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Why You Should Disable Lower Legacy Data Rates

Discussion in 'General Wireless Discussion' started by thiggins, Apr 14, 2016.

  1. thiggins

    thiggins Mr. Easy Staff Member

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    A little on the technical side, but worth a read. Also talks about sticky clients.
    http://divdyn.com/disable-lower-legacy-data-rates/

    Good argument for using APs vs. converted consumer routers. Most don't allow controlling supported data rates.

    If you want to at least disable B rates, look for settings for 1,2,5.5 and 11 Mbps data rates. This Cisco article has a good screenshot of one of their controllers that makes it easy.
     
    joegreat, Nullity, sm00thpapa and 2 others like this.
  2. coxhaus

    coxhaus Part of the Furniture

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    I use Cisco WAPs and they have on their forum how to do this for my Cisco WAP321 units. I did this over a year ago. You pull out all the low connection rates.

    PS
    I think this is how I evolved to only running 5GHz. I dropped 2.4GHz altogether. It seemed simpler than managing slow connection rates.
     
    Last edited: Apr 14, 2016
    Nullity likes this.
  3. Shabbir Rao

    Shabbir Rao Regular Contributor

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    Thumbs Up :)
     
  4. Ronv42

    Ronv42 Senior Member

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    I miss some of the great configuration settings of Cisco hardware but again you have to know what you are doing when you get into this type of detailed configuration.
     
  5. sfx2000

    sfx2000 Part of the Furniture

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    Basic Rates - one cannot disable the basic rates, which are 1, 2, 5.5, and 11 - this is mandatory per 802.11 in the ISM 2.4GHz band... many reasons for this, but much has to do with modulation and how receivers self-calibrate (open loop) to determine appropriate Tx power - this is why Beacon's in 2.4GHz are always transmitted at the 1Mbps rate...

    Supported Rates - this is a different story, and this is where the guidance for high-density deployments rings true, in that 18Mbps is probably the minimum for an 802.11 client to attach - and the setting for enterprise level AP's can allow for this... 18Mbps is important, as most silicon supports this in their supported rate set epigrams on the beacon - some offer different rates as well, and enterprise AP's can manage that list to some extent, and then offer additional supported rates in the Extended Support epigram - but the Supported Rate epigram dates back to 802.11b, as part of the legacy support mandate that IEEE is held to...

    HT/VHT have different mechanisms - but keep in mind that Basic Rates will always be there...

    Attached - Did a quick scan, and was able to catch most of the major silicon vendors - so you can review and make decisions..
     

    Attached Files:

  6. sfx2000

    sfx2000 Part of the Furniture

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    And following up - 11b/g/n clients send their supported rates as part of the 802.11 Probe Request, so the AP can make some decisions before allowing a client to connect - e.g. if the client doesn't support 18Mbps, then don't associate - still have to send a Probe Response to stop the client from continuing to Probe, but the AP is not required to complete the association.

    The big thing - don't want 11b clients on the network at all - as they will force 11g/11n AP's into ERP Protection, and this hurts all clients associated within that Basic Service Set. One also doesn't want low data rate 11g/11n clients in the BSS, as they will suck up all the airtime (Airtime fairness helps out a bit here, but still...).
     
  7. sfx2000

    sfx2000 Part of the Furniture

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    For many consumer grade AP's - while you might not have all the flexibility of an enterprise/carrier grade AP, one thing you can do is put the AP into 11g/11n mode (if allowed by the UI), and many AC1900 class AP's have a multicast rate, which if you set it to 11Mbit or above, can keep slow clients from sucking up airtime...

    That setting, in a small multiple AP environment, typical of the SNB forum crowd, can also help with "sticky" clients, as the AP can use that rate to force a disassociate to the client, and put the client back into AP search mode for a better AP.

    YMMV - as tweaking these rates can lead to usability issues if trying to cover a large footprint with a few possible AP's - we're all frugal at the end of the day, and I know, speaking for myself, that I try to get by with as little as possible...
     
  8. stevech

    stevech Part of the Furniture

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    Using 11g or even 11b rates.. some use cases with lower data rate needs trade using that low rate for much longer range. Because the lower rates tolerate a weak signal better (low SINR tolerated).

    Example: infrequent telemetry in machine to machine (M2M) applications.
     
  9. thiggins

    thiggins Mr. Easy Staff Member

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    SFX: How about writing up a short How To article using an actual example or two?
     
  10. sfx2000

    sfx2000 Part of the Furniture

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    I'm thinking perhaps not, as it's a loaded gun, and for many, it might harm than help and lead to the usability issues I mentioned above...

    In a high density layout (many clients/many AP's) this makes sense, but this is a bit out of scope for SNB for the gear than most folks have at hand, and I don't think most would want to invest a couple of thousand dollars (US) to make the most of it.
     
  11. sfx2000

    sfx2000 Part of the Furniture

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