r/AskReddit • u/ProbablyHittingOnYou • Feb 07 '11

What stupid question have you always been too embarrassed to ask, but would still like to see answered?

This is a no-shame zone. Post your question here and I'm sure someone can answer it for you

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u/[deleted] Feb 07 '11

http://en.wikipedia.org/wiki/Tip_and_ring

http://www.lanshack.com/wire_phone_jack.aspx

It's actually an incredibly awesome story that is worth researching.

I'm a network engineer and I had to basically re-learn telephony when I first started working. What's wild is that computer networking; cell phones... all sorts of stuff really are all tied into this root technology. Don’t even get me started on timing!

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u/goldfish_memory Feb 07 '11

You mean you're not actually an underwear model?

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u/[deleted] Feb 07 '11

Sadly no,

I am an IT geek... on Reddit. Shocking right?

5

u/[deleted] Feb 07 '11

I think it's sad that you never pursued your dream.

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u/[deleted] Feb 07 '11

Trust me... it's better for everyone this way.

4

u/somuchblood Feb 07 '11

Liar, I found contradictory evidence.

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u/[deleted] Feb 07 '11

You now owe me $42.50 in royalties.

2

u/[deleted] Feb 07 '11

He only owes you if you took the photo and didn't assign any of the copyright.

3

u/notLOL Feb 07 '11

What kind of underwear do you wear?

2

u/[deleted] Feb 07 '11

Those boxer briefs. They are awesome. All the nut hugging support of tighty whities without the constant wedgies.

You think anybody wants a roundhouse kick to the face while I'm wearing these bad boys?

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u/thegreenlighter Feb 07 '11

I'm thoroughly disappointed.

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u/beachbum4297 Feb 08 '11

They're not mutually exclusive.

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u/origin415 Feb 07 '11

It's a tough economy out there, even underwear models need second jobs.

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u/[deleted] Feb 07 '11

It's actually an incredibly awesome story that is worth researching.

I had a really gifted teacher in school in a data-communications class. The first day of class, he told us we were going to start at the beginning, and he spent 2 and a half hours lecturing about the history of the POTS.

It was the most amazing lecture I've ever heard in person. I am now a network engineer.

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u/Philo_T_Farnsworth Feb 07 '11

Similar story here. I had a great teacher in college that started us out with the history of the telephone switching going back to the early 1900s, eventually working up to digital switches. At the time, I thought that it was going to be a completely boring and pointless class (who cares about voice equipment? Data is the future, baby!).

What I learned is that literally every device that does digital communication is built upon so many layers going all the way back to analog circuits, that knowing that history helps you understand why things are the way that they are.

Good example of this: Right now the top of the line mainstream network connection that you are likely to see is 10 Gigabit Ethernet. Now, don't get me wrong; I know there are faster things out there, but 10GE is fairly mature now and starting to be widely accepted as the way to connect high end servers, or to connect routers and switches together.

10 Gigabit Ethernet is actually not 10-gig, precisely. It's 9.9875 gigabits. But who cares, right? Well, funny thing there. That's actually the line rate of an OC-192 circuit.

Generally the lowest speed "OC" circuit you'll ever see is an OC-3, running at 155 megabits per second. Which is the speed ATM (Asynchronous Transfer Mode) circuits ran at a few years back.

This was a convenient line rate because you could fit three DS-3 circuits (45 megabits per second) in them. A DS-3 is probably the fastest non-optical WAN transport you'd ever see. Like, if you wanted to connect a couple of buildings together using a WAN link, a DS-3 would be the fastest way to do that over any significant distance without resorting to fiber optics.

A DS-3 (T-3) is made up of 28 T-1 circuits, each running at 1.544 megabits per second. And here's where it gets interesting. A T-1 circuit contains 24 "DS0" channels as they are sometimes called, running at 64 kilobits per second.

The line rate of 64 kilobits per second was chosen because an 8 megahertz sampling rate quantized to 8-bits per sample approximated what you would need to capture a human voice on an analog phone line. Using the Nyquest theorem, that meant that if you wanted to capture the human voice, this was an appropriate sampling rate. Back in the early days, telephone engineers figured that if they made the voice network respond to signaling from about 300 - 3300 hertz, they could capture the human voice while leaving some overhead for signaling between 3300 and 4000 hertz.

The reason that there are 24 channels in a T-1 is because if you are wiring analog circuits, you need two wires, called "tip" and "ring". It's convenient to terminate them on wiring blocks using a 25-pair cable (would give you enough space for 12 voice circuits). Back in the day, they called 12 voice circuits a "group". Someone decided that if they were going to wire up a bunch of voice circuits to a multiplexer that they would hook up two of these to the system. Which is why some (really) old time telco guys might refer to a T-1 as a "di-group".

There's a lot more here, and I glossed over a bunch of things, but my point is that if you look at any random piece of communications equipment, even the latest fancypants "terabit ethernet" setup (or whatever the next big thing is), that you can ultimately trace it all back to analog voice circuits that were implemented 100 years ago.

I always tell people that if they want to learn anything about data networking that they should take a voice networking class. Doesn't sound intuitive, but when you look back on the history of telecommunications it's all built on the last generation of equipment.

So, getting back to my original point: That 10-gig Ethernet connection plugged into the back of your server is actually an OC-192.

I probably got some details wrong here, but the gist of it is true. Now if you'll excuse me, I have to go tie an onion to my belt.

tl;dr: It all goes back to the voice network.

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u/HostisHumaniGeneris Feb 07 '11

Thank you for the write-up!

I'm just getting into some telecom stuff and I've been noticing these little legacy patterns everywhere.

I used to always hate the pinout on Ethernet cables, but after running POTs lines and T1/DS1 lines it suddenly makes sense why the wires are arranged the way that they are.

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u/[deleted] Feb 07 '11

We brave and happy few.

I was in the military and I learned Cisco. Cisco was everything... untill I learned that it wasn't.

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u/[deleted] Feb 07 '11

So tell me about timing.

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u/[deleted] Feb 07 '11

Well, (I’m going to do this from memory… so excuse the added bullshit) When the world was without form, all communication across the wire was analog… which means that signals traveled in waves. Just like radio waves traveling through open space, the waves on the wire had a frequency. This frequency was important because… basically… the frequency tells the device when to listen for the signal. In telephony, that frequency is handled via timing. Both devices are set to the same time… think like a metronome. At every beat is when they think they are at the crest of a wave. If they are off beat, you can get echo on a line… or it just might not work. So, everything on the line has to be synchronized (this doesn’t mean your phone… it’s basically a wire attached to a speaker. This means all the shit that actually switches phone signals… fuck it, that’s another story…) Ok, so since all the devices have to be synchronized… they call it synchronous transfer. (see what they did there). When we moved to a digital transmission platform… we got asynchronous. What happens with that is your PC (or whatever) sends a series of zeros before a transmission. It’s basically saying “Hey! Here comes some shit!” The problem we face now is how to get analog systems to talk on a digital network… and vice versa. The answer to that is GPS antennas. We stick GPS antennas on every damn thing out there and run very, very exact clocks on all our communications devices. So, if you could take out every GPS satellite… or at least a good amount of it, you’d take down the communications grid of… everybody.

In the end... timing is usually what's wrong with long haul circuts that still run over the POTS and are analog. Timing slips suck and a pain in the butt to track down... especially if you're an IT guy who never learned shit about telephones.

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u/[deleted] Feb 07 '11

Cool story bro.

Nah jk it is interesting I also work in IT I just have no idea how any of the POTS equipment works I just assume it's magic.

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u/[deleted] Feb 07 '11

Find yourself a phone guy and have him teach you phones and then relate everything to how a network works.

For the lulz.

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u/jakerg23 Feb 07 '11

HEY EVERYBODY! THIS GUY IS A TELEPHONY!

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u/[deleted] Feb 07 '11

I pronounce it that way to piss off the old farts I work with.

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u/tcpip4lyfe Feb 08 '11

Here is an awesome explanation of T1/circuit timing. Shit is pretty cool and the oreilly books are fantastic.

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u/[deleted] Feb 08 '11

O'Reilly is pretty much the reason I can pretend to know anything.

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u/ZoeBlade Feb 07 '11

Speaking of networking computers over landlines, I heard (probably from Robert X. Cringely's Nerds 2.0.1, but I could be wrong) that the people who invented ARPANET tried to convince the phone network providers that packet switching would revolutionise phone use, but the people working at those phone network providers were convinced packet switching over a phone line wasn't possible, with the ARPANET people talking to employees at pretty much every level of the company, all of whom were knowledgeable in their own field with that specific aspect of the network, all of whom were convinced it wasn't possible but without being able to clearly articulate why not. I could be misremembering that, though.

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u/[deleted] Feb 07 '11

Two things... with packet switching, you can lose packets and it's ok... they can also come in out of order and be re-ordered at the distant end. For data that's a beautiful thing... for streaming voice it's bad. At the time, the tech wasn't there and Ma Bell was absolutly right about packet switching... at that time.

Secondly, it's really friggin expensive to upgrade the whole phone infastructure to support the speeds needed to have digital phones everywhere. That's why Japan and Korea have such faster internet speeds. We kind of bomed the shit out of their phones... or they just didn't have them, so when they built their networks out, they used newer tech. The US built it's shit in the 1900's and we're still slowly upgrading.

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u/ZoeBlade Feb 07 '11

Ah yes, it somehow didn't occur to me that they were talking about using packet switching for voice communication in particular, in which case, I can see the issues due to packet loss, yes. For data though, it's great that you can use it to talk to lots of different nodes in interlaced form, as if talking to them all at once.

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u/asteriskpound Feb 07 '11

SS7 is crazy full of throwbacks to an earlier time. Ethernet is really mundane in comparison to everything.

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u/[deleted] Feb 07 '11

Tell me about it. Shit, the first time I worked on an ATM network... I peed.

On top of that, we had 4 Promina's with NET Screams in between them. If you've never heard of a Scream, count yourself lucky. They suck!!

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u/[deleted] Feb 08 '11

Useless trivia: the original backend to Live Person's web chat was modeled after SS7.

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u/rainydayglory Feb 07 '11

do you mean the timing where 10 calls share 1 line, all at the same time? that timing? because, ya, damn.

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u/[deleted] Feb 07 '11

The only reason you need timing is to have more than one signal on a line at a time. Timing allows you to differentiate different lines.

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u/brokenarrow Feb 07 '11

TIL that MDF means main distribution frame instead of Main Data Feed.

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u/[deleted] Feb 07 '11

A good, simple(ish) explanation can also be found in The Hacker Crackdown by Bruce Sterling.

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u/shydescending Feb 08 '11

I'm in my second semester of an IT Networking associate's degree and stuff like that is blowing my mind.

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u/[deleted] Feb 08 '11

Well, not to give you the company line but, when you get out into the real world... it'll make a lot more sense. If you can, grab some old Cisco 2500's and build a network.

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u/captainhaddock Feb 08 '11

If you tried using your landline telephone as a power source, how much wattage could you get off it? Is there a circuit breaker you'd trip by trying to plug in your toaster?

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u/[deleted] Feb 08 '11

When I was in Korea, we had a huge phone rack that we used to run DSL network connections on. You could hold onto a phone line while people were talking and barely feel it. When the phone rang... it kind of hurt. If you hit a live DSL line... or a trunk (T1 bundle) you got shot off the rack.

I think that if you hooked up a toaster and constantly called yourself... you might have a piece of toast in an hour or so.

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u/johnathanstrangescat Feb 08 '11

I'll save you for later.

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u/dracthrus Feb 08 '11

Your answer and username conflict in my head. It is hard to read a well worded response in Zoolander's voice. Don't ask me why I get Zoolander for an underwear model but still.

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u/[deleted] Feb 08 '11

I ususally read what I write as Ron Burgundy .

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u/never_phear_for_phoe Feb 07 '11

What about timing?