Circuit Switching vs. Packet Switching

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Del curso dictado por Princeton University

Networks Illustrated: Principles without Calculus

43 calificaciones

Princeton University

Networks Illustrated: Principles without Calculus

43 calificaciones

What makes WiFi faster at home than at a coffee shop? How does Google order its search results from the trillions of webpages on the Internet? Why does Verizon charge $15 for every GB of data we use? Is it really true that we are connected in six social steps or less? These are just a few of the many intriguing questions we can ask about the social and technical networks that form integral parts of our daily lives. This course is about exploring the answers, using a language that anyone can understand. We will focus on fundamental principles like “sharing is hard”, “crowds are wise”, and “network of networks” that have guided the design and sustainability of today’s networks, and summarize the theories behind everything from the social connections we make on platforms like Facebook to the technology upon which these websites run. Unlike other networking courses, the mathematics included here are no more complicated than adding and multiplying numbers. While mathematical details are necessary to fully specify the algorithms and systems we investigate, they are not required to understand the main ideas. We use illustrations, analogies, and anecdotes about networks as pedagogical tools in lieu of detailed equations. All the features of this course are available for free. It does not offer a certificate upon completion.

De la lección

Routing Traffic through the Internet

It is hard to overstate the impact that the Internet has had on society. In this lesson, we will overview the fundamental concepts behind the way the Internet is designed. We will also take a look at routing, which is the process of determining how packets of information are transported.

Conoce a los instructores

Christopher Brinton
Lecturer
Electrical Engineering
Mung Chiang
Professor
Electrical Engineering

So let's return now to their discussion of circuit switching versus packet switching.

So, the debate between the two runs far and deep.

There, there's a lot of different comparisons that have been made, and so we

just want to understand the, the main ones, the main pros and cons to each.

So, for circuit switching, there's one main

advantage and that is the guarantee of quality.

Right.

So you can guarantee under circuit switching,

you can guarantee at given amount of performance.

Given amount of

[INAUDIBLE]

how many bits per second you're going to get?

Because the, the network is dedicating the

resource to you, right, so for whatever resource

you have, you're going to get the entirety of that and be able to have that.

so that's the main thing is that each session has one dedicated circuit.

Whether that circuit is frequency, time.

Or codes as we had said is still dedicated

and the throughput and the delay performance will not change.

Under packet switching that's

not true because we're sharing all the network resources.

So packet switching is what we call best effort service.

that's what it calls it says, we're going to

do the best that we possible can to make

sure that your packet gets there with a

certain throughput, but there's no guarantees that's going to happen.

And links get congested, messages arrive out of order and so on.

So there's a lot of things in packet switching that can

affect the performance and you know, that's, that's not, that, that's not

going to, packet switching can not guarantee a performance within a

given bound so that's one of the downsides of packet switching.

Now, on the other hand, packet switching has a few advantages.

the first one, we'll look at two of the

advantages the first one is ease of connectivity, right?

So you don't really need to allocate the network resources first, right?

So.

You don't have to under circuit switching right, if you had

a link or something you would need to set up the session

on the link, right, in time, right, so you have to say, okay, well now, you're

going to have the session talking to this

receiver for this amount of time here, right?

And for that time it's going to be yours.

So you have to do session establishment.

Under packet switching you don't have to do,

everybody sends their packets right through to the network.

And then the network deals with the ordering and re-ordering.

So again transmit at will and protocols need to be followed 'cuz your

devices have to follow the network protocols where IP, depending up on what

layer we're at, which is something we'll talk about more in the next lecture.

Then, the third main, one, there advantage, for the packets

[UNKNOWN],

second advantage of packets distribution, the third comparison point.

First one, guaranteed quality, second one, ease

of connectivity, the third one is scalability.

Yeah, this is the main one we're going to look at.

you could support under Packet Switching, a

really large number of diverse sessions, right, and,

a way you achieve, scalability, is through having

a really efficient, means of doing the switching.

And so packets switching usually happens to have high efficiency for two reasons.

The first one is statistical multiplexing and the second one is resource pooling.

And we're going to look at both of these in detail in just a second.

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