WiFi Rates

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And let me clarify one more thing on my earlier discussion:

If you see the ERP stanza, this indicates that the AP is 11g or later - it's a mandatory field

If you see Non-ERP Present set to true, this means there is an 11b STA attached (11b or earlier)

If you see UseProtection - this means that there is an adjacent AP that also has UseProtection set, or has a non-ERP STA associated with the adjacent AP - that AP may be part of the same BSS, or may be another BSS

If you see Barker Mode Preamble set to true - this means long preamble is in use here

 

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Long and short of it - try to keep 11b STA's off the network - 11a/g/n/ac, these generally get along well these days with current chipsets (as of Q302014) - you've tested and documented how well newer 11ac chipsets at the AP can improve performance for all clients associated with the newer AP - nice work there, BTW

If one must support 11b - the guidance posted in the post/thread below is absolutely valid - set aside an AP with a unique SSID to support those legacy STA's

http://forums.smallnetbuilder.com/showthread.php?t=2506


sfx

 

[sfx2000]

And let me clarify one more thing on my earlier discussion:

If you see the ERP stanza, this indicates that the AP is 11g or later - it's a mandatory field

If you see Non-ERP Present set to true, this means there is an 11b STA attached (11b or earlier)

If you see UseProtection - this means that there is an adjacent AP that also has UseProtection set, or has a non-ERP STA associated with the adjacent AP - that AP may be part of the same BSS, or may be another BSS

If you see Barker Mode Preamble set to true - this means long preamble is in use here

And normally one should not see the ERP stanza in 5GHz - as it's not needed - and the Basic Rates generally tend to be more akin to 802.11a (6,12,24 as a baseline).

5GHz is nicer in so many ways, it really is 802.11 done right - 2.4GHz just has too many legacy issues...

 

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Goes back to 802.11b:

1) We define the broadcast Rate of the beacon - at least one rate is mandatory because of this - all associated STA's and candidate STA's (present but not attached) must monitor the broadcast beacon frames - since most 11b and later STA's support at least 1Mbps, this is why you see it here.

2) Other rates in this information element - any STA that wants to join must support the basic rates advertised in this information element (this is somewhat implied obviously, as 11b doesn't support 18Mbps for example, but it does support 1,2,5.5,11, an 11g/n might support 6,9,12 in addition to the 11b ratesets

Hope that clarifies things...

Now whether to allow at STA to attach to the AP, this can be done within the AP chipset firmware/real time configs - remember that the STA also presents it's capabilities when it attaches to the AP - so for example, if I only want 11g STA's to attach, I can configure the AP chipset to deny 11b - doesn't remove the need to advertise the ratesets in the beacon as discussed above.

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And when digging thru wireshark and packet traces, you might see somethink like below - just keep in mind that this is not 802.11b, this is 802.11 BSS (Basic Service Set) Basic Rates, it's a low data rate for all STA's that are attached, or can attach to the AP transmitting the Beacon Frame:

        Tag: Supported Rates 1(B), 2(B), 5.5(B), 11(B), 18, 24, 36, 54, [Mbit/sec]
            Tag Number: Supported Rates (1)
            Tag length: 8
            Supported Rates: 1(B) (0x82)
            Supported Rates: 2(B) (0x84)
            Supported Rates: 5.5(B) (0x8b)
            Supported Rates: 11(B) (0x96)
            Supported Rates: 18 (0x24)
            Supported Rates: 24 (0x30)
            Supported Rates: 36 (0x48)
            Supported Rates: 54 (0x6c)

You'll see the same tags in 5GHz, just different rates.

Little known item - most STA's also use this for link estimation, as the Beacon frame has the lowest data rate and the highest signalling gain, as such, it can then decide what rates to transmit at. It's also used for part of handover decisions depending on client SW implementation.

sfx

(apologies if I've gotten too deep into the wires here, most folks probably don't care, lol)