Packet switching is a foundational networking concept that replaced circuit switching by breaking data into discrete packets that can travel independently across a network. This approach enables more efficient use of available bandwidth and supports the scalability modern networks require.
Packet Switching
When we originally connected devices together, it looked quite a bit different. We realized that the method that we were using to interconnect these devices wasn't scalable. We needed a new technology that scaled better, that we could interconnect a lot more devices with. So we came up with this idea of packet switching. Let's take a look at what packet switching is.
Really, one of the original forms of electronic communication was the telegraph. We had some sort of telegraph key that we would tap out signals to and relay the message to the other side, and that was just a hard line between two devices.
As we progressed and got phone systems, we started moving into what's called circuit switching. Now, when the phone system first came out, there would be an operator, and you'd call up the operator and then they would connect you to whoever you wanted to communicate with. So there was an actual physical line, and these would slide in from your line into somebody else's line. That's what would interconnect you between you and whoever you're trying to communicate with. Eventually, this was replaced with more automated switching, but the idea of this was still the same.
Circuit switching created a circuit between you and the other device, that you had a phone connecting to another phone, and there would be some sort of routing that would connect you to the proper switches that would then connect you to the phone. There's a physical connection between these devices.
Now, the problem with circuit switching is that you're taking up a whole line just to communicate between two devices. So we furthered the technology by creating multiplexing, or channels. What we see here is that there's a conversation A going on between these two phones, and conversation B going on between these two phones, and a conversation C between these two phones. Now each one of these conversations has a channel, or a moment in time in which they can utilize this link between them. They are each given this moment in time, enough to not interrupt the conversation. So it's happening enough where you can get enough data down it during those moments that the communication seems fluid, seems all like one conversation.
No matter how we tried to compensate for the circuit switch technology, we saw problems with this. So for instance, if two people are having a conversation across the phone, one of the things that we see is that if there is no talking going on, if there's not any talking between these two devices, we still take up that moment in time. So now no one else can connect as long as these two devices are connected.
That's probably actually what we want for a phone call. After all, even if I stop talking, I don't want my call to drop. However, when we're interconnecting devices together like computers, then it's a different story. We don't want to utilize up these lines that whole time, because this traffic that goes back and forth can be a lot or very little, depending on what the needs are with this connection.
Packet switching really allows us to be much more adaptable. So in this case right here, we have a conversation A going on, and it's just a lot of little information going back and forth. So we just have little packets that are being sent back and forth. Conversation C, on the other hand, looks like it's exchanging a lot of data. So we have a lot of communication with C, while B just needs to communicate once in a while. So now each one of these is maintaining some level of communication, and they've established some level of connection, and they're fully utilizing the bandwidth that goes between whatever these networks are at.
Packet switching has a lot of advantages. For instance, this computer, if it's talking to this computer and sending a stream of packets, those packets can take different routes. So one packet may go this route to get there, while the next packet goes a different route. So we find that this creates a lot of efficiency. There's a lot of cost effectiveness that comes into play here. It allows things to be very scalable. We can have a very dynamic network and set it up in a lot of different ways, so it's very adaptable.
Then we also get some reliability out of this, because we can have a lot of different routes. Although in some ways circuit switching can be more reliable, with the newer technology when it comes to packet switching, we've gotten a lot of reliability out of packet switching now.
So the idea behind packet switching is just that we are going to send out messages between devices using one or more of these packets that we're sending back and forth. You'll see me represent packets in a few different ways. Number one is you'll see me represent it as like a letter that's going back and forth — this is just a message. Or you'll see me represent it as what looks like a little more technical, with the layers and the data going across. So you'll see me represent it in both of these ways.
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