Subject: [Mip6] Requirement for NAT traversal (was: v4 CoA and route optimization)

From: "Pascal Thubert \(pthubert\)" <[email-masked]>
Date: Thu, 7 Apr 2005 09:32:44 +0200

Hi Vijay:

| Being behind a NAT or not can be detected very simply by the GW by
| checking the src address and some address that MN puts in the payload.
| 

This seems to omit reverse NATs where the HA is actually within an IPv4
private network, which is a case that we face in small/medium
corporations which can not afford a DMZ. That's also the simplest way
for me to set it up at home so I can keep my DSL connection the way it
stands.

So maybe it's time to discuss what the NAT traversal requirement is. The
way I see it, we need to go through NAT, PAT and reverse NAT. In other
words, MR encapsulates an IPv6 packet into IPv4 UDP. Any of (IPv4
source, IPv4 destination, UDP source port) might be changed. IPv4
destination port should be standardized to avoid confusions.

Pascal

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From: Alexandru Petrescu <[email-masked]>
Date: Thu, 07 Apr 2005 13:38:24 +0200

Pascal Thubert (pthubert) wrote:
>  | checking the src address and some address that MN puts in the 
> payload. |
> 
> This seems to omit reverse NATs where the HA is actually within an 
> IPv4 private network, which is a case that we face in small/medium 
>  for me to set it up at home so I can keep my DSL connection the way 
> it stands.

I think both cases are valid but only the direct (non-reverse) NAT can
be done with my implementation.  Traversing a pair of NAT and reverse
NAT induces a need for a box outside both domains that would need to be
standardized.  At this point I think it would be an unncessary burden.
I think.

> So maybe it's time to discuss what the NAT traversal requirement is. 
> The way I see it, we need to go through NAT, PAT and reverse NAT. In 
> other words, MR encapsulates an IPv6 packet into IPv4 UDP. Any of 
> (IPv4 source, IPv4 destination, UDP source port) might be changed.

Only the source address and the src/dst ports may change, but not the
dst address.  I would agree with this requirement.

> IPv4 destination port should be standardized to avoid confusions.

Ok but standardizing an IPv4 destination port does not mean that a
firewall filter will not block it.

Alex