How does a telecom carrier such as AT&T or Verizon send an SMS message to a Twilio number?

Question

I'm trying to further my understanding of how the SMS messaging system or 'texting' works.

Can someone explain how the back-end mechanisms work to deliver an SMS message from someone with an AT&T number to a number owned by Twilio?

This link Can a Twilio SMS number be sent via email to one of the big carriers? explains how a third-party provider can send "SMS messages" to your phone (via email), but I would like to know more about how the SMS messaging system works.

Thanks in advance.

Answer 1

Read over this article, provides some insights.

How One Company You’ve Never Heard Of Swallowed Tens Of Thousands Of Text Messages — Then Spit Them Back Out

AT&T, T-Mobile, and Sprint currently use Syniverse to route text messages to people on other networks, according to data available to Tyntec, a smaller messaging services company that spoke with The Verge. T-Mobile confirmed that it uses Syniverse, AT&T declined to comment, and Sprint did not respond to a request for comment. Verizon confirmed that it uses a competitor, SAP.