Subject: [nat66] [Fwd: Re: [BEHAVE] FYI: draft-despres-sam-02 enclosed]

From: Rémi Després <[email-masked]>
Date: Tue, 17 Mar 2009 10:05:59 +0100

FYI

-------- Message original --------

Sujet :

Re: [BEHAVE] FYI: draft-despres-sam-02 enclosed

Date :

Tue, 17 Mar 2009 09:39:13 +0100

De :

Rémi Després <[email-masked]>

Pour :

Margaret Wasserman <[email-masked]>

Copie à :

Internet Area <[email-masked]>, Softwires WG
<[email-masked]>, Behave WG <[email-masked]>

Références :

<[email-masked]>
<[email-masked]>

Margaret Wasserman - le (m/j/a) 3/17/09 1:13 AM:
>
> Hi Remi,
>
> I have a few high-level comments/questions on this draft from my first
> reading, and I may have more after I have reviewed it in more detail.
>
> (1) You have indicated that you would like to discuss this draft in
> the 6AI BOF, but you have not cc:ed the mailing list for the 6AI BOF
> ([email-masked]). Also, have you talked to the chairs of the 6AI BOF
> (Bob Hinden and Dan Wing) about whether they are willing to include
> this draft on the agenda, despite the fact that it has not been posted
> to the I-D archive? There doesn't appear to be an agenda online for
> the 6AI BOF yet, so I am not sure if it will be included.
I started with the NAT66 mailing list, and only followed with WG lists.
See also Dan's answer.
>
> (2) The end hosts in the SAM system need to know their globally
> routable addresses, so how can SAM be said to provide address
> independence?
Routing within the site is based on local addresses, e.g. ULAs.
That's only in SAM-capable CPEs and in SAM-capable hosts that, knowing
SAM parameters, global-address packets can be encapsulated in
local-address packets.
> (3) Exactly what formulation of the end-to-end principle are you
> referring to in this paper when you indicate that SAM preserves it in
> IPv6?

Thanks for the remark.
There should be a reference, e.g. to RFC 1958.
What is meant is IP-layer network transparency, e2e.
Addresses and ports that are seen by two communicating applications must
be the same at both ends.

> My understanding of the end-to-end principle is that it has to do with
> putting intelligence at the edges of the network (in hosts vs.
> routers/middleboxes) and with putting certain function at the top of
> the protocol stack (apps layer vs. lower layers). This is based on my
> understanding (and recollection) of a paper by Jerry Saltzer, D. Reed
> and Dave Clark written in the mid 1980s, which you can find here:
>
> http://web.mit.edu/Saltzer/www/publications/endtoend/endtoend.txt
>
> It is also reasonably well-summarized in this Wikipedia article.
>
> http://en.wikipedia.org/wiki/End-to-end_principle
>
> Based on my understanding of the end-to-end principle, I don't see any
> significant difference in SAM vs. NAT66 WRT how much they maintain (or
> violate) the end-to-end principle, as both mechanisms place some
> functions/intelligence in the infrastructure.
With SAM, hosts know their global addresses, and can use them, e.g. with
SCTP or Shim6.
In my understanding, this is a difference (an an important one).

Regards,

RD

---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 17 Mar 2009 09:49:52 -0400

On Mar 17, 2009, at 5:05 AM, Rémi Després wrote:>
> In my understanding, this is a difference (an an important one).
Yes, this is an important difference between SAM and NAT66, although  
comparing them is like comparing apples and oranges, since they don't  
solve the same problems...

IMO, SAM does not provide a solution to the Address Independence  
requirement, as the local hosts need to know their global addresses.   
Therefore, I am not sure why it is being proposed for discussion in  
the IPv6 Address Independence (6AI) BOF.  Could you explain?

Margaret

---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 17 Mar 2009 15:34:11 -0400

Hi Remi,

> SAM parameters, global-address packets can be encapsulated in
I have read the SAM draft a few times now, and I still don't really  
understand what you are proposing...

I understand how communication could happen across a SAM zone when  
both end nodes have global addresses.  The global packet could be  
encapsulated in an IP header that uses local addresses and routed  
across the SAM zone.  When it leaves the SAM zone, the outer header  
would be removed and end-to-end transparency would be maintained.  I  
also understand how this might be useful in situation where, for  
example,

But, I don't understand how a host that does not know its global  
address can use SAM to communicate with other hosts on the global  
Internet.  If such a host sends from a local source address to a  
global destination address, where is the local source address mapped  
or translated into a global address, so that the global destination  
receives a packet with a source IP address that can be used to route a  
packet back to the sender?
> be the same at both ends.
If you were to change your text to refer to end-to-end transparency  
(as discussed in RFC 1958) instead of the end-to-end principle (as is  
also discussed in RFC 3724) that would address my terminology concern.

Margaret

---

From: Rémi Després <[email-masked]>
Date: Sat, 21 Mar 2009 17:10:53 -0700

Attached the answer I had sent to Margaret, but mistakenly not copied
to the list (apologies).

I hope it helps.

RD

Dan Wing  -  le (m/j/a) 3/21/09 11:23 AM:

Rémi,

Please do followup to Margaret's post so that at least I can understand SAM-02
better.

-d

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Margaret Wasserman
Sent: Tuesday, March 17, 2009 12:34 PM
To: Rémi Després
Cc: [email-masked]
Subject: Re: [nat66] [Fwd: Re: [BEHAVE] FYI:
draft-despres-sam-02 enclosed]

Hi Remi,

Routing within the site is based on local addresses, e.g. ULAs.
That's only in SAM-capable CPEs and in SAM-capable hosts

that, knowing

receives a packet with a source IP address that can be used
to route a

(3) Exactly what formulation of the end-to-end principle are you
referring to in this paper when you indicate that SAM

preserves it

in

IPv6?

Thanks for the remark.
There should be a reference, e.g. to RFC 1958.
What is meant is IP-layer network transparency, e2e.
Addresses and ports that are seen by two communicating

applications

must

If you were to change your text to refer to end-to-end transparency
(as discussed in RFC 1958) instead of the end-to-end
principle (as is
also discussed in RFC 3724) that would address my terminology concern.

Margaret

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Subject: Re: [nat66] [Fwd: Re: [BEHAVE] FYI: draft-despres-sam-02 enclosed]
From: Rémi Després <[email-masked]>
To: Margaret Wasserman <[email-masked]>
Date: Tue, 17 Mar 2009 21:22:15 +0100

Margaret Wasserman  -  le (m/j/a) 3/17/09 8:34 PM:
> also understand how this might be useful in situation where, for example,
>
> Internet.
It doesn't.
- If it has SAM and at least one CPE has SAM, then it knows its global 
address.
- Otherwise, it cannot use SAM and, in a private addressing site, e2e 
transparency is lost. This is why SAM is _complementary_ of the network 
prefix mapping you have proposed with Fred.
> If such a host sends from a local source address to a global 
> destination address, where is the local source address mapped or 
> translated into a global address, so that the global destination 
Thanks.
This should be fixed.

RD