T-Mobile’s path to IPv6 Only

> Isn’t essentially the entire US on CG-NAT for IPv4 on mobile data? T-Mobile, for one, has had their handsets IPv6-only for a few years, so if your Android/iOS does a DNS lookup and gets an AAAA record back, it will skip CG-NAT. T-Mobile presenting at NANOG in 2018 on IPv6: * link And Rocky Mountain IPv6 Taskforce in 2017: * ▶ this video Further data: > Chances are if you use the Internet on your smartphone, you are connecting via IPv6. According to the Internet Society’s 2018 State of IPv6 Deployment,[1] 80% of smartphones in the US on the major cellular network operators use IPv6 and major mobile networks are driving IPv6 adoption with Verizon Wireless at 84%, Sprint at 70%, T-Mobile USA at 93%, and AT&T Wireless at 57%. Plus, some mobile networks are taking the step to run IPv6-only to simplify network operations and reduce costs. * link Though some folks aren't happy with the implementation: > But from my own experience, neither T-Mobile nor AT&T allows inbound traffic to the phone's IPv6 address. This negates some of the advantages of having a globally routable IPv6 address. * link

Trying to re-engine a 747 in mid-air is a challenging operation. > So IPv6 is about 30 years old, and the testimony being shared is the chair of the group spending years of research and millions of dollars, finally launching ipv6 corporate lans in 2023. And how many years of research and millions of dollars was spent in the 1990s on IPv4? People used to use workstations as routers (e.g., see SunOS routeadm(1M)) and DNS caching servers before a lot of money was poured into ASICs for routing (and switching). There are all sorts of dumbass things with IPv4: how much time has been wasted on engineering solutions around NAT (e.g., STUN/TURN/ICE)? But because IPv4 just happens to be the default we accept them as 'normal' and anything that is different is treated as 'abnormal'. > You're not selling me on it's viability. I'm not sure how it's not viable given there are mobile telco networks with tens (hundreds?) of millions of people getting only IPv6 addresses on their devices. * ▶ this video * link There are some folks who (a) were lucky enough to get in early on the IPv4 address land rush, or (b) are rich enough to be able to purchase IPv4 addresses, but there are also (c) plenty of folks who are left with scraps for IPv4 connectivity. The fact that you happen to fall into (a) or (b) does not mean you get to dismiss the folks in (c) who need IPv6, as otherwise they'd have no connectivity at all.

> At the rate it's going, IPv6 should be ready […] It's ready now. T-Mobile US is IPv6-only on handsets, as are many other carriers: * ▶ this video Microsoft went towards IPv6-only in corporate networks so that their IPv4 address could be moved to Azure to generate revenue: * link See also Google and their offices: * link Facebook/Meta is IPv6-only in their DCs: * link According to Google, the US and UK is half IPv6 (France and Germany are >75%): * link

Tell that to T-Mobile US: * ▶ this video Wells Fargo: * link Microsoft: * link * link Google: * link LinkedIn (pre-Microsoft): * link

> I have yet to meet an infrastructure engineer or even hear of one who switched to IPv6 on purpose because they thought it was better. T-Mobile US: * ▶ this video Wells Fargo: * link Microsoft * link * link Google: * link LinkedIn: * link Facebook is famously IPv6-only internally (and as of 2016, 60% of user traffic was over IPv6): * link * link * link

> Ha! I have an iPhone 15 and when I switch to mobile I get an IPv4-only address! My mobile provider is Verizon. APNIC 34 (2017) presentation on Verizon and IPv6: * link Also, a 2017 presentation on T-Mobile US going IPv6-only: * ▶ this video

> AFAIK, IPv6 adoption is held back by hardware. What hardware, especially ASICs, do not support wire speed IPv6 and have not for a decade or two? T-Mobile was gave a presentation on going IPv6-only in 2017: > For the past 10 years T-Mobile has worked towards creating an IPv6 environment and we are now getting very close to our goal. Stephan presents learning on how to successfully enable IPv6-only using DNS64 with or without 464XLAT. He will do a live demo of the different IP interfaces on an Android handset. Finally, he will discuss and give some best practices on how to handle DNS, applications, and websites that are having issues with DNS64. * ▶ this video So they started in 2007. Whatever ISP you're with has probably had at least 2-3 tech refreshes in which IPv6 hardware has been available. For the CPE, Free in France had IPv6 in 2007: * link

> T-Mobile and Verizon both use CGNAT (but do issue individual ipv6 addresses to end user devices). More specifically, T-Mobile US only assigns IPv6 addresses to devices, and to reach the IPv4 world you have to go through a translation mechanism. Presentations from T-Mobile at NANOG and Rocky Mountain IPv6 Taskforce: * link * ▶ this video

> All mobile clients are behind CG-NAT. Demonstrably false. T-Mobile US mobile clients are IPv6-only and connect via IPv6 to IPv6 sites: * link * ▶ this video NAT is only used to connect to IPv4-only hosts via DNS64 (with or without 464XLAT). As of 2022Q2, T-Mobile US has 110 million customers: * link One-third of the US population is connecting via IPv6-only on a day-to-day, hour-to-hour basis every time their smartphone reaches out over the radio.

> […] ipv4 is still the majority of internet traffic. Not if you're on mobile. Lots of cell networks only give IPv6 addresses to phones. E.g., T-Mobile in the US: * ▶ this video

> Anyone running v6 only and bridging to v4 on the edge? If you are on T-Mobile USA you are IPv6-only on your mobile device: * link * ▶ this video Lots of folks are probably IPv6-only without realizing it.

iPhones on T-Mobile do not use 464XLAT, they use native IPv6 only. Some system frameworks like URLSession can do the NAT64 translation of hard-coded IPv4 addresses but it still goes over IPv6. In the video linked above: ▶ this video

"T-Mobile’s path to IPv6 Only": > For the past 10 years [US] T-Mobile has worked towards creating an IPv6 environment and we are now getting very close to our goal. Stephan presents learning on how to successfully enable IPv6-only using DNS64 with or without 464XLAT. He will do a live demo of the different IP interfaces on an Android handset. Finally, he will discuss and give some best practices on how to handle DNS, applications, and websites that are having issues with DNS64. * ▶ this video Apple mandated that all app in the iOS/mobile App Store had to support working on IPv6-only networks: * link Perhaps they should to the same thing for the macOS App Store.

> What's really interesting is how many of these "we fear change" IT people don't realize they're already using IPv6 on their phones every day, with a majority of the sites they visit. For example see the video "T-Mobile’s path to IPv6 Only": * ▶ this video

> I wonder when (or if) we will see new IPv6 only ISPs. If you have a mobile device on US T-Mobile you only get a IPv6 address on it: * ▶ this video * link * link Any access to IPv4 is through a proxy.

> This should help address these types of issues so more devs can get onto iOS more easily without having to meet Apple's level of requirements. Well if an app developer does not ensure that their code works on a device that only has an IPv6 address they will be in for a big surprise: lots of mobile telcos only give out IPv6 addresses. Connecting to the IPv4 world is done via CG-NAT with the first few hops being IPv6-only. Here's a guy from T-Mobile presenting on it: * ▶ this video

I'm not sure what you're referring to. Here's a dude from T-Mobile explaining how they have (in 2017) over ten million end-customer devices without any IPv4 addresses assigned: * ▶ this video For reaching services that are IPv6 only they use(d) DNS64 (with and without 464XLAT).

It's interesting how his chart deflects somewhere around 80%, since at the 2017 Rocky Mountain IPv6 Summit that's about where T-Mobile US (who probably have the highest penetration of IPv6-capable endpoints of any ISP) noted their transition started slowing drastically.[0] The main reasons are that the remaining devices are old (e.g. 3G phones), have limited capabilities/needs (e.g. embedded IoT devices which just need to phone home once in a while), or are using odd configurations (e.g. for some reason T-Mobile doesn't currently support IPv6 for tethering). Another good talk from that conference is about how Carrier Grade NATs are (amazingly) even worse in practice than they sound in theory[1]. During the Q&A portion one of the audience members points out that as technologies like CGN become required to provide IPv4 service it will cause the cost of supporting IPv4 to rise over time and naturally push ISPs to kill IPv4 as the use of v4 drops while the costs to support it do not. I can also recommend a short talk by Cloudflare about their experience serving IPv6 traffic[2] and another on the history and future of IPv6[3]. [0] ▶ this video [1] link [2] link [3] link