Understanding 802.11b client on g network

[leonardo_ortiz]

Hello guys.

We know that if we have a mixed enviroment, with 802.11g and b clients, the b client will be slow down the g clients.

Ok, but it is per "segment" ? I mean, how it works ? By BSS, by SSID, By AP ?

If i I have 15 AP's working in 802.11/b/g/n and one 802.11b client connect at my network, all other aps and clients will be affected ?

Sry for my bad english

[Rasika Nayanajith · Accepted solution]

It is in the BSS. Refer below post for some more detail on this protection mechanism & under which condition it is enable.

http://mrncciew.com/2014/11/02/cwap-802-11-protection-mechanism/

As you can see below , it has ripple effect & can impact whole of your wireless. specially if a 802.11b client is roaming.

http://www.cwnp.com/uploads/protection_ripple_in_erp_802-11_wlans.pdf

So best is to disable 802.11b rates & migrate 802.11b only clients to later standards (802.11g/n or 802.11a/n/ac)

HTH

Rasika

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[leonardo_ortiz]

So, if I have 4 BSS, and the 802.1b clients are just in BSS1, the another BSSs will not be affected ?

[Rasika Nayanajith]

Yes, that will be impacted. If you read that Protection Ripple ERP document you will fully understand it (page 3-4).

"As soon as a NonERP STA associates to an ERP AP, the AP will signal for protection in the ERP Information Element of its Beacon using the Use_Protection bit, and it will immediately enable the NonERP_Present bit which instructs other nearby APs to enable Use_Protection.Frames sent at 1 Mbps can be read reliably at a considerable distance by other wireless STAs and APs on the same channel, which means that enabling protection in one BSS may cause the enabling of protection in other BSSs across a large physical area"

HTH

Rasika

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[George Stefanick · Accepted solution]

To help drive the point home .. You can have a neighboring network running 802.11b clients and it will impact your network if in range. They don't have to connect to your network at all.

Your APs will heard the DSSS frames and will be like, wait there is a b client. And then your aps will mark protection.

[leonardo_ortiz]

Wow, 802.11b don't like the "new wireless standards" :O

Guys, thanks for the explanations!

[George Stefanick]

The underlining issue, so you know and have a complete picture, is that 11b devices only modulate frames at DSSS and HRDSSS. 

When a 11g or 11n radio tx with OFDM 11b clients don't understand it .. 

Before 11g and 11n devices want to punch data at the higher modulation  they need to clear the medium and how they know about 11b clients in the area is because the ap tells them in the protection bit ..