Subject: Re: (ngtrans) SITT -05 Review Input

From: Erik Nordmark <[email-masked]>
Date: Sat, 3 Jul 1999 21:35:24 -0700 (PDT)

A long overdue response.

> 1.  The spec in the beginning talks about dual stacks and then V6 ONLY.
> Some diagrams in the beginning stating the problem with examples and the
> the path solution SIIT is taking would clear this up.  For example it is
> important to identify if the Hosts "may" be v6/v4 capabale but are 
> using SIIT because there are not enough addresses to assign the nodes
> addresses in SIITs set of assumptions.  Which might be stated more
> clearly.

I can make those clarifications in the next rev.

> 2.  This is a biggie and affects NAT-PT to some degree too.
> 
>     My first impression is that the IPv4 Translated Address is not an
>     optimal idea.  I would like to know why and stated in the spec why
>     SIIT does not use an IPv4 Mapped Address for both cases.

I though the spec did that where it defined the addresses.
The IPv4-mapped address refers to the IPv4-only (or dual with IPv4 apps
as you point out) side of the traffic.
The IPv4-translated address refers to the IPv6-only node.
Using the same type of address for both will force some
odd requirements on routing since you can't tell
which packets are going towards the translator and which ones are
sent from the translator towards the IPv6-only hosts.

>     Using the IPv4 Translated address will cause IPv6 apps and ported 
>     apps to now check IPv4 Mapped and IPv4 Translated.  This is not good
>     we should not have multiple representations for IPv4 addresses.

No, the translated addresses will be assigned to the IPv6-only host
for packets sent to/from the translator. Thus the translated address 
will not appear in the DNS and nothing above the IP layer in
the translator and IPv6-only node needs to be aware of its
existence.
The apps just need to check for IPv4-mapped as they do on dual
hosts today (see section 1.2).

>     If the only reason is because RFC 2373 says IPv4 Mapped cannot 
>     represent an IPv6 Node, we should fix RFC 2373 not use IPv4 
>     Translated addresses.
> 
> 3.  In the spec first it says ESP may work then in the Security
> Considerations it says it will work with Transport mode preferred.
> Can the spec please tighten the wording up here and state if it does or
> not.

I'll clarify this. ESP transport mode works. ESP tunnel mode does not
work.

> One NIT:  RFC 2133 REF should be changed to RFC 2553.

I'll fix that. (Even missed it in the recent update since it wasn't
in the references section.)

Thanks for the comments,
  Erik

---

From: Jim Bound <[email-masked]>
Date: Wed, 07 Jul 1999 10:30:45 -0400

>hosts today (see section 1.2).

I will read the latest draft OK and see if this is clear at my end.

>>     represent an IPv6 Node, we should fix RFC 2373 not use IPv4 

This is my main issue and it could be I need to parse it further in the
spec.  An app on an IPv6 only node will be able to speak with an IPv4
mapped address I agree.  But not a translated one cause it will no
nothing of such an address type.  So I need to look at the point where
the IP layer uses a translated address and will do that again.

thanks
/jim