Subject: [Capwap] Issue 225: Need to provide clarity on use of ports to support middleboxes

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Fri, 10 Oct 2008 08:12:18 -0700

All,

During the IESG review, the following issue was raised:

> Section 11 and 9:
> 
> Another issue with NATs that my read through don't think is covered in
> enough detail is the importance of the source address for the CA->WTP
> Image Data Request messages. They need to be sent from the CA control
> channel destination port on which it received the Image Data Request
> from the WTP. And it needs to send to the source address present in
that
> download initiating request.
> 
> For the CA behind NAT the same applies for the WTP data upload.

The issue being raised is that the WTP and the AC need to ensure that
they are responding back on the same port on which a request was
received. This is necessary for NAT traversal. I have proposed the
following text, which the commenter agreed with:

<proposed text>
3.  CAPWAP Transport
[...]
   In order for CAPWAP to be compatible with potential middleboxes in
   the network, CAPWAP implementations MUST send return traffic from the
   same port on which it received traffic from a given peer.  Further,
   any unsolicited requests generated by a CAPWAP node MUST be sent on
   the same port.

11.  NAT Considerations
[...]
   In order for CAPWAP to be compatible with potential middleboxes in
   the network, CAPWAP implementations MUST send return traffic from the
   same port on which it received traffic from a given peer.  Further,
   any unsolicited requests generated by a CAPWAP node MUST be sent on
   the same port.
</proposed text>

PatC
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