Network Working Group A. Keranen
Internet-Draft J. Arkko
Intended status: Informational Ericsson
Expires: January 5, 2012 July 4, 2011
Some Measurements on World IPv6 Day from End-User Perspective
draft-keranen-ipv6day-measurements-00
Abstract
During the World IPv6 Day on June 8th, 2011, several key content
providers enabled their networks to offer both IPv4 and IPv6 service.
Hundreds of organizations participated in this effort, and in the
months and weeks leading up to the event worked hard on preparing
their networks to support this event. The event was largely
unnoticed by the general public, which is a good thing as no major
problems were detected. For the Internet, however, there was a major
change on such a small timescale. This memo discusses measurements
that the authors made from the perspective of an end-user with well-
working IPv4 and IPv6 connectivity. Our measurements include the
number of most popular networks providing AAAA records for their
service as well as delay and connection failure probabilities.
Status of this Memo
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This Internet-Draft will expire on January 5, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Internet-Draft IPv6 Day Measurements July 2011
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation and Goals . . . . . . . . . . . . . . . . . . . . . 3
3. Measurement Methodology . . . . . . . . . . . . . . . . . . . . 4
4. Measurement Results . . . . . . . . . . . . . . . . . . . . . . 5
4.1. DNS Measurements . . . . . . . . . . . . . . . . . . . . . 5
4.2. Delay and Failure Measurements . . . . . . . . . . . . . . 6
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. Informative References . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
Many large content providers participated in World IPv6 Day on June
8, 2011. On that day, IPv6 [RFC2460] was enabled by default for 24
hours on numerous networks and sites that previously supported only
IPv4. The aim was to identify any remaining issues with widespread
IPv6 usage in these networks. Most of the potential problems
associated with using IPv6 are, after all, of a practical nature,
such as: ensuring that the necessary components have IPv6 turned on;
that configurations are correct; and that any implementation bugs
have been removed.
Some content providers have been reluctant to enable IPv6. The
reasons for this include delays for applications attempting to
connect over broken IPv6 links before falling back to IPv4, and
unreliable IPv6 connectivity. Bad IPv6 routing has been behind many
of the problems. Among the causes are broken 6to4 tunneling protocol
connectivity, experimental IPv6 setups that are untested and
unmonitored, and configuration problems with firewalls. The
situation is improving as more users and operators put IPv6 to use
and fix the problems that emerge.
World IPv6 Day event was largely unnoticed by the general public,
which is a good thing as no major problems were detected. For the
Internet, however, there was a major change on such a small
timescale. This memo discusses measurements that the authors made
from the perspective of an end-user with well-working IPv4 and IPv6
connectivity. Our measurements include the number of most popular
networks providing AAAA records for their service as well as delay
and connection failure probabilities.
The rest of this memo is structured as follows. Section 2 discusses
the goals of our measurements, Section 3 describes our measurement
methodology, Section 4 gives our preliminary results, and Section 5
makes some conclusions.
2. Motivation and Goals
Practical IPv6 deployment plans benefit from accurate information
about the extent to which IPv6 can be used for communication, and how
its characteristics differ from those of IPv4. For instance,
operators planning to deploy dual stack networking may wish to
understand what fraction of their traffic would move to IPv6. This
information is useful for estimating sufficient capacity to deal with
the IPv6 traffic and impacts to the operator's IPv4 infrastructure or
carrier-grade NAT devices as their traffic is reduced. Network
owners also wish to understand the extent to which they can expect
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different delay characteristics or problems with IPv6 connectivity.
The goals of our measurements were to help with these topics by
answering the following questions:
o What fraction of most popular Internet sites offer AAAA records?
How did the World IPv6 Day change the situation?
o How do the traffic characteristics differ between IPv4 and IPv6 on
sites offering AAAA records? Are the connection failure rates
similar? How are RTTs impacted?
There have been many measurements about some of these aspects from a
service provider perspective, such as the Google studies on which end
users have broken connectivity towards them. Our measurements start
from a different angle, by assuming a well-working dual-stack
connectivity on the measurement end, and then probing the rest of the
Internet to understand, for instance, how likely it is to have IPv6
connectivity problems, or what are the delay differences between IPv4
and IPv6 towards the rest of the Internet. Similar studies have been
performed by the Comcast IPv6 Adoption Monitor [IPv6Monitor] and RIPE
NCC [RIPEv6Day].
3. Measurement Methodology
We used the top 10,000 sites of the Alexa 1 million most popular
sites list [Alexa] from June 1st 2011. For each domain name in the
list, we performed DNS queries with different host names. For IPv4
addresses (A records) we used host name "www" and also performed a
query with just the domain name. For IPv6 addresses (AAAA records)
we used also different combinations of host names that have been used
for IPv6 sites, namely "www6", "ipv6", "v6", "ipv6.www", "www.ipv6",
"v6.www", and "www.v6".
All DNS queries were initiated in the order listed above (first "www"
and just the domain name for A-records, then "www", domain name, and
different IPv6-host names for AAAA records) but the queries were done
in parallel (i.e., without waiting for the previous query to finish).
The first response for A and AAAA record and the corresponding host
name were recorded. The queries had 3 second re-transmission timeout
and if there wasn't any response for 10 seconds, all remaining
queries for the site were canceled. We used a custom-made Perl
script and the Net::DNS module for the DNS queries.
The measurement script used a bind9 DNS server running on the same
host that was performing the measurement. The DNS cache of the
server was flushed before each measurement run to be able to detect
the changes in the DNS records in real-time. The host, and thus the
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DNS server, was not part of DNS IPv6 whitelisting agreements.
After obtaining IP addresses for the site, if a site had both A and
AAAA records, a simple C-program was used to create TCP connections
at the same time with IPv4 and IPv6 to the IP addresses discovered
from the DNS. The connection setup was repeated for 10 times and the
connection setup delay was measured by recording the time right
before and after the connect system call. The host used for
measurements is a regular Linux PC with 2.6.32 version kernel and
dual stack Internet connection via Ethernet.
The measurements were started one week before the World IPv6 Day (on
Wednesday, June 1st, 17:30 GMT) and have been running since, once
every three hours. One test run takes from two to two and a half
hours to finish.
4. Measurement Results
4.1. DNS Measurements
When the measurements begun on June 1st, there were 245 sites (2.45%)
with both A and AAAA record in the top 10,000 sites. During the
following days the number of sites was slowly increasing, reaching
306 sites at the measurement that was started 22:30 GMT on June 7th,
the evening before the World IPv6 Day. When the World IPv6 Day
officially started, the following measurement (1:30 GMT) recorded
already 383 sites, and the next one 472 sites. During the day number
of sites with AAAA records peaked at 491 (4.91% of the measured
10,000 sites) on 19:30 GMT.
When the World IPv6 Day was over, also the number of AAAA records
dropped nearly as fast as it had increased just 24 hours earlier.
However, the number of sites stabilized around 310 and has not
dropped below 300 since, resulting in over 3% of the top 10,000 sites
having AAAA records today.
While 274 sites had IPv6 enabled in their DNS for some of the tested
host names one day before the World IPv6 Day, only 116 had it for the
"www" host name that is commonly used when accessing a web site. The
number of "www" host names with AAAA records more than tripled during
the World IPv6 Day reaching 374 sites for 3 consecutive measurement
runs (i.e., at least for 6 hours). Also the number of AAAA records
for the "www" host name dropped steeply after the day and has
remained around 160 sites since.
Similar trends, but with larger impact, can be seen if only top 100
of the most popular sites are taken into considerations. Here, the
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number of sites with some of the tested host names having AAAA record
was initially 14, jumped to 36 during the day, and eventually dropped
to 13. Also, while none of the top 100 sites apparently had AAAA
record for their "www" host before and after the World IPv6 day,
during the day the number peaked at 30. Thus, roughly one third of
the 100 most popular sites was enabling IPv6 for the World IPv6 Day.
4.2. Delay and Failure Measurements
Based on the TCP connectivity tests, the IPv6 addresses obtained from
the DNS appear to work less often than IPv4 addresses. Also, some
sites show considerable differences in the RTTs. However, at the
time of writing, further analysis of the delay and failure results is
still ongoing.
5. Conclusions
The World IPv6 Day had a very visible impact to the availability of
content over IPv6, particularly when considering the top 100 content
providers. It is difficult to find other examples of bigger one day
swings in some characteristic of the Internet. However, real impacts
to end users were small, given that when dual stack works correctly
it should not be visible at the user level and that IPv6 availability
for end users themselves was small.
The key conclusions are as follows:
o The day caused a large jump in the number of content providers
supporting AAAA on that day.
o The day caused a smaller but apparently permanent jump in the
number of content providers supporting AAAA.
o Large and quick swings in the relative amount of IPv4 vs. IPv6
traffic are possible merely by supporting a dual-stack access
network and having a few large content providers offer their
service either globally or to this particular network over IPv6.
The analysis is not complete, however. The authors plan to update
this memo as soon as their analysis of connectivity failures and RTT
impacts are complete.
6. Security Considerations
Security issues have not been discussed in this memo.
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7. IANA Considerations
This memo has no IANA implications.
8. Informative References
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[IPv6Monitor]
Comcast and University of Pennsylvania, "IPv6 Adoption
Monitor", <http://ipv6monitor.comcast.net>.
[RIPEv6Day]
RIPE NCC, "World IPv6 Day Measurements",
<http://v6day.ripe.net/>.
[Alexa] Alexa the Web Information Company, "Alexa Top 1,000,000
Sites",
<http://s3.amazonaws.com/alexa-static/top-1m.csv.zip>.
Appendix A. Acknowledgments
The authors would like to thank Suresh Krishnan, Fredrik Garneij,
Lorenzo Colitti, Jason Livingood, Alain Durand, Emile Aben, Jan
Melen, and Tero Kauppinen for interesting discussions in this problem
space.
Authors' Addresses
Ari Keranen
Ericsson
Jorvas 02420
Finland
Email: ari.keranen@ericsson.com
Jari Arkko
Ericsson
Jorvas 02420
Finland
Email: jari.arkko@piuha.net
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