Circuit Switching and Packet Switching – CompTIA Network+ N10-007 – 1.3

There are many different ways to get data from one end of the network to the other. In this video, you’ll learn about some of the popular technologies that use circuit switching and packet switching.

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If we’re setting up a circuit switched network communication, then we’re establishing a connection between two endpoints before we ever send data between those two devices. This is very similar to using your telephone. You dial a phone number, the other end picks up the phone, and after that circuit has then been established, both of you can talk to each other.

Once you have called someone’s number and they pick up the phone and they say hello, the circuit is then established and there is a connection between those two phones that may go through a number of different phone switches in the phone providers network. If you were both going to be on the phone but really not saying anything, the circuit would still be established and you would still be using those resources on the inside of the provider’s phone network. Because you’ve built this circuit between these two telephones, no one else is able to use those resources on the inside of the phone network anyway.

But that might be an advantage to you as well. You may want to be able to bring up a circuit between two remote sites. You don’t want to share capacity with someone else, and you don’t want to have the network unavailable when you’re trying to send data to the other remote site. As we’ve just described, a traditional telephone service is a circuit switched network. We often refer to this as a POTS line, a plain old telephone service, but you might also see it referred to as a PSTN or a public switched telephone network.

Another type of circuit switching network is a T1 or a T3. Outside of the United States, it might be an E1 or an E3. With these types of wide area network connections a circuit is created between two lengths and that circuit will always be there and available between those two connections. Integrated Services Digital network is another good example of circuit switching. An ISDN modem would call another ISDN modem, and just like the telephone, that circuit is always there and available until you hang up that ISDN connection.

Packet switching is where we’re grouping data into packets and sending it across a network. You may be sending a video stream or a voice communication or sending data over that link and you’re sending this information out over a network that is shared with everyone else. So if you’re not streaming videos, someone else could be streaming video over that same network connection. Packet switching also supports qualities of service, so you might have one person that might be able to have a higher priority than someone else on that same packet switched network.

Packet switching would be associated with the network technologies that you probably already heard of, things like SONET or ATM. If you have a DSL connection at your home, that’s a packet switched network. Older frame relay networks and the newer MPLS are also packet switched networks, and cable modem internet connections and satellite connections can also be considered packet switching. And if you’re on a wireless network inside of your home, you’re using a packet switched network.