Why packet switching is a big deal...
Looking at the packet switching demo, it didn't really explain why using packet switching to move data around the Internet is such a good thing. So here's a little analogy I thought of that made more sense to me!
Imagine I want to send a ten page paper document from DC to New York. In days past, the fastest way might have been to put in on a train to be collected at the other end. I would send the whole document as one, but if the train or the track had a problem, the document would never arrive.
Using packet switching, I split the ten page document into ten separate pages and put them in ten numbered envelopes. I give them to the mail room, and ask them to get them to the destination as fast as possible using the road network which is cheaper. The mail room gives them to several different carriers which all take them on their trucks to New York. As they all make their way there they often change direction as they hit traffic or an accident until they eventually arrive.
When the mail room at the other end receives the document, it realizes envelope eight is missing, so they request a new copy and it is sent again. Once all 10 pages have been delivered, they are re-assembled in the correct order, and you have the whole document again, ready for the recipient.
They key to all this is that sending it by rail meant you had a SINGLE point of failure. If the train couldn't get there, nor could your document. In the same way, if the phone line was busy or broken at any point, you couldn't make the call. With the Internet, there should be no single point of failure (in truth, there are some vulnerabilities, but it is nevertheless much more robust) - if one route is blocked, we can use another.
Until recently, a lack of sufficient network capacity and reliability meant packet switching was fine for data, but not suitable for making voice calls. However, as these two things have improved, it has been possible to use the Internet to make phone calls (known as Voice over IP or VoIP.) Just as trains were replaced by cars and trucks, so the Internet will one day replace phone systems as the main way to make a call anywhere in the world.
Imagine I want to send a ten page paper document from DC to New York. In days past, the fastest way might have been to put in on a train to be collected at the other end. I would send the whole document as one, but if the train or the track had a problem, the document would never arrive.
Using packet switching, I split the ten page document into ten separate pages and put them in ten numbered envelopes. I give them to the mail room, and ask them to get them to the destination as fast as possible using the road network which is cheaper. The mail room gives them to several different carriers which all take them on their trucks to New York. As they all make their way there they often change direction as they hit traffic or an accident until they eventually arrive.
When the mail room at the other end receives the document, it realizes envelope eight is missing, so they request a new copy and it is sent again. Once all 10 pages have been delivered, they are re-assembled in the correct order, and you have the whole document again, ready for the recipient.
They key to all this is that sending it by rail meant you had a SINGLE point of failure. If the train couldn't get there, nor could your document. In the same way, if the phone line was busy or broken at any point, you couldn't make the call. With the Internet, there should be no single point of failure (in truth, there are some vulnerabilities, but it is nevertheless much more robust) - if one route is blocked, we can use another.
Until recently, a lack of sufficient network capacity and reliability meant packet switching was fine for data, but not suitable for making voice calls. However, as these two things have improved, it has been possible to use the Internet to make phone calls (known as Voice over IP or VoIP.) Just as trains were replaced by cars and trucks, so the Internet will one day replace phone systems as the main way to make a call anywhere in the world.
