Capwap Mailing List: RE: Proposed Text for Issue 53

[Bob O'Hara (boohara) (boohara]

Pat,

A suggestion for better language defining the value of the Data Rate
field:

Replace only the second sentence with the following:
"The content of the field is a value representing the data rate of the
frame received by the WTP.  The value is in units of 100kbps." 


 -Bob
 
-----Original Message-----
From: Pat Calhoun (pacalhou) 
Sent: Monday, April 03, 2006 8:45 PM
To: capwap
Subject: [Capwap] Proposed Text for Issue 53

Here is my proposed text for Issue 53, which is the addition of a Data
Rate In the CAPWAP header.

Please let me know if you have any comments.
 
4.1.  CAPWAP Transport Header

   All CAPWAP protocol messages are encapsulated using a common header
   format, regardless of the CAPWAP control or CAPWAP Data transport
   used to carry the messages.  However, certain flags are not
   applicable for a given transport.  Refer to the specific transport
   section in order to determine which flags are valid.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |VER| RID |F|L|R|    Frag ID    |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Reserved                            |
<=== CHANGED!!!
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Payload...  |
     +-+-+-+-+-+-+-+-+

[...]
4.1.8.  Reserved

   This 32 bit field is reserved and may be used by a binding specific
   extension.  Refer to the transport portion of the binding for a
   specific wireless technology for the definition of this field.

[...]

11.3.2.  CAPWAP Header Reserved field

   The reserved CAPWAP header field (see figure Section 4.1) is only
   used with CAPWAP data frames, and it serves two purposes, depending
   upon the direction of the frame.  For packets from the WTP to the AC,
   the field uses the format described in Section 11.3.2.1.  However,
   for frames sent by the AC to the WTP, the format used is described in
   described in Section 11.3.2.2.

11.3.2.1.  IEEE 802.11 Frame Info

   When an CAPWAP data frame is received from a station over the air, it
   is encapsulated and this field is used to include radio and PHY
   specific information associated with the frame.

   When used with the IEEE 802.11 binding, the field follows the
   following format:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     RSSI      |     SNR       |           Data Rate           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   RSSI:  RSSI is a signed, 8-bit value.  It is the received signal
      strength indication, in dBm.

   SNR:  SNR is a signed, 8-bit value.  It is the signal to noise ratio
      of the received IEEE 802.11 frame, in dB.

   Data Rate:  The data rate field is a 16 bit unsigned value.  The
      contents of the field is set to 1/10th of the data rate of the
      packet received by the WTP.  For instance, a packet received at
      5.5Mbps would be set to 55, while 11Mbps would be set to 110.

11.3.2.2.  Destination WLANs

   The Destination WLAN field is used to specify the target WLANs for a
   given frame, and is only used with broadcast and multicast frames.
   This field allows the AC to transmit a single broadcast or multicast
   frame to the WTP, and allows the WTP to perform the necessary frame
   replication services.  The field uses the following format:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              WLAN             |            Reserved           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   WLAN:  This bit field indicates the WLAN ID (see section
      Section 11.8.1.1) which the WTP will transmit the associated frame
      on.  For instance, if a multicast packet is to be transmitted on
      WLANs 1 and 3, bits 1 and 3 of this field would be enabled.  Note
      this field is to be set to zero for unicast packets and is unused
      if the WTP is not providing encryption services.

   Reserved:  This field MUST be set to zero.
 
 

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems
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