Now that I’ve lost 99% of the readers, please join me on the exciting journey of SMS with first looking at the basics of text messaging and then exploring the “grey zones” of SMS delivery.
For example, if Ana sends a text message to Kate, they are either on the same mobile network, which makes it an “on-net” SMS handled internally by their common mobile provider, or they are both subscribers of different mobile operators, which means the SMS goes “off-net.” The on-net case is great for the provider, as it can deliver the SMS without any additional costs except internal network expenses. The beef lies in the latter, so let’s look at that more closely. Ana and Kate both have mobile numbers from the UK, i.e. with the same international prefix +44, and both are currently located in England. All mobile operators in the UK have so-called “interworking agreements” between each other, which means that they are technically interconnected, know each other’s mobile prefixes and have a commercial arrangement to pay each other the “interworking fee” for delivering an SMS to their subscribers. In this case, Ana’s operator ‘AA’ pays Kate’s mobile provider ‘K²’ for sending the message to Kate. Of course AA has charged Ana for that message, either directly on a per message basis or through the bundle that includes a specific amount of messages. Similarly, if Ana sends a text to her friend Christian, who is with the German provider ‘C-Mobile’, AA will pay C-Mobile for delivering the SMS to Christian’s handset. And when Kate and Christian are replying to Ana, AA receives the same interworking fee it previously had paid K² and C-Mobile. So far so good, it’s a zero sum game for the operators given that Person-to-Person (P2P) traffic is, in the grand scheme of things, perfectly balanced. And every operator reaps the benefits of charging its own SMS sending subscribers. Wonderful world.
Now, Kate is traveling on vacation to the exotic island of Tabaluga. Not much communication is going on between the UK and Tabaluga, hence AA and K² haven’t established a full interworking agreement for SMS with the island’s carrier TabaCom, as the overhead of a monthly billing run is more expensive than the few exchanged messages are worth. Still, Kate wants to use her Kphone on Tabaluga for reaching Ana in the UK. AA and K² have established a technical connectivity with TabaCom, a so-called “roaming connection” that allows communication to flow between TabaCom and the UK operators without any monetary obligation in either direction – plus K² will charge Kate some additional SMS roaming fees for texting with her phone abroad. Even better!
Thanks for having followed this post so far. Now we can finally start embarking on Application-to-Person (A2P) SMS and its grey routes. Just think of the SMS aggregator, XBipTecOxTel, who runs a significant amount of SMS traffic to the UK. It could either agree with AA and K² to deliver its traffic to the UK, of course, for a per message charge – this would be an official direct route. Or, it could find TabaCom! Remember TabaCom can send messages for free to AA and K². So XBipTecOxTel “helps monetize” TabaCom’s asset by paying them a small fraction of what AA and K² would charge and suddenly millions and millions of messages flow from Tabaluga to the UK. The low price to the UK (and to all other destinations TabaCom has free roaming agreements with!) would allow XBipTecOxTel to offer extremely low A2P prices, attracting a lot of A2P customers that are thrilled to cut their messaging costs.
Is it illegal? No, it isn’t. Is this meeting the intention of AA and K²? No, since they rightly want to get paid for their service. That’s why it is called a “grey route.” So what happens next? Well, after a while AA and K² will notice this unusual messaging traffic from Tabaluga and either block that traffic or set-up a proper interworking agreement. Then, XBipTecOxTel would seek another small operator and start over, e.g. with Lilliput Island Telecom. A few years ago this detection time would be very long, and a grey route could have lasted for years – especially if XBipTecOxTel was not being overly aggressive by keeping its traffic numbers low enough to stay under the radar. Fast forward to today where most networks have developed much better monitoring and filtering capabilities so that the time to detect a grey route has been reduced to mere days or even hours.
While we are at it, let’s darken the grey towards dark grey and even black shades. Another interesting concept is called “GT spoofing.” GT means “Global Title” and that is how C-Mobile presents itself towards AA. So if an aggregator imitates having the GT of C-Mobile, it can send messages to AA and AA would charge the real C-Mobile. Another example is “SIM card farms,” which is buying SIM cards with an SMS flat rate, putting them into a modem and cranking text messages out of them 24×7. In order to not get detected, you would need to rotate the numbers and some companies allegedly even put the SIM card farms on a truck so that they are moving locations like a real humanly-operated SIM. Needless to say, all mobile operators are actively trying to stop all of these shady activities. It is a true cat and mouse game.
As the saying goes, you get what you pay for. If you find very low prices on the SMS A2P market, there is a high likelihood that your messages will use one of the grey routes described above, thereby risking stoppage of service unpredictably.