[HN Gopher] VoWiFi
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VoWiFi
Author : zdw
Score : 88 points
Date : 2022-03-25 13:59 UTC (9 hours ago)
(HTM) web link (computer.rip)
(TXT) w3m dump (computer.rip)
| kevincox wrote:
| I also find it annoying that basically all roaming works by
| tunneling traffic back home. I guess it kinda makes sense for
| calls where it needs to be routed by the home carrier but for
| data it adds a lot of latency and cost.
|
| In Canada our data is stupidly expensive such that as a fairly
| small data user I was considering getting a PAYG "global data
| plan" instead of a monthly local phone plan (I don't use a local
| number anyways, so I just need data). And while it would be
| cheaper for me (and be extraordinarily cheaper when traveling)
| basically all of these sims have a "home" country that traffic is
| routed to. Not only is this slower but it also results in funny
| behaviour for sites that try to optimize/block users based on
| GeoIP.
|
| If one of these global sim providers could do local egress I
| would be all over that plan.
| andix wrote:
| This behavior can make your internet on the phone really slow,
| especially if your SIMs home country is on the other end of the
| world.
|
| But with 5G there is a mode for routing IP traffic directly to
| the internet during roaming, without sending it ,,home" first.
| Let's see if providers will implement that.
| xenadu02 wrote:
| I wasn't aware Mexico had intended to join NANA and use the NANP.
| It's a shame they didn't.
|
| For non North Americans: the telephone networks use an
| international numbering plan so Canada, the US, and about 18
| smaller countries use a single numbering scheme and issue area
| codes out of the same pool. So for me in the US dialing Canada or
| Bermuda is the same as dialing somewhere in the US.
|
| It is much nicer than the international dialing system where each
| country has its own rules about what parts of the number are
| area, local exchange, etc. I wish the old ATT had designed a
| larger scale numbering plan that could have been worldwide and
| everyone could have adopted it.
|
| (Imagine if IP addresses were different lengths and subnets were
| described differently based on the country of connection)
| smachiz wrote:
| Hard disagree - it's actually pretty awful from a mobile user's
| perspective.
|
| You dial a number that is +1 and looks like a normal 10 digit
| phone number.... and bam, you're paying $3/minute to call
| Canada (back when everyone charged more for Canada) or Bermuda
| that is still expensive I think on every carrier.
|
| Everyone could use 10 digit dialing and have their own country
| codes still... it's silly that 19 countries are sitting behind
| +1 and that they might have a significant surcharge to call.
| msh wrote:
| Why would you ever care about area codes? At least if not for
| ancient carrier billing practices.
| Kwpolska wrote:
| > It seems to be a general trend that countries with variable-
| length area codes lack well agreed upon phone number formatting
| conventions. In the UK, for example, there is also variability
| (albeit much less of it). This speaks to one of the disadvantages
| of variable-length area codes: they make digit grouping more
| difficult, as there's a logical desire to group around the "area
| code" but it's not obvious what part of the number that is.
|
| It's trivial for computers. For example, using Google's
| libphonenumber [0]. For example, Poland uses `000 000 000` for
| mobiles, and `00 000 00 00` for landlines. libphonenumber knows
| how to handle this [1]: <!-- Mobile, pager
| and a few fixed-line numbers. (70 numbers are
| formatted as per mobile numbers, based on information from some
| Polish people). --> <numberFormat
| pattern="(\d{3})(\d{3})(\d{3})"> <leadingDigits>
| 21| 39| 45|
| 5[0137]| 6[0469]| 7[02389]|
| 8(?: 0[14]| 8
| ) </leadingDigits> <format>$1 $2
| $3</format> </numberFormat> <!-- 9-digit
| fixed-line numbers. --> <numberFormat
| pattern="(\d{2})(\d{3})(\d{2})(\d{2})">
| <leadingDigits> 1[2-8]| [2-7]|
| 8[1-79]| 9[145] </leadingDigits>
| <format>$1 $2 $3 $4</format> </numberFormat>
|
| [0]: https://github.com/google/libphonenumber [1]:
| https://github.com/google/libphonenumber/blob/master/resourc...
| ggeorgovassilis wrote:
| A few updates ago VoWiFi seems to have disappeared from Android.
| Anyone know how to get it back?
| stavros wrote:
| For Xiaomi, _#_ #869434# _#_ , I'm not sure about other
| devices. Mine doesn't work, for some reason, but everyone
| else's works fine. I think my SIM is somehow misconfigured.
| AshamedCaptain wrote:
| You don't need eUICC or anything of the sort to do roaming, which
| is just what he's describing. Even the behavior with the
| international prefix on numbers.
|
| Also, the simultaneous data + voice story is kinda more
| complicated. You couldn't do simultaneous voice+data on 2G
| phones. You could do it on UMTS/HSDPA for sure (it was one of the
| marketing points...). Then when LTE came, for a time phones could
| not do phone calls over LTE (VoLTE) (something which I was told
| was just a "missing software thing") so they had to drop down to
| some 3G standard during any phone call. If your 3G standard
| didn't have support for simultaneous voice+data, like it used to
| be on CDMA networks, then you just didn't have data (see CDMA
| iPhone 5). But it was just fine on GSM ones.
| avianlyric wrote:
| > You don't need eUICC or anything of the sort to do roaming,
| which is just what he's describing. Even the behavior with the
| international prefix on numbers.
|
| I don't think the author made this claim at all. He just
| mentioned that he thinks that Google are using eUICC to make
| roaming on Google Fi cheaper than traditional roaming
| agreements. And he's basing this on the fact that the dat
| connection can drop out for a little while as the phone roams
| internationally, presumably because it's reprogramming the
| eUICC.
|
| I would assume that if you're running a service like GoogleFi,
| where the phone number isn't associated with an actual phone
| network, then you can do international roaming cheaper because
| you just setup direct agreements with local telecoms to provide
| local data access, and then route the "shadow number" assigned
| to the SIM to a local Google endpoint. Thus you can create a
| setup where international roam is achieved by having local only
| carrier agreements, and doing clever call routing to local
| Google forwarding numbers, which Google then routes over its
| own network to the destination country, where a local Google
| endpoint then pushes the call back into the local telco
| network.
|
| Doing this completely removes the need to have a traditional
| roaming agreement where carrier backhaul alien subscribes back
| to their home carrier, charging a hefty fee for the privilege.
| And instead replaces it all with local only call and data
| routing, with Google infrastructure providing international
| transit, and Google software masquerading the local subscriber
| identities, so GoogleFi customers don't see the messy details
| underneath.
| jcrawfordor wrote:
| Yeah, I really don't know for sure, I just know that my Fi
| phone behaves oddly when crossing into Mexico and Canada
| compared to my Verizon phone a bit ago and I'm guessing it
| has to do with some of the less typical cost optimization
| Google does wrt carriers. I don't know a lot of technical
| detail about how Fi does that and I don't think there's much
| info about it out there in general, but my theory at least
| makes sense to me... well-standardized VoLTE and eUICC are
| pretty recent developments (the same capabilities have
| existed for much longer but in the form of various
| proprietary solutions). So this could explain why, early on,
| Fi was limited to only a few Android devices with bespoke
| kernels, while nowadays (as VoLTE and eUICC have become much
| better supported) it works correctly on a much broader range
| of devices.
|
| VoLTE, for example, has been around in concept for longer
| than LTE, but it has had a complex standards history that I
| did not try to really explain because it would get lengthy.
| "VoLTE" and "IMS" can actually refer to different systems
| (not all VoLTE uses IMS) but it all gets sort of vague and
| contextual. LTE phones with VoLTE capability have been around
| basically as long as LTE has been in service in the US, but
| for a long time were mostly proprietary systems that required
| per-carrier support. This is still true to some extent but US
| carriers and device vendors are now much more converged on an
| IMS-esque architecture than they were even just a few years
| ago, so it's now a lot more likely that you can e.g. switch
| to a different carrier and still have VoLTE work... although
| not guaranteed!
|
| One hint that might help reveal how Google Fi handles this is
| the source of web traffic on my phone... web requests from my
| phone in Mexico are coming from an IPv4 address registered
| via ARIN to Airlinq with a contact address in the UK! Airlinq
| has some kind of relationship to Hong Kong ISP Hutchison and
| it seems like the takeaway is that they offer a "global
| cellular mobility" solution. My guess is that Telcel is being
| used as the mobile provider (I did some checking of intercept
| recordings which confirms my voice calls at least are going
| via Telcel) and IP traffic is being routed via Airlinq, whom
| Google presumably contracts to handle international IP
| connectivity. Normally, in the US, my traffic emerges via
| IPv6 from T-Mobile. This is an indication that my traffic is
| not being tunneled back to the "home" provider as is the
| typical case with roaming.
| pxeboot wrote:
| It has been a few years, but when I last used Google Fi, all
| international roaming was handled by the T-Mobile SIM
| profile, except when using Three UK, which had it's own
| profile/shadow number.
|
| VoLTE roaming agreements do not exist everywhere, so it is
| still very common to fall back to 3g for calls when roaming.
| ac29 wrote:
| > I don't think the author made this claim at all. He just
| mentioned that he thinks that Google are using eUICC to make
| roaming on Google Fi cheaper than traditional roaming
| agreements.
|
| Maybe, but as far as I can tell Google Fi is just a T-mobile
| MVNO (they used to also use Sprint, but T-mobile bought
| Sprint ~2 years ago). My direct-with-Tmobile service also
| includes free international roaming in a ton of countries, so
| it would make sense if Google just took advantage of the
| agreements T-mobile already has in place.
| jcrawfordor wrote:
| The lack of VoLTE early on was not quite as simple as missing
| software as there was, at the time, not really any agreed upon
| VoLTE architecture or implementation. IMS has existed since
| before LTE, but carriers have been very reticent to implement
| it because the choice to architect around existing internet
| protocols actually leads to a relatively high degree of
| complexity from the perspective of legacy telcos. For most of
| the early years of LTE, most carriers just didn't support VoLTE
| as an intentional business decision, to avoid the expense of
| deploying infrastructure. Those that did mostly deployed "lite"
| VoLTE stacks that were simpler and less capable than the IMS
| architecture, and this is the big issue that leads to the
| situation we still have today in some cases were given phone
| models are only capable of VoLTE with specific carriers, due to
| those carriers using a non-standard architecture.
|
| Most LTE phones could do HSDPA+ during voice calls but some
| couldn't. I'm not sure why, it may have just been a simplifying
| decision by the vendors. This was more of an issue in the very
| early days of LTE, e.g. my hazy memory is that the HTC
| Thunderbolt completely dropped data during voice calls.
| kim0 wrote:
| Wondering if it's possible to use VoWIFI from a third party
| provider that's not my phone service provider?
| aftbit wrote:
| Interesting discussion on telephone numbers. I didn't know that
| Mexico has 2 and 3 digit area codes, or that +1 includes more
| than just USA.
| psim1 wrote:
| For those of us in the VoIP industry, VoWiFi offers no surprises.
| The phone establishes an IPSEC tunnel back to the provider for
| secure calling using the SIP/IMS stack. Much of the time when I
| am at home and not planning to go out, I turn on airplane mode
| then enable WiFi. Calling, SMS, MMS, etc. all work fine. It's a
| battery saver.
| mdb31 wrote:
| Yes, when roaming, VoWiFi or VoLTE can have quite unexpected
| results due to your 'data' being backhauled to your 'home'
| provider, for both billing and dialing. Former you can't do much
| about, except complain when things go wrong, but as for numbers:
| always store (and dial) these in +countrycode-subscribernumber
| (minus the leading 0, _unless_ it 's an Italian number, +39)
| format, and you'll be mostly* fine.
|
| *Unless visiting countries that have providers with woefully
| misconfigured dial plans, say, Nigeria...
| AshamedCaptain wrote:
| This is not related to LTE, just to roaming itself. In fact,
| even the manual of the first GSM phone I ever bought said as
| much (to store your numbers with the international prefix on
| the address book -- otherwise, they could fail to be matched
| while roaming).
| nathancahill wrote:
| The fact that iOS (not sure about Android) doesn't
| automatically add the local international prefix when you
| store a new contact is surprising. Seems like an easy quality
| of life win.
| kevincox wrote:
| Android also doesn't automatically store numbers in
| international format (at least for the default and Google
| contacts apps).
|
| Maybe the reason is either:
|
| 1. The phone doesn't always know the international prefix.
|
| 2. This raises the risk of accidental long-distance calls
| and may piss of users.
| mdb31 wrote:
| Well, it is related to LTE, in the sense that VoLTE calls are
| treated as 'data' (and thus backhauled to your 'home'
| provider, as per your (e)SIM), whereas 'voice' calls are
| handled by whichever provider you happen to be connected to.
|
| But the advice to always dial calls in 'international' format
| is helpful.
| AshamedCaptain wrote:
| In fact the author is describing the opposite situation,
| where his "LTE calls" require the international prefix
| while the "Wi-Fi" calls do not require it (not sure if
| VoWifi or plain VoIP, it's not clear from the description,
| and I don't know of any phone provider which allows true
| VoWifi while roaming).
|
| Note most modern dialing programs (and likely all of the
| VoLTE-capable ones) will silently add some prefix to your
| calls anyway, so it's really hard to know what's going on
| behind the scenes. But you usually can't dial your
| provider's special phone numbers "as if your calls where
| backhauled to their network through VoIP" when you are
| roaming, even with VoLTE. To e.g. check voicemail you will
| still need to dial your provider's roaming-specific number,
| which will come with an international prefix.
| th3typh00n wrote:
| Always storing contacts using the full international phone
| number is definitely the way to go. As someone who, at least
| before the pandemic, used to travel a fair amount this
| basically eliminates all issues and makes everything "just
| work" everywhere.
|
| To be honest I'm surprised that phones doesn't do this
| automatically when you type in a local number.
| kevincox wrote:
| I was also surprised by this. I moved country and was shocked
| that none of my phonebook worked and I needed to run a script
| to add a +1 to all of the non-international numbers in my
| phonebook.
|
| Maybe phones don't necessarily know the current international
| prefix?
| mindslight wrote:
| Tangentially related, does anybody have experience with libre SIP
| over LTE (eg native Android VoIP dialer)? With the partial 4G
| shutdown in the US, I'm reluctant to buy a new pocket
| communicator. LTE data continues to work just fine, and I've
| already got an Asterisk setup for my home phones. VoLTE seems
| like it's doing the exact same thing just with the carrier's
| blessing, and the less proprietary crap in my life the better. My
| current plan is to try out SIP over wireguard [0] over LTE, and
| see how that treats me. The biggest problem I foresee is a lack
| of QoS, but given that carriers' main concern seems to be
| streaming video, I'm hoping that best effort on a lower bandwidth
| stream will work alright.
|
| [0] Wireguard is to solve the NAT issues, make QoS predictable on
| different networks, and gain secure calls to home as a bonus.
| dragontamer wrote:
| I had a friend try VoIP on a dataplan a few years ago.
|
| > The biggest problem I foresee is a lack of QoS,
|
| Bingo. QoS for voice is about jitter and consistency of your
| stream.
|
| > I'm hoping that best effort on a lower bandwidth stream will
| work alright.
|
| Lets put it this way: you don't care if your webpage loads 0.2
| seconds slower. But a few random 0.2 second delay in your
| conversations will make them utterly, and completely
| unintelligible. Low QoS is something data can afford because
| little "sprints" of high bandwidth is good for webpages and
| streaming video.
|
| But "live", and "realtime" voice communications, the jitter is
| just too awful.
|
| If no one else is on the cell-tower, you might be fine. But
| every now and then, you'll just get completely terrible phone
| calls that are unusable.
| davidholdeman wrote:
| I've been using SIP on my Android phone for a couple of months
| now, and QoS hasn't been an issue at all. I'm using Voip.ms so
| I can have SMS and MMS. There's a SMS app but it doesn't
| support MMS; MMS messages are emailed to me and I just log on
| the Voip.ms portal and message there. I use Linphone as the
| client, and Strongswan for VPN.
| leeoniya wrote:
| the biggest issue i ran into when trying voip with a cell phone
| is lack of functioning mms (and therefore also group sms). that
| ended up being the dealbreaker.
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