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Here is a question, I thought I would throw out there and see what peoples opinions are:

Should vendors support the protection mechanism when operating in ?¡é?€??802.11g only?¡é?€?? mode?

Or put another way: When you setup your AP in ?¡é?€??G only' mode but are in range of another network on the same channel that has 802.11b clients connected should your AP implement protection? It would appear that some vendors do and some don?¡é?€??t

My initial thoughts are that the protection mechanism in the 802.11g standard is not optional and therefore applies to all 802.11g networks (include g only). If I had lots of 802.11b clients (lets say handheld devices) and a neighbouring network was g only but did not implement the protection mechanism, I?¡é?€??m not sure I would be too happy.

Let me know what you think?

I think APs should support protection mechanism even when operating in 11g only mode. I am not sure about it.

This is what the official guideV4, Pg 331 says:

Of course, the ERP protection mechanism kicks in whenever an HR/DSSS PHY device is associated with the ERP AP.

11g only is a vendor implementation not outlined in the amendment. You are correct that different vendors implement it differently, but in general it means that it won't allow 11b devices to associate. However, keep in mind that there are two other ways an 11g device will still go into protection. There are other threads that I have responded to that have a lot of detail on that but simply the other two ways an 11g AP will go into protection is the existence (hears a beacon) of an 11b AP on the same channel or another 11g AP in protection because of an 11b device.

Also remember that this isn't limited within an SSID. ANY 11b AP or 11g AP in protection because of 11b will send your device into protection no matter what SSID etc.

To completely disable protection most vendors require you shut down DSSS support. Let me know if I need to dig deeper.

GT

GTHill Escribi?3:

There are other threads that I have responded to that have a lot of detail on that but simply the other two ways an 11g AP will go into protection is the existence (hears a beacon) of an 11b AP on the same channel or another 11g AP in protection because of an 11b device.

Hi GT,

I've read all those threads related to protection mechanisms and even the whitepaper mentioned on it. I still have a doubt:
Protection mechanisms kicks in when an 11b station associates with 11g AP or it gets enabled even if the STA doesn't associate but enters(transmits a Beacon) in BSS?

As I've mentioned in my prev post in this thread, the official guide says, "it kicks in when 11b STA associates".

It does kick in when an 11b STA associates, but it will go into protection for two other reasons.

11b AP beacon is heard by an 11g AP.

11g AP beacon is heard and that beacon indicated protection because of an ERP device is present.

GT

GTHill Escribi?3:

It does kick in when an 11b STA associates, but it will go into protection for two other reasons.

11b AP beacon is heard by an 11g AP.

So that means: If I've 11g only network and some rogue 11b client enters(not associate) into my network then the performance will degrade significantly even though I've implemented my network to not allow any 11b clients.
Don't you think this implementation is somewhat incorrect? What can be done to avoid this?

GTHill Escribi?3:

11g AP beacon is heard and that beacon indicated protection because of an ERP device is present.

GT

I completely agree with this.

The 11g only mode that vendors employ will not allow an 11b device to associate. However, most vendors AP's will still go into protection for the other two reasons.


How can it be avoided? Most vendors have a "data rates" selection on the AP. Disabling the DSSS data rates (1,2,5.5, 11 Mbps) will completely disable protection on *most* vendor's equipment.

GT

1. Refereing to your post: http://cwnp.com/phpBB2/viewtopic.php?t=4240
I guess you and neilmac, agreed on the fact that "Protection mechanisms kicks in after assoc.".

2. Even if I disable 11b data rates(1, 2, 5.5, 11), the 11g data rate won't fall from 54Mbps to 24Mbps?

3. Leave apart the vendors implementation, what does the standard say? I couldn't get a firm answer from the standard too :(

The standard has no provisions for disabling the use of protection.

Yes the data rate will fall to 24Mbps but that is an OFDM data rate and has no effect on protection.

I have to keep reiterating. For an 11b Client STA to induce protection it must associate. However, the other two ways an 11g AP device will go into protection still exist.

GT

alright.
Thanks for your patience and clearing the doubts.