in a test environment, which gate to
a QA environment before hitting the
production environment. Right?
Once IPv6 is enabled from the ISP
to the load balancer, and the load balancer is accepting IPv6 connections
but sending out IPv4 connections to
the Web farm, new opportunities present themselves. As each Web server becomes IPv6 ready, the load balancer no
longer needs to translate for that host.
Eventually your entire Web farm is
dual stack. This technique provides a
throttle to control the pace of change.
You can make small changes, one at a
time, testing along the way.
In doing so you will have upgraded
the routers, DNS server, and other
components. While your boss would
shriek if you had asked to change every
layer of your network stack, you have
essentially done just that.
Of course, once you have completed
this and shown that the world didn’t
end, developers will be more willing to
test their code under IPv6. You might
need to enable IPv6 to the path to the
QA lab. That’s another bite-size project. Another path will be requested.
Then another. Then the LAN that the
developers use. Then it makes sense to
do it everywhere. You’ve now achieved
the goal of the person from Story 1, but
you’ve gotten management approval.
During Google’s IPv6 efforts we
learned that this strategy works really
well. Most importantly we learned that
it turned out to be easier and less expensive than expected.
story 3: “one thing”
This story involves a strategic approach
in which an organization picked a single application—its “one thing”—and
mounted a focused effort to move it to
IPv6. Again, being focused appealed
to management and still touched on
many of the upgrades requested by our
Comcast presented a success story
at the 2008 Google IPv6 Symposium,
demonstrating how it chose one stra-
tegic thing to upgrade: the set-top
box management infrastructure. Ev-
ery set-top box needs an IP address so
the management system can reach it.
That’s more IPv4 addresses than Com-
cast could reasonably get allocated.
Instead it used IPv6. If you get Internet
service from Comcast, the set-top box
on your TV set is IPv6 even though the
cable modem sitting next to it is provid-
ing IPv4 Internet service.
7 Comcast had
to get IPv6 working for anything that
touches the management of its net-
work: provisioning, testing, monitor-
ing, billing. Wait, billing? Well, if you
are touching the billing system, you are
basically touching a lot of things. Ooh,
shiny dependencies. (This is why we
put “one thing” in quotes.) The person
from Story 1 must be jealous.
IPv4 address space is depleted. People
who have been ignoring IPv6 for years
need to start paying attention. It is
real—and really important. IPv6 de-
ployment projects seem to be reveal-
ing two successful patterns and one
unsuccessful pattern. The unsuccess-
ful pattern is to scream that the sky is
falling and ask for permission to up-
The lessons we have learned:
1. Proposals to convert everything
sound crazy and get rejected. There is
no obvious business value in making
such a conversion at this time.
2. Work from the outside in. A load
balancer that does IPv6-to-IPv4 translation will let you offer IPv6 to external
customers now, gives you a “fast win”
that will bolster future projects, and
provides a throttle to control the pace
3. Proposing a high-value reason
(your “one thing”) to use IPv6 is most
likely to get management approval.
There are no simple solutions, but
there are simple explanations. Convert
that “one thing” and keep repeating
the value statement that got the project approved, so everyone understands
why you are doing this. Your success
here will lead other projects.
For a long time IPv6 was safe to ignore as a “future requirement.” Now
that IPv4 address space is depleted, it
is time to take this issue seriously. Yes,
A Conversation with Van Jacobson
Principles of Robust Timing
over the Internet
Julien Ridoux, Darryl Veitch
1. cerf, V., dalal, y., sunshine, c. 1rFc 675. specification
Internet transmission control Program, 1974.
2. cerf, V., kahn, r.e. a protocol for packet network
intercommunication. Ieee transactions on
Communications 22, 5 (1974), 637–648.
3. donley, c., howard, V., kuarsingh, V., chandrasekaran,
a. and Ganti, V. assessing the impact of nat444 on
network applications; http://tools.ietf.org/html/draft-
4. doyle, J. understanding carrier-grade nat (2009);
5. Google IPv6 conference. IPv6, nokia, and
Google (2008); http://www.youtube.com/
6. Google IPv6 Implementors conference; http://sites.
7. kuhne, M. IPv6 monitor: an interview with alain
durand (2009); https://labs.ripe.net/Members/
8. Marsan, c.d. Google: IPv6 is easy, not expensive
9. Miller, r. the billion-dollar htMl tag (2009);
10. Morr, d. 2010. t-Mobile is pushing IPv6. hard
Vinton G. Cerf is Google’s vice president and chief
Internet evangelist. as one of the “Fathers of the
Internet,” cerf is the codesigner of the Internet’s tcP/
IP protocols and architecture. he holds a b.s. degree in
mathematics from stanford university and M.s. and Ph.d.
degrees in computer science from ucla.
Thomas A. Limoncelli is an author, speaker, and system
administrator. his books include The Practice of System
and Network Administration (addison-wesley, 2007) and
Time Management for System Administrators (o’reilly,
2005). he works at Google in new york city and blogs at
© 2011 acM 0001-0782/11/04 $10.00