wdiff rfc6948.original rfc6948.txt

Network Working Group
Independent Submission A. Keranen
Internet-Draft
Request for Comments: 6948 J. Arkko
Intended status:
Category: Informational Ericsson
Expires: March 15,
ISSN: 2070-1721 June 2013 September 11, 2012

Some Measurements on World IPv6 Day from an End-User Perspective
draft-keranen-ipv6day-measurements-04

Abstract

During the World IPv6 Day on June 8th, 8, 2011, several key content providers
enabled their networks to offer both IPv4 and IPv6 services.
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 since it means
that no major problems were detected. For the Internet, however,
there was a major change on such a small short timescale. This memo discusses
measurements that the authors made from the perspective of an end-user end
user with good IPv4 and IPv6 connectivity. Our measurements include
the number of most popular networks providing AAAA records for their service
service, as well as delay and connection failure statistics.

Status of this This Memo

This Internet-Draft document is submitted in full conformance with not an Internet Standards Track specification; it is
published for informational purposes.

This is a contribution to the
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This Internet-Draft will expire on March 15, 2013.
http://www.rfc-editor.org/info/rfc6948.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2
2. Motivation and Goals . . . . . . . . . . . . . . . . . . . . . 3
3. Measurement Methodology . . . . . . . . . . . . . . . . . . . 4
4. Measurement Results . . . . . . . . . . . . . . . . . . . . . 5
4.1. DNS AAAA Records . . . . . . . . . . . . . . . . . . . . . 5
4.2. TCP Connection Setup . . . . . . . . . . . . . . . . . . . 7 6
4.3. TCP Connection Delays . . . . . . . . . . . . . . . . . . 7
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . . 10
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11

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: as ensuring that the necessary components have IPv6 turned on; on,
that configurations are correct; 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 [RFC6555], [RFC6555]
and unreliable IPv6 connectivity. Bad IPv6 routing has been behind
many of the problems. Among the causes are broken 6to4 tunneling
protocol [RFC3056] 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.

The World IPv6 Day event was largely unnoticed by the general public,
which is a good thing since it means that no major problems were
detected. Existing IPv4 connectivity was not damaged by IPv6 IPv6, and
also new IPv6 connectivity worked as expected in vast majority of
cases. For the Internet, however, there was a major change on such a
small
short timescale. This memo discusses measurements that the authors
made from the perspective of an end-user end user with well-working IPv4 and
IPv6 connectivity. Our measurements include the number of the most
popular networks providing AAAA records for their service service, as well as
delay and connection failure statistics.

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
draws 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, 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 the necessary capacity necessary to deal
with the IPv6 traffic and the 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 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 the 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 round-trip times (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 about broken
connectivity towards them. between Google and its end users. Our measurements
start from a different angle, by assuming good dual-stack
connectivity at the measurement end, and then probing the rest of the
Internet to understand, for instance, how likely there are to be IPv6
connectivity problems, problems or what the delay differences are between IPv4
and IPv6. Similar studies have been performed by the University of
Pennsylvania and 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 1, 2011. For each domain name in the
list, we performed DNS queries with different host names. For IPv4
addresses (A records) records), we used host name "www" and also performed a
query with just the domain name. For IPv6 addresses (AAAA records) records),
we used also different combinations of host names that have been used for
IPv6 sites, namely 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, A records, then "www", domain name, and
different IPv6-host names for AAAA records) 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 records and the
corresponding host names were recorded. The queries had 3 second re-transmission
timeout a 3-second
retransmission timeout, and if there wasn't any was no response for 10 seconds,
all remaining queries for the site were canceled. We used a custom-made custom
Perl script and the Net::DNS [net-dns] module for the DNS queries.

The measurement script used a bind9 DNS server running on the same
host as was performing the measurement. The DNS cache of the server
was flushed before each measurement run in order to detect the
changes in the DNS records in real-time. real time. The host, and thus the DNS
server, was not part of DNS IPv6 whitelisting agreements. (See
Section 4.3 of [RFC6589] for information on DNS resolver
whitelisting.)

The local network where the host performing the measurements was has had
native IPv6 (dual-stack) connectivity. The IPv6 connectivity to the
local network was provided by an IPv6-over-IPv4 tunnel from the
network's default router to the ISP's IPv6 peering point.

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
to the port 80 (HTTP) simultaneously using both IPv4 and IPv6 to the
(first) IP addresses discovered from the DNS. The connection setup
was repeated up to 10 times, giving up after the first failed attempt
(but only after normal TCP re-transmissions). retransmissions). The connection setup
delay was measured by recording the time immediately before and after
the connect system call. The host used for measurements is was a
regular Linux PC with a 2.6.32 version kernel and a dual-stack
Internet connection via Ethernet.

The measurements were started one week before the World IPv6 Day (on
Wednesday, June 1st, 1, 17:30 UTC) and were running until July 11th, ran once every three hours. hours until
July 11. One test run takes took from two to two and a
half two-and-a-half hours to
complete.

The accuracy and generality of the measurement results is are limited by
several factors. While we ran the tests in at three different sites,
most of the results discussed in this document present snapshots of
the situation from just one measurement point, the Ericsson Research
Finland premises, near Helsinki. Also, since one measurement run
takes
took quite a long time, the network characteristics and DNS records
may change
might have changed even during a single run. The first DNS response
was used for the TCP connectivity tests tests, and this selection may result might
have resulted in selection of a non-optimal host; yet, a slight
preference is was given to the "www" and only-domain-name records since
their queries were started before the others. While the host
performing the measurements was otherwise idle, the local network was
in regular office use during the measurements. The connectivity
setup delay is was collected in user space, with a regular, non real-time, non-real-
time kernel implementation, resulting in small inaccuracies in the
timing information.

4. Measurement Results

4.1. DNS AAAA Records

The number of top 10,000 sites with AAAA DNS records before, during,
and after the World IPv6 Day, Day is shown in [DNS-top10k]. Figure 1. The measurements
performed during the World IPv6 Day are shown on the light gray
background.

[See the PDF.]

Figure 1: Number of sites with AAAA DNS records in the top 10,000
most popular sites

When the measurements began on June 1st, there were 1, 245 sites (2.45%) of the top
10,000 sites with had both A and AAAA record. records. During the following days days,
the number of such sites slowly increased, reaching 306 sites at in the
measurement that was started at 22:30 UTC on June 7th, 7, the evening
before the World IPv6 Day. When the World IPv6 Day officially started, the
following measurement (1:30 (at 01:30 UTC) recorded 383 sites, and the next
one 472 sites. During the day day, the number of sites with AAAA records
peaked at 491 (4.91% of the measured 10,000
sites) sites), at 19:30 UTC.

When the World IPv6 Day was over, the number of AAAA records dropped
nearly as fast as it had increased just 24 hours earlier. However,
the number of sites stabilized at around 310 and did not drop below
300
since, after that, resulting in over 3% of the top 10,000 sites still
having AAAA records at the end of our measurements. measurements, on July 11.

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 Day, reaching 374 sites for 3 consecutive measurement runs
(i.e., for at least 6 hours). Also Also, the number of AAAA records for
the "www" host name dropped steeply after the day and remained at
around 160 sites since. after that.

Similar but more pronounced trends can be seen if only the top 100 of
the most popular sites are taken into considerations, as show in
[DNS-top100]. are taken into considerations, as shown in
Figure 2.

[See the PDF.]

Figure 2: Number of sites with AAAA DNS records in the top 100 most
popular sites

Here, the number of sites with some of the tested host names having an a
AAAA record was initially 14, 14; then, it jumped to 36 during the
day, day
and eventually dropped to 13. Also, while none of the top 100 sites
apparently had an a AAAA record for their "www" host name 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 had IPv6 enabled for the
World IPv6 Day.

Two other test sites in Sweden and Canada experienced similar trends
with the DNS records. However, one of the sites used an external DNS
server that was part of whitelisting agreements. There There, the number
of sites with AAAA records before the World IPv6 Day was already higher
(above 400)
(more than 400), and hence the impact of the day was smaller as smaller, because
the amount of sites increased to the same numbers as seen by the test
site in Finland. With the whitelisted DNS server server, the level number of
sites remained above 450 after the day.

4.2. TCP Connection Setup

To test whether the IP addresses given by the DNS actually provide
connectivity to the web site, site and if whether there is any difference in
the connection setup delay and failure rates with IPv4 and IPv6, we
attempted to create TCP connections for all domains that contained
both A and AAAA DNS records. The fraction of sites for which the
first DNS response gave addresses that were not accessible with TCP
to port 80 over IPv4 or IPv6 is shown in [TCP-fails]. Figure 3.

[See the PDF.]

Figure 3: TCP connection setup failure ratio (for the first DNS
response)

There is was a baseline failure rate with IPv4 of around 1-3% that is was
fairly static throughout the test period. For hosts with AAAA
records, the fraction of inaccessible sites was much higher: in the beginning
beginning, up to one fourth of the tested hosts did not respond to
TCP connection attempts. Much of this was likely due to the various
test sites with different "IPv6 prefixes" (as discussed in
Section 3); in the first
run run, more than half of the tested sites with
AAAA records used them for the first DNS response. Also, some of the
hosts may were not even be supposed to be accessed with HTTP but provide provided
AAAA records for other
purposes purposes, while some sites had clear
configuration errors, such as localhost or link-local IPv6 addresses.

As the World IPv6 Day came closer, the number of inaccessible IPv6 sites
decreased slowly and the number of sites with AAAA records increased
at the same time, resulting in the failure ratio dropping to roughly
20% before the day. During the day day, the number of IPv6 sites
increased rapidly rapidly, but also the number of failures decreased decreased, and
hence, at the end of the day, the failure ratio dropped to just above
10%. After the World IPv6 Day Day, when many of the participating IPv6 hosts
were taken off-line, the fraction of failed sites for IPv6 increased.
However, since there was no increase in the absolute number of failed
sites, the fraction of inaccessible sites remained at a lower level,
between 15% and 20%, than before the day.

4.3. TCP Connection Delays

For sites that were accessible with both IPv4 and IPv6, we measured
the time difference between establishing a TCP connection with IPv4
and with IPv6. We took the median (as defined in Section 11.3 of
[RFC2330]) of the time differences of all 10 connections, and then
the median and mean (of the median) over all sites; the result is sites. The results are
shown in [timediff]. Figure 4.

[See the PDF.]

Figure 4: TCP connection setup delay differences (IPv4 - IPv6)
In general, the delay differences are were small: the median of medians stays
remained less than 3ms 3 ms off from zero (i.e., IPv4 and IPv6 delays being equal)
were equal), and even the mean, which is more sensitive to outliers, stays
remained within +/-5 ms most of the time within +/- 5ms; time, with the greatest spikes
reaching to roughly
-15ms -15 ms (i.e., the mean of median IPv6 delays being 15ms was
15 ms larger than for IPv4 delays). Closer inspection of the results
shows that the spikes
are were often caused by only one site or a handful
of sites with bad connectivity and multiple re-transmissions retransmissions of TCP
SYN and ACK packets packets, resulting in connection setup delays an order of
magnitude larger.

Surprisingly larger than those for the other sites.

Surprisingly, the median delay for IPv6 connections is was, in most cases
cases, equal to or smaller than the IPv4 delay, but during the World IPv6
Day, the IPv6 delays increased slightly and became (as a median)
slower than their IPv4 counterparts. One reason for such an effect
was that some of the sites that enabled IPv6 for the World IPv6 Day, Day had
an extremely low, low IPv4 delay, less than 10ms, IPv4 delay 10 ms (e.g., due to the
Content Delivery Network (CDN) provider hosting the IPv4 site), but
"regular", over hundred millisecond, a
"regular" delay (over 100 ms) for the IPv6 host.

More detailed analysis of the TCP connection setup delay differences,
and the reasons behind for them, is left for future work.

5. Conclusions

The

World IPv6 Day had a very visible impact to on 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 one-day
swings in some characteristic characteristics of the Internet. However, the impact
on end users was small, given that when dual-stack works correctly correctly,
it should not be visible at the user level level, and given that IPv6
availability for end users themselves is small.

The key conclusions are as follows:

o The day caused On that day, there was a large jump in the number of content
providers providing AAAA DNS records on that day. records.

o The day caused On that day, there was a smaller but apparently permanent increase
in the number of content providers supporting AAAA.

o Large and sudden 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
services either globally or to this a particular network over IPv6.

o Large A large fraction of sites that published AAAA records for a name
under their domain (be it "www" or "www6" "www", "www6", or something else) were
actually not responding to TCP SYN requests on IPv6. This
fraction is was far higher than that which we've seen in our previous
measurements, and we are still determining why that is was the case.
Measurement errors or problems on our side of the network cannot
be ruled out at this stage. In any case, it is also clear that as
new sites join, joined, incomplete or in-progress configurations create
more connectivity problems in the IPv6 Internet than we've seen
before. Other measurements are needed to verify what the general
level of IPv6 connectivity is to addresses publicly listed in AAAA
records.

o Even if the overall level of connection failures was high,
activities on and around the IPv6 day appear to have caused a
significant permanent drop in the number of these failures.

o When IPv6 and IPv4 connectivity were both available, the their delay
characteristics appear appeared very similar. In other words, most of
the providers that made IPv6 connectivity available appear to provide have
provided a production quality production-quality network. TCP connection setup delay
differences due to RTT differences between IPv4 and IPv6
connections are were, in general general, low. In the remaining differences
in our measurements, random packet loss plays played a major role.
However, some sites can could experience considerable differences
simply because of different content distribution mechanisms used
for IPv4 and IPv6 content.

It is promising that the amount of the most popular Internet content
on IPv6 was surprisingly high, roughly one third of top 100 sites
(during the World IPv6 day Day or with whitelisting enabled). However, other
content on the Internet forms a long tail that is harder to move to
IPv6. For instance, only 3% of the 10,000 most popular web sites
provided their content over IPv6 before the World IPv6 day. Day. On a
positive note, the top 100 sites form a very large part of overall
Internet traffic [Labovitz] [Labovitz], and thus even the top sites moving to
IPv6 could represent a significant fraction of Internet traffic on
IPv6. However, this requires that users are be enabled to use IPv6 in
their access networks. We believe that this should be the goal of
future global IPv6 efforts.

6. Security Considerations

Security issues have not been discussed in this memo.

7. IANA Considerations

This memo has no IANA implications.

8. References

8.1. Normative References

[timediff]
Keranen, A., "TCP connection setup delay differences [RFC
editor: please change the references to the graphs to
refer to the PDF version of the document]", June 2011,
<http://users.piuha.net/akeranen/drafts/v6day/mda.pdf>.

[DNS-top10k]
Keranen, A., "Number of sites with AAAA DNS records in the
top 10,000 most popular sites", June 2011,
<http://users.piuha.net/akeranen/drafts/v6day/
v6sites.pdf>.

[DNS-top100]
Keranen, A., "Number of sites with AAAA DNS records in the
top 100 most popular sites", June 2011, <http://
users.piuha.net/akeranen/drafts/v6day/v6sites-top100.pdf>.

[TCP-fails]
Keranen, A., "TCP connection setup failure ratio (for the
first DNS response)", June 2011, <http://users.piuha.net/
akeranen/drafts/v6day/tcp-fails.pdf>.

8.2. Informative References

[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330, May
1998.

[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.

[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.

[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", RFC 6555, April 2012.

[RFC6589] Livingood, J., "Considerations for Transitioning Content
to IPv6", RFC 6589, April 2012.

[net-dns] Fuhr, M., "Net::DNS", <http://www.net-dns.org/>.

[IPv6Monitor]
Comcast and
University of Pennsylvania, Pennsylvania and Comcast, "IPv6 Adoption
Monitor", <http://ipv6monitor.comcast.net>. Monitoring @
Penn", 2012, <http://mnlab-ipv6.seas.upenn.edu/>.

[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>.

[Labovitz]
Labovitz, C., Iekel-Johnson, S., McPherson, D., Oberheide,
J., and F. Jahanian, "Internet Inter-Domain Traffic",
Proceedings of ACM SIGCOMM 2010, August 2010.

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. Thanks also to Tom Petch and Bob Hinden for thorough reviews
and many helpful comments.

Authors' Addresses

Ari Keranen
Ericsson
Jorvas 02420
Finland

Email:

EMail: ari.keranen@ericsson.com

Jari Arkko
Ericsson
Jorvas 02420
Finland

Email:

EMail: jari.arkko@piuha.net