Capwap Mailing List: Re: Proposed Text for Issue 254

[Abhijit Choudhury (achoudhu) (achoudhu]

While trying to address Issue 254, I realized that there are a number of

places in the CAPWAP protocol spec that we need to fix.

I also noticed that in the spec, we start using "data channel"

and "control channel" without defining what they are.

 

I propose the following changes:

 

1. Add the following to Terminology (Section 1.4)

 

      CAPWAP Control Channel:  A connection defined by (WTP-IP-Addr, AC-IP-Addr,

        WTP-Control-Layer4Port, AC-Control-Layer4Port) over which CAPWAP control 

        packets are sent.

 

        CAPWAP Data Channel:  A connection defined by (WTP-IP-Addr, AC-IP-Addr,

        WTP-Data-Layer4Port, AC-Data-Layer4Port) over which CAPWAP data packets

        are sent.
 

2. In Section 3.1

    Replace

        CAPWAP protocol control packets sent between the WTP and the AC use
        well known UDP port [to be IANA assigned].  CAPWAP protocol data
        packets sent between the WTP and the AC use UDP port [to be IANA
        assigned].

    With
         CAPWAP protocol control packets sent from the WTP to the AC use
         well known UDP port [to be IANA assigned] at the AC and any

         port selected by the implementation at the WTP. CAPWAP protocol data
         packets sent from the WTP to the AC use UDP port [to be IANA
         assigned] at the AC and any port selected by the implementation 

         at the WTP. In either case, for packets sent by the AC to the WTP, 
         the source and destination ports are reversed.

3. In Section 4.1

    Replace

         Payload Type:  A 4 bit field which specifies the payload type that
          follows the preamble header.  The following values are supported:

 

          0 -  Clear text.  If the packet is received on the data UDP port,
             the CAPWAP stack MUST treat the packet as a clear text CAPWAP
             data packet.  If received on the control UDP port, the CAPWAP
             stack MUST treat the packet as a clear text CAPWAP control
             packet.  If the control packet is not a Discovery Request or
             Response packet, the packet MUST be dropped.

 

          1 -  DTLS Payload.  The packet is a DTLS packet and MAY be a data
             or control packet, based on the UDP port it was received on
             (see Section 3.1).

 

    With

         Payload Type:  A 4 bit field which specifies the payload type that
          follows the preamble header.  The following values are supported:

 

          0 -  Clear text.  If the packet is received on the CAPWAP data channel,
             the CAPWAP stack MUST treat the packet as a clear text CAPWAP
             data packet.  If received on the CAPWAP control channel, the CAPWAP
             stack MUST treat the packet as a clear text CAPWAP control
             packet.  If the control packet is not a Discovery Request or
             Response packet, the packet MUST be dropped.

 

          1 -  DTLS Payload.  The packet is a DTLS packet and MAY be a data
             or control packet, based on the channel it was received on
             (see Section 3.1).

 

 

4. In Section 4.3

   Replace

      Both CAPWAP data messages are transmitted on the data channel UDP port.

   With

       Both CAPWAP data messages are transmitted on the data channel.

Thanks,

Abhijit