Subject: draft-pref64folks-6man-ra-pref64

From: Jen Linkova <[email-masked]>
Date: Sat, 21 Jul 2018 00:47:40 +1000

Hello,

We've just uploaded -01 version of draft-pref64folks-6man-ra-pref64
which discussed an RA option for discovering NAT64 prefix(es):

https://datatracker.ietf.org/doc/html/draft-pref64folks-6man-ra-pref64

Any comments are highly appreciated. In particular there is one thing
which we'd like to discuss:
- the proposed option format does not support NAT64 prefixes if the
prefix length != 96 (and based on the discussion we've had in v6ops@
it looks like non-96 prefixes are not really common in the scenarios
when the RA option would be useful).  Other approaches considered:
   a) significantly increase the size of the option by adding the
prefix length and allowing longer prefixes. The question is: would it
be useful? Or shall we take the opportunity to simplify things?
  b) use  3 bits for the prefix length (as there are only 6 allowed
prefix length as per RFC6052 and do some very dirty hacks with the
remaining 13 bits for the lifetime (as it would be highly undesirable
to have NAT64 prefix lifetime lower than router lifetime (a.g. "13
bits should be multiplied by 8 + 7 to get the lifetime in seconds...)

What do you think?

-- 
SY, Jen Linkova aka Furry

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From: Brian E Carpenter <[email-masked]>
Date: Sat, 21 Jul 2018 06:19:59 +1200

On reflection, I think that only supporting /96 is OK. It would be
a good idea to mention this in the Abstract.

(A contorted alternative would be that if the option length
is 3, the content is a prefix-length octet followed by the
prefix in 16 octets. But why bother?)

Nit: Figure 1 actually shows a /64. Did you run out of +-+-
characters?

Regards
   Brian

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From: Jen Linkova <[email-masked]>
Date: Sat, 21 Jul 2018 08:19:36 +1000

> a good idea to mention this in the Abstract.

Good point, I've added it to the TODO list.

> prefix in 16 octets. But why bother?)

Actually what we are trying to do is to avoid inflating the option
size w/o good reason.

> Nit: Figure 1 actually shows a /64. Did you run out of +-+-

;)))) Wow, did you count lines?! Impressive ;)

Will be fixed in -02!

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From: Brian E Carpenter <[email-masked]>
Date: Sat, 21 Jul 2018 13:50:38 +1200

> Actually what we are trying to do is to avoid inflating the option

Sure. The normal case would be option length = 2.
 
> ;)))) Wow, did you count lines?! Impressive ;)

Not really - I just realised that it needed to be divisible
by 3, if it really was 96. (And after all, I'm a fully
qualified Gen-ART reviewer :-).

   Brian