AP communication during roaming

julfle01rhi · ‎07-12-2008

Can anyone point me to some docs or share any info on how AP's communicate *between* each other when a wireless client attempts to roam between them.

Do Cisco AP's behave any differently than other vendors ?

I am assuming a simple network here (only APs connected by a simple switch)- no wireless controllers, etc.

What about a wireless solution where multiple vendor APs are involved. Does hand-off between these different APs always occur smoothly.

What about the really budget APs ? do they handle roaming properly ? I ask this as its sometimes a struggle to convince some clients to make the investment in Cisco rather than budget brands. Any info on issues with non-Cisco would be useful.

Thanks

Julian

Scott Fella · ‎07-13-2008

Its really the client that decides the roaming. Here is a good link:

http://www.ciscopress.com/articles/article.asp?p=102282&seqNum=2

-Scott
*** Please rate helpful posts ***

julfle01rhi · ‎07-13-2008

yep - good link - thanks.

Quoting the article, it says the following :- "The new AP should indicate to the previous AP that the client has successfully roamed. This step usually happens via a unicast or multicast packet from the old AP to the new AP with the source MAC address set to the MAC of the roaming client.*"

but it says "usually". :-)

There is clearly a lot of potential detail in this exchange. I was looking for some Cisco specifics, (if possible)

Scott Fella · ‎07-13-2008

This issue is with the vendor as it is stated here:

Because the IEEE and the 802.11 standard do not address AP-to-AP communications via the distribution system (the wired interfaces in this case), AP vendors are left to implement such mechanisms on their own.

If you need specifics, then you will have to research the vendor whom wireless card you want information on.

If you look under Roaming Algorithms, it states that:

Roaming algorithms become a vendor's "secret sauce," and as a result are kept confidential

-Scott
*** Please rate helpful posts ***