[Softwires] ALG section in draft-ietf-softwire-dual-stack-lite-06

["Dan Wing" <[e-mail]>]

http://tools.ietf.org/html/draft-ietf-softwire-dual-stack-lite-06 says:

   8.3. Application Level Gateways (ALG)

   The AFTR should only perform a minimum number of ALG for the classic
   applications such as FTP, RTSP/RTP, IPsec and PPTP VPN pass-through
   and enable the users to use their own ALG on statically or
   dynamically reserved ports instead.

Comments:

* To my knowledge, this would be the first time IETF suggests using an ALG
in a NAT44 in a standards-track document.

* Both IPsec and PPTP are protocols, not applications.  IPsec is 50
(assuming you mean IPsec ESP, which I'm sure is what was intended) and PPTP
uses protocol 47 (GRE).  Thus, these do not belong in the Application Level
Gateway section.  Rather, IPsec and PPTP should be moved to the previous
section (NAT Conformance) which already mentions other protocols like TCP
and ICMP.

* There aren't specifications describing an ALG for FTP, RTSP, RTP, IPsec,
or PPTP VPN.

* What is "RTSP/RTP"?  Is this trying to say "RTSP, when it is using RTP",
or is it trying to say "RTSP and other uses of RTP".  Text needs to be
clarified.

* IPsec Passthru is pretty common on residential NATs.  However, in a CGN,
IPsec Passthru is difficult when multiple users connect to the same VPN
concentrator.  When that concentrator re-keys a session, the incoming IPsec
SPI changes and there is no simple way to determine which user should
receive that packet.  There are several workarounds to this problem,
including just ignoring it.

-d