1. Going IPv6 only For profit and for fun
Stephan Lagerholm, T-Mobile

2. T-Mobile | stick together
Wednesday, July 24, 2019
Introduction
Stephan Lagerholm
@ipv4depletion
2007 Infoweapons
2008 August ARIN
2009 March Google IPv6
2009 April TXv6TF.org
2009 April RMv6TF conference
2009 Secure64
2010 Contact with T-mobile
2011 first DNS64 product
2014 left Secure64 for Microsoft, took a break from IPv6
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3. Agenda T-Mobile’s IPv6 journey Background DNS64 and 464XLAT
Some best practices and DNS learnings from our IPv6 only rollout
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4. T-Mobile Customer Base
At WWDC 2015 Apple announced the transition to IPv6-only network services in iOS 9. Starting June 1, 2016 all apps submitted to the App Store must support IPv6-only networking.
IOS 10.3 is IPv6 only on the T-Mobile network
Android have support for IPv XLAT
About 10 Million IPv6 only clients on the T-Mobile network today!
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5. Our Progress towards IPv6
Internet2
March 2018
91%
DNS-OARC
September 2017
89%
V6 Summit 2017
April 2017
84%
NANOG 64
June 2015
54%
NANOG 61
June 2014
27%
Apricot 37
Feb 2014
16%
Android 4.3
July 2013
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6. The remaining 9% TMUS Enterprise clients (Guests are dual stack)
Really old handsets
Tethering
Some Tablets
MVNO (Mobile Virtual Network Operators)
Retries over IPv4 for one or another reason
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7. Who is still on IPv4 (number of sessions)
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T-Mobile Internal Use Only

8. DNS64/NAT64 (RFC6147)
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9. 464 XLAT (RFC 6877)
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10. Discovery of IPv6 Prefix (RFC 7050)
Alternative to hardcoded pref64
Sends DNS query for ipv4only.arpa
Extract the pref64
Happens during startup of 464XLAT
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11. Happy Eyeballs (RFC6555, RFC8305)
Fallback to IPv4 after a reasonable time
Happy Eyeballs work well for Dual Stack and 464XLAT clients
Note! Happy Eyeballs have no effect on IPv6 only devices
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12. Application level fallback
NSURLsession on Apple devices handles IPv4 literals
Note there is no fallback if IPv6 fails, no Happy Eyeballs
UnderstandingandPreparingfortheIPv6Transition/UnderstandingandPreparingfortheIPv6Transition.html#//apple_ref/doc/uid/TP CH213-SW13
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13. Android Interfaces Network Info II app can be found
In Google/Apple Store
Tethering
IPv4 address
Internet
IPv6 address
VoLTE
IPv6 address
WiFi
IPv4 address
464XLAT
IPv4 address
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14. Failure scenarios DNS Related failures Network related failures
RCODE – Does not return EMPTY NOERROR or NXDOMAIN (rare)
Flag – Does not return the AA flag in the empty answer (rare)
Major cloud storage app
Special use – Special use AAAA record such as ::1, link-local, etc (common)
Edu22.info
SOA – Does not provide SOA for the same domain as asked for (somewhat common)
Photo site
Timeout – Simply does not return anything when asked for AAAA (common)
Routing – AAAA returned, but unable to connect to the IP, :: (very common)
Fortinet.com
RCODE – Fixed in our network but Bind still does not resolve this
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15. Testbed for response to failure scenarios
Expected result:
timeout.dns64.lagerholm.com IN AAAA 64:ff9b::6464:6464
example:
soa.dns64.lagerholm.com AAAA
flag.dns64.lagerholm.com AAAA
rcode.dns64.lagerholm.com AAAA
timeout.dns64.lagerholm.com AAAA
Google DNS64 rcode and timeout used to be NOERROR
7/24/2019
T-Mobile Internal Use Only

16. Results response to failure scenarios
Google DNS64
As of 3/15/2018
Secure64
CEM A
Bind
ubuntu0.14
Unbound
1.6.2
soa
SERVFAIL OK
timeout
TIMEOUT
TIMEOUT*
flag
rcode
SERVFAIL*
* On first try and after TTL expire
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17. IPv6 Only Learnings Determine what sites/apps are important
Proactively scan top sites
Reach out to broken sites
Don’t try to fix things with local overrides
Scan social media for direct customer feedback
Don’t try to change the world
Keep things in perspective
Enterprise rollout – 464XLAT for Windows 10 coming? NO
…Creators Update adds support for 464XLAT on cellular-equipped desktops and tablet…

18. T-Mobile Confidential
Questions
T-Mobile Confidential