Subject: [Capwap] Issue 19: Issue with Image Data to Reset

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 16 Nov 2007 15:29:47 -0800

While fixing this issue, I found that the timer that I had introduced
for issue 23 could be re-used. However, a small tweak was required to
the text in issue 23, where the timer isn't disabled by the AC when it
receives the Image Data Request from the WTP, but instead it resets the
timer. If the timer resets, then it is an indication that no further
packets are to be expected, and the firmware download is complete. Note
that the AC no longer performs the (o) state transition when it believes
the firmware download is complete.

Here is the proposed text

<proposed text>
2.3.  CAPWAP State Machine Definition
[...]

   Image Data to Image Data (4):  The Image Data state is used by the
      WTP and the AC during the firmware download phase.
[...]

      AC:  This state transition occurs when the AC receives the Image
         Data Request message from the WTP while already in the Image
         Data state.  The AC resets the ImageDataStartTimer timer.

   Image Data to Reset (o):  This state transition is used to reset the
      DTLS connection prior to restarting the WTP after an image
      download.
[...]

      AC:  The AC enters the Reset state when an error occurs during the
         image download process or if the ImageDataStartTimer timer
         expires.

</proposed text>

PatC
-----Original Message-----
From: Pat Calhoun (pacalhou) 
Sent: Friday, October 12, 2007 1:30 PM
To: capwap
Subject: [Capwap] Issue with Image Data to Reset

All,

The current text states that the AC can transition from the Image Data
to Reset, but this is a problem since the last image data response sent
by the AC may not have been received by the WTP, and therefore the Image
Data Request may need to be retransmitted. There are really only two
alternatives to this situation:
1. Let the WTP reset, but require that the AC set the NeighborDead timer
and wait for expiration before the WTP is marked dead, or 2. Create a
uni-directional message from the WTP to the AC to indicate that the
download is complete, at which time the AC would set the WTP to dead.
This is not very reliable, because the message would not be
retransmitted, and therefore a timer would be necessary anyhow.

My preference is to go with option 1. Any objections?

Issue 19 created to track this issue.

PatC
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