Subject: RE: DSTM Considered Harmful [Re: (ngtrans) final ngtransagendafor IETF-53 in Minneapolis]

From: BAUDOT Alain FTRD/DMI/CAE <[email-masked]>
Date: Tue, 19 Mar 2002 22:00:01 +0100

>I've always assumed that DSTM would only be useful in the very late 
>stages of IPv6 rollout. Also, I believe that BIA is just as useful 
>for the interesting scenario (IPv6 clients using IPv4-only apps on an 
>IPv6 server). But BIA is much simpler to implement and deploy,
>and it doesn't consume real IPv4 addresses.

AB> 3G is actually in this very late case. I always believed that DSTM was 
very well designed for the 3G transition case, where one can imagine most
of the new services are IPV6-only, so that IPv4 connectivity need is
minimum.
Of course, DSTM requires more ressource from a dual-stack UE.
But, as it was reminded yesterday, a 3G terminal is much more powerful than 
any terminal at the time IPv6 design started. So...

>So my opinion is that DSTM could safely be put on ice for a couple
>of years, for future review. Certainly, we should wait until the NGTRANS
>scenarios have been defined, as discussed in the meeting yesterday.

AB> IMHO, DSTM should at least, be very usefull in a 3G scenario.

Alain.

Christian Huitema wrote:
> 
> > On a deployment viewpoint, a MS implementation would be very useful,
> > given we have good v6 app support in Linux and BSD.   Can any of the
> MS
> > people comment on their own plans here?
> 
> I am personally not convinced of the urgency of implementing and
> deploying DSTM. The stated goal of DSTM is to let users of an IPv6 only
> network gain IPv4 connectivity. Think about it: IPv6 only networks. Does
> not look like a year 2002 problem to me. I would rather concentrate on
> making sure that users in an IPv4 only network can get some IPv6
> connectivity.
> 
> I am also not convinced that DSTM is the right solution to the stated
> problem. It goes to great length to assure that the IPv6 only nodes can
> get a global IPv4 address, but it is very unclear that we will have
> enough available IPv4 addresses to allow that. DSTM attempts to reduce
> IPv4 address consumption by "time sharing" the address, but we have
> experience and theory that tells us that time sharing does not work
> well: in short, all nodes tend to need addresses at the same time.
> 
> If you remove the "global address" property, then DSTM is in fact an
> inferior solution, compared to NAT-PT (provided we remove the DNS ALG
> from NAT-PT.) At least, with NAT-PT, I don't even need an IPv4 stack in
> the IPv6 only nodes, and I also don't need any address allocation
> protocol between the v6 only node and the server.
> 
> -- Christian Huitema

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 20 Mar 2002 01:41:28 +0100

The advantage of the BIA scenario is that *no* IPv4 connectivity
whatever is required to allow IPv6 hosts to talk to legacy IPv4
applications in other IPv6 hosts. As far as I can see that achieves
everything that DSTM achieves without most of the machinery.

I'd be interested to see a scenario where this isn't the case.

   Brian

> BAUDOT Alain FTRD/DMI/CAE wrote:
> 
> of the new services are IPV6-only, so that IPv4 connectivity need is minimum.

---

From: Pekka Savola <[email-masked]>
Date: Wed, 20 Mar 2002 03:10:07 +0200 (EET)

> I'd be interested to see a scenario where this isn't the case.

Some of this is probably obvious, but anyway..

BIA: "IPv4 application on IPv6 node can talk to an IPv6 application on
another IPv6 node"

DSTM: "IPv4 application on IPv4/v6 node can talk to an IPv4 application on 
IPv4(/v6) nodes" (in addition to full IPv6 connectivity).

So, if the destination site does not have all the services IPv6-enabled,
BIA won't help (at least completely) and DSTM is rather useful if one
wants to avoid protocol translation.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

---

From: Francis Dupont <[email-masked]>
Date: Wed, 20 Mar 2002 04:32:51 +0100

In your previous mail you wrote:

   
=> I like BIA because this is an easy way to add support for
the protocol X to a system which doesn't know it (i.e. as a
temporary solution waiting for full support of X BIA is very nice).
But I have a basic concern with BIA: a BIA is essentially limited,
it can't work with real applications using X.
Applied to a current BIA I've seen, the result is netscape for instance
gets magically IPv6 support but it doesn't work at all with mozilla
(which has IPv6 support).
In the DSTM context things are different because DSTM is a mechanism
for a dual stack node configured only for IPv6 to stay IPv4 capable,
so the BIA should be for an IPv6-only stack (a bit strange these days
because this assumes the IPv4 part has been removed?), it will give
access to IPv4 nodes using IPv6-only applications but can't do anything
for legacy IPv4 applications. If I suppose (still strange but we don't
know what will happen) there will be no legacy IPv4 application, DSTM
is still strictly more powerful than BIA because it works both with
local private IPv4 nodes (printers for instance) and remote global
IPv4 nodes. You can even use DSTM only for remote IPv4 "access"
if you'd like: DSTM is far more flexible than BIS/BIA.

About NAT-*, I don't believe I have to convince someone here than
a tunneling mechanism like DTSM is always better than a NAT-*.
In fact, I tolerate NAT-* only with the word abomination is near
the word NAT (Keith's rule :-) and if there is already a NAT in
the scheme (so Alain's NATv6 is not worse (or better) than a regular
NAT, NATv6 just replaces private IPv4 addresses by IPv6 addresses,
and throws away DNS ALG madness of NAT-PT *).

A last word, 5 years ago an IPv6-only network was a laboratory
curiosity (I remember some discussions with MITRE folks about this
at Stockholm IETF) but today this can be so hard to get IPv4 addresses
in a reasonable quantity than unfortunately the IPv6-only case could
become a real world case...

Regards

[email-masked]

PS *: sorry, it seems we have to wait in order to get a document
specifying Alain's NATv6...
PPS: I was a bit unfair about DSTM+ports: this is more DSTM+RSIP
than DSTM+NAT.
PPPS (the last one :-): about dynamic address allocation: this is
the principle of DHCP (v4!) and real world measures have shown that
if some heavily used applications (HTTP for instance) are dealt with
ALGs only a small number of global IPv4 addresses are needed.
Unfortunately I may not say more (NDA).

---

From: "GwangHoon Kwark" <[email-masked]>
Date: Wed, 20 Mar 2002 15:53:41 +0900

> -----Original Message-----
> From: [email-masked] [mailto:owner-
> [email-masked]]On Behalf Of Francis Dupont
> Sent: Wednesday, March 20, 2002 12:33 PM
> To: Brian E Carpenter
> Cc: BAUDOT Alain FTRD/DMI/CAE; Christian Huitema; Tim Chown; Octavio
> Medina; NGtrans List
> Subject: Re: DSTM Considered Harmful [Re: (ngtrans) final
> ngtransagendaforIETF-53 in Minneapolis] 
> 
> 

Native IPv6 Connection request from Application (IPv6 enable application) can be worked with BIA also. With the local socket info and the result from DNS query, Native IPv6 Connection can be handled instead of BIA. In other words, If the Implementation module comprise BIA and If that host node is dual stack, it can select mechanism among BIA, IPv6 Native Connection and even IPv4 Native connection.  So, If DSTM want to be together with BIA, it can be co-existed. And we have secceed in it already with our CHADH.