Subject: RE: [Capwap] Proposed Resolution to Issue 45 - Issue on combiningmessages

From: "Saravanan Govindan" <[email-masked]>
Date: Tue, 11 Apr 2006 13:23:12 +0800

Hi Dorothy,

I think this recommendation add substantial value to the CAPWAP
protocol. There have been discussions on the need for aggregating
statistics information from the WTP to AC. The Echo Request offers a way
for achieving this. The mechanisms for statistics exchanges - timer,
periodic exchange - are available with Echo Request. So I think it is of
value to keep Echo Request and add statistics information fields to it. 

Cheers,

Saravanan

  _____  

From: Dorothy Stanley [mailto:[email-masked]] 
Sent: Tuesday, April 11, 2006 1:20 AM
To: capwap
Subject: [Capwap] Proposed Resolution to Issue 45 - Issue on
combiningmessages

All,

Issue 45, Issue on Combining messages currently has the following
discussion in the issues database:

Currently, the keepalive and statistics messages are separated. Separate

messages for keepalive signaling and statistics can lead to high
overhead. 

Initial analysis have shown that these overhead can be reduced
significantly 

if the messages can be combined.

Recommendation:

To combine the keepalive and statistics message into one combined
message, 

thus reducing overhead significantly.

Discussion:

The CAPWAP protocol specification currently supports the
Echo Request Message and Echo Response Messages, which are used for
keep-alive
purposes, and do not carry message elements.

There is an IEEE 802.11 Statistics measurement element(11.7.2.1), and
several CAPWAP statistics related
measurement elements: decryption error report, WTP descriptor, WTP radio
information, WTP reboot statistics.
There is no statistics message. 

There is no requirement on how often the statistics related measurement
elements must be reported
to the AC from the WTP, there is a Statistics timer, see 7.2.5, which is
used by the AC to indicate the
timer value to the WTP. (separate question - should the statistics timer
be made general, and indicate the
values for the other Section 12 CAPWAP timers too?  Assume that the
CAPWAP statistics timer used
to determine how often to send the 802.11 specific statistics).

It is not clear that there is a high overhead in keeping the
echo/keep-alive mechanism from
the statistics reporting. There is some benefit in keeping the echo
messages simple,
rather than complicating the processing of those messages.  It is true
that small messages (echo request, response) have high overhead.
In this case, the design choice is to accept the overhead as the cost of
simplicity in design and implementation.

Recommended resolution: reject the comment, with the explanation in the
above paragraph

Comments please.

Thanks,

Dorothy

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---

From: "Dorothy Stanley" <[email-masked]>
Date: Tue, 11 Apr 2006 07:50:22 -0700

Saravanan, Richard,

First of all, thank you for your comments.

Clearly, the WTP must have a means to provide statistics and other relevant
data to the AC..

The question becomes, what specific mechanism should be used?
Overloading the echo request message is one way. CAPWAP  has the WTP event
request message,
section 8.5, and already includes the decryption error report, and can
include the .11 specific
statistics report.

Why is using the WTP event report to report statistics not sufficient? We
should add other applicable CAPWAP message elements
to be included in it.

Thanks,

Dorothy

On 4/10/06, Saravanan Govindan <[email-masked]> wrote:
>
>  Hi Dorothy,
>
>
>
> I think this recommendation add substantial value to the CAPWAP protocol.
> There have been discussions on the need for aggregating statistics
> information from the WTP to AC. The Echo Request offers a way for achieving
> this. The mechanisms for statistics exchanges – timer, periodic exchange –
> are available with Echo Request. So I think it is of value to keep Echo
> Request and add statistics information fields to it.
>
>
>
> Cheers,
>
>
>
> Saravanan
>
>
>
>
>
>
>  ------------------------------
>
> *From:* Dorothy Stanley [mailto:[email-masked]]
> *Sent:* Tuesday, April 11, 2006 1:20 AM
> *To:* capwap
> *Subject:* [Capwap] Proposed Resolution to Issue 45 - Issue on
> combiningmessages
>
>
>
> All,
>
> messages for keepalive signaling and statistics can lead to high overhead.
>
> Initial analysis have shown that these overhead can be reduced significantly
>
>
>
> To combine the keepalive and statistics message into one combined message,
>
> values for the other Section 12 CAPWAP timers too?  Assume that the CAPWAP
> statistics timer used