Subject: [BEHAVE] Section 5 in RFC5508

From: WashamFan <[email-masked]>
Date: Thu, 29 Apr 2010 16:58:53 +0800

Hi,

I have a confusion about hairpinned ICMP query support described
in section 5 in rfc5508. ICMP query msg has no indication for dest
port and the NAT should have no idea how to forward this ICMP
query msg to the intented host behind it. Am I missing something?

THanks in advance.
washam

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From: "Dan Wing" <[email-masked]>
Date: Thu, 29 Apr 2010 14:12:48 -0700

> query msg to the intented host behind it. Am I missing something?

The requirement for hairpinning ICMP queries applies to "Basic NAT" 
-- which is not NAPT.  It says:

   REQ-7: NAT devices enforcing Basic NAT [NAT-TRAD] MUST support the
          traversal of hairpinned ICMP Query sessions.  All NAT devices
          (i.e., Basic NAT as well as NAPT devices) MUST support the
          traversal of hairpinned ICMP Error messages:

          a) When forwarding a hairpinned ICMP Error message, the NAT
             device MUST translate the destination IP address of the
             outer IP header to be same as the source IP address of the
             embedded IP packet after the translation.

"Basic NAT" does not change transport-layer (UDP, TCP) ports.  NAPT 
changes transport-layer ports.  "Basic NAT" is not NAPT.

Hope that helps,
-d

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From: WashamFan <[email-masked]>
Date: Fri, 30 Apr 2010 09:37:23 +0800

>  changes transport-layer ports.  "Basic NAT" is not NAPT.

It does help, thanks.
washam