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How do text messages travel from one phone carrier to another?

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dmills:
As I said, old, complicated, very 'Telecom' and baroque as hell, but SS7 works.
There is no magic, it is just Engineering, all the way down, and is actually rather well documented.

Regards, Dan.

Beamin:
So I read up on the SS7 pretty interesting stuff. I guess my question is more basic, is there a dedicated line set up between exchanges that's like a dial up or terminal connection that is always connected that would have sent the data? Kind of like how a BBS system worked but it would be on a dedicated physical line between exchange offices that could relay all the messages together. The reason I kept saying "twisted pair" is because I was thinking in terms of how you would actually build this or if you hopped a ride on the messages where would the signal physically travel. It would make a really interesting video if you could watch someone send a text then show the route your electrons and photons are traveling and all the complexity and equipment that is required to send your "LOL" or "BRB" text to a friend hundreds of miles away in less then a second. Also interesting would be how much $ in equipment is used to send that text or hours spent installing it and the lines.

madires:
Please see https://en.wikipedia.org/wiki/T-carrier for the old workhorse of the US telecommunications industry.

tggzzz:

--- Quote from: Beamin on December 07, 2018, 02:47:42 pm ---I guess my question is more basic, is there a dedicated line set up between exchanges that's like a dial up or terminal connection that is always connected that would have sent the data?

--- End quote ---

There are many many lines between exchanges, usually fibre optic since the early/mid 80s.

Dedicated? Yes, repeat no - depending on the level at which you are considering them.

By analogy, consider a  VPN. Is that dedicated or not?

Ditto, consider subsea fibre links.

IanB:

--- Quote from: Beamin on December 07, 2018, 02:47:42 pm ---I guess my question is more basic, is there a dedicated line set up between exchanges that's like a dial up or terminal connection that is always connected that would have sent the data?
--- End quote ---

This is kind of a strange question. Ever since the phone system has existed,since over 100 years ago, the phone company has installed and maintained dedicated wires between exchanges and between cities to carry voice and data messages around the country. From the phone company's point of view there is nothing strange or unusual about lines being always connected. All the phone company's wires are always connected all the time--it is their business to install and maintain these wires.

When you make a dial up connection the phone company decides where your connection needs to go and it than allocates a channel over its installed network of dedicated, always-on connections to carry your call. When you make a phone call you are basically renting some time on that permanent, always on network that the phone company maintains.

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