Subject: [v6ops] FW: ULA & Basic Requirements for IPv6 Customer Edge Routers

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Mon, 13 Dec 2010 14:03:37 -0600

FYI to v6ops.  Also, James, please note that Brian Carpenter already
said that the ULA text in the IPv6 CE router document was already agreed
upon (with rough or whatever consensus) and then the document went past
the IESG and to the RFC Editor queue.  So we could avoid debating the
existing ULA text in the document.  The only debate is related to new
text which relates to the coexistence problem with the solution to the
problem as the MSR in the RA for the ULA.  As Fred also says, any other
issue can be taken up in the IPv6 CE router bis document.  

The reason I am sending the email below to a wider audience is to bring
out one key fact.  The fact being that the private IPv4 and IPv6 ULA
coexistence problem causing Internet access delay for the host in the
home is NOT merely a coexistence problem with the ULA.  The problem also
exists with the IPv6 GUA (Globally Unique Address).  See below.

Thanks,

Hemant

-----Original Message-----
From: Hemant Singh (shemant) 
Sent: Thursday, December 09, 2010 6:53 PM
To: james woodyatt; Ole Troan
Cc: [email-masked]
Subject: RE: [v6ops] ULA & Basic Requirements for IPv6 Customer Edge
Routers

James,

Not quite.  Please see in line below.

-----Original Message-----
From: james woodyatt [mailto:[email-masked]] 
Sent: Thursday, December 09, 2010 5:54 PM
To: Ole Troan
Cc: [email-masked]
Subject: Re: [v6ops] ULA & Basic Requirements for IPv6 Customer Edge
Routers

>Actually, I think my disagreement is much narrower than that.

>1) I think recommending the advertisement of only a ULA prefix on LAN
interfaces, when the router is dual-stack and also advertising IPv4
public Internet service with NAT and RFC 1918 addresses, >directly leads
to the coexistence problem that I identified in
<http://www.ietf.org/mail-archive/web/v6ops/current/msg06363.html>, and
that this IPv4 coexistence problem is too serious for IETF to allow
>this RFC to be published at this time with any such recommendation.

This problem was reported to us on Wednesday evening (EST) before
Thanksgiving and in one week or less we had a solution to the problem.
The same Wednesday the first response we gave was to have the host
implement Happy Eyeballs.  Since one cannot be sure when a host would
implement Happy eyeballs, we then proposed a solution which was to say
the IPv6 CE router sends a RIO (MSR of RFC 4191) for the ULA prefix and
this solution was at least satisfactory to some of the parties who
contacted us - Tore Anderson is one.  Tore, Lorenzo, and Erik Kline were
amongst the folks who contacted us with the problem and our thanks to
them. They worked with us for the new text once the solution was
devised.  We authors of the IPv6 CE router document also raised a bug in
the tested IPv6 CE router.  The bug was why didn't the router send an
ICMPv6 Destination Unreachable to the host on seeing an IPv6 packet with
a IPv6 Globally Unique Address (GUA) for destination and a ULA for
source address?  Such a packet cannot be sent out the WAN as per zone
violation rules in RFC 4193.  We already have some ULA zone boundary
warnings in the IPv6 CE Router document.

[In this role, the IPv6 CE router is responsible for ensuring that
traffic using its ULA addressing does not go out the WAN interface, and
does not originate from the WAN interface.]

>2) The authors of the draft seem to believe one or more of the
following propositions, which I reject:

>  a) the coexistence problem is not serious enough to warrant
withdrawing the draft to address it;

We have a solution to the problem.  So what specifically problem do you
have with the solution?  Also, on the first day of the problem reported
to us, I said, this is not just a coexistence problem.  When the host is
provisioned with an IPv4 private address and an IPv6 GUA, and if the
IPv6 WAN link (IPv4 link is still active) of the IPv6 CE router goes
down, the host will send sent packets to the Internet and the host would
still experience a delay with Internet access. This delay with Internet
access is the problem of coexistence of private IPv4 address and the
ULA. 

Also, note my responses to you in the email message URL shown below.  No
satisfactory IPv6 solution has been given to us for the 3 problems we
have always listed where the ULA is needed. 

http://www.ietf.org/mail-archive/web/v6ops/current/msg06315.html

Hemant

---

From: Mark Smith <[email-masked]>
Date: Tue, 14 Dec 2010 07:37:44 +1030

On Mon, 13 Dec 2010 14:03:37 -0600

> exists with the IPv6 GUA (Globally Unique Address).  See below.

I've been wondering a bit why ICMPv6 destination unreachables didn't
solve the problem, but figured I didn't completely understand the
the problem yet.

I don't think announcing a router lifetime of zero solves it for the
ULA only case, as I think it would prevent inter-LAN interface routing
between ULA subnets in a ULA only scenario. I'd think nodes would
consider every off-link destination to be unreachable if they don't
consider the CPE a default router.

I think it would also think the coexistence issue, in the absence
of ICMPv6 destination unreachables, would occur for ULA only
devices when there are some LAN interfaces with a global + ULA prefixes
and others that are ULA only. The current RA lifetime zero text wouldn't
apply in that situation.

Regards,
Mark.

> _______________________________________________
> v6ops mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/v6ops

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Mon, 13 Dec 2010 15:35:04 -0600

-----Original Message-----
From: Mark Smith
[mailto:[email-masked]] 
Sent: Monday, December 13, 2010 4:08 PM
To: Hemant Singh (shemant)
Cc: [email-masked]
Subject: Re: [v6ops] FW: ULA & Basic Requirements for IPv6 Customer Edge
Routers

>consider the CPE a default router.

The IPv6 CE router has IPv6 routing in the home LAN as out of scope.
Anyway, with the RIO solution (RFC 4191) where the RIO is used to
advertise the ULA route, the hosts do know how to reach other ULA
addressed nodes (hosts or routers) in the home.  

>and others that are ULA only. The current RA lifetime zero text
wouldn't

Yes.  That is why our new text all along has said "if the IPv6 CE router
has no default router on the WAN interface...".  You see, if a LAN
interface has a GUA, then the WAN interface will have a default router
for the GUA when the WAN link is up. Further, I would assume if you say
that one LAN interface has only ULA and another LAN interface has both a
GUA and ULA, then each of these LAN interfaces are different routed
interfaces on the CE router and hence each LAN interface has its
associated default router on the WAN.  Thus our RA Lifetime zero text
still works. 

Thanks,

Hemant

---

From: Mark Smith <[email-masked]>
Date: Tue, 14 Dec 2010 19:06:35 +1030

Hi Hemant,

On Mon, 13 Dec 2010 15:35:04 -0600

> addressed nodes (hosts or routers) in the home.  

I agree the RIO is a solution, however I wonder how widely it is
implemented in end-nodes. RFC4191 says that this is an optional
mechanism, so I'm not sure we can rely on it being widely available.

Regards,
Mark.