Subject: [Capwap] Issue 70: Section 5.2.2 Minor Editioral Comment

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Sat, 29 Apr 2006 14:04:48 -0700

The issue stated that the following section refered to radios instead of
WTPs,
which was a bug in the text. I have made the necessary correction and am
closing
the issue.

5.2.2.  AC Descriptor

   The AC payload message element is used by the AC to communicate it's
   current state.  The value contains the following fields.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Reserved    |                 Hardware  Version ...         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     HW Ver    |                 Software  Version ...         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     SW Ver    |            Stations           |     Limit     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Limit     |          Active WTPs          |   Max WTPs    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Max WTPs    |    Security   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  6 for AC Descriptor

   Length:  18

   Reserved:  MUST be set to zero

   Hardware Version:  The AC's hardware version number

   Software Version:  The AC's Firmware version number

   Stations:  The number of mobile stations currently associated with
      the AC

   Limit:  The maximum number of stations supported by the AC

   Active WTPs:  The number of WTPs currently attached to the AC

   Max WTPs:  The maximum number of WTPs supported by the AC

   Security:  A 8 bit bit mask specifying the authentication credential
      type supported by the AC.  The following values are supported (see
      Section 10):

      1 - X.509 Certificate Based

      2 - Pre-Shared Secret

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems
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From: "David T. Perkins" <[email-masked]>
Date: Sun, 30 Apr 2006 08:52:06 -0700 (PDT)

HI,

I don't remember if I sent in comments specifically about this
and the the similar one for WTPs.
In general, the value for hardware and software versions doesn't
match typical practices, and also does not follow the values
found in the Entity MIB module.

Secondly, originally this info was provided in Discovery
responses and used by WTPs in choosing which AC to connect
to. This provides for either active or passive elements
the opportunity to gather "static" and dynamic info about
ACs and help them choose attack targets.

Thirdly, as specified in the LWAPP-03 (and I believe
in the CAPWAP-00) docs, the versions are used for
matching during WTP image selection. For WTPs and ACs
with different versioning schemes, a version match
is not the appropriate image selection rule.

Fourthly, a only a limited discussion was taken place
about what fields must be included in the X.509 certs
and how should certs be validated. There are a few
interesting cases, such as when a WTP has no calendar
clock, or when it does have a clock and the value is
way off, and thus validating the AC's cert may fail.
 
I hope to soon send out a proposal to help clarify the
discovery, control channel set up, and WTP image
selection and transfer. 

>    current state.  The value contains the following fields.
Regards,
/david t. perkins