Re: [BEHAVE] Stateless Address Mappings (SAMs)

I have read this draft.  In my opinion, it is within the scope of Softwires
but may be of interest to some Behave folks.  The only real part I can see
that might be within the scope of Behave is section 3.6 where it discusses
scrambling IPv6 addresses as packets flow through a SAM.  I'd suggest this
be separated into its own draft since it's largely orthogonal to the rest
of the document (which is more about encapsulation, not translation).

Technical comments:

1) The draft doesn't say what will break and probably should (ping,
   well-known ports, etc).  Some of the same problems that occur with
   multilink subnets (RFC 4903) occur in this proposal too, since
   not everything will be aware that the "subnet" isn't an IP prefix.
   Similarly, the required Subnet-Router Anycast addresses (RFC
   4291 section 2.6.1) may not work correctly.

2) The draft assumes that the first fragment always arrives first.
   As discussed in draft-iab-ip-model-evolution-01.txt section 3.1.7,
   this is not a safe assumption today.

3) The use of the "u" bit in IIDs seems problematic for several reasons.
   One, it only applies to IPv6 addresses that don't start with binary 000.
   Two, the semantics of the bit defined in RFC 4291 have to do with
   making it easy to configure non-conflicting addresses, and are not
   about privacy demands; overloading this bit for a second purpose
   seems problematic.

4) Regarding the IPv6 address scrambling in section 3.6, not defining
   the scrambling (or at least not providing requirements for it) would be
   problematic in two regards.  1) If you allow asymmetric paths then
   you need the same algorithm in each SAM at the edge of your network;
   2) some implementations may pick a weak method that allows an
   outsider to guess the algorithm.

Comments inline (along with a bunch of editorial nits) in PDF attached.

-Dave

> -----Original Message-----
> From: behave-bounces@ietf.org [mailto:behave-bounces@ietf.org] On
> Behalf Of Rémi Després
> Sent: Wednesday, November 05, 2008 8:46 AM
> To: Softwires WG; Behave WG
> Cc: v4v6interim-bounces@ietf.org
> Subject: [BEHAVE] Stateless Address Mappings (SAMs) - new draft
>
> The new draft on SAMs is at
> http://www.ietf.org/internet-drafts/draft-despres-sam-01.txt.
>
> It deal with global connectivity, in IPv4, IPv6,  and extended IPv4,
> across local domains where routing is different.
>
> - Its automatic tunneling aspects are in the new scope of Softwires
> - Its IPv4 address extension aspects, based on dynamic-port prefixes,
> are in the scope of Behave.
>
> Regards
> RD
>
> _______________________________________________
> Behave mailing list
> Behave@ietf.org
> https://www.ietf.org/mailman/listinfo/behave

Re: [BEHAVE] Stateless Address Mappings (SAMs) - new draft

Attachment: draft-despres-sam-01.pdf