1.3 The network core

Video presentation: Computer Networks and the Internet: the network core. Core network functions, packet swtiching, circuit switching, the Internet: a network of networks.
Computer networks class.
Jim Kurose
Textbook reading: Section 1.3, Computer Networking: a Top-Down Approach (8th edition), J.F. Kurose, K.W. Ross, Pearson, 2020.
See gaia.cs.umass.edu/kurose_ross for more open student resources.

[@karanpreetsingh5966]

What a heart-melting smile.

[@abdulfaiqkhattak8557]

00:11 The network core operates based on packet switching
02:36 Routing determines the paths taken by packets in a network
04:55 Packets arriving at a router can create a queue if they arrive faster than the router can transmit.
07:11 Packet switching and circuit switching are two different approaches to building a network.
09:36 Circuit switching is inefficient and can only support 10 users at a time
12:00 Packet switching offers statistical multiplexing gain
14:30 The internet is a network of networks.
16:52 The internet is composed of different networks
Crafted by Merlin AI.

[@hantak07]

Thanks professor for the videos, the books contains very well explanation and well resources for enthusiastic people

[@Anonymous-dk5qu]

Thank you so much for these very interesting lectures!

[@soho7799]

14:43 🤣 Thank you for great video :)

[@mrbhutto948]

Very useful lecture.

[@devmahad]

Understanding the core of network

[@KhanhTran-qp5pm]

Thank you!!!

[@omersahar7738]

hey, in the book (8th edition) is says that 640,000 bits / 64 kbps = 10 sec. i don't understand why though.. if i convert the bits to kbytes, i get 80 kbytes , and then the division is 80kb/64kbps = 1.25 sec. can you help me understand which one is true and if the book wrong? thank you

[@imabstrong]

1 kb = 1000 bits which means 640,000 bits / 64 kbps = 640,000 bits / 64,000 bps = 10 sec

[@user-iz7jg7jz7f]

bps stands for bits per second, not bytes per second.

[@wassimhaimoudi]

Bps is the same as bits/sec so when you try to study the expression in terms of dimensions in physics both bit units will be reduced to 1 and the rest is 1/(1/[time]). We are reversing the time twice which results in [time] and after doing the calculations you will get the 10 [time] which is the result you wrote.

[@user-wz7wg8lx2h]

Thak very much for these videos, they help me to a lot to get familiar to the concepts of the book.
I have a question from the book 7th edition. On page 30, line 7, there is this calculation: (1.536 Mbps)/24 = 64 kbps. Why the units of this division don't remain Mbps? The result should be 64 Mbps, isn' it? Thanks in advance.

[@hammadtufailjhujh6542]

how 35 user? Anyine?

[@donnabellevarona5813]

Can i ask how did we get the value of 0.0004 please? 😭 At 12:03

[@royeap3404]

(35Cx)*(0.1^x)*(0.9^(35-x))
substitute [11,35] (x>10 active users) into x and add them all up (can't use the sigma notation here sorry) and you get 0.0004 :)

[@johnbob37774]

If you have taken probability, you learn about something called a Binomial distribution. Testing each person of the 35 to see how many are actively is like flipping a coin 35 times and seeing how many land heads, instead of it being 50/50, in this case, it's 10/90 for success/failure. Calculating the probability is pretty much how user royeap showed before me, except that you can "simplify" the calculation further, instead of calculating P(X > 10) directly, you can instead calculate P(X > 10) = 1 - P(X

[@abdulrahmannight5910]

@@royeap3404 can i ask how do u guys learn doing those calculations?

[@pathikritsyam3687]

@@abdulrahmannight5910 class 11-12 probability course in my country.

[@FortheLoveofAutomation]

In Excel the formula is: 1-BINOM.DIST(10, 35, 0.1, TRUE)
So in this example we want to know the probability of strictly more than 10 users, when there are 35 trials (e.g. total users), the probability of a user is 10% (i.e. 0.1). The bit on the right actually calculates the probability of between 0-10 users (the true gives the cumulative total up to and including 10), and that amount is deducted from 1 to get the probability of 11+ users.

[@user-to5yn6zc4z]

is 35 a fixed value or i can vary

[@thecurious6721]

Thats just an example. You may put as much as you want. Just there will be a queue.

[@keremokumus2834]

07:00 If brits think that they are number one at queueing, just wait until they hear about engineering students at ESOGÜ.

[@itselfintime]

Ah yes, biggest enemy of esogu engineering students, faculty of education bois

[@user-ei9jp4nm3k]

9/7

[@balabalan1846]

- 10 secs

[@lol2309]

how did u get 35 users plz help