Capwap Mailing List: Issue 181: ImageDataStartTimer not necessary on AC

[Pat Calhoun (pacalhou) (pcalhoun]

Yong Zhang brought up the following to my attention on draft -12. I have
created issue 181 to track this. This issue does not impact
interoperability. In fact, what happens is that the AC enables the
timer, then disables the timer at the next response it gets from the WTP
- so there is no bug per se. The only issue is that the timer is
unnecessary. If the group decides the change needs to be done, I wonder
if we could make this change post IESG Review.

> 
> 5. page 25
> 
>       AC:  This state transition occurs when the AC receives the Image
>          Data Request message from the WTP, after having sent its Join
>          Response to the WTP.  The AC stops the WaitJoin timer.  The
AC
>          MUST transmit an Image Data Response message (see
>          Section 9.1.2) to the WTP, which includes a portion of the
>          firmware.  The AC MUST start the ImageDataStartTimer timer
(see
>          Section 4.7).
> 
> Here AC will first send Image Data Response, then another Image Data
Req, which has the image data.
> 
> The ImageDataStartTimer in WTP side is used ensure wtp receives image
data req from AC.
> What is it used for in AC now? For the image data resp?

Hmmm.... That's a good question. The current text reads that the timer
is started, but it is then stopped when the AC receives the next Image
Data Response. This would obviously be covered through the normal
retransmission timer, so it appears as if this timer is completely
unnecessary on the AC.

PatC