Re: [v6ops] draft-anderson-v6ops-siit-eam-01

[Tore Anderson <[e-mail]>]

Hi Cameron,

> I have read draft-anderson-v6ops-siit-eam-01
> 
> I support the working group adopting this document, this is helpful and
> meaningful work.
> 
> I have a few comments that are mostly editorial in nature, i believe the
> document is technically sound as written today.

Thank you!

> Purely editorial, i suggest locally adding the definitions
> for IPv4-converted IPv6 addresses and IPv4-translatable IPv6 addresses.  If
> you are taking up space to define them, then go ahead and do the reader the
> favor of defining them.
> 
> In section 3.2 there is this sentence:  "If a matching
>       EAM entry is found, the address MUST be translated to IPv6 by
>       substituting its IPv4 Prefix value for the corresponding IPv6
>       Prefix from the EAM entry."
> 
> I don't like the word "substituting" since a reader my believe that one
> simply does  a substitution of the IPv4 address for the IPv6.  It would be
> more precises to continuing using the term translate which explicitly
> references the packet treatment procedure in SIIT.  Perhaps rephrase to
> "... MUST be translated to IPv6 in accordance with the EAMT..."

This text has undergone a lot of back and forth between myself and
another reviewer (Alberto Leiva). The problem he identified with saying
something like what you propose, is that it fails to say *exactly* what
should happen. Say you have $addr="192.0.2.123", $eam4="192.0.2.0/24",
$eam6="2001:db8::/112". Now what? You have those three pieces of
information, but nothing saying how those should be combined or
manipulated to form a new IPv6 address.

You could certainly say that it goes without saying and needs no further
explanation, but Alberto thought it was best if it was explicit and as
clear as possible. That's why we landed on "substitute", the reasoning
is that if you start out with $addr="192.0.2.123", then you first take
away the prefix bits found in $eam4, temporarily leaving you with
$addr=".123" (i.e., "0x7b"), and then putting in the $eam6 prefix bits
instead, leaving you with $addr="2001:db8::7b", and you're done. So
what you do, essentially, is to substitute the EAM4 prefix for the EAM6
prefix. (If you're familiar with Perl, the pseudocode would go something
like "$addr =~ s/^$eam4/$eam6/".)

That said, I'm not terribly happy with the current text either. If you
or anyone else have any suggestions on how to make it better and
clearer, while still remaining explicit about the procedure/algorithm,
that would be much appreciated.

Tore