Subject: [Capwap] New Issue: Data Check has no timeout on AC

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 16 Nov 2007 15:13:59 -0800

All,
 
While removing the NeighborDead timer, I notice that it was incorrectly
used while in the Data Check mode by the AC. Interestingly enough, the
timer was actually incorrect since the description of the timer was only
valid for Echo Requests, and only by the WTP. So I had to create a new
timer, and a new state transition to allow for this state to timeout.
The issue is that when the AC enters the Data Check state, it needs to
have a fail safe if the WTP doesn't transmit close the loop. So the new
text requires that the AC set the timer when it enters the Data Check
state, and it disables the timer if the WTP doesn't transmit the Data
Channel Keep Alive packet. I also added text to have the AC disable the
timer if it does receive the packet from the WTP.
 
Here is the proposed text:
<text>
2.3.  CAPWAP State Machine Definition
[...]
                            /-------------------------------------\
                            |          /-------------------------\|
                            |         w|                         ||
                            |    5+----------+ x +------------+  ||
                            |     |   Run    |-->|   Reset    |-\||
                            |     +----------+   +------------+ |||
                           6|  u      ^           ^     ^      y|||
                +------------+--------/           |     |       |||
                | Data Check |             /-------/    |       |||
                +------------+<-------\   |             |       |||
                                      |   |             |       |||
                       /------------------+--------\    |       |||
                      r|             t|  s|    4   v   o|       |||
               +--------+     +-----------+     +--------------+|||
               |  Join  |---->| Configure |     |  Image Data  ||||
               +--------+  q  +-----------+     +--------------+|||
                ^  p|                  V|                    x| |||
                |   |                   \-------------------\ | |||
                |   \--------------------------------------\| | |||
                \------------------------\                 || | |||
         /--------------<----------------+--------------\  || | |||
         | /------------<-------------\  |              |  || | |||
         | |                         m|  |n            z|  vv v vvv
         | |   +----------------+   +--------------+   +-----------+
         | |   |   DTLS Setup   |   | DTLS Connect |   |  DTLS TD  |
         | |   +----------------+   +--------------+   +-----------+
         | |    g|  ^     ^   |h         ^               ^
         v v     |  |     |   |          |               |
         | |     |  |     |   \-------\  |   /-----------/
         | |     |  |     |           |  |   |
         | |     v  |e   f|      2    v  |j  |k
         | \->+------+   +------+   +-----------+
         |    | Idle |-->| Disc |   | Authorize |
         \--->+------+ a +------+   +-----------+
              b|    ^           |c
               |    |      /----/
               v   d|      |
              +---------+  |
              | Sulking |<-/
            3 +---------+

[...]
   Configure to Data Check (t):  This state transition occurs when the
      WTP and AC confirm the configuration.
[...]

      AC:  This state transition occurs when the AC receives the Change
         State Event Request message (see Section 8.6) from the WTP.
         The AC responds with a Change State Event Response message (see
         Section 8.7).  The AC MUST start the DataCheckTimer timer (see
         Section 4.7).

   Data Check to DTLS Teardown (6):  This transition occurs when the WTP
      does not complete the Data Check exchange.

      WTP:  This state transition occurs if the WTP does
            not receive the Change State Event Response before a CAPWAP
            transmission timeout occurs.

      AC:  The AC enters this state when the DataCheckTimer timer
         expires (see Section 4.7).

   Data Check to Run (u):  This state transition occurs when the linkage
      between the control and data channels has occured, causing the WTP
      and AC to enter their normal state of operation.
[...]

      AC:  This state transition occurs when the AC receives the Data
         Channel Keep Alive packet (see Section 4.4.1), with a Session
         ID message element matching that included by the WTP in the
         Join Request message.  The AC disables the DataCheckTimer
         timer.  Note that if AC policy is to require the data channel
         to be encrypted, this process would also require the
         establishment of a data channel DTLS session.  Upon receiving
         the Data Channel Keep Alive packet, the AC transmits its own
         Data Channel Keep Alive packet.

4.7.  CAPWAP Protocol Timers
[...]
4.7.4.  DataCheckTimer

   The number of seconds the AC will wait for the Data Channel Keep
   Alive, which is required by the CAPWAP state machine's Data Check
   state.  The AC resets the state machine if this timer expires prior
   to transitioning to the next state.

   Default: 30
</text>

PatC
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---

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 16 Nov 2007 15:15:19 -0800

I should have noted this is issue 22.

PatC 

-----Original Message-----
From: Pat Calhoun (pacalhou) 
Sent: Friday, November 16, 2007 3:14 PM
To: capwap
Subject: [Capwap] New Issue: Data Check has no timeout on AC

All,

[...]

   Default: 30
</text>

PatC