[Here is an excellent article on the uncertainties of IPv6
transition. R&E networks and universities probably have the single
largest number of unallocated IPv4 address space.
Therefore I think
they have a critical role in enabling and ensuring a smooth transition
from IPv4 to some future network addressing scheme that enshrines the
end-to-end principle and layer Internet architecture. Providing address
blocks to open access community networks as part of the institution’s
address space, retiring IP address blocks to insure elimination of
energy hogging servers, partnering on deployment of R&E IPv6 3G/4G
wireless networks, etc are some of the ideas I have blogged about in the
past on how R&E networks can help in this transition.
Although
I agree with Geoff that we need to prevent accidental transitional
strategy, I remain skeptical that IPv6 is the future nirvana of
networking. Maybe it is time to start thinking beyond IPv6 and DNS and
look for solutions that are not only backwards compatible, but also
provide significant new value to the end user. Alphanumeric addressing,
XML routing, delay tolerant networking, etc are some of the ideas
floating out there. –BSA]
Moving Beyond IPv6 and DNS
http://billstarnaud.blogspot.com/2010/12/what-comes-after-ipv6-and-dns.html
The Address plus Port (A+P) Approach to the IPv4 Address Shortage
http://www.rfc-editor.org/rfc/rfc6346.txt
IPv6 Transitional Uncertainties
http://www.circleid.com/posts/ipv6_transitional_uncertainties/
By Geoff Huston
When we look back at previous technology transitions in our industry, they all look just so logical.
[..]
What
about the transition from IPv4 to IPv6? Is this also an inevitable
transition? There is no doubt that the designers of IPv6 certainly
envisaged this as an inevitable transition. But there are some
challenges here.
The first is that the transition does not provide
for backwards compatibility. A host cannot switch from using IPv4 to
IPv6 and still communicate with all the hosts still using IPv4. So the
transition has an essential “dual stack” phase where, during the
transition, hosts operate with both protocol stacks concurrently, using
the IPv6 protocol stack to speak to other IPv6 hosts and the IPv4
protocol stack to speak to other IPv4 hosts. This lack of backwards
compatibility in IPv6 makes the transition slightly more complex, but
not prohibitively so. What it means is that applications and host
operating systems need to be aware of IPv6 and explicitly have
capabilities to use IPv6. It’s not a seamless augmentation at the
application interface level.
There an additional challenge here
that is formidable, and one that was largely unforeseen when IPv6 was
being designed. At the time there was the general impression that the
telecommunications industry behaved prudently, and given the warnings of
the prospect of exhaustion of the IPv4 address space, industry actors,
being prudent and risk averse, would embark on the transition to IPv6
well in advance of IPv4 address exhaustion. And one or two did. But
everyone else did not. And now we have the challenge of trying to
undertake this dual stack transition while one stack is critically short
of further address space. This factor radically alters the dynamics of
the transition. In order to make the IPv4 part of the transition work
for the requisite number of additional years it will be necessary to
deploy additional “middleware” in the network, and head in a different
direction architecturally.
The most obvious shift is probably
going to be one of deployment of Carrier Grade NATs (CGNs) in access
networks. This will allow a single public IPv4 address to be shared
across multiple end clients. The longer the transition takes the more
likely that this alone will not be sufficient, and we may expect to see a
push to re-architect content into Content Distribution Networks that
have points of presence in major access networks. It is also possible
that network providers may resort to Application Level Gateways (ALGs)
and managed services in an effort to further contain the level of IPv4
address and port consumption by user services.
The risk here is
that after making this additional capital investment in network
infrastructure, the network service provider is then highly motivated to
protect the value of this investment. What lengths will network service
providers be prepared to go to in order to protect this investment in
transitional services? And if these transitional services generate
higher revenues for the network service provider than basic commodity
packet transit services, to what extent is the network service provider
then motivated to lock itself into this “transitional” service model for
an extended period? Would this imply that rather than being a
transitory state we see these changes to the network lasting for an
indefinite period.
If one sector of the industry finds that this
transitional model of providing services sufficiently attractive, is it
possible that it could have sufficient market influence such the entire
service provider industry collectively locks into this “transitional”
model as an enduring service model? If this was to eventuate the
internet would be driven in an entirely different direction than IPv6!
[..]
The
challenge we face is to sustain the IPv4 half of the dual stack
environment in the face of continuing escalation of demand for
addresses. For many years the conventional networking environment has
included the use of a NAT device at the interface between the network
and the user. Increased pressure on addresses is now forcing network
service providers to place a second level of NAT inside their network as
part of the network infrastructure.
This process of transition is
expected to take many years, I have heard commentary to suggest that
five years is unrealistically short, and we should expect a transition
that may take a decade or longer. But will CGNs last for a further
decade of network growth during this extended transition? The next step
after CGNs is to break apart the end-to-end network model and start to
erect connectivity “barriers” or “walled gardens”. The tools to do this
include re-homing a copy of certain content “inside” the network as a
next step, then, as a further step in address ‘compression’, using
application level gateways rather than address level IP header
translators.
The current approach to IPv4 exhaustion will see
different regions experiencing different IPv4 scarcity pressures at any
point in time. In the Asia Pacific Region the momentum to deploy CGNs as
the first response to IPv4 address scarcity is already visible.
However, other regions are not experiencing the same pressure at this
time. If one were to project this further forward by 18 months to 2013
the European region would also have exhausted its pool of IPv4
addresses, but the other three regions may well be operating in a mode
that is still able to meet regional demands for IPv4 addresses. It is
highly likely that at that time the different regions will be
experiencing very different market pressures for the provision of
Internet services, due to differing transitional pressures from IPv4
exhaustion.
The consequent question is: What’s the level of risk that
the differing environments of transition lead to significantly
different outcomes in each region as the process of transition takes of a
different momentum in different regions? And if this eventuates will we
still have a single coherent Internet as a common asset, or will we
find that market forces interact in unpredictable ways that create
different outcomes in each region?
What of the plan to ultimately
converge to an IPv6 network? It may be useful to remember the myth of
the long term plan. Are we still as firmly committed to the long term
plans we formulated 5 or 10 years ago? Or have we found that our plans
are continually modified and refined over time, and there is actually
little left of the original plan. So will we be as firmly committed to
the transition to IPv6 in five years time? Or will we manage to lose the
plot and head into different directions because of the different spread
of pressures on service providers in each of the regions. We will
forget about the intention to preserve the concept of a single global
network in amidst the difficulties of this disparate transition?
On Maintaining the Momentum for IPv6
Can
we help the Internet during this transition, and try to ensure that the
Internet remains a single coherent network with some essential
architectural attributes of end-to-end clarity? Or, if we want to aim a
little lower, can we at least minimize the potential for disastrous long
term damage to this phenomenally productive and valuable networking
environment that the Internet has enabled?
I don’t know the answer to
those questions, but I would like to offer a small number of thoughts
that I have had when thinking about this topic.
If we want a single
working Internet at the end of all of this, then we need to keep an eye
on the larger picture of network evolution during transition. We need to
find ways for self interest and local interest to converge with what is
in our common interest. Without that convergence we will see a form of
market failure where the common interest of a single global network, and
the value that such a service can generate, being lost to network
divergence through the exercise of differing local market pressures. I’m
not sure that I understand how to ensure that self interest aligns with
common interest in every circumstance, but what would be good to avoid
is building a network that imposes major barriers and inefficiencies all
in the name of address conservation in IPv4, and then citing the
investment in this additional infrastructure as grounds for not
progressing with the transition to IPv6.
Secondly, IPv4 addresses
should be used in working networks and not hoarded. Its probably a
natural reaction to impending scarcity to hoard a resource, but its not
necessarily a good reaction. Hoarding behaviour exacerbates the scarcity
of the resource in both its intensity and duration. This generalization
is also true in the specific context of IPv4 exhaustion and transition.
The scarcity of IPv4 addresses creates market uncertainty and market
pain in the form of a reduced revenue outlook across the transition
period. Extending this scarcity through hoarding and other forms of
witholding addresses from use in the network acts to prolong the market
pain and increase the unpredictability of the entire transition process.
And
finally, we need to keep the transition as quick as possible. A rapid
transition represents the best chance of achieving an IPv6 network as an
outcome of this process. The more time we spend investing time, money
and effort in deploying IPv4 address extension mechanisms, the higher
the risk that we will lose track of the temporary nature of transition
and the higher the possibility that we’ll get stuck with the wrong
Internet at the end! If we are truly committed to achieving a single and
coherent IPv6 Internet then perhaps its necessary to act now to
compress the timelines for transition, not extend them!
By Geoff
Huston, Author & Chief Scientist at APNIC. (The above views do not
necessarily represent the views of the Asia Pacific Network Information
Centre.)
Related topics: IP Addressing, IPv6, Regional Registries, Top-Level Domains
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