In the world of voice the whole idea of switching takes on kind of a different meaning than the one we
understand within the networking world.
You have to appreciate that back in the old days you used a concept called circuit switching.
I mean you would have an analog signal that would travel from one telephone to the next and you literally
via hard circuits carrying voltage would have to switch in order to get to the other phone so that they
could talk to each other.
Now circuits switching is fine but it's kind of a concept that's faded out.
There have been a number of different ways that we've tried to do switching in the telephone world.
They have some older technologies which thank goodness are no longer on the Network+,
but there's a couple that are at least made a quick mention of and you need to be aware of them.
If nothing else as forms of switching technologies.
So as we move out of circuits which we move more into a world of packet switching which does give us
some pretty strong similarity to what we see in the networking world.
When we talk about packet switching there are two big technologies you need to be able to go those are
packet switching.
The first one is called Frame Relay. Frame relay's
been around since the 1980s and frame relay's job was to come up with a type of packet switching that
didn't care about errors but it was very very quick.
So frame relay has been around for a long time and most of the time when you're buying for example of
a T1 line people aren't going to say oh you want a T1 line, they're going to say oh do you want to frame
relay line because everyone knows it's T1.
But what you're actually paying for is a type of switching that's placed on top of it.
Now frame relay has been around for a while but frame relay has faded out pretty heavily for something
else called ATM. ATM stands for asynchronous transfer mode.
However ATM is a complete networking solution.
ATM is what is used on for example are huge SONET lines that are the backbone of the Internet.
But even ATM has begun to fade out.
The reason that ATM has a problem is that ATM was invented in the 1990s as some kind of do it all
form of switching technology.
It was designed to be able to handle voice and data and video and everything.
Bottom line is in todays world almost everything is now data.
Theres a little bit of pure voice but even most phone calls end up running under voice over IP.
So the whole idea of ATM, the beauty of it being able to do everything, has started to fade away.
Today when we start talking about switching technologies we tend to think about switching technologies
that are very very IP centric.
And one of them right now is called MPLS. And MPLS is designed really for IP based networks and it
has it takes advantage of some really big mistakes that we made with ATM. For example, for ATM
each one of its little frames are only 53 bytes long.
That makes a big fifteen hundred byte ethernet packet end up being badly fractionalized as it has to
be dispersed through an ATM network. Well,
now Mike Its not that the ATM packets were a mistake.
Its just that they were also designed to work with voice. MPLS kind of fades all that away.
And the beauty of MPLS is that because it is designed primarily to work within an IP environment it
doesn't matter whether you're sending data over a T1 line, over a DOCSIS cable modem, over DSL, satellite,
or ethernet.
MPLS works for all of these.
So MPLS is really what we see today more than anything else.
Keep in mind that unless you're actually working for an ISP or a very large enterprise the chances of
you actually having to deal directly with any of these packet switching technologies is pretty small.
Which brings us to the last and most interesting point.
All of these packet switching technologies could conceivably eventually fade away.
In a world that we call all IP. We're getting to the point now where we're having ethernet based technologies
that are so powerful 10 gigabits per second single mode fiber optics they can run for miles where in
theory one day we can see a world where the entire Internet is pure Ethernet.
So all of the old telephone technologies that we've known and loved will eventually fade away.
Now there's plenty of people in the telephone industry who think I'm crazy but there are large Consortium's
that are taking place even right now that are trying to come up with ways where all voice is going to
be voice over IP all data is going to be IP based and it's going to be a big happy IP world.