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| layout | title | description | date | tags | draft | extra | ||||
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| page | I built my own private telephone network | Nobody makes phone calls anymore | 2022-02-14 | project pbx | true |
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Over the past few months, I have built my own internet backbone router (and an internet exchange). So logically, the next step is to branch off into telephony... right?
Eh, even if I never get any practical use out of any of this in the end, at least its content for the blog.
A simplistic introduction to telephone networking
This is all coming from someone that has very little experience with the telephony world, but I have managed to make all my gear work, so this can't go too badly.
As far as I have ever been concerned, the telephone network looks as follows:
But in reality, it looks a little more like the internet (I guess that makes sense, since dialup was a thing).
The Dark Magic still exists, and I am still not entirely sure whats going on there. Presumably some kind of routing protocols exists to handle country codes and such, but I have had no need (yet) to explore this further.
Continuing on with terminology, Phones are simply endpoints. Such endpoints could be cellphones, VOIP clients, automated answering machines, etc. Carriers are the same as the internet world. Big companies that own switching gear and phone number blocks they charge you to connect up to.
Finally, PBXes. A Private Branch eXchange (PBX) combines the concepts of routers and NATs in the telephony world. A PBX can be hardware-controlled, or software-defined through something like Asterisk.
I have personally used Asterisk a fair bit due to its heavy use in the Amateur Radio world as the backbone for repeater interconnections. More on this in a bit.