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Wireless Networks Thread, Slow login when a whole class logs in over wifi in Technical; Originally Posted by SYNACK Um, I'm pretty certain that unless your waps has a stack of radios (xirrus) you are ...
  1. #16

    Michael's Avatar
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    Quote Originally Posted by SYNACK View Post
    Um, I'm pretty certain that unless your waps has a stack of radios (xirrus) you are limited to the max single rate. Under g that is 54mbit between all devices as that is the max you can fit in to the radio band available at that modulation. It shared so one device and wap have to share this, you add more devices and it drops like a stone especially with collisions. With n you can get 300mbits which easily overwhelms a poltry 100mbit link so gig is really needed to make it not pointless. This is also why the ac waps have two gig ports that can be teamed as a gig link could be overwhelmed.
    I know about the differences between G and N, but I can see why you thought that way

    That's interesting however that AC APs come with two gigabit ports. I still think it'll only be a matter of time before someone works out how to get 10Gbps over CAT5e, working to 100m.

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    Remember that 300 Mbps is only the maximum data rate available in 5 GHz with 2 spatial streams with a 40MHz channel and short guard interval.

    WLAN devices are only required to support up to MCS 7, so in 2.4 GHz that's a maximum data rate of 72 Mbps. With no frame aggregation, the maximum throughput you will get is 57 Mbps, and this needs to be shared between ALL devices. This is a theoretical maximum, once you factor in multiple devices the true throughput drops.

    1 AP with 5 clients all modulating at MCS7 in 2.4 GHz gives a throughput of around 40 Mbps, about 6.7 per device.

    1 AP with 10 clients, all at MCS 7 will get about 3 .7 Mbps per device.

    And, this is with everyone modulating at the highest rate available, if stations have to rate shift down, then the picture gets worse.

    There are tools to analyze this, when you plan your network before deployment these are all the sorts of scenarios you need to consider.

    W7_AM_Build__Running_-2.jpg

    NM
    Last edited by neilmac; 21st October 2013 at 02:47 PM.

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    The 300Mbps figures given for N wifi reminds me of the "up to" figures on ADSL lines.

    It seems I have found the source of the problem rather more easily than I feared. Symantec Endpoint appears to be downloading 300MB of updates on each client, every time each one turns on, at least if it has not been turned on today already. So it is not really surprising connection speeds grinds to a halt. After waiting half an hour for Symantec to sort itself out, the laptops take about 40 seconds to turn on and another 40 to log in - not great, but acceptable.

    Now to work out how to get Symantec to behave! I think I might have to get the laptops to turn on each night to update or something.

  4. Thanks to Jollity from:

    psydii (22nd October 2013)

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    And we conclude, the wifi was behaving as it was designed to ....

    Great you got it worked out.

    NM

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    Quote Originally Posted by neilmac View Post
    And we conclude, the wifi was behaving as it was designed to ....
    Indeed...

    Well I gained some useful insights on WiFi issues for the future.

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    Quote Originally Posted by Jollity View Post
    The 300Mbps figures given for N wifi reminds me of the "up to" figures on ADSL lines.

    It seems I have found the source of the problem rather more easily than I feared. Symantec Endpoint appears to be downloading 300MB of updates on each client, every time each one turns on, at least if it has not been turned on today already. So it is not really surprising connection speeds grinds to a halt. After waiting half an hour for Symantec to sort itself out, the laptops take about 40 seconds to turn on and another 40 to log in - not great, but acceptable.

    Now to work out how to get Symantec to behave! I think I might have to get the laptops to turn on each night to update or something.
    The only way I've found to get Symantec to behave is to uninstall it. Good luck!

  8. Thanks to seawolf from:

    Jollity (22nd October 2013)

  9. #22

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    Synack hit the point. Many wifi companies and brands are awesome for single user through to 10 user wifi but add more in or larger profiles etc things will suck. Ruckus has stepped forward on this and can be used to handle a large amount of users (provided profiles are reasonably small...ie arpund the 3mb mark).

    Other brands of wifi (xirrus, aruba, meraki) are also stepping up now and I would be willing to bet that out of all, xirrus would be the next brand that says yes, one AP can service X range, with Y many users, and do it well.

    In all my final advice is this...test every brand thoroughly. Have a class willing to help out. Install each brand individually, test the log ins and speeds of 30 machines at once...then rinse and repeat. Also another thing to factor...thickness of walls between AP and machine, any wire msh in the walls, other RF antenna causing havok or all APs on the same chanmel for example etc. Factor in everything and move forward.

    Good luck

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    Only 1 device can talk at once, so if your design is going to be critical you need to work from the very beginning with a good understanding of how WiFi works. The differences between vendors are not so great unless you know how to configure it to get the extra benefits.

    Manufacturers will give figures but you have to understand how AP loading works, plus how to make extra gains with QoS, balancing, toggling data rates and other tweaks that will change the environment.

    10 internet users will behave vastly different to 10 VoIP phones, simply adding more access points does not increase performance and can often make things worse. It's never about how many devices per access point.

    You have to start with the client devices and work up from there. Complex network design needs a skilled professional, if you try and do it cheaply and with minimal skills then you design faults into the network that will be difficult to put right later. You should thoroughly analyse your client devices and their needs, this will tell you how many access points you have to install, then you have to try and balance the signals.

    Vendor selection is about in the middle on a task list of things to do when planning a network.

    Really, if it's an important network that will be used for more than just casual browsing, you need to plan correctly, and get professional help.

    NM

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