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Comment by scrooched_moose | Hacker News Reader

> unreliable

Really? It's the only messaging format that works without a data connection and is an absolute godsend when I'm out camping, rural biking, or at large sporting events and the towers are absolutely swamped.

I'm in a situation at least once a month where the only reliable communication method is SMS.

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Unreliable in the sense, that it is on the discretion of the network, whether it will drop your message somewhere in transit, without letting you know. Just like UDP.

SMS supports delivery notifications, I think I've been using them for almost, if not 20 years

I get a little display under the message saying 'delivered' in the standard android SMS app

That's another message that may or may not be lost, if it is checked at all.

I've got my lesson about SMS reliability few years ago: I've bought a bus ticket via SMS, it was never delivered, but I got charged for it and the operator claimed that it was sent, when disputed. Except I've never received it, and couldn't ride the bus without it.

> That's another message that may or may not be lost, if it is checked at all.

that's a general problem with acknowledgements and is not specific to SMS

TCP is exactly the same

But tcp detects this and recovers or explicitly kills the connection.

Sometimes carriers will send a "delivered" even though it only made it as far as a cell tower (and not an actual phone)

Is it a practical issue where you are? In France I can't remember the last time I've had issues with undelivered text messages and I use them quite a lot (I generally use the cheapest plan I can find which usually doesn't contain data, so I default to texts).

For important messages I'll expect an explicit confirmation anyway, it's not enough that the message reaches the recipient's phone, they also have to read it!

My main problem with texts is lack of privacy which is why I'm slowly pivoting towards Signal instead.

If you've had a long running group chat over MMS, ask to see everyone else's phones. Messages will be in a different order on every phone and there will be many missing messages.

My wife and I do this regularly because we won't understand something said and we'll see one of us didn't get a message from the group.

It's 2018 and I learn that there's MMS group chat o_O

-- a guy who used SMS and then had 90% of friends being reachable via IRC and email, and SMS for the rest - before entering the world of smartphones.

Dropped SMS messages, particularly between Android and and iPhones, have caused some catastrophes at my work. I no longer trust them enough to use them to communicate with staff.

Isn't that usually because iMessage doesn't actually send SMS if it thinks it can send something else?

Wow - infrastructure varies. Here in Eastern Oregon the pattern is pretty reliably that data and signal drop out at the same time, at least on Verizon which is the carrier with the best coverage.

I really thought the pattern that you describe, which I've seen plenty of in the past, had just died out over time and tower upgrades.

I routinely see SMSs fail to deliver, deliver multiple times, deliver weirdly out of order, or deliver at random times, hours or days after they were sent. And this is in a relatively well-served area fifty miles out of Boston.

I still have the issue where MMS seems to just sometimes not work for days or even weeks on end, then suddenly start working again. No OS updates and no APN settings changes in the meantime. Normally it's not an issue, since I don't really use SMS all that much anymore, but my mother and I tend to send pictures back and forth a lot and she still uses SMS.

SMS itself usually works fine, but MMS is particularly bad.

It all depends if there's a 2G network to fall back on if 3G+ data goes down. Most places have shut down their 2G.

>Most places have shut down their 2G.

Citation? I haven't seen this to be the case in California - at least on Verizon.

There was a big story about it when ATT shut down their 2G network in SF since MUNI used that to report their locations.

http://sfist.com/2017/01/06/nextmuni_glitch_problem.php

Only AT&T shut down 2G. T-Mobile reiterated recently that their 2G network will probably be shut down after their 3G one, since it hardly uses any spectrum.

With places that have shutdown 2G, there is no "voice only" network anymore since 3G is required for the voice traffic.

T-Mobile and AT&T have very different planning. AT&T shut down their 2G because it mostly ran on 850mhz and this was needed for LTE and their legacy band 5 WCDMA (hspa) network.

T-Mobile mostly ran its 2G on 1900mhz, but had beefy midband spectrum holdings there and in AWS (and AWS-3) for most markets. Since you can run GSM down in like 200khz or so it's not a huge deal to have a small slice allocated to legacy voice fallback. You can't do that with 3G... you can thin it down but it's still going to need 3.8mhz or so. (T-Mobile has experience thinning HSPA down prior to the MetroPCS CDMA shutdown... which they had legacy CDMA running in guard bands)

Verizon and Sprint used to mostly be on CDMA-based technology. So their 3G 'EVDO' can't do calls.. it needs cdma2k layer to go back to, or full voLTE support. VZW has its shit together on voLTE, sprint will probably never launch volte at this rate.

Sorry was thinking up in Canada only Rogers maintains 2G still.

Same with Eastern WA and CA, you basically just drop behind a big hill/mountain or into a valley and lose all service. I still sometimes use texts since I can turn off data to save power and still send SMS.

SMS is a best-effort protocol; that is inherently unreliable.

Business class SMS is quite reliable.

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