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<div class="author">
by Jonathan Zittrain, Leslie Daigle </div>
<div class="date">
January 10, 2011 </div>
<div class="family">
Filed under <a href="https://www.cdt.org/issue/internet-openness-standards">Internet Openness & Standards</a>, <a href="https://www.cdt.org/issue/technical-standards">Technical Standards</a> </div>
<div class="terms terms-inline">Tags: <ul class="links inline"><li class="taxonomy_term_1406 first"><a href="https://www.cdt.org/category/blogtags/ipv4" rel="tag" title="">IPv4</a></li>,
<li class="taxonomy_term_1407 last"><a href="https://www.cdt.org/category/blogtags/ipv6" rel="tag" title="">IPv6</a></li></ul></div>
<p><b>How the Internet is running out of room, and what we must do about it</b></p>
<p><i>"CDT Fellows' Focus" is a series from CDT that presents the views
of other notable experts on tech policy issues. This week, CDT Fellow <a href="http://cdt.org/personnel/jonathan-zittrain" target="_blank">Jonathan Zittrain</a> and
Leslie Daigle write about the end of IPv4 address space. Guest posts
featured in "CDT Fellows' Focus" don't necessarily reflect the views of
CDT; the goal of the series is to present diverse, well-informed views
on significant tech policy issues.</i></p>
<p>The Internet's framers famously designed it without predicting much
about how, or how much, it would be used. For example, the network's
capacity was conceived less in a count of precisely how many could
participate at once – the way traditional phone circuits worked – and
more in flexibly divisible bandwidth. As that bandwidth got saturated,
it would degrade gracefully: data might move slower for everyone, but no
one would get an "all circuits are busy" message. In ways large and
small, what animates Internet protocol design is a <a href="http://yupnet.org/zittrain/archives/10#49" target="_blank">procrastination principle</a>:
if something can work well, it doesn't have to be perfect, and not
every problem or limit must be anticipated and preempted. Potential but
still speculative flaws can be fixed later – possibly somewhere other
than inside the network.</p>
<p>Unfortunately "later" is arriving now for a crucial piece of the
Internet: its ability to tell one attached device from another. Internet
architects designed a simple way to identify participating computers
and route data among them: assign each a unique number: an Internet
Protocol (IP) address. No IP address, no delivery. The routers in
between you and your friend use your friend's number the way a postal
service would – the number says something about where she is. That's
made possible because IP addresses are clustered together, just like
street addresses grouped in a ZIP or other postal code.</p>
<p>The system has an Achilles' heel: there are a limited number of
numbers. It might seem that you could add 1 to whatever the last number
is and keep going, but there's a hard cap in venerable Internet Protocol
Version 4 (IPv4): 4 billion IP addresses, which the Internet is
outgrowing in much the same way that applications outstripped the
original 64K of memory expected for a PC running Microsoft DOS. There is
now general agreement among Internet technologists that the end days
are upon us: the last block of fresh IPv4 addresses will likely be
allocated to the Internet's North American address warehouse <a href="http://www.potaroo.net/tools/ipv4/index.html" target="_blank">in early 2011</a>, to be passed out to Internet Service Providers here by mid- to late-2011.</p>
<p>Worse, because of the clustering of addresses, we can't squeeze the
last bit of digital toothpaste out of the tube as fresh numbers become
scarce. There's a gray market for chunks of already-allocated numbers
despite restrictions against selling them – and some telecommunications
providers are rumored to have been purchased only for their numbers! –
but such used numbers carry their own risks. Anyone who has inherited
the former phone number of a pizza shop will appreciate that some
numbers are less desirable than others. Moreover, some IP addresses have
at one time been the source of cyberattacks, or hosted politically
sensitive content, and the resulting blocking of traffic originating
from them by various ISPs is rarely revisited by those ISPs. (Who wants
an old Wikileaks IP address?)</p>
<p>Running out of fresh numbers will not stop the Internet from working.
But, unchecked, it will greatly complicate growth. As new computers and
devices come online, something has to give – making more use of
existing addresses, or finding a new way to address things.</p>
<p>In the first category – making do – the procrastination principle has
bought us some time. Enterprising engineers developed an ingenious
baling-wire-and-twine workaround to the one-number-per-computer rule.
Known as network address translation, or NAT, it allows the holder of a
single IP address to share it among a group of computers. This happens
nearly every time you hook up a wireless router and access point at
home: your ISP only gives you one number, and you use your inexpensive
router to share it with everyone who connects to your network. Cable and
DSL ISPs are considering the same thing to put larger networks of
multiple customers behind a single address, at least as an <a href="http://www.networkworld.com/news/2008/072108-comcast-ipv6.html?page=2" target="_blank">interim measure</a>.
Unfortunately, like most such workarounds, it doesn't really work as
well as having one number per machine: the fancy footwork required to
share a number around can limit the kinds of applications you can run,
and greatly increase the complexity of some software, such as Skype
Internet telephony, if it's to work at all. NAT has bought us some time –
much of Qatar has been known to share one IP address – but it's spackle
covering a rapidly-rusting architecture stretched far beyond its
creators' wildest ambitions.</p>
<p>Which brings us to a more comprehensive solution. Internet
technologists did not sit idly by when it became clear IPv4 could not
last. Over a decade ago, they specified its successor, IPv6 (don't ask
what became of IPv5), with a few hundred trillion trillion trillion
addresses. Such huge swaths of address space promise something even
better than a well-functioning market for valuable but limited assets:
abundance so great that no market is required, only careful
administration. Unfortunately, for IPv6 to work, nearly every piece of
networking software and hardware from one end of a data transmission to
the other needs to be upgraded. If just one link in the chain hasn't
been upgraded to understand the new numbers, IPv4 will still have to be
used.</p>
<p>The idea for transition was that systems would work with both
protocols for awhile, and gradually IPv4 would end not with a bang, but
with a whimper – fading away like, say, the telegraph or telex addresses
that used to share letterhead with telephone and fax numbers. However,
even though many operating system and hardware vendors have been
anticipating IPv6 for years (current Mac and Windows systems now support
it out of the box), there are still gaps in available products and
little business dependency on it, and there has been remarkably little
deployment. This is consistent with the procrastination principle: the
only networks that have deployed IPv6 are those that have found a
business model for which it as a requirement. And, because the benefits
are, generally, global rather than local to one network, the
procrastination principle becomes a Prisoner's Dilemma: we're all better
off if we all move to IPv6, but the worst case is if you pay to move
while others don't. So why not wait – forever, if others act similarly –
for everyone else to do it before making the investment?</p>
<p>We've spent a decade with few networks taking the plunge to deploy IPv6.</p>
<p>This holding pattern is not likely to persist. With the larder dry,
in the absence of fundamental innovation in Internet Protocol, we'd see
an unfortunate ramp up in the use of NAT and its complications, coupled
with parties' tussles over existing 'pure' IP addresses like rats
fighting over crumbs. Demonstrated shortcomings of the type of IPv4
address sharing include degraded performance of network-intensive web
services: web pages where different pieces show up slowly, rather than
seamlessly. Customers will not see a poor network connection – they will
perceive poor service from the product or company.</p>
<p>More directly, IPv6 is gaining ground among new entrants (who have
little choice), so the days of an all-IPv4 Internet are numbered. In
developing its broadband strategy, India went for IPv6. New industries
looking at wide scale networking are also looking to IPv6 in order to
have access to adequate address space, and to be able to build novel
network architectures, unencumbered by the structural assumptions needed
<a href="http://www.ipso-alliance.org/" target="_blank">to support address sharing</a>.</p>
<p>The best future for the Internet is for all networks to deploy IPv6,
and pay the price of working in a dual IPv6 / IPv4 world for a period of
transition. If companies wait until the business impacts of degraded
IPv4 network experience or the identification of opportunities to work
with new (IPv6) networks are upon them, the need to make a transition
more quickly than a multi-year equipment refresh cycle will likely be
more costly and difficult. So how to encourage enough entities to take
the plunge?</p>
<p>One way out of a classic problem demanding collective action is
through regulation. A government can incent or compel everyone to
contribute. However, this would require coordinated regulation across
boundaries not recognized by network traffic – the intricacies are
daunting, and for the Internet without precedent. And if successful,
governments might gain an appetite for controlling the direction of an
Internet which previously managed growth and innovation through elective
uptake. Few are enthusiastic about mandated transitions.</p>
<p>Another way out is through leadership by big players. For example,
governments aren't just regulators of information technology, they're
purchasers of it. By insisting that government- and military-run
subnetworks are IPv6, they'll stimulate demand for the newer
technologies and encourage intertwined private parties to follow suit.
The US government's Office of Management and Budget followed just such a
route in 2005, requiring all government services to be <a href="http://www.networkworld.com/news/2005/080105-ipv6.html" target="_blank">IPv6 capable by 2008</a>. In September, Vivek Kundra crystallized requirements for government websites to be <a href="http://gcn.com/articles/2010/09/28/kundra-sets-new-ipv6-deadlines.aspx" target="_blank">IPv6 capable</a>.</p>
<p>China has been leading IPv6 adoption for years, in part because it
may otherwise feel the IPv4 number crunch most acutely, and perhaps
because the government has determined that it's in the country's <a href="http://news.cnet.com/China-launches-largest-IPv6-network/2100-1025_3-5506914.html" target="_blank">best commercial interests</a>.
Some large companies have placed bets on an upgrade. Google has been
public about its activities to deploy IPv6, and a business rationale to
not be last to market with <a href="http://www.networkworld.com/news/2009/032509-google-ipv6-easy.html?hpg1=bn" target="_blank">IPv6 support</a>.</p>
<p>A cold calculus on such investments for many Net-connected
enterprises may indeed suggest holding off. But what has made the
Internet better than the more proprietary networks that it eclipsed is
that its participants have had a sense of stewardship of the space,
justifying the absence of government planners and sheriffs, or a single
corporate umbrella. Engineers from the public and private sectors labor
on Internet protocols with loyalty to a network functioning as a
commons, not simply to their employers' particular business models. An
investment in IPv6 from enough corners is sensible if each corner
decides to factor in the benefit to the overall ecosystem – not just
itself.</p>
<p>If such capacious thinking comes through, the Internet won't run out
of space – and we can go back to procrastinating on its future.</p>
<p><i>Jonathan Zittrain is Professor of Law at Harvard Law School, where
he co-founded its Berkman Center for Internet & Society, and </i><em>Professor of Computer Science at the Harvard School of Engineering and Applied Sciences</em><i>.
He is a member of the Board of Trustees of the Internet Society. Leslie
Daigle is Chief Internet Technology Officer for the Internet Society.</i></p>