Subject: new version of draft-narten-ipv6-3177bis-48boundary-03.txt

From: Thomas Narten <[email-masked]>
Date: Mon, 03 Dec 2007 11:45:45 -0500

I'd like to call attention to a revised version of the previously
expired document (the previous version was dated June, 2006). It was
revved in response to discussion that occurred on the ietf mailing
list a couple of months ago. Plus, the topic continues to receive
attention within the RIRs.

I did not ask for agenda time as I think it better to comment on the
list, based on the wording that is in the document.

The document is short enough that I think the best think for people to
do is just read it and then comment here on the list.

That said, I do point out the common complaint that giving home users
and businesses the same amount of address space strikes some people as
absurd.

Also, I better clarify the motivations behind the original 3177
recommendations, to make clear that changing the boundary to something
else needs to (and can) still satisfy the original motivations.

Finally, I am sending this to v6ops (rather than 6man) for discussion
because I believe the end site boundary is more of an operational
issue than an architectural one.

Thomas

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 04 Dec 2007 09:18:57 +1300

> do is just read it and then comment here on the list.

I think it's significantly improved from the -02 version
and should be published. It's important to get this analsysis
out into the wider community.

     Brian

---

From: Brian Dickson <[email-masked]>
Date: Mon, 03 Dec 2007 19:18:24 -0800

> out into the wider community.
+1 (including the "Brian" :-))

---

From: "Tony Hain" <[email-masked]>
Date: Tue, 4 Dec 2007 11:44:19 -0800

There is no discussion about negating the overly conservative mindset of the RIR membership, and that the reason they didn't take this up until 2005 was that they were not really serious about IPv6 before that. That overly conservative mindset still exists, with no consideration about the long term impact of their oppressive behavior. 

There is no discussion of the point raised in the intro about the scaling impact on the public routing system. I would suggest after the last paragraph of section 2:
Being overly conservative on end site assignment size also has a direct impact on the potential size of the global routing system. When longer prefixes are assigned to end sites, the public routing table has the potential to grow 2^n times larger than with shorter prefixes. Many of the same people that complain about assigning the same size prefix to large enterprises and home users also complain about the scale of the public routing system, without acknowledging that the longer prefixes make that problem worse.

The summary comment about bridging not being desirable appears to assume that it is even technically possible because all the subnets will use Ethernet framing. There should be some discussion about the potential for new framing formats to be developed that will not be technically compatible with existing link technologies. When that happens the braindead single-subnet model will result in another nat fiasco.

The summary comment about 'generally unacceptable' is probably the wrong language. Maybe reword the comment something like:
- assigning a longer prefix to an end site, compared with the existing prefixes the end site already has assigned to it, is likely to increase operational costs and complexity for the end site, with no discernable cost savings to anyone. 

Tony

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
> Behalf Of Brian E Carpenter
> Sent: Monday, December 03, 2007 12:19 PM
> To: Thomas Narten
> Cc: IPv6 Operations
> Subject: Re: new version of draft-narten-ipv6-3177bis-48boundary-03.txt
> 
>

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Tue, 4 Dec 2007 12:11:21 -0800

"The above-mentioned RFC3177 goals can easily be met by giving home  
users a /56 assignment by default."

I disagree. A /56 is still wasteful if we assume that home users are  
only going to need a very small number of subnets.

Additionally, many people will be tempted to start using a /56 for  
purposes that really need more subnets than about 250. Renumbering  
when a network needs its 257th subnet will be painful. It would be  
much better to a have a clear distinction between very small networks  
and all other networks, and not have a size that is still to large for  
most while at the same time being too small for some, even if they  
don't realize it at first.

So I'd like to see /60 for consumers and /48 for anyone who feels /60  
isn't enough.

---

From: Thomas Narten <[email-masked]>
Date: Tue, 04 Dec 2007 17:09:59 -0500

Hi Iljitsch.

> only going to need a very small number of subnets.

To be clear, the wastefulness of a /56 was not a concern of
3177. Remember, it recommended a /48. So moving to /56 would be less
wasteful and I think the statement is correct. :-)

I understand your point  that a /60 would also be OK for home end
sites.

Couple of points.

The sentence in the document isn't technically recommending a /56. It
is simply saying it would meet the requirements. So, it could be
changed to something like "by giving home users a /56 or /60
assignment by default". I think I would be OK with that, but I suspect
others would be less willing to accept that.

I too think one could argue that a /60 for typical home sites is
sufficient _today_. But I also don't know that we really need to go
this far. Going from /48 to /56 is the big savings.

> purposes that really need more subnets than about 250.
> Renumbering when a network needs its 257th subnet will be
> painful. It would be much better to a have a clear distinction
> between very small networks and all other networks, and not have a
> size that is still to large for most while at the same time being
> too small for some, even if they don't realize it at first.

> So I'd like to see /60 for consumers and /48 for anyone who feels /60  

Note: it is the RIRs/ISPs who make this decision, not the IETF. So I
don't think it is too useful to get too wrapped up over the exact
value specified in _this_ document.

Thomas

---

From: james woodyatt <[email-masked]>
Date: Tue, 4 Dec 2007 14:19:32 -0800

On Dec 4, 2007, at 12:11, Iljitsch van Beijnum wrote:
>
> So I'd like to see /60 for consumers and /48 for anyone who feels / 
> 60 isn't enough.

FWIW, my ISP allocated me a /60 when I signed up for their IPv6  
tunnel service (which I used to make sure the IPv6 "manual tunnel"  
feature in the AirPort Extreme base station worked properly).  I'm  
using exactly two of the sixteen subnets this provides me.  I don't  
expect to exhaust my /60 for as long as I live at my current address.

That said... I would *STRONGLY* advise against condoning the  
allocation of only one /64 per residential ISP customer site.

Why?  Let me explain why I'm using two subnets and not one, and you  
can tell me what I should do if my ISP wants to charge me a flat fee  
per /64 allocation.

I have one subnet that has all my private services and home appliance  
devices.  I have another subnet on an open 802.11 access point for my  
friends and houseguests with 802.11-enabled personal devices can get  
to the Internet at my house without me having to give them a WPA  
password that allows non-firewalled access to my whole private  
network.  My private network has an RFC 1918 private address realm  
for IPv4, and its access to the Internet is through a NAT device.  My  
guest network is in a different RFC 1918 private address realm, and  
its access to the Internet is through a differnent NAT device.  Both  
of them are IPv6-enabled, and each has a different /64 subnet carved  
from the /60 allocated to me by my ISP.

If my ISP wants to charge me a fee for each /64 it allocates for me,  
and I can avoid that charge by using IPv6 NAT, then you get three  
guesses what I'm going to do.  I expect you'll guess correctly the  
very first time.

--
james woodyatt <[email-masked]>
member of technical staff, communications engineering

---

From: Brian Dickson <[email-masked]>
Date: Tue, 04 Dec 2007 16:52:33 -0800

> Being overly conservative on end site assignment size also has a direct impact on the potential size of the global routing system. When longer prefixes are assigned to end sites, the public routing…
It's a huge leap from "potential size" to "make that problem worse".

In a nutshell, the router-slot usage problem is a demand-side problem - 
there is a real need for reliable internet presence (not just 
client-side connectivity).

And, using assignment policy to address this is a supply-side solution. 
Those don't generally work for demand-side problems (q.v. the war on drugs).

The real place this needs to be addressed is in the solution space to 
multi-homing. Currently the only viable answer for multihoming is PI 
space (in both v4 and v6).

Until we come up with a better solution, the scaling problem 
fundamentally cannot be prevented.

As such, I have to disagree with Tony on this one; the recommendation 
fits well with the long-term goal of conserving limited (albeit 
enormous) resources.

Brian Dickson

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 05 Dec 2007 14:13:31 +1300

> There is no discussion about negating the overly conservative mindset of the RIR membership, and that the reason they didn't take this up until 2005 was that they were not really serious about IPv6…

I think time will be the great healer on that point; it really
does no long term harm if allocations are on the small side for the
first few years. As long as policies are mutable, that is.

On 2007-12-05 09:11, Iljitsch van Beijnum wrote:
...
>  So I'd like to see /60 for consumers and /48 for anyone who feels /60 

Are you sure that 16 subnets is enough for a large family house with
entertainment, building services, and home office all running on
various technologies? I'm not, but I'm pretty sure /56 is enough.

    Brian

---

From: james woodyatt <[email-masked]>
Date: Tue, 4 Dec 2007 18:04:39 -0800

On Dec 4, 2007, at 17:13, Brian E Carpenter wrote:
>>  So I'd like to see /60 for consumers and /48 for anyone who  
>> feels /60 isn't enough.
>

I'm pretty sure /60 isn't big enough over the foreseeable future.   
I'm *also* not sure that /56 is big enough.  I'm concerned about a  
problem I can see arising in a world of zero-configuration IPv6  
router/firewalls that implement "CPE simple security" by default, and  
they're scattered around the interior of residential networks, i.e.  
all over inside people's homes— possibly because they are integrated  
into consumer devices that require expert users to turn them off.

I'm foreseeing these devices negotiating with one another what  
subnets to advertise in much the same way that Appletalk routers once  
did— like back in the old hellish days when people could just buy  
routers, plug them together and they'd just work without people  
having to configure them with all kinds of arcane code numbers.

---

From: Mark Smith <[email-masked]>
Date: Thu, 6 Dec 2007 07:44:20 +1030

On Tue, 4 Dec 2007 18:04:39 -0800

> having to configure them with all kinds of arcane code numbers.

And I think that is one of the key things IPv6 should achieve. More
"modern" protocols than IPv4, like IPX and Appletalk (late 80s
protocols), set an example for how easy IPv6 should be to use and
operate. If IPv6 doesn't meet or exceed the capabilities of those
protocols, then the designers and operators of the Internet have failed
their end-users - the designers and operators parents, sisters,
brothers etc. - those people who don't care how it works, they just
want it to work, and want to not have to fiddle with it to get it to
work.

For those who worry about /48s being "wasteful", and are therefore
advocating /56s or longer, would you also worry about wasting sand if
you lived in a desert, or water if you lived in a rainforest?

Address conservation in IPv4 is quite valid, as it is a significantly
limited resource ("water in a desert"). It isn't justified in IPv6 when
the address space is 2^96 times bigger. Convenience of use can and
should trump the necessity of conservation.

Regards,
Mark.

---

From: "Tony Hain" <[email-masked]>
Date: Wed, 5 Dec 2007 15:04:11 -0800

I agree with James here. Zero-conf router deployments will need to assume a
substantial number of subnet bits are available, else the zero part goes
away. 

Moving the bits from the consumer side of the allocation to the provider
side only -assures- that they will never be used. Once ISPs build a practice
around any specific prefix length, that will never change, because the
business case for changing it will never be satisfied. If the prefix length
is too small to begin with there is no hope that the consumer will be able
to get more, because that will not conform to the one-size-fits-all
provisioning model that will be deployed (it already exists for IPv4 at
/32). 

This document should clearly state that there is no -technical- reason for
anything longer than a /48, and there are clear technical reasons for
nothing longer than a /60. There may be -business- reasons for nibble values
in between, but those should not be confused with technical requirements. 

Tony

> Behalf Of james woodyatt
> Sent: Tuesday, December 04, 2007 6:05 PM
> To: IPv6 Operations
> all over inside people's homes- possibly because they are integrated
> did- like back in the old hellish days when people could just buy

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Wed, 5 Dec 2007 15:28:56 -0800

> various technologies? I'm not, but I'm pretty sure /56 is enough.

Switches are cheap, routers much less so, especially if you want the  
traffic to flow at line rate. You need routers to keep subnets apart.  
So I don't see how an average home is going to use more than a handful  
of subnets the way things are now.

There is one exception: the case where multiple routers are deployed  
in a cascading style and each provisions address space to the next  
one. Assuming a router gives up half of its own address space to its  
subordinate, you can have four levels of routing in your home with a / 
60.

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Wed, 5 Dec 2007 15:31:03 -0800

On 4 dec 2007, at 18:04, james woodyatt wrote:

> I'm *also* not sure that /56 is big enough.

The trouble with /56 is that it's enough for people to shoot  
themselves in the foot. You can build quite a large network with 256  
subnets and if you then discover that you have to renumber when you  
need that 257th subnet that's not a good deal. If you have a /60 on  
the other hand, you're going to ask for something larger (which should  
be a /48) pretty quickly.

---

From: Gert Doering <[email-masked]>
Date: Thu, 6 Dec 2007 18:24:52 +0100

Hi,

> in between, but those should not be confused with technical requirements. 

Agree.

(I do wonder a bit why zero-conf devices would all of a sudden invent lots of 
independent *subnets*, though).

Gert Doering
        -- NetMaster
-- 
Total number of prefixes smaller than registry allocations:  110584

SpaceNet AG                        Vorstand: Sebastian v. Bomhard
Joseph-Dollinger-Bogen 14          Aufsichtsratsvors.: A. Grundner-Culemann
D-80807 Muenchen                   HRB: 136055 (AG Muenchen)
Tel: +49 (89) 32356-444            USt-IdNr.: DE813185279

---

From: james woodyatt <[email-masked]>
Date: Thu, 6 Dec 2007 11:22:30 -0800

On Dec 6, 2007, at 09:24, Gert Doering wrote:
>
> (I do wonder a bit why zero-conf devices would all of a sudden  
> invent lots of independent *subnets*, though).

Consider how RTMP worked in Appletalk (except, try not to get hung up  
about the historical problem of excessive unsolicited broadcasts—  
pretend it was designed by people who understand how to do  
exponential backoff and keep multicast traffic to a minimum).

Zero-configuration IPv6 routers would need to generate random subnet  
identifiers from a sufficiently large space to ensure that collision  
is statistically rare, because collision requires renumbering, which  
causes more traffic.  When the subnet identifier space is large  
enough, then the network stabilizes quickly after a collision, i.e.  
typically after only one iteration.  If the subnet identifier space  
is too small, then network add/join events might require many  
iterations of the resolution protocol before an available subnet  
number is found.

Why might zeroconf routers be more prevalent in the future than they  
are now?  Answers: p1) IPv6 forwarding is cheaper and easier to do in  
hardware than IPv4 forwarding, so L3-switches should become cheaper;  
p2) the day might never come that IEEE 802.1 is the only sub-IP layer  
one ever needs and bridging (not routing) is how networks might  
therefore be interconnected in residential environments; and p3)  
consumer devices are rarely configured for any mode other than the  
factory default, and developers need to choose defaults that are  
optimized for the broadest possible set of usage scenarios, i.e.  
secure out of the shipping container, with a firewall turned on until  
the user encounters a need to reconfigure or disable it.

---

From: Brian E Carpenter <[email-masked]>
Date: Fri, 07 Dec 2007 10:21:30 +1300

On 2007-12-06 12:28, Iljitsch van Beijnum wrote:
> traffic to flow at line rate. You need routers to keep subnets apart. So 
> I don't see how an average home is going to use more than a handful of 
> subnets the way things are now.

Switches don't work well between different technologies. I remember reading
that luxury cars today contain at least ten different level 2 networks
in various technologies. I don't see why we should expect future homes
to be much different - and as soon as you have multiple technologies,
cheap switches can't be assumed. So I don't think we should be conservative.

      Brian
> 
> There is one exception: the case where multiple routers are deployed in 
> a cascading style and each provisions address space to the next one. 
> Assuming a router gives up half of its own address space to its 
> subordinate, you can have four levels of routing in your home with a /60.
>