Re: [BEHAVE] Handling fragments in the stateful NAT64

> -----Original Message-----
> From: behave-bounces@ietf.org 
> [mailto:behave-bounces@ietf.org] On Behalf Of marcelo bagnulo braun
> Sent: Tuesday, December 01, 2009 1:42 AM
> To: Behave WG
> Subject: [BEHAVE] Handling fragments in the stateful NAT64
> 
> Hi,
> 
> after the discussion in hiroshima, I have updated the draft.
> The current 03 version reads:
> 
>    If the incoming IP packet contains a fragment, then more processing
>    may be needed.  This specification leaves open the exact details of
>    how a NAT64 handles incoming IP packets containing fragments, and
>    simply requires that a NAT64 handle fragments arriving 
> out-of-order.

That sentence above says "requires that a NAT64 handle fragments arriving
out-of-order", yet ... (see "A", below)

>    A NAT64 MAY elect to queue the fragments as they arrive 
> and translate
>    all fragments at the same time.  Alternatively, a NAT64 
> MAY translate
>    the fragments as they arrive, by storing information that allows it
>    to compute the 5-tuple for fragments other than the first.  In the
>    latter case, the NAT64 will still need to handle the 
> situation where
>    subsequent fragments arrive before the first.
> 
>    Implementors of NAT64 should be aware that there are a number of
>    well-known attacks against IP fragmentation; see [RFC1858] and
>    [RFC3128].

RFC4963 might be useful to cite, as well.

>    Assuming it otherwise has sufficient resources, a NAT64 MUST allow
>    the fragments to arrive over a time interval of at least 
> 10 seconds.

"A":  The sentence below does *not* require the NAT64 to handle out-of-
order fragments.  The sentence below contains a RFC2119 keyword, so
I guess it is normative and overrides the non-RFC2119 sentence above,
but it would be better if the descriptive text above matched the 
RFC2119 keyworded sentence below.  Or remove one or the other.

>    A NAT64 MAY require that the UDP, TCP, or ICMP header be completely
>    contained within the first fragment.

-d

> 
> Let me know if you have issues witht eh current text. I hope 
> it reflects 
> the received feedback.
> 
> Regards, marcelo
> 
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