Lack of IPv6 traffic stats makes judging progress difficult
eugen at leitl.org
Tue May 24 17:22:42 CEST 2011
Lack of IPv6 traffic stats makes judging progress difficult
Data spotty on how much IPv6 traffic is flowing across ISP, enterprise nets
By Carolyn Duffy Marsan, Network World
May 24, 2011 12:03 AM ET
The Internet is poised to undergo the biggest upgrade in its 40-year history:
from the current version of the Internet Protocol known as IPv4 to a new
version dubbed IPv6, which offers an expanded addressing scheme for
supporting new users and devices.
However, it will be difficult for Internet policymakers, engineers and the
user community at large to tell how the upgrade to IPv6 is progressing
because no one has accurate or comprehensive statistics about how much
Internet traffic is IPv6 vs. IPv4.
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The issue of IPv6 traffic measurement is timely given that the Internet
engineering community is preparing for its biggest trial of IPv6: World IPv6
Day on June 8. So far, 225 website operators -- including Google, Yahoo and
Facebook -- have agreed to participate in the event by serving up their
content via IPv6 for 24 hours.
Without accurate IPv6 traffic statistics, neither the sponsors nor the
participants of World IPv6 Day will be able to tell for sure how much IPv6
traffic is sent over the Internet on June 8 or how much difference the event
has on IPv6 traffic volumes afterward.
"Being able to measure IPv4 vs. IPv6 is very important," says John
Brzozowski, distinguished engineer and chief architect for IPv6 at Comcast,
which has deployed an emerging tool called NetFlow 9 in parts of its network
to measure IPv4 and IPv6 traffic volumes. "We as a community need to be able
to measure our progress and success. IPv4 vs. IPv6 traffic is one of many
IPv6 traffic data "is useful in understanding the trend of adoption, but I
don't think it's critical for a carrier to understand that they have to
properly support their customers," says Dave Siegel, vice president of IP
Services Product Management at Global Crossing. Siegel adds that "it's most
important to have tools available to troubleshoot IPv6 issues."
IPv6 traffic volumes are likely to remain a hot topic as the pressure
intensifies for network operators to deploy IPv6, a 13-year-old standard
whose primary advantage over IPv4 is an expanded addressing scheme. While
IPv4 uses 32-bit addresses and can support 4.3 billion devices connected
directly to the Internet, IPv6 uses 128-bit addresses and can connect up a
virtually unlimited number of devices: 2 to the 128th power.
The Internet needs IPv6 because it is running out of IPv4 address space. The
free pool of unassigned IPv4 addresses expired in February, and in April the
Asia Pacific region ran out of all but a few IPv4 addresses being held in
reserve for startups. The American Registry for Internet Numbers (ARIN),
which doles out IP addresses to network operators in North America, says it
will deplete its supply of IPv4 addresses this fall.
DETAILS: Asia out of IPv4 addresses
But as necessary as IPv6 seems, there is a major stumbling block to its
deployment: It's not backward compatible with IPv4. That means website
operators have to upgrade their network equipment and software to support
IPv6 traffic. So far, most have been unwilling to do so because IPv6 traffic
has been so scarce.
One of the only regular surveys of Internet traffic is compiled by Arbor
Networks, which recently reported that IPv6 represented less than 0.2% of all
Internet traffic. Arbor said IPv6 traffic -- both tunneled and native -- had
declined 12% in the last six months, even as momentum for World IPv6 Day was
building. Arbor gathered this data by surveying six carriers in North America
Not everyone believes Arbor's assertion that IPv6 traffic is declining while
so many website operators are preparing for World IPv6 Day.
"I did not see this [data], and I am also very surprised if it is accurate,"
says Russ Housley, chairman of the Internet Engineering Task Force, a
standards body that created IPv6. "I am aware of many organizations preparing
for World IPv6 Day."
Martin Levy, director of IPv6 strategy at Hurricane Electric, a Fremont,
Calif., ISP that claims to have the world's most interconnected IPv6
backbone, says he is struggling with how the Arbor Networks data can be true
given the network industry momentum behind IPv6. "Where Arbor measures is not
where the predominant IPv6 usage is," Levy says.
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What's preventing the Internet engineering community from coming up with more
complete IPv6 traffic statistics is the fact that few ISPs or their hardware
suppliers have deployed a network management tool called NetFlow 9. This
industry standard export protocol sends data about traffic flows through the
router to an external collection host so that the flow information can be
analyzed. NetFlow 9 can be used to separate out and measure IPv6 and IPv4
NTT America, a leading provider of IPv6 transit services, concedes that it
doesn't measure the IPv6 traffic it is carrying separate from overall
Internet traffic, so it doesn't know the rate at which its IPv6 traffic is
"Most routers don't have support for counting IPv6 traffic separate from IPv4
traffic on their physical interface counters," explains Dorian Kim, vice
president of IP engineering, Global IP Network at NTT America. "By and large,
bits are bits to interfaces, and there's been no particular driver for us to
track IPv4 and IPv6 separately, especially when measuring IPv6 in the network
requires one to instrument NetFlow 9 collection of traffic from the routers."
Kim says NetFlow 9 is "the most likely way we'll be able to account for IPv6
traffic separately from IPv4 traffic. ...We are working with our equipment
vendors to have NetFlow 9 export capabilities across all of our network, but
that is something that'll happen over time."
NTT America isn't the only ISP that hasn't been able to deploy NetFlow 9. "I
heard from a significant cable operator that they don't run NetFlow 9 and
hence can't measure IPv6 flows," Levy says.
One reason most carriers don't have NetFlow 9 gathering statistics across
their peering and edge routers is because it can cost millions of dollars to
"It's pretty expensive to do complete traffic measurement across your entire
network," says Siegel, pointing out that Global Crossing has deployed NetFlow
9 in Europe. "It's kind of a luxury."
Siegel says Global Crossing will have NetFlow 9 deployed across a third of
its network footprint by the end of the year. He says the carrier has run
into trouble deploying NetFlow 9, including the discovery that its edge
routers didn't have enough horsepower to collect data on every port,
resulting in a limited view of traffic patterns. Global Crossing plans to use
NetFlow 9 to create customized billing models rather than to monitor IPv6,
which represents only 0.1% of its traffic in Europe.
"We only started making [traffic measurement] more of a priority lately as a
way of analyzing customer profitability," Siegel says, adding that measuring
IPv6 traffic flows is not a driver for the purchase. "The variability of how
a customer is using the network plays an extremely large role in whether or
not we see profit at any given price point. That's our primary purpose behind
ponying up the cash to buy the [NetFlow 9] software and the hardware
Some experts argue that measuring IPv6 traffic with NetFlow 9 is not the best
way to determine the rate at which IPv6 is being adopted.
Traffic is too ephemeral, says Geoff Huston, chief scientist at APNIC, the
regional Internet registry for the Asia Pacific Region. Huston prefers to
measure how many end users have IPv6 enabled on their devices. He points out
that this figure is as disappointingly low as the Arbor Networks IPv6 traffic
"When you look at end users and their predilection to use IPv6, the story is
pretty bad," Huston says. "I see 0.2% of clients prefer to use IPv6 on a
dual-stack environment. ... Since November, that number has risen by a little
under 0.1%. Yes, that's a 50% jump. No, these are still tiny numbers and
cannot be interpreted as a wave of IPv6 adoption."
Huston says end user IPv6 adoption rates are not rising faster because recent
versions of the Windows and Mac operating systems prefer to use IPv4 in dual
stack environments where IPv4 and IPv6 are running side-by-side, rather than
using IPv6-based tunneling techniques such as 6to4 and Teredo.
"The reason why modern end host systems prefer to use IPv4 is that
auto-tunneling using either 6to4 or Teredo is lousy. The experience simply is
atrocious!" Huston says. "So when we measure the amount of end hosts that
prefer to use IPv6 in a dual stack scenario we are in fact looking at old end
host systems that are not being maintained in terms of software releases from
the vendor and a small number of end hosts that have native IPv6 service from
their service providers."
Huston says observers shouldn't expect IPv6 traffic volumes to rise
significantly on or immediately following World IPv6 Day. That's because IPv6
traffic volumes will only rise for end users with native IPv6 service from
"How many folk will see a difference [on World IPv6 Day]?" Huston asks. "At
most 0.3% of folk. It's hardly a shattering number."
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Instead, Huston recommends that the Internet engineering community measure
the success of World IPv6 Day in terms of reducing the fear that website
operators have about the cost and hassle of upgrading to IPv6.
World IPv6 Day "is intended to turn the Internet, or at least the Web content
delivery part of the network, into a laboratory for 24 hours [so we can] see
what happens when a mono-stack world turns into a dual-stack world," Huston
says. "In and of itself, it won't get the IPv6 ball rolling."
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