Subject: [Capwap] Proposed Resolution to Issue 45 - Issue on combining messages

From: "Dorothy Stanley" <[email-masked]>
Date: Mon, 10 Apr 2006 10:19:58 -0700

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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