Subject: [Capwap] Data Length invalid in Image Identifier

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Thu, 4 Sep 2008 13:31:26 -0700

I have forwarded this e-mail to the list on behalf of Glenn.

Hi Glenn,

I have created issue 176 to track this one. You are correct, the Data
Length field shouldn't have been referenced, as it is not in the actual
figure. The new text reads:

<new text>
4.6.26.  Image Identifier
[...]

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Vendor Identifier                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                             Data...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:   25 for Image Identifier

   Length:   >= 5

   Data:   A variable length UTF-8 encoded string [RFC3629] containing
      the firmware identifier to be run on the WTP, whose length MUST
      NOT exceed 1024 octets.  The length of this field is inferred from
      this message element's length field.
</new text>

PatC

------------------------------------------------------------------------
--------

From: Glenn Chagnot [mailto:[email-masked]] 
Sent: Tuesday, September 02, 2008 6:29 PM
To: [email-masked]'
Subject: Image Identifier Potential Issue

Hi Pat,

As I have been working my way through the CAPWAP Protocol Base -11
draft, I found the encoding information for the Image Identifier a bit
confusing.  In addition to Pasi's earlier feedback that the length
should be >= 5, I also found the description of Data Length confusing.
The line that confuses me states:

"Data Length:   Length of data field, with a maximum size of 65535. 

In the description for the Data field, the statement is made:

"The length of this field is inferred from this message element's length
field."

It seems to me that the Data Length line does not belong in this
description at all, particularly since it is not shown in the message
element diagram.  In other words, I think the message element should
contain:

Type                        2 octets
Length                      2 octets
Vendor ID                   4 octets
Data                        1-1024 octets

 If it does belong in the description, then the diagram probably should
be updated and a description an update to the text is in order to
clarify its usage further.

Thanks!

Glenn
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