Subject: [Capwap] Join to Image Data State is broken

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Thu, 25 Jan 2007 04:30:07 -0800

The current state machine shows that in order to get to the Image Data
state, 
it is necessary to go from the Join to Configure. This is broken. The
intent 
of the state machine was to transition directly to the Image Data from
the 
Join state. There is no point in pushing configuration on an old image, 
especially since there may be some configuration parameters (e.g.,
message 
elements) that are unsupported on the current WTP firmware.

Issue 235 has been created.

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems
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From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 26 Jan 2007 04:46:01 -0800

Find below the proposed text for this issue.

2.3.  CAPWAP State Machine Definition
[...]
                                       /-------------------------\
                                      w|                         |
                                 5+----------+ x +------------+  |
                                  |   Run    |-->|   Reset    |-\|
                                  +----------+   +------------+ ||
                               u      ^           ^     ^      y||
                +------------+--------/           |     |       ||
                | Data Check |             /-------/    |       ||
                +------------+<-------\   |             |       ||
                                          |             |       ||
                       /------------------+--------\    |       ||
                      r|             t|  s|    4   v   o|       ||
               +--------+     +-----------+     +--------------+||
               |  Join  |---->| Configure |     |  Image Data  |||
               +--------+  q  +-----------+     +--------------+||
                ^  p|                  V|                    x| ||
                |   |                   \-------------------\ | ||
                |   \--------------------------------------\| | ||
                \------------------------\                 || | ||
         /--------------<----------------+--------------\  || | ||
         | /------------<-------------\  |              |  || | ||
         | |                         m|  |n            z|  vv v   vv
         | |   +----------------+   +--------------+   +-----------+
         | |   |   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 +---------+

                 Figure 3: CAPWAP Integrated State Machine

   Join to Image Data (r):  This state transition is used by the WTP and
      the AC to download executable firmware.

      WTP:  The WTP enters the Image Data state when it receives a
         successful Join Response and determines and the included Image
         Identifier message element is not the same as its currently
         running image.  Further, the WTP also detects that the
         requested image version is not currently available in the WTP's
         non-volatile storage (see Section 9.1 for a full description on
         the firmware download process.  The WTP transmits the Image
         Data Request (see Section 9.1.1) message requesting that a
         download of the AC's latest firmware be initiated.

      AC:  This state transition occurs when the AC receives the Image
         Data Request message from the WTP.  The AC must transmit an
         Image Data Response message (see Section 9.1.2) to the WTP,
         which includes a portion of the firmware.

   Join to Configure (q):  This state transition is used by the WTP and
      the AC to exchange configuration information.

      WTP:  The WTP enters the Configure state when it receives a
         successful Join Response, and determines that the included
         Image Identifier message element is the same as its currently
         running image.  The WTP transmits the Configuration Status
         message (see Section 8.2) to the AC with a snapshot of its
         current configuration.  The WTP also starts the ResponseTimeout
         timer (see Section 4.6).

      AC:  This state transition occurs immediately after the AC
         transmits the Join Response message to the WTP.  If the AC
         receives the Configuration Status message from the WTP, the AC
         must transmit a Configuration Status Response message (see
         Section 8.3) to the WTP, and may include specific message
         elements to override the WTP's configuration.

Pat Calhoun

> -----Original Message-----
> From: Pat Calhoun (pacalhou) 
> Sent: Thursday, January 25, 2007 4:30 AM
> To: [email-masked]
> Subject: [Capwap] Join to Image Data State is broken
> 
> The current state machine shows that in order to get to the 
> Image Data state, it is necessary to go from the Join to 
> Configure. This is broken. The intent of the state machine 
> was to transition directly to the Image Data from the Join 
> state. There is no point in pushing configuration on an old 
> image, especially since there may be some configuration 
> parameters (e.g., message

---

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 26 Jan 2007 05:38:59 -0800

Sorry, this was issue 235, not 253 :(

Pat Calhoun

> Sent: Friday, January 26, 2007 4:46 AM
> To: [email-masked]
> Subject: [Capwap] Issue 253: Join to Image Data State is broken
> 
> Image Data 
> > state, it is necessary to go from the Join to Configure. This is 
> > broken. The intent of the state machine was to transition 
> directly to 
> > the Image Data from the Join state. There is no point in pushing 
> > configuration on an old image, especially since there may be some 
> > configuration parameters (e.g., message
> > CTO, Wireless Networking Business Unit Cisco Systems

---

From: "Sudhanshu" <[email-masked]>
Date: Fri, 26 Jan 2007 10:32:18 -0800

As per current consensus, where is the "Image Filename" message element is
carried from WTP to AC? If it is part of the Join request then the proposed
solution is OK. 

My 2 cents...

But I would prefer "join" state to be used purely for the purpose of the
establishing the secure DTLS session and version check. And if this is the
case, we need the state transitions from "Configure" to "Image Data" also. 

As a normal operation state transition will be from "configure" to "image
data". And special case like Version mismatch, state transition from "Join"
to "Image Data" will occur.

Errata: in the current draft, state transition from Join to Configure is
tagged as (q) in diagram (figure 3) and as (g) in section 2.3.1.

-Suds

-----Original Message-----
From: Pat Calhoun (pacalhou) [mailto:[email-masked]] 
Sent: Friday, January 26, 2007 4:46 AM
To: [email-masked]
Subject: [Capwap] Issue 253: Join to Image Data State is broken

Pat Calhoun

---

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 26 Jan 2007 10:42:44 -0800

Having shipped products in this space, I disagree. The
"special case" you list below will end up being the normal
case. Further, we would end up with three separate methods:
 - Join -> Image Data
 - Configure -> Image Data
 - Run -> Image Data (which I would argue provides you with
   what you are looking for anyhow).

Thanks for the errata. caught it this am.

The Image Filename has been replaced with Image Identifier. Please
take a look at the proposed text for issue 238 I sent yesterday.

Pat Calhoun

> From: Sudhanshu [mailto:[email-masked]] 
> Sent: Friday, January 26, 2007 10:32 AM
> To: Pat Calhoun (pacalhou); [email-masked]
> Subject: RE: [Capwap] Issue 253: Join to Image Data State is broken
> 
> As per current consensus, where is the "Image Filename" 
> message element is carried from WTP to AC? If it is part of 
> the Join request then the proposed solution is OK. 
> 
> My 2 cents...
> 
> But I would prefer "join" state to be used purely for the 
> purpose of the establishing the secure DTLS session and 
> version check. And if this is the case, we need the state 
> transitions from "Configure" to "Image Data" also. 
> 
> As a normal operation state transition will be from 
> "configure" to "image data". And special case like Version 
> mismatch, state transition from "Join"
> Errata: in the current draft, state transition from Join to 
> Configure is tagged as (q) in diagram (figure 3) and as (g) 
> in section 2.3.1.
> 
> -Suds
>