Subject: why I'm not implementing IPv6

From: "D. J. Bernstein" <[email-masked]>
Date: 21 Nov 2002 18:38:50 -0000

[ post by non-subscriber.  with the massive amount of spam, it is easy to
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In short: the same reasons I didn't implement OSI. In detail:

   http://cr.yp.to/djbdns/ipv6mess.html

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago

---

From: Pekka Savola <[email-masked]>
Date: Sat, 23 Nov 2002 17:42:38 +0200 (EET)

>    http://cr.yp.to/djbdns/ipv6mess.html

Speaking of which, I'll add my private (but smaller, more constrained) 
rant.

IMO, it was a serious mistake to make the system libraries sort AAAA DNS
replies before A records (btw: I'm not aware of any implementation where
you could actually specify the order) when using getaddrinfo and
AF_UNSPEC.

This is because now people are afraid of deploying v6-enabled software
because v6 connectivity is not really there, and contacting dual-stack
servers is only likely to cause problems when done over v6.  Only when
explicitly configured, v6 would be used over v4, until some more or less 
"magic moment" (at different times in different regions etc.)

If this would have been different, we migh have a significantly higher
number of v6-enabled applications etc. enabled in the mainstream
distributions.

Further, this will affect the transition scenarios.  I surely wouldn't
like regular customers' getting v6-enabled yet with this bad connectivity.

-- 
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: Margaret Wasserman <[email-masked]>
Date: Sat, 23 Nov 2002 20:08:17 -0500

Hi Pekka,

>you could actually specify the order) when using getaddrinfo and

Specifically, what problem does this cause?  Are there many hosts
that have IPv6 AAAA records in the DNS, but no connectivity via
IPv6?

>"magic moment" (at different times in different regions etc.)

I don't believe in a "magic moment"...  In order for IPv6 to get
deployed, we have to make dual stack nodes work properly throughout
the transition AND build an IPv6 protocol and network architecture
that has sufficient benefits for some situations, users and/or
applications that it gets deployed and used.

>number of v6-enabled applications etc. enabled in the mainstream

How would specifying a different order for DNS records achieve
this?

Margaret

---

From: Pekka Savola <[email-masked]>
Date: Sun, 24 Nov 2002 11:28:04 +0200 (EET)

On Sat, 23 Nov 2002, Margaret Wasserman wrote:
> Specifically, what problem does this cause?  

Applications which support v4 and v6 try to use v6 first when trying to 
contact dual-stack nodes.

> Are there many hosts

How many hosts are there that have IPv6 AAAA records in the DNS, but 
connectivity is *not* significantly worse than with IPv4?
 
> applications that it gets deployed and used.

I agree -- I had a different meaning for "magic moment" than djb.  To me 
it was the moment a site's operator feels confident enough to prefer v6 
connectivity to dual-stack nodes instead of v4.

Somewhere, this is today.  At production networks, I don't feel it's time 
for that yet.

> How would specifying a different order for DNS records achieve

People could deploy v6-enabled applications and enable v6 by default on 
their boxes without a fear of it interfering with v4.  That'd be a *huge* 
benefit.

I've already expressed my fear about this, see e.g.
http://staff.csc.fi/psavola/residential.html
"Migration and Co-existence Scenarios" section.

That section would have been entirely different if the sort order had been 
reversed.

---

From: Tim Chown <[email-masked]>
Date: Sun, 24 Nov 2002 11:48:53 +0000

> that have IPv6 AAAA records in the DNS, but no connectivity via

Maybe you missed the 6bone thread on this :)   If you take the IETF meeting
example my IPv4 RTT home was 100ms, but my IPv6 RTT home was 400-500ms.  I was
trying to run IPv6-only (including DNS transport) at the site, but ended up
using IPv4 (except when due to the L2/L3 local WLAN issues we had this year 
IPv6 was present when IPv4 was not :)

Note in some cases it is not a problem, e.g. between the UK and Abilene
west coast via 6NET and SURFnet I have a 20+ hop path for IPv4 and IPv6, 
and both perform equally well.  But those paths are dual-stack and similar,
whereas "in the wild" your connectivity is not predictable or reliable enough
to use IPv6 day-to-day (or at least enough that you wish to use IPv4 ahead
of IPv6 to reach a dual-stack service).  

While it was great of Itojun et al to get IIJ connectivity for IETF, it was 
ironic that we were a few blocks from an Abilene gigapop, but that traffic 
still went via Japan to Abilene sites (and this path also doubled the RTT 
to the UK research networks).  I think Itojun fixed this before the end of
the event, which was good :)

I appreciate the intent of preferring v6 ahead of v4 where a host has A and
AAAA records, but the reality is dictated by the 6bone-mess as written down
by Pekka in draft-savola-v6ops-6bone-mess-01 and discussed at the Atlanta
6bone meeting.   It is a problem we are trying to tackle between 6NET, Euro6IX
and Abilene (and WIDE) by getting some sane policy and community tagging
running, to get a stable and well-connected international research network
that may connect some 6bone sites but that is relatively shielded from the
"6bone-mess".   We had a meeting about this in Atlanta, and will be trying 
some new policies soon.

In short, we need to unravel the 6bone mess or, more realistically, build
some good policies between connected networks and transit providers, to
begin to make IPv6 usable internationally.   Note I am talking here about 
Pekka's 6bone-mess thesis, and not Dan's ipv6-mess document which started
this thread and which I largely don't agree with.

Cheers,
Tim

---

From: Stephane Bortzmeyer <[email-masked]>
Date: Mon, 25 Nov 2002 13:30:49 +0100

On Sat, Nov 23, 2002 at 08:08:17PM -0500,
 Margaret Wasserman <[email-masked]> wrote 

> that have IPv6 AAAA records in the DNS, but no connectivity via

Even if the *server* has an IPv6 connection, the *client* may not. And
there is no easy way for its resolver to ask only A records when there
is no IPv6 connectivity.
 
That's why many people put all their AAAA records in an
ipv6.example.com subdomain.