Subject: RE: [Capwap] BSSID-WLAN mappings

From: "Bob O'Hara (boohara)" <[email-masked]>
Date: Fri, 14 Apr 2006 12:13:26 -0700

Puneet,
 
The 1:1 mapping of WLAN to BSSID is all that is described in the 802.11
standard.  There is no method in that standard defined to support more
than a single BSS on a BSSID.  Adding such a mechanism to CAPWAP would
only serve to promote noninteroperable implementations of 802.11 on
various WTPs.

 -Bob

________________________________

From: Puneet [mailto:[email-masked]] 
Sent: Friday, April 14, 2006 12:29 AM
To: [email-masked]
Subject: [Capwap] BSSID-WLAN mappings

the BSSID description in Section 11.9.1 'WTP Radio Configuration' notes
that a WTP that supports 16 WLANS MUST have 16 MAC addresses reserved
for it. Why? ie. what part of the protocol does not work if we have
multiple SSIDs on a single BSSID? (whether thats good design or bad is a
different matter). Since the WLAN ID could be used in all such places to
convey WLAN information back to the AC, why do we need to mandate this
1:1 BSSID-WLAN mapping?

Thanks,
Puneet

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From: Puneet <[email-masked]>
Date: Fri, 14 Apr 2006 17:01:01 -0700

Bob,

>From the CAPWAP protocols point of view, what messages cannot handle this
mode? (ie. over the air 802.11 interoperability issues aside, is there a
problem between the WTP-AC in this mode). There are many APs/WTPs today that
use this mechanism, and mandating a 1:1 mapping excludes all of them, maybe
unnecessarily.

If there is no message in CAPWAP that cannot handle (or, cannot be made to
easily handle) multiple SSIDs on a single BSSID, then maybe that sentence
should be a recommendation instead. That would serve both purposes (lets
people know that its nice to have a 1:1 mapping, allows those WTPs that use
multiple SSIDs on a single BSS to be a part of CAPWAP).

thanks,
Puneet

On 4/14/06, Bob O'Hara (boohara) <[email-masked] > wrote:
>
>  Puneet,
>
> The 1:1 mapping of WLAN to BSSID is all that is described in the 802.11standard.  There is no method in that standard defined to support more than
> a single BSS on a BSSID.  Adding such a mechanism to CAPWAP would only serve
> to promote noninteroperable implementations of 802.11 on various WTPs.
>
>  -Bob
>
>
>
>  ------------------------------
> *From:* Puneet [mailto:[email-masked]]
> *Sent:* Friday, April 14, 2006 12:29 AM
> *To:* [email-masked]
> *Subject:* [Capwap] BSSID-WLAN mappings
>
> that a WTP that supports 16 WLANS MUST have 16 MAC addresses reserved for
> it. Why? ie. what part of the protocol does not work if we have multiple
> SSIDs on a single BSSID? (whether thats good design or bad is a different
> matter). Since the WLAN ID could be used in all such places to convey WLAN
> information back to the AC, why do we need to mandate this 1:1 BSSID-WLAN
> mapping?
>
> Thanks,
> Puneet
>

---

From: "Saravanan Govindan" <[email-masked]>
Date: Sun, 16 Apr 2006 08:26:52 +0800

Hi Puneet,

My concern regarding the BSSID - WLAN mapping is based on the mandatory 
Objective "Logical Groups" (Section 5.1.1 of CAPWAP Objectives).

The Objective requires that WTP traffic be kept logically distinct among 
logical groups. This arises from the commercial need of service providers 
sharing WLAN infrastructure equipment. Service providers want their traffic 
to be distinguished both over the wireless environment (e.g. BSSIDS) and 
over the AC-WTP environment (e.g. WLANs).

The BSSID-WLAN mapping issue is the technical requirement coming from this 
commercial need. It allows an AC - or WTP - to decide how logical groups are 
separated over the wireless and AC-WTP segments. So by making this mapping, 
CAPWAP frames of different logical groups (WLANs) can be distinctly 
exchanged.

I agree with others that this mapping should not exclude any implementation 
- my concern is that the mapping be including in the first place.

Cheers,

Saravanan

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From: Puneet <[email-masked]>
Date: Sun, 16 Apr 2006 16:47:17 -0700

Hi Saravanan,

I see your point, but this seems to address a very specific deployment
scenario (service providers sharing WLAN equipment). If nothing else in the
CAPWAP messages is dependent on this, then this should be a recommendation
instead of a mandate. That way the protocol remains inclusive, and also
meets its objective.

I think it is very important that existing implementations are not excluded
just because they dont seem to meet one specific need in a specific
deployment scenario.

Thanks,
Puneet

On 4/15/06, Saravanan Govindan <[email-masked]> wrote:
> for