Subject: [Capwap] Issue 141: Inconsistent usage of Radio ID and WLAN ID

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Thu, 31 Aug 2006 15:40:47 -0700

I've seen several places where the range of the
Radio ID and WLAN ID is inconsistant.

In section 4.1, in the transport header, the RID is
5 bits (a range of 0-31), but in section 4.4.34,
the max radios and radios in use is a 8 bits (range
of 0-255). Also, in sections 4.4.8, 4.4.11, 4.4.14,
4.4.15, 4.4.17, 4.4.28, 4.4.39, 11.10.1, 11.10.2,
11.10.5, 11.10.6, 11.10.8, 11.10.9, 11.10.10,
11.10.11, 11.10.13, 11.10.14, 11.10.15, 11.10.16,
11.10.17, 11.10.18, 11.10.19, 11.10.20, 11.10.21,
11.10.22, 11.10.23, and 11.10.24 the radio ID
field is 8 bits.

<PRC>
ok, well this is done in order to be more efficient
on the CAPWAP header. I see no need to increase the Radio ID
to greater than 5 bits at this time. So I can make the change in 
one of two ways. 

The first is to make an actual change to the figures,
which honestly to me seems overly complex. The new diagrams
would now look like:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | PAD | Radio ID|                  MAC Address                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Where everytime the PAD would be defined as MUST BE ZERO. An
alternative is simply to be more prescriptive in the definition of the
Radio ID fields, such as:

    Radio ID:
      An 8-bit value representing the radio. Note the supported values
      are between 0 and 31.

Any preferences? I would opt for the second approach
</PRC>

In section 11.4, WLAN is a bit map of length 16
(thus a range of 0-15). However, in the following
sections, WLAN ID is 8 bits (a range of 0-255):
11.10.1, 11.10.9, 11.10.10, and 11.10.11.
And in sections 11.10.5 and 11.10.21 the WLAN ID
is 16 bits (0-65535)

<PRC> Actually, section 11.4 is a bitmap, and not the
WLAN ID. However, I have made the change to be clearer.

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems
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