I am starting a class for school. It’s a business computer networking course and we’re focusing on history of the internet (ARPANet, etc) right now. Our textbook keeps taking about packet-switching but the explanations are never fleshed out enough. It’s hidden behind CS vocabulary I don’t understand. Any help?
In: Technology
Information is broken down into bite-sized pieces and sent to the other person. That’s it.
Instead of sending a box with a book, you send each page in a letter. Even if a few go missing, the receiver probably has enough information to keep the conversation going. Computers can break down the “book” into “pages” and reassemble them lighting-quick, so when there’s a problem, the receiver can say “resend packets 1123, 6590, and 10258” instead of “send the book again.”
Edit: internet speeds used to be fucking SLOW. Being able to resend only a few pages rather than the book was a HUGE advantage.
Before packet-switching we had circuit switching. In circuit switching a dedicated signal path is established between distant ends. This is burdensome if lots of connections need to be established as there would need to be enough dedicated lines at some choke point to support them all. The benefit is you can send data along the connection as a long continuous stream and not need to add any identifying information as the sender and receiver are the only nodes on the connection.
Packet switching lets individual connections share the same dedicated line by grouping the data in packets and identifying which connection they belong to so they can be routed like mail.
It’s from the long ago history of telephones.
With the very first telephones, you’d get a phone, and a small number of your other millionaire buddies would also get a phone. To call Buffy down the road, your servant would plug your phone into the wire that went to Buffy’s house.
Pretty soon, the obvious flaw (everyone needs a wire to everyone) was obvious, and they made “telephone switches”. Now, one person’s servant was called an operator and would sit at a “switch”. When you wanted Buffy, your servant would get the attention of the operator (by cranking a little crank which would ring a bell at the switch). The operator would make a little patch connection between your line and Buffies.
This means that yes, you had a unique line all of your own that went to the switch, and so did Buffy.
The key is that during your call, there’s essentially a wire running from your house all the way to Buffy’s.
With packet switching, it’s like you have a couple of wires, going to a couple of the switches, and the switches are all connected to together. And now they are called routers, because of course they are. And when you talk, every little bit of sound is called a packet gets a little address on it and gets sent on whatever router makes the most sense right at that moment. The packets all flow from one router to another, until they end up at Buffy’s house.
A fun annecdote about circuit (telephone-like) and packet (internet-like) switching from the early days. At one of the early demos of packet switching, people from Bell Labs, the telephone people, who had spent decades perfecting and optimizing circuit switching, got to see the new packet-switch equipment (for internet, they didn’t do phoen calls on the internet then).
And they were absolutely delighted to see that during the demo, the packet switch equipment failed. “See!” they cackled, “this new thing is bad, and our stuff that we know better is awesome, and we shouldn’t waste any time on that internet thing”.
Latest Answers