The coolest part of the Internet and the part you're probably never going to see unless you have a really
cool job.
And if you get one of these jobs, call me because I would love to get a tour of some of these places,
is at the very top of the Internet. The very top the Internet is pretty much all fiber optic cabling.
The main fiber optic standard this runs most of the top of the Internet is called
SONET. A SONET signalling uses a particular type of optical carrier or kind of the optical equivalent
of T1 called OC lines. The slowest OC line there is the OC1 and it runs at fifty one point eight
five megabits per second.
Now there's a whole bunch of increments that go beyond that for example the OC3 line runs at
exactly three times.
OC1 so it runs at about 155 megabits per second.
Now if you want to see all of the OC carriers, Well here let me put up a chart.
Wow that's a lot of different OC carriers.
Now listen don't panic trying to memorize that entire chart for the Network+ exam.
If you concentrate on the first three: OC1, OC3, and OC12 you'll be perfectly fine for the
Network+. Now there's another column on that chart and that's called the STS. STS is simply the
framing type. For example OC1 uses an STS-1 type frame and that's really all that means.
So if you remember the OC number the STS number's exactly the same.
Pretty easy stuff.
Now one thing that's very interesting that's been going on for about the last five years is that
SONET which has traditionally been the very top of the Internet is starting to fade out a little bit.
It's in competition with something very new and cool called gigabit or 10 gigabit ethernet.
Yep that's right folks the very top of the entire Internet is slowly being replaced with full blown
Point to Point Ethernet and it's really pretty cool.
Now the SONET people don't like that because they want you to keep buying SONET stuff.
So SONET as a way to keep the standard going has actually come out with something called DWDM.
That's Dense Wave Division Multiplexing. DWDM basically uses multiple light colors for one piece of
fiber and can take an existing connection and multiply it by as much as 150 times.
So you can take any of these OC carriers and just by plugging new boxes into the end can kick it up
times up to 150.
So that's when you DWDM it really still is a SONET line.
But it's SONET on steroids.
OK.
So for the Network+ the big thing I want you to memorize more than anything else are those first
three OC lines.
Make sure you know the speeds.
And just remember all you have to do is remember fifty one point eight five megabits per second and
multiply it by the OC number and you'll get the answer right on the test.