[Simh] Klh10 vs Simh

[Johnny Billquist]

On 2016-02-28 21:36, Peter Svensson wrote:
> On Sun, 28 Feb 2016, Johnny Billquist wrote:
>
>> On 2016-02-28 20:47, Peter Svensson wrote:
>>>  Hi all,
>>>
>>>  There is a lot of incorrect information about the 802.11 capabilities
>>>  going around on this list lately.
>>>
>>>  Normally 802.11 (all versions) uses 3 mac addresses instead of 4 to
>>>  conserve capacity. This is purely a legacy issue from way back when.
>>>  These addresses are used as follows.
>>>
>>>  - Station to AP:
>>>     - AP MAC address (BSSID)
>>>     - Station MAC address
>>>     - 802.1 destination MAC address
>>>     - (802.1 source address is copied from Station MAC field by the AP)
>>>
>>>  - AP to Station
>>>     - Station MAC address
>>>     - AP MAC address (BSSID)
>>>     - 802.1 source MAC address (SA)
>>>     - (802.1 dest address is copied from the Station MAC filed by the
>>> STA)
>>
>> Do I understand you right in that when you write 802.1 destination
>> address, you are in fact talking about the 802.2 frame destination MAC
>> address?
>>
>> If so, this makes sense, it would match what I seem to have observed.
>
> First of all, I am sorry for writing "802.1" when I meant "802.3". I was
> at least consistenly mistyping/misthinking throughout the whole email.
> Please substitute "802.3" whenever I wrote "802.1".

Thanks. I was constantly confused when you repeated 802.1, which didn't 
make sense to me.

> I am not sure what you mean by the 802.2 frame MAC address. The 802.2
> specification specifies the LLC which AFAIK does not include any
> addresses. It does include protocol type information. 802.2 LLC headers
> can sometimes be seen on on eathernet when using LLC+SNAP headers, but
> that is rare these days. Most Ethernet networks use the EtherType
> mechanism. 802.2 is still in use on some non-Ethernet networks, and
> 802.2 LLC+SNAP in some more. I think (but I am not sure) that 802.11
> uses 802.2 LLC+SNAP instead of raw EtherType.

You are right. 802.2 specifies other details of the packet, but not 
addressing. On "ethernets", it would be a 802.3 frame that contained the 
802.2 packet. (Sorry about my mixing up here.)

However, as far as I could figure out, 802.11 also uses 802.2 packets 
inside the frame.

And 802.11 do not look like an 802.3 frame either, so it don't really 
make sense to talk about 802.3 here, I'd say. But let's say that the two 
last addresses in the 802.11 frame are the ones then used to recreate a 
802.3 frame, which holds a 802.2 packet (ugh).

I guess it matches my observation, that the destination mac address is 
messed up on packets sent from the station.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol