Circuit Switching and Packet Switching – CompTIA Network+ N10-006 – 1.4

There are two categories of network communication that we’ve used through the years. In this video, you’ll learn about circuit switching and packet switching, and you’ll learn which technologies fall under these two categories.

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Two connection types that are used whenever we send data from one place to the other– we have circuit switching and packet switching. And in this video, we’ll look at these two and see what technologies we’re using today to take advantage of these two different mechanisms. With circuit switching, we are building a connection between different locations so that we can then send data over those lines.

Things like a phone call use circuit switching. We’re picking up the phone, we’re dialing a number, we’re connecting to that site, and we’re sending data. We’re not able to talk to anyone else or make any other phone calls until we hang up with that connection. And then we establish a new circuit to someone else.

An important consideration with circuit switching technologies is once you build that circuit, it’s in place until you tear it down. Even if you’re not sending data over that connection, the circuit is still in place, and those two sides are connected. And if you’re only sending data during the day and nothing’s going across the link at night, then it’s certainly a waste of resources. And that’s one of the challenges with circuit switching.

But the connection is always there. And it’s yours. You can use that connection anytime you’d like. It’s one that nobody else can take advantage of using. It’s something that is also generally a guaranteed amount of bandwidth, because you built a circuit between those two locations, and you can put whatever you would like over that link.

Common circuit switch networks are things like the telephones that we use. The plain old telephone service, or POTS lines, or PSTN– the public switch telephone network– those are effectively the same thing. Of course if you lease a connection, those are circuit switch. So a T1, E1, T3, or E3 type connection is certainly going to be used as circuit switch, where we build the connection, and it’s always going to be there.

ISDN is a bit of an upgrade from the telephone. But it is still dialing a phone number and creating a circuit. And that is what you’re going to send the data over an ISDN network.

Packet switching is how we think of networking today. We take our data, we put it into a wireless network, or a wired network, and we send the traffic on its way, and it finds its way to its destination. This might be data, it might be video, it might be voice– doesn’t matter. We’re sending this data out over the network and it’s finding its way and switching based on what’s in the packet. Usually this media is shared.

We have many people sharing a connection to the internet. Maybe the internet links themselves are shared between locations. That way when we’re not using the connection, someone else could certainly be using exactly that connection. In this regard, the internet service providers generally charge us based on how much bandwidth we’re going to use. And if we want to pay more money, we will have more bandwidth available to us than someone who perhaps pays less money every month.

Common packet switching technologies are the SONET, the ATM networks of today, DSL links, frame relay, MPLS, the cable modems that we might have in our business or at home, satellite connections, wireless, and many of the other local area network based technologies. As you could imagine, it’s common to see the older circuit switch networks being phased out. And everyone migrating to the faster and much more flexible packet switch networks.