you are getting high results even if the two devices are sitting right next to one another (which would admittedly be a valid result, but not too practical since most users will need WiFi access from at least several feet away). For example, that peak 99.1Mbps result from smallnetbuilder was from a distance of six feet (same room, clear line-of-sight).

    Also, your initial response was in reply to my statement of, "Now, before someone comes in and claims that they're getting well over 200mbps on their 802.11n setup you need to understand the difference between link rate and real data throughput." But you reported 165.6Mbit/s which by my way of thinking is not "well over 200Mbps."

    If you think the overview I gave is "know nothing" then maybe you can explain why review sites like smallnetbuilder consistently report WiFi throughput of under 100Mpbs for nearly all 802.11n devices (in practical use cases, not link rates, or when sitting right on top of the base station). I guess they've just been "holding it wrong." ;)
     
  11. BertyBoy macrumors 6502

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    Feb 1, 2009
    #11
    Another useless post.

    How does that detect and count packet failures on a home user wireless LAN ?
     
  12. assembled macrumors regular

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