BSS transition

[avigder]

Hello,
when a station moves from one BSS to another, do the APs of the ESS inform each other about the transition?

Is there a standard protocol for this notification?

or in more general form is there any way of knowing to which AP a station is currently connected?

Thanks

[JimGeier]

The 802.11 standard does not define a protocol for communicating between access points to support roaming. Vendors, however, seem to follow somewhat of a defacto stanard for this. One way of knowing which AP a particular user is assocated with is to read the BSSID out of one the user's 802.11 frames. The BSSID is the MAC address of the access point.

[avigder]

Hi, thanks,
Is there a place I can find out more about this defacto standard?
The bssid id ony part of the 802.11 frame right? it doesn't exists in the ethernet frame that was produced by the AP integration service (when I communicate with the mobile station from a regular station connected to the LAN) is there a way I can know from a regular LAN station the BSSID of the wireless station?

[JimGeier]

For more details on 802.11, I recommend that you download a free pdf of the standard at http://grouper.ieee.org/groups/802/11/. You might need to scroll down a bit on that page to see the advertisement for the download page.


It sounds like you want to determine what wireless stations are associated with a particular access point by running a utility from the wired side of the network (not the RF site). You're correct, the BSSID only applies to the header of the 802.11 frame. To determine the associated stations from the wired side, you'll need to communicate with the access point through an SNMP interface over the Ethernet network. I believe that the MIB on the access point maintains a list that you can grab that identifies the associated wireless stations.

[avigder]

HI, thanks for the information, it realy helped a lot.

My original intent was to try and find out the BSSIDs from the AP through SNMP but I've seen that the MIB proposed by the 802.11 standard is not mandatory. (posted a thread here a few weeks ago)

so is there another standard MIB all AP use? (even a defacto one that most of the big manufacters support?)

Thanks again.
avigder.

[oshea85]

Any MIBs that are not IEEE are going to be proprietary; they will not be implemented consistently.