Subject: [pcp] NAT-PMP and PCP and DTLS

From: "Dan Wing" <[email-masked]>
Date: Mon, 14 Mar 2011 14:22:20 -0700

I'm sure many of you recall the discussions on how we might handle running
NAT-PMP and PCP on the same port, and how we might need to support DTLS in
the future.  The simple approach to demultiplex 'naked' PCP and DTLS on the
same port was to use "1" in the first bit of the first byte, which isn't
used by DTLS itself.  However, this causes problems if we want to run
NAT-PMP and PCP on the same port.  On closer examination, the first byte of
DTLS payloads will use the TLS 'type', 
http://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parame
ters-5
so as long as we don't step on one of those (or values near that), we still
have the flexibility to use DTLS, _and_ we have the flexibility to operate
NAT-PMP and PCP on the same port (or, with the same server code, using port
forwarding if desired).  With this change, NAT-PMP and PCP can be on the
same port.
 
I just wanted to give a heads-up on this change that you'll see in -07.

-d