Subject: [RRG] IPv4 shortage, new features and IPv6 inevitability

From: Robin Whittle <[email-masked]>
Date: Thu, 22 Nov 2007 14:59:41 +1100

Hi Iljitsch and Xu,

I am responding to your replies to "Inviting people to join the RRG":

  http://psg.com/lists/rrg/2007/msg00512.html

Xu, regarding IPv4 address depletion and the routing scalability
problems you wrote:

> I agree that a new Internet architecture should address both
> issues. Otherwise, Internet will need another evolution after we
> just finished an evolution for routing scalability purpose. If
> the routing scalability issue is not so urgent as imaged, we need
> to give the matter further thought.

I think the only solution to address depletion is to divide the
remaining free space and currently allocated but underutilized space
into smaller blocks than has been the case (longer prefixes), down
to /30 or whatever.  With the existing reliance on BGP alone, that
would lead to a completely unsustainable explosion in the number of
prefixes.  So I think better utilisation of IPv4 space can only be
achieved with a more scalable routing architecture.

On its own, the current growth in the ~240k IPv4 prefixes is
regarded as alarming by some, but not by all.  Those who are not
alarmed are probably not on this list.  Few of the many people who
are concerned about IPv4 depletion seem to think there is scope for
better utilization - but I think that will change as the crunch
progresses and more and more space is in fact better used.

I and a few others - I think including Geoff Huston:

  http://psg.com/lists/rrg/2007/msg00512.html

- think there is a lot of room for improvement.

The stability and responsiveness of the BGP system is not ideal, but
is not nearly disastrous.

I understand (can someone confirm this?) that the CPU and memory
burden on each DFZ router scales roughly in proportion to the number
of prefixes multiplied by the number of peer routers, with a
significant contributing factor being the number of changed
advertisements.  This last factor is driven by outages, permanent
changes in network structure and in particular by a small subset of
operators chopping and changing their advertised prefixes between
different routers on an hourly or daily basis to achieve Traffic
Engineering of incoming traffic.

Since current routers are working with a wide range of numbers of peers:

  http://psg.com/lists/rrg/2007/msg00253.html

as far as I know, there isn't some threshold over which the number
of advertised prefixes would cause a precipitous increase in the
number of current routers being unable to perform their tasks
adequately.

I think that growth rate will increase enormously (unless we have a
new ITR-ETR scheme in place) once the only way of getting fresh
space is to carve smaller chunks out of larger slabs of space which
are currently not fully utilized.

>> 2 - All the ITR-ETR schemes are capable of slicing and dicing
>> IPv4 address space in many more pieces, and in finer pieces,
>> than is ever likely to be practical with BGP. 3 - Therefore,
>> any of the ITR-ETR schemes could make a major contribution to
>> the more efficient utilisation of IPv4 space.

> The current ITR-ETR schemes use IPv4 address as EID namespace,
> and they do make some contribution to the efficient utilization
> of IPv4 address space. But is that enough?

I think the continuing need for IPv4 address space, including
smaller chunks of it with greater use of NAT, will continue for the
foreseeable future - 5 to 10 years at least.  Having an IPv6 address
does not alter the need of the vast majority of users for direct (or
via NAT) access to IPv4.

My guess is that a combination of these two approaches, either of
which is effective on its own, will keep virtually all end-users
(apart perhaps from research and cellphone networks) connected to
the IPv4 Internet for the next 5 to 10 years at least - and perhaps
for much longer:

1 - Better utilisation of IPv4 space through more dense address
    usage by existing address holders, combined with splitting
    up space into far more, smaller, chunks for new ISPs and
    end-user networks.

2 - Increased use of NAT.  All home and office applications have
    to work with NAT now, so despite its ugliness and the terrible
    burdens it places on application developers and (when it doesn't
    work) on end-users and hapless ISP help-line people, I think
    NAT is part of life, except for servers, and will be used more
    and more.

I am not saying this is elegant or desirable.  Its just that no-one
has been able to convince me that IPv6 will in fact be widely enough
adopted in the next decade or two for ordinary end-users to be happy
without IPv4 access.  Until then, IPv6 is no solution to the IPv4
address crisis.

> Provided that a new address space needs to be deployed as EID
> namespace sooner or later in order to provide enough address
> space, should we go ahead further to embed some useful features in
> this new namespace from the start, such as build-in security
> mechanism?

Hmmm . . . If my prediction about continuing ubiquity of IPv4 turns
out to be valid, then the new ITR-ETR scheme should definitely be
amenable to important extensions such as this.  (I believe an
ITR-ETR scheme will be developed and widely deployed, though it will
probably take quite a few years.)

I think at this early stage of development it would be premature to
hard-wire a new feature into the ITR-ETR scheme, but I think it
would be good to ensure the system is expandable to do things we can
and can't think of now.  We may be stuck with the scheme for decades.

I can't imagine a new feature giving benefits to the end-user
without host changes.  Perhaps some new features might work with
only an OS change, or only an application change.  Others would
require both.  Assuming the new features were genuinely useful and
elegant - so as not to tangle the Net with complexities of marginal
value - perhaps this could encourage adoption of the ITR-ETR mapped
address space.

>> 4 - We are stuck with IPv4 for the next decade or so.  IPv6
>> provides few, if any, benefits for ordinary end-users, is
>> complex and is not ubiquitously supported by applications,
>> firewalls etc.  No ordinary Internet user is likely to be
>> happy with an IPv6-only address in the foreseeable future.

> Agree.

Thanks for agreeing with this, which is an unpopular view in some
quarters.

> Sooner or later we will need a global unique EID namespace
> and locator namespace with enough space in order to realize
> ubiquitous communication. It's better not to patch the Internet
> architecture again and again because each upgrade will be a hard
> experience.

I agree.

Both NAT and an ITR-ETR scheme are kludges, with real costs and
limitations.  Neither would have been necessary if IPv4 had more
than 32 bits of address space - probably 48 would have been fine -
and if the routing system could cope with millions or billions of
separately routed prefixes.

The first might have been vaguely possible, but most computers were
32 bits.  The latter could only be achieved by some really elaborate
protocols and far more CPU power, memory and bandwidth than could
have been contemplated in the early 80s.  I think this latter goal
can really only be solved by an ITR-ETR scheme.  As far as I know,
no single, unified, routing system can scale to those sizes and at
the same time remain responsive to changes.

Iljitsch, despite what you wrote and what quite a few people believe
about IPv6 and about IPv4 utilization, still I believe (for all the
reasons I stated) that IPv6 offers no short to medium term (1 to 5
years) benefit to ordinary Internet users (and therefore their ISPs)
compared to the costs of adopting it.

I still believe that for the next 5 to 15 years most users will find
it better to squeeze more usage out of IPv4 address space than to
adopt IPv6-only space, where they can only communicate with other
IPv6 users or with IPv4 users via a strictly limited range of
protocols (via proxies or a handful of dual-mode applications).  I
still believe any of the ITR-ETR schemes can and should be used to
finely slice and dice IPv4 space.

NAT is ugly but I think that most most users would prefer it to
having no direct IPv4 reachability.  Theoretically, IPv4 can't be
the long-term (~forever) future, but either can burning fossil
fuels.  Still, most folks will be burning coal, oil and natural gas
until the immediate (personal, a few years timeframe) incremental
costs exceed the alternatives.

I think we may be stuck with IPv4 and NAT for a very long time
(decades), with higher overall costs than would be entailed by a
wholesale upgrade to IPv6 - because the shorter term costs of
abandoning direct (including via NAT) IPv4 connectivity are too high
at any one time for most users.

You wrote:

>> 1 - IPv4 address depletion is the most urgent architectural
>> problem facing the Internet - and far better recognised than
>> BGP stability and router scaling problems with the growth of
>> advertised prefixes.
>
> Ah, but that's a solved problem. RRG = research, IETF =
> engineering. IPv4 depletion = operation. We all know what needs
> to be done here. A wise man once said: just do it.

I see no consensus at all on what needs to be done regarding IPv4
address depletion.

I think you imply that we all agree the answer is to move to IPv6.

The trouble is, as I outlined above, IPv6 only solves the IPv4
address depletion problem once everyone - or almost everyone - has
moved to IPv6.  Until then, IPv6 offers no benefit to most users,
since they can't do anything with it they can't already do with
IPv4.  An important exception is the highly complex IP Multimedia
Subsystem - which was apparently designed to work only over IPv6.
This was intended for 3G cellphone systems, but is apparently being
considered for other uses as well.

It is not IPv6's fault that this is the case.  IPv4 had no upgrade
path.  I think it was a mistake for IPv6 to have such long
addresses, adding to the length of every packet.  64 bits should
have been fine - this would have saved 16 bytes of overhead per
packet.  But that is not what is holding up IPv6 adoption.  It had
to be a completely new address space, with correspondingly new
protocols.  It had to have a major impact on the OS and
applications, making life costly and difficult for developers,
network administrators and often users.

>> 2 - All the ITR-ETR schemes are capable of slicing and dicing
>> IPv4 address space in many more pieces, and in finer pieces,
>> than is ever likely to be practical with BGP.
>
>> 3 - Therefore, any of the ITR-ETR schemes could make a major
>> contribution to the more efficient utilisation of IPv4 space.
>
> I'm not convinced. The issue isn't the number of places that need
> an address block, but the number of places that need an
> individual address.

I think it is both, although NAT tends to reduce the quantity of
addresses each end-user network needs.

>> 4 - We are stuck with IPv4 for the next decade or so.  IPv6
>> provides few, if any, benefits for ordinary end-users, is
>> complex and is not ubiquitously supported by applications,
>> firewalls etc.  No ordinary Internet user is likely to be happy
>>  with an IPv6-only address in the foreseeable future.
>
> The alternative is NAT, which is worse.

NAT sucks immensely, but people live with it now.  Just like
Windoze.  (I am using both at this moment.)

Virtually no Internet user can live without IPv4 connectivity.  So
expecting them to be happy with only an IPv6 address any time in the
next 5 years is like expecting them to stop breathing entirely -
rather than expecting them to continue to suck as they (we) have
learned to do already.

>> 5 - IPv4 address space utilisation could easily be improved if
>> there were suitable policies and slicing and dicing
>> technologies. Ping responsive host rates in advertised space
>> are around 4%:
>
> Meaningless. First of all, they also pinged unrouted space.

It is not meaningless.  My survey and the much better work at USC ISI:

  http://www.isi.edu/ant/address/
  http://www.firstpr.com.au/ip/host-density-per-prefix/

both surveyed address space which was advertised in BGP.

If you criticise these results as being so quantitatively inaccurate
as to be meaningless, I think you need to provide quantitatively
verifiable estimates of how many genuinely used addresses are not
being picked up by ping.

The ISI people face the same critique, also without any quantitative
estimates of how inaccurate their figures are.

> Second, current Windows doesn't respond to pings.

Googling indicates Vista doesn't respond to pings.  Firstly, not
that many people use Vista.  Secondly, many who do would have their
machine behind NAT - and plenty of NAT devices such as DSL and cable
modems do respond to ping.

> Third, there's NATs and firewalls.

I got high ping response rates from prefixes with reverse address
mapping indicating they were DSL blocks.  Also, the cable modem
block 24.0.0.0/8 had a 17.6% response rate.

> Fourth, not all systems are
> turned on 24/7. Fifth, this is an average that includes both stuff
> given out under the current fairly tight policies and large
> amounts of stuff given away to people who aren't using it anymore.

There is a wide distribution of ping response rates, as the graphs
at my site show:

  http://www.firstpr.com.au/ip/host-density-per-prefix/all-graphs/

This wide distribution of rates is surely explained, to quite a
large degree, by genuine variations in utilization.

>> So there is plenty of room for improvement.
>
> No. Any effort spent on getting back IPv4 space for new uses is
> wasted effort, because we need to move to IPv6 in the slightly
> longer run anyway.

Geoff Huston estimates 5 to 20% utilization.

http://www.ripe.net/ripe/meetings/ripe-55/presentations/huston-ipv4.pdf

Even with 20% - which means 3/4 of used addresses don't respond to
pings - there is great scope for improvement.

In the really long term, IPv4 with an ITR-ETR scheme and ubiquitous
NAT would be a horrible kludge - but perhaps it may still be
tolerable enough to keep sucking at, unless and until so many people
have fully IPv6 compatible OSes and applications, without any
investment of effort on their own, that the few people without IPv4
addresses can be forgotten about, except via proxies for a few key
protocols.

IPv6 is years - probably decades - away from being sufficiently
widely and robustly deployed in applications and OSes.

>> We are attempting to devise something really challenging here -
>> and I think more expertise, more energy and wider perspectives
>> would be very helpful.
>
> Again: no. We made our beds over the past 15 years. We have
> another few years to fluff the pillows, then it's time to go to
> sleep. Even if it's possible to go back and redo the IPv6 effort
> and arrive at substantially better results (debatable), it's too
> late for that now. The message should be: you have three more
> years to start running IPv6 if you don't want to be left behind
> on a network that isn't going anywhere in the medium- to long
> term.

That is the message from the IPv6 camp.

But why would I, or most other end-users (and their ISPs) get IPv6
connectivity, ensure our most important devices, hosts OSes and
applications are IPv6 compatible, when there is no benefit now or in
the next few years over continuing to use IPv4 and leaving my
computer undisturbed?

That is just the first stage - to convince individual end-users and
network operators to adopt IPv6, whilst retaining IPv4 connectivity.
 I can't think of a single practical, businesslike reason most users
should do this.

But in order for IPv6 to help at all with the IPv4 address shortage,
you need to get "enough" end-users to adopt IPv6 in order that a
significant number of end-users will be happy not to have an IPv4
address.  "Enough" is probably close to 100%.

Year after year we hear the same thing from the IPv6 camp and
nothing substantial in user-land or ISPs happens - because IPv6
adoption involves effort and confusion and no tangible benefits.

I am not saying it is good that the only viable complete alternative
to IPv4 is so hard to get going.  I am just saying it is.

  - Robin

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---

From: Iljitsch van Beijnum <[email-masked]>
Date: Thu, 22 Nov 2007 11:22:11 +0100

On 22 nov 2007, at 4:59, Robin Whittle wrote:

> to /30 or whatever.

This completely ignores the current reality that the average address  
block given out is almost 30,000 addresses. 90% of the address space  
given out is very large blocks going to ISPs, who presumably need it  
for their access services. If you need a million addresses you could  
also take 16 /16 blocks or maybe even 256 /24 blocks, but certainly  
not a quarter million /30s. Also, IF IPv4 address space is available  
it's going to be in blocks significantly larger than that, not only  
because the smallest that can be used today is /24, but also because  
the vast majority of the presumably reclaimable address space is in  
the form of /8s (and almost all of the rest in /16s). Some slicing and  
dicing may be required, but from a /8 down to a /30? Don't think so.

> With the existing reliance on BGP alone, that
> prefixes.

An interesting thing about BGP is that if you break it, you see that  
immediately. That means you'll revert back to the previous  
configuration within minutes. So anything that has enough impact to  
really break BGP simply won't be deployed.

> does not alter the need of the vast majority of users for direct (or

It's interesting to contrast the situation the big content players are  
in versus the one ISPs are in. As a content network, you need very  
little IPv4 space. Moving to IPv6 is pretty much a binary thing: you  
either enable it or you don't. So for content people enabling IPv6 is  
hard and sticking to IPv4 is easy. ISPs on the other hand needs lots  
of fresh IPv4 space to connect new customers, but they are in the  
position to roll out new deployments for new users and keep existing  
customers on existing stuff so they don't have to go to IPv6 wholesale  
at once. So for ISPs sticking to IPv4 is going to be problematic due  
to the depletion while introducing IPv6 is relatively easy.

So we'll probably see a world where more and more eyeballs are on IPv6  
(which means in practice either IPv6-only with proxies/NAT-PT or  
IPv6+IPv4/NAT dual stack) while most of the content will stick to IPv4- 
only for a much longer time.

Any claims of 5 or 10 years or even longer is highly suspect because I  
don't see a quantitative basis for it. My best guesstimate about the  
IPv4 depletion is that we'll run out in 2012, so yes, in 5 years most  
people will still be running IPv4. But if good transition mechanisms  
are available, it will be easy to move to IPv6-only while still having  
access to IPv4 resources and then a significant number of people could  
be living on an IPv6-only network fairly soon.

> compared to the costs of adopting it.

The benefit is that you get to connect new users to the network for  
more than just the next 5 years.

Building a house also doesn't give you an immediate benefit: it costs  
a lot of money while building but you can't start living in it until  
you're done. But houses are built every day.

The costs of adopting IPv6 are quite small, especially if you take  
enough time to do it.

> it better to squeeze more usage out of IPv4 address space

That only prolongs the pain. Worst case would be that address policies  
become very strict and people spend enormous amounts of time and money  
getting a few IPv4 address but we don't really "run out" so IPv6  
deployment doesn't happen. We need fresh IP addresses to be available  
one way or the other, without that, we'll all be wasting a lot of time  
and money on addressing that could have gone to something productive.

> I think you imply that we all agree the answer is to move to IPv6.

Knowing that something needs to be done and agreeing to do it aren't  
the same thing.

> moved to IPv6.

That's why we still need to work on transition mechanisms in the IETF.  
Dual stack isn't it.

> I think it was a mistake for IPv6 to have such long
> have been fine

That wouldn't have made any difference to our deployment issues, it  
would just have meant no CGA/HBA or stateless autoconfig. The real  
answer is of course that addresses need to be variable length.

> addresses each end-user network needs.

You assume a model where it would be possible for every device that  
connects to the network to get an individual public address. That's  
simply not possible with IPv4, because the need for addresses is so  
dynamic that ISPs can't realistically provision addresses this way.  
(For instance, currently I don't need any addresses at home. When I  
get home and start copying some data between different computers I  
need 4 or 5 addresses.)

The current model is that in most cases, an ISP provisions one address  
per line to a customer. If this changes to a larger number of lines  
per address this makes NAT more problematic for end-users, but yes,  
that could save a lot of address space.

> both surveyed address space which was advertised in BGP.

I asked the guy from ANT, he said that they also pinged unrouted space.

> Geoff Huston estimates 5 to 20% utilization.

Could be. I'm pretty sure that many ISPs never bother to reuse old  
address space when customers leave etc but simply request new stuff.

The real question is: why is the utilization so low? And is that  
reason still present today? If so, what would we need to do to  
overcome that factor? And if we do that, how much extra IPv4 time  
would that give us?

We already see that ARIN doesn't want to reclaim any of the legacy  
class A address space, even though that only means 40 instances of  
administrative work for 650 million IPv4 addresses - a pretty sweet  
deal compared to pretty much any other effort that you can think of.

> widely and robustly deployed in applications and OSes.

Nonsense. I'll prove it to you by turning off IPv4 right now on my  
system and sending you this message running IPv6-only using only  
software that came with my Mac and a dual stack server elsewhere on  
the network.

I'm not saying it's possible to turn off IPv4 today without any impact  
on functionality (I can't print or use my instant messaging client  
right now for instance) but we've come a long way since when I started  
with IPv6 and I could only do ping6 and traceroute6.

> the next few years over continuing to use IPv4 and leaving my

Forget end-users. They don't know about this stuff. ISPs will start at  
some point but they're going to wait some more because if you have the  
choice between spending money now or spending it tomorrow, the latter  
is usually a no-brainer.

---

From: Mark Prior <[email-masked]>
Date: Thu, 22 Nov 2007 21:24:37 +1030

Iljitsch van Beijnum wrote:

> people will still be running IPv4. But if good transition mechanisms are
> available, it will be easy to move to IPv6-only while still having

As Geoff mentioned recently at the AusNOG conference the guestimate is
optimistic at best because it is just based on the current pattern of
usage and does not take into account that human nature will cause a rush
on addresses as the count down gets ever closer.

> The benefit is that you get to connect new users to the network for more
> than just the next 5 years.

I think there is also a financial opportunity for ISPs that have IPv4
address space but could migrate customers to IPv6 and thus build a free
pool of a commodity that everyone else wants. Could be a nice little
earner as the dinosaurs get more desperate :)

> That's why we still need to work on transition mechanisms in the IETF.

We don't need a transition mechanism we need a coexistence solution so
"the Internet" remains accessible to all irrespective of what protocol
is in use under the hood.

> address space when customers leave etc but simply request new stuff.

I find that somewhat hard to believe. When I was working at a major
Australian ISP our system would return address space back into our free
pool when the customer left (quarantining it for a period) and then
reused it.

If it's really being wasted like that then perhaps it's time for the
RIR's to audit usage before assigning more space to existing customers.

> choice between spending money now or spending it tomorrow, the latter is
> usually a no-brainer.

End users couldn't care less about the plumbing (aside from possibly
reading about it in the press). ISPs could be using RFC1149 based
networks for all they care :) It's the ISPs who should be the ones
caring since they need the extra addresses to continue to grow so they
need a workable solution to the problem. The danger for the ISPs in this
game of chicken is how much it costs to do something now versus how much
it's going to cost later and it would appear that they think it's going
to be cheaper later.

Mark.

---

From: [email-masked]
Date: Thu, 22 Nov 2007 07:35:10 EST

Two further thoughts about IPv4 address completion:
1) Why to keep the Multicast address space ? Multicast means a special  
precedural behaviour which could be indicated by a single MC-bit in the  IP-header
2) I submitted a multicast model which would have exploited unicast for the  
sake of multicast, with the advantage that millions, spread all over the 
world,  could be the receivers, 90 % of them without  even knowing that the  get a 
multicast stream rather than a unicast stream (but that was  rated  to be even 
VERY POOR:-(
 
For this discussion: there are also a lot of MC addresses around.
 
Heiner 

In einer eMail vom 22.11.2007 11:56:45 Westeuropäische Normalzeit schreibt  
[email-masked]:

Mark.

---

From: Robin Whittle <[email-masked]>
Date: Fri, 23 Nov 2007 17:51:04 +1100

* IPv6 transition mechanisms.

* Ping surveys of IPv4 and how well the space is used at present.

* Therefore, with NAT, how much scope is there for continuing
  to rely on IPv4?

Hi Iljitsch,

LISP, eFIT-APT, Ivip and TRRP are perfectly capable of slicing a /8
or any other length prefix into as many /30s or even /32s as you
like - without any extra burden on the BGP system.

Regarding my comment that this number of long prefixes wouldn't fly
with the current BGP-only routing architecture, but would be fine
with one of these ITR-ETR schemes, you wrote:

>> With the existing reliance on BGP alone, that would lead to a 
>> completely unsustainable explosion in the number of prefixes.
> 
> An interesting thing about BGP is that if you break it, you see 
> that immediately. That means you'll revert back to the previous 
> configuration within minutes. So anything that has enough impact 
> to really break BGP simply won't be deployed.

Your response doesn't seem to relate to my intended meaning.

>> smaller chunks of it with greater use of NAT, will continue for
>>  the foreseeable future - 5 to 10 years at least.  Having an 
>> IPv6 address does not alter the need of the vast majority of 
>> users for direct (or via NAT) access to IPv4.
> 
> It's interesting to contrast the situation the big content 
> players are in versus the one ISPs are in. As a content network, 
> you need very little IPv4 space. Moving to IPv6 is pretty much a 
> binary thing: you either enable it or you don't. So for content 
> people enabling IPv6 is hard and sticking to IPv4 is easy. ISPs 
> on the other hand needs lots of fresh IPv4 space to connect new 
> customers, but they are in the position to roll out new 
> deployments for new users and keep existing customers on existing
>  stuff so they don't have to go to IPv6 wholesale at once. So for
>  ISPs sticking to IPv4 is going to be problematic due to the 
> depletion while introducing IPv6 is relatively easy.

I don't think it is "easy" for ISPs to deploy IPv6 to their
customers.  Few seem to do it.  Getting the address space is easy,
but upgrading and/or managing the routers, billing systems, security
arrangements, DNS, making sure all servers are dual stack etc. is a
lot of work.

The support costs would be massive.

The hapless ISP would get all manner of calls when users don't
understand what IPv6 means, when something doesn't work etc. - even
though the problem is likely to be in their application, their OS,
or the remote host and nothing to do with the ISP's service.

Having an IPv6 address or /64 does not alter the fact that virtually
all end-users - individuals, corporate networks etc. - still need
IPv4 space just as much as they do without the IPv6 space.

> So we'll probably see a world where more and more eyeballs are on
>  IPv6 (which means in practice either IPv6-only with 
> proxies/NAT-PT or IPv6+IPv4/NAT dual stack) while most of the 
> content will stick to IPv4-only for a much longer time.

Can you give me an example of a set of proxies which provide
adequate support for ordinary home or office users who need to
communicate with IPv4 hosts, but who have only an IPv6 address?
Protocols to be supported (in a way that bog-standard Windoze apps -
probably not IPv6 aware - will work) include:

  HTTP, HTTPS
  SMTP, POP3 IMAP4
  FTP, SSH
  IRC
  (Any number of streaming media protocols.)
  (Any number of instant messenger protocols.)
  (Any number of VoIP systems, including Skype.)
  (Any number of P2P filesharing systems.)
  (Any number of commercial games.)
  etc.

> Any claims of 5 or 10 years or even longer is highly suspect 
> because I don't see a quantitative basis for it. My best 
> guesstimate about the IPv4 depletion is that we'll run out in 
> 2012, so yes, in 5 years most people will still be running IPv4. 
> But if good transition mechanisms are available, it will be easy 
> to move to IPv6-only while still having access to IPv4 resources 
> and then a significant number of people could be living on an 
> IPv6-only network fairly soon.

I still don't see how this is going to happen - there are no good
transition mechanisms.

There probably cannot be any good transition mechanisms.

>> Iljitsch, despite what you wrote and what quite a few people 
>> believe about IPv6 and about IPv4 utilization, still I believe 
>> (for all the reasons I stated) that IPv6 offers no short to 
>> medium term (1 to 5 years) benefit to ordinary Internet users 
>> (and therefore their ISPs) compared to the costs of adopting 
>> it.
> 
> The benefit is that you get to connect new users to the network 
> for more than just the next 5 years.

Virtually no ordinary users will do something tricky and/or costly
now - or accept a lower grade of service - for the sole benefit of
themselves or someone else in 5 years time.

I don't see what use an IPv6 address is to ordinary users.

After years of global publicity, some folks today might walk to the
shops instead of driving, or run their air-conditioner or heating
system a bit less comfortably, in the hope that this will reduce
global warming in the years to come.  They might be motivated by
concrete goals - perhaps remote in time and space - such as saving
someone from drowning in Bangladesh or saving their own home from
being ripped apart as hurricanes / tropical cyclones move further
towards the poles.

But how much consciousness raising would be required to get a
sizable proportion of ordinary end-users to pay for an Internet
service with massively reduced connectivity, year after year, for
the good feeling they get knowing they are no longer reliant upon,
or burdening, the dear old battlefield IPv4.

They would never do it if they knew how sparsely IPv4 address space
was used.

> Building a house also doesn't give you an immediate benefit: it 
> costs a lot of money while building but you can't start living in
>  it until you're done. But houses are built every day.
> 
> The costs of adopting IPv6 are quite small, especially if you 
> take enough time to do it.

I don't see why most users, business or home-based, would spend any
time on it.

>> I still believe that for the next 5 to 15 years most users will
>>  find it better to squeeze more usage out of IPv4 address space
> 
> That only prolongs the pain.

This is probably true - but I think that NAT and ITR-ETR schemes
will bulldoze a path in front of the great majority of users
(billions of dollars worth of paying customers) smoothing the way so
that at no point is there a bump big enough to motivate users to do
something tricky and expensive (in terms of time and attention, if
not upgrades to software) such as getting IPv6 space and software
which can use it.

> Worst case would be that address policies become very strict and
>  people spend enormous amounts of time and money getting a few 
> IPv4 address but we don't really "run out" so IPv6 deployment 
> doesn't happen.

I think this is what will happen.

> We need fresh IP addresses to be available one way or the other,
>  without that, we'll all be wasting a lot of time and money on 
> addressing that could have gone to something productive.

There are endless addresses available behind NAT, and most client
software works fine in the majority of NAT settings.  It
is a horrible kludge, but this is the situation.  ISPs, network
managers and DSL modem providers who foist unfriendly NATs on people
need to change their ways.  End-users need to be wary of plugging
NAT box into NAT box.

>> I see no consensus at all on what needs to be done regarding 
>> IPv4 address depletion.
> 
> Knowing that something needs to be done and agreeing to do it 
> aren't the same thing.

I assume you are implying that the solution to the IPv4 address
depletion problem is to move everyone to IPv6 addresses - which is

>>  address depletion problem once everyone - or almost everyone -
>>  has moved to IPv6.
> 
> That's why we still need to work on transition mechanisms in the 
> IETF. Dual stack isn't it.

OK, so you agree that adoption of IPv6 requires more work in the
IETF - which I understand as contrary to your earlier statement that
"We all know what needs to be done here".

I don't think there ever will be a transition mechanism which solves
the problem that:

1 - Most of the world uses IPv4.

2 - The central purpose of the Internet is to allow direct,
    unmediated (though NAT is a form of mediation) host-to-host
    communication on a global scale.

3 - Hosts without an IPv4 address can't communicate with hosts
    with an IPv4 address, except perhaps via a small number of
    complex, kludgy, "proxy" systems for a handful of protocols.

This has nothing to do with IPv6.  It is a failing of IPv4 that
without an IPv4 address, there is no conceivable seamless upgrade
path from it to some other address system and set of protocols.

>> I think it was a mistake for IPv6 to have such long addresses, 
>> adding to the length of every packet.  64 bits should have been
>> fine
> 
> That wouldn't have made any difference to our deployment issues, 
> it would just have meant no CGA/HBA or stateless autoconfig. The 
> real answer is of course that addresses need to be variable 
> length.

I see some sense in "variable length addresses", in that a pure
"IPv6" system could then communicate with IPv4 addresses, without
requiring a dual IP stack.  This, I imagine, would reduce the
headaches of trying to write an application which works seamlessly
in IPv4 only, IPv6 only and dual stack mode.

Still, I don't see how this hypothetical "IPv6" host could
communicate with an IPv4 host without an IPv4 address.

>>> I'm not convinced. The issue isn't the number of places that 
>>> need an address block, but the number of places that need an 
>>> individual address.
> 
>> I think it is both, although NAT tends to reduce the quantity 
>> of addresses each end-user network needs.
> 
> You assume a model where it would be possible for every device 
> that connects to the network to get an individual public address.

I would really like every device to have an individual public
address, but that is not possible without everyone upgrading to IPv6
or something better.  Because NAT compatibility is now so ubiquitous
in applications, and since NAT has some attractions in terms of
reducing attacks, I don't assume this is a requirement for most
users.  I figure most users would rather have one or more behind-NAT
addresses on IPv4 than only have an IPv6 address, no matter what
proxies were available.

My understanding is that servers need to have public addresses and
that suitably designed client and peer-to-peer applications can run
fine on a host behind NAT as long as they can use external servers
to coordinate their communications with other such peer-to-peer
software on other hosts behind NAT.  (Though some NATs are hostile
and make things really difficult, or impossible.)

The application has to figure out on its own that it is behind one
or more NATs, and figure out how to fight its way out, and tickle
the NAT(s) in whatever way they individually require to keep the
translation stable.  This is a nightmare, but humans have already
adapted to it - or reached some kind of accommodation with it.

(Some of your comments generally agreed to and not quoted here.)

>>>> 5 - IPv4 address space utilisation could easily be improved
>>>>  if there were suitable policies and slicing and dicing 
>>>> technologies. Ping responsive host rates in advertised 
>>>> space are around 4%:
> 

  http://www.isi.edu/~johnh/PAPERS/Heidemann07c.pdf

    We determine the currently assigned address space from
    IANA [http://www.iana.org/assignments/ipv4-address-space].

  This list is actually a superset of the routable addresses,
  since addresses may be assigned to registrars but not yet
  injected into global routing tables [23].

You are right - they pinged unrouted (= unadvertised) space too.
The result (Table 1, November 2006) is 102.96 million Acks.

My random sampling ping survey in March 2007 extrapolates to 107.96
million Acks, with a single ping probe.  At that time 1,694,827,520
addresses were advertised.

This is:

  6.37% of advertised space.

  4.38% of space assigned by RIRs to ISPs and end-users

  2.89% of the 222 /8 prefixes which ultimately can, or I think
        should, be assigned to end-users.

Even if these ping surveys only show half or a third the addresses
which are actively used, this is still a low rate of address
utilization.

>>> No. Any effort spent on getting back IPv4 space for new uses 
>>> is wasted effort, because we need to move to IPv6 in the 
>>> slightly longer run anyway.
> 
> Could be. I'm pretty sure that many ISPs never bother to reuse 
> old address space when customers leave etc but simply request new
>  stuff.
> 
> The real question is: why is the utilization so low?

OK - I am glad you agree the utilization rate is low.

> And is that reason still present today?

As long as it is easier to apply for and get more space, rather than
 use existing space more densely, utilization will be low.  That
will be increasingly difficult over the next few years.

Also, some organisations are simply sitting on huge slabs of space
they were given in the early 1990s.

> If so, what would we need to do to overcome that factor? And if 
> we do that, how much extra IPv4 time would that give us?

It depends on how much more NAT can be used, and how small a piece
of address space can be used to supply entire end-user networks.
This in part depends on there being a slicing and dicing scheme
which does a much finer job than the current BGP system.

> We already see that ARIN doesn't want to reclaim any of the 
> legacy class A address space, even though that only means 40 
> instances of administrative work for 650 million IPv4 addresses -
>  a pretty sweet deal compared to pretty much any other effort 
> that you can think of.

I haven't been following this - it is hard to understand their lack
of motivation to do this.

I doubt that space will remain barren for long after the fresh space
runs out and people start scrambling for IPv4 space, asking
questions about how it is currently used and forking out real money
to get what they need, or what makes them feel secure.

> Nonsense. I'll prove it to you by turning off IPv4 right now on 
> my system and sending you this message running IPv6-only using 
> only software that came with my Mac and a dual stack server 
> elsewhere on the network.

Email is probably the easiest major form of communication which
could be handled by an IPv6-IPv4 proxy, dual-stack server etc.

> I'm not saying it's possible to turn off IPv4 today without any 
> impact on functionality (I can't print or use my instant 
> messaging client right now for instance) but we've come a long 
> way since when I started with IPv6 and I could only do ping6 and 
> traceroute6.

Coming a long way is very different from arriving.

>> But why would I, or most other end-users (and their ISPs) get 
>> IPv6 connectivity, ensure our most important devices, hosts 
>> OSes and applications are IPv6 compatible, when there is no 
>> benefit now or in the next few years over continuing to use 
>> IPv4 and leaving my computer undisturbed?
> 
> Forget end-users.

OK.  I am chiselling out IPv6's gravestone - leaving a blank for the
'x' - in readiness for whenever the life-support is disconnected.

                 -------------
                /             \
               /     IPv6      \
              /                 \
             |   1996 - 201x     |
             |                   |
             |       RIP         |
             |                   |
             | Forget end-users  |
             |     -IvB 2007     |
             |                   |
             |                   |
             |                   |
      ___.~\|//-=\\~|/..\|/_\\||//~,___

> They don't know about this stuff.

They shouldn't have to know or care about IPv4, IPv6 or anything
else.  They want to do IM, P2P, VoIP etc. with their friends,
relatives, business contacts etc. all over the world with not a clue
or a care about how the technology works.  They want to be able to
reach every website in creation, without any glitches, slowdowns or
fuss.

> ISPs will start at some point but they're going to wait some more
> because if you have the choice between spending money now or
> spending it tomorrow, the latter is usually a no-brainer.

This condition will persist.

Widespread IPv6 adoption is not inevitable in the foreseeable future.

I rest my case.

   - Robin

---

From: Stephane Bortzmeyer <[email-masked]>
Date: Fri, 23 Nov 2007 18:40:51 +0100

On Thu, Nov 22, 2007 at 11:22:11AM +0100,
 Iljitsch van Beijnum <[email-masked]> wrote 
 a message of 202 lines which said:

> > short to medium term (1 to 5 years) benefit to ordinary Internet
> > users (and therefore their ISPs) compared to the costs of adopting
> > it.
...
> costs a lot of money while building but you can't start living in it
> until you're done.  But houses are built every day.

There is a big difference: when you build the house, you are
reasonably certain that the house will be completed and that it will
be usable. When you deploy IPv6 (or HIP or HRA or ...), there is a
risk, that the rest of the world won't follow and that you'll have
wasted your time and money. So, deploying a new technologgy is an act
of faith, unlike building an house.

Instead of "immediate benefit" as a criterion, we should request
"certain benefit" for the user.

---

From: "Tom Petch" <[email-masked]>
Date: Mon, 26 Nov 2007 09:17:06 +0100

----- Original Message -----
From: "Iljitsch van Beijnum" <[email-masked]>
To: "Robin Whittle" <[email-masked]>
Cc: "Routing Research Group list" <[email-masked]>
Sent: Thursday, November 22, 2007 11:22 AM
Subject: Re: [RRG] IPv4 shortage, new features and IPv6 inevitability

> On 22 nov 2007, at 4:59, Robin Whittle wrote:
<snip>

> overcome that factor? And if we do that, how much extra IPv4 time
<snip>

What strikes me is that I - we? - really have no idea why IP addresses are
needed.  We can see who has the allocations, we can follow (and shape) the
policy for this, but I do not see why the number of addresses in use is rising
and I think it matters because the 'why' will affect predictions of future
growth.

If, for example, it is because addresses are being used to provide dial-up
access for new users in India and China, then clearly there is a latent demand
in the billions, which will continue for decades.

If instead it is because of the recent mass migration from dial-up to
broad-band, from a contended-for pool to a permanent /30 per potential user  -
and there is as much evidence to support this hypothesis as there is of the
widespread adoption of IPv6 - then this is a temporary phenomenon and the demand
will dry up in a few more years.

I really don't know (and see it as significant to the debate); does anyone?

Tom Petch

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 26 Nov 2007 10:57:16 +0100

> in the billions, which will continue for decades.

It doesn't have to be dial-up... Broadband is even "worse" here.

I download all the RIR allocation data a few times a week and put it  
in a database that's available through http://www.bgpexpert.com/addrspace.php

If you look at India:

RIR     Country   Addresses    Date

                      0.18 M  2003
                      2.36 M  2004
                      1.04 M  2005
                      2.23 M  2006
                      5.60 M  2007

That doesn't amount to much. I suspect that India may use space from  
American ISPs that doesn't show as "in", though. But China is going  
strong:

                     12.16 M  2003
                     18.69 M  2004
                     14.01 M  2005
                     23.66 M  2006
                     36.06 M  2007

The US seems to be over the hill, though (caveats apply due to ARIN's  
backdating practices):

                     20.71 M  2003
                     29.81 M  2004
                     49.68 M  2005
                     47.01 M  2006
                     25.30 M  2007

But not Europe (RIR = ripencc):

                     29.58 M  2003
                     47.63 M  2004
                     58.09 M  2005
                     56.43 M  2006
                     60.77 M  2007

> I really don't know (and see it as significant to the debate); does  

Not really. It seems the US is finally slowing down in the number of  
new addresses that it uses every year, but the rest of the world, even  
western Europe, isn't. This could be a temporary thing, such as one or  
two of the largest ISPs working off of addresses they got last year.  
It could also be a trend. On the other hand, new devices such as the  
iPhone use up extra address space, which could reignite address use in  
the coming years.

The only thing that's obvious is that China is using up address space  
really fast with no end in sight.

---

From: Tony Li <[email-masked]>
Date: Tue, 27 Nov 2007 11:17:42 -0800

On Nov 22, 2007, at 4:35 AM, [email-masked] wrote:

> 1) Why to keep the Multicast address space ? Multicast means a  
> special precedural behaviour which could be indicated by a single  
> MC-bit in the IP-header

Reserving one bit of address for multicast is equivalent to reserving  
half of the address space.  ;-(

Tony

---

From: Tony Li <[email-masked]>
Date: Tue, 27 Nov 2007 11:16:28 -0800

[Catching up on old threads...]

> Engineering of incoming traffic.

I can confirm that.  Each BGP speaker needs to store per-prefix, per- 
neighbor state.  Implementation hacks make the amount of such state  
very much non-linear, so direct proportionality isn't appropriate,  
but those are indeed the contributing variables.

Tony

---

From: "Tom Petch" <[email-masked]>
Date: Wed, 28 Nov 2007 18:14:14 +0100

----- Original Message -----
From: "Iljitsch van Beijnum" <[email-masked]>
To: "Tom Petch" <[email-masked]>
Cc: "Routing Research Group list" <[email-masked]>
Sent: Monday, November 26, 2007 10:57 AM
Subject: Re: [RRG] IPv4 shortage, new features and IPv6 inevitability

> in a database that's available through http://www.bgpexpert.com/addrspace.php

I should have known:-)

> But not Europe (RIR = ripencc):

But I still wonder about the why, at a deeper level, of what use (dial-up,
broadband, enterprise, personal, VoIP, ... ) these are being put to, something
that someone who has worked in or closely with one of the ISPs making use of the
larger allocations might have an insight into.

As I said, knowing more would enable better estimates of exhaustion, and would
inform discussions about such as IPv6 migration strategies.

Tom Petch