Subject: [Capwap] Proposed Text for Issue 254

From: Abhijit Choudhury <[email-masked]>
Date: Mon, 2 Apr 2007 10:38:37 -0700 (PDT)

Hi Puneet,

Does this text help make it clear ? 

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.  CAPWAP protocol data
     packets sent from the WTP to the AC use UDP port [to be IANA
     assigned] at the AC. In either case, when a reply is generated by the AC, 
     the source and destination ports are reversed.

Thanks,
Abhijit

-----Original Message-----
From: Pat Calhoun (pacalhou) 
Sent: Monday, April 02, 2007 9:44 AM
To: Puneet Agarwal; [email-masked]
Subject: Re: [Capwap] Proposed Text for Issue 249: IPv6 UDP Lite

Created new issue 254

PatC

-----Original Message-----
From: Puneet Agarwal [mailto:[email-masked]]
Sent: Tuesday, March 27, 2007 5:50 PM
To: Pat Calhoun (pacalhou); [email-masked]
Subject: RE: [Capwap] Proposed Text for Issue 249: IPv6 UDP Lite

Hi Pat,

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

Does this mean that if the IANA assigned CAPWAP control port is "x",
then for all capwap control packets between WTP and AC (in both
directions), the udp src and the udp dest will always be set to "x"?

Thanks.

-Puneet

-----Original Message-----
From: Pat Calhoun (pacalhou) [mailto:[email-masked]]
Sent: Monday, March 19, 2007 2:26 AM
To: [email-masked]
Subject: [Capwap] Proposed Text for Issue 249: IPv6 UDP Lite

All,

In the event that the WG agrees that we are to proceed with this change,
I would like to submit proposed text to the list. As discussed on the
mailing list previously, UDP-Lite would be restricted to IPv6. Yes, it
does have some NAT transversal issues, which is why some text was added
to the NAT Considerations section. However, there are no IPv6 NATs
today, so there is nothing legacy broken in this proposal. Note that I
also added the proper reference to UDP number assignment in the IANA
considerations as well.

3.  CAPWAP Transport

   Communication between a WTP and an AC is established according to the
   standard UDP client/server model.  The CAPWAP protocol supports two
   different transport protocols.  When used over IPv4, the UDP protocol
   is utilized.  When CAPWAP is used over IPv6, the UDP-Lite RFC 3828
   [13] is used.  This section details the specifics of how the CAPWAP
   protocol works with IP.

3.1.  UDP Transport

   One of the CAPWAP protocol requirements is to allow a WTP to reside
   behind a firewall and/or Network Address Translation (NAT) device.
   Since the connection is initiated by the WTP (client) to the well-
   known UDP port of the AC (server), the use of UDP is a logical
   choice.  The UDP checksum field in CAPWAP packets MUST be set to
   zero.

   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].

3.2.  UDP-Lite Transport

   When CAPWAP is run over IPv6, the UDP-Lite is used as the transport.
   The reason for using UDP-Lite is because when UDP is run over IPv6,
   it MUST NOT have its checksum field set to zero, which increases the
   processing cost for each CAPWAP packet.  When UDP-Lite is used, the
   checksum field MUST have a coverage of 8 RFC 3828 [13].

   As defined in RFC 3828 [13], UDP-Lite uses the same port assignments
   as UDP.
[...]

11.  NAT Considerations
[...]
   When CAPWAP is run over IPv6, NAT support can only be provided if the
   IPv6 NAT system is capable of performing address translation over the
   UDP-Lite 3828 protocol [13].

[...]
14.  IANA Considerations

   A separate UDP port for data channel communications is (currently)
   the selected demultiplexing mechanism, and a port must be assigned
   for this purpose in section Section 3.1.  The UDP port numbers are
   listed by IANA at http://www.iana.org/assignments/port-numbers.

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems
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---

From: "Abhijit Choudhury (achoudhu)" <[email-masked]>
Date: Tue, 24 Apr 2007 19:25:35 -0700

Below is the proposed text for Issue 254, which has been updated based
on feedback on the list.
 
Thanks,
Abhijit
 
-------------------------PROPOSED
TEXT---------------------------------------
 
1. Add the following to Terminology (Section 1.4)

      CAPWAP Control Channel:  A bi-directional flow defined by AC's
IP-Addr, 

       WTP's IP-Addr, IP protocol, AC's control port and WTP's control
port, 

       over which CAPWAP control packets are sent. 

       CAPWAP Data Channel:  A bi-directional flow defined by IP-Addr, 

       WTP's IP-Addr,  IP protocol, AC's data port and WTP's data port, 

       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

         the CAPWAP control channel, as defined in Section 1.4.  The
CAPWAP 
         control port at the AC is the well known UDP port [to be IANA
assigned] 
         while the control port at the WTP can be any port selected by
the 
         implementation at the WTP. CAPWAP protocol data packets sent
from 
         the WTP to the AC use the CAPWAP data channel, as defined in
Section 1.4.  
         The CAPWAP data port at the AC is the well known UDP port [to
be IANA 
         assigned], while the data port at the WTP can be 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.