Flow Control and ARQ 3: Go-back-N and Selective-reject ARQs

[@shinigamiraito42]

finally, a video that isn't in hindi ;u;

[@Fiji_water_man]

they been all over youtube lately...

[@michaelbuchler2743]

@@Fiji_water_man So annoying!!!

[@Ha-nz2vy]

@@michaelbuchler2743 hmm its like people speak other languages besides English...who would've thought

[@martinprochazka3714]

Yeah, who would have though that KZbin would even offer you a video in hindi unless you explicitly search for it...

[@johnbarnhart378]

thank you for your service to engineering/it/comp sci students everywhere man

[@onemoretube]

Today (27 May 2020) is exactly 4 year since you posted this video. I'm watching it for my assignment. Thank you!

[@biramanpreetsingh2025]

your way of teaching is simple and effective!!!! Good Job!!! Thanks for sharing !!!

[@invinciblesword9107]

This is a very concise and accurate sliding window explanation! Thank you.

[@floatoss]

At 2:15, won't we have a Frame 2 re-transmission by the sender because the receiver only sends an ACK2 (RR 2), and the sender goes like "okay, the receiver got 0, 1; but he missed a 2". It then shrinks its window, removing the 0 and 1, BUT it still transmits the Frame 2 (F2) that you did not do at 2:20? Also, do we really have the "reject" messages that are sent by the receiver, or do we just have a time-out on the sender side that makes the sender to repeat the transmissions that are in it's current window? I ask this because a few other sources (I am not very sure I believe them, but it is good to clarify I think) do not mention these "reject" messages

[@JacobSchrum]

The sender knows that it already sent Frame 2, and the RR 2 doesn't mean that the transmission of Frame 2 failed, merely that the receiver has not acknowledged it yet. From the sender's perspective, it assumes that RR 2 was sent while its own Frame 2 message was enroute, and until it has evidence to the contrary, it will assume that Frame 2 message could still have been received. If there is a time-out, then the sender will eventually check to see what is going on, but if the receiver rejects a frame as soon as it sees a gap, it can likely get a quicker response, and possibly spare the sender from transmitting a lot of data that will be discarded anyway.

[@floatoss]

​@@JacobSchrumah okay, thanks! This is a bit different than how I have been taught. Could you please also let me know about: 1) the "reject" messages by the receiver? I have not come across such messages specifically for Go-Back-N, only for Selective Repeat. But I can understand the logic behind it. 2) I have been told that there aren't any NAK's in GBN, but that the "time-out" is the only event in which retransmissions can occur, aiding the receiver in getting those lost frames. Even the "poll" message that you mentioned that the sender has the capability to send. I have not come across those. This is making me even more confused because, everything you say also makes logical sense. Of-course I understand that I am newbie, and really want to know the 'standard' way. I would really appreciate if you have a great resource that I can rely on to study this. 3) Does the sender, in GBN, have logic involved in it's side that allows it to keep track of what are the ACK'ed, UNACK'ed, can-transmit packets in it's window? Because when you mention at 2:15 that the sender just sends the frame 3 after the RR2, it makes me believe that there is some state saving going on the sender side to keep this information. Thanks a ton for such a quick response, I really appreciate it! You are a fantastic source to learn Computer Science from :)

[@huwenjie7420]

why isit that there have never been acknowledgements for frame 0?

[@martinprochazka3714]

By acknowledging N you also acknowledge N-1, N-2, ..., 0.

[@MrXskillerx]

I am pretty sure that both algorithms do not work with Reject messages but with Timeouts of the source. Am I wrong?

[@ΑντρέαςΣωτηρίου-π8γ]

this is for data link protocol layer or the transport protocol layer >????

[@amoghrajanna3795]

Thank you very much for the informative video. Much appreciated.

[@nikolasioakimidis3003]

This example is for N=4 right?

[@TheNugass]

if the window size is 3, should it not not send the F1 that ends up failing?

[@huyvole9724]

Hi RR2=ACk2 ?

[@Play4fuNNNNNnn]

i really appreciate your videos. According to this video you shouldve explained the function between the buffer and the ARQ protocolls in a more detailed way.

[@DaywaIker]

Love your videos

[@gayanrukshanthaperera5333]

perfect !! what is the different between those 2

[@Champz2323]

This is pretty lit tbh

[@Kyle-uz1yr]

thanks

[@shishirparajuli1681]

when do the source and the destination agree on the size of the window?

[@bilaljan321]

awesome work. can u please tell is there any difference between Go-Back-N and Go-Back N ARQ both are same things?

[@JacobSchrum]

same

[@bilaljan321]

Thanks sir

[@moehirzalla]

for selective repeat doesn't each frame have its own timer ?

[@JacobSchrum]

For the sender, it is sufficient to base the timeout on the last reply from the receiver. Or were you referring to something else? Perhaps you could clarify.

[@faizanshahansari1193]

Nice video but there is a slight error in go back n since window size is 3 u cannot send f1 until rr3/rr0/rr1 is received..☺️

[@amitmunjal5972]

that is what I thought too......can the author confirm this

[@crafterko]

Still helps

[@hasanshovon3402]

good video

[@12bucukfalandim]

jacob, ADAMSIN!

[@idogilboa]

Thank you! Great video :)

[@TheDefiniteKingHomie]

very nice!

[@ramirocordero5185]

Hi! first of all thanks for the awesome video! Only one question on the Go-Back-N : let's assume that an RR from Reciever gets lost so the Source sends a RR (poll) that also gets lost due to some network error. Does the Reciever have to wait for another Source Timeout and RR(poll) ? Thank you!

[@iremlergun]

awesome! thank you so much:)

[@osmantoplica8912]

amazing thanks!

[@huyvole9724]

Something missing. You need define Window Size!

[@ethendixon4612]

Shouldn't it be 0,1,2 for N=3? Not 0,1,2,3. Please, I need to know for my test lol.

[@MrSkatosakoulas]

Hello sir. Great videos. But that haircut though :P

[@Sabiok]

klaiw

[@stoksc]

thanks

[@wajeehhasan4860]

thanku sir :)

[@DeepakBastakoti]

thnx

[@mrchow3177]

Selctive repeat, not reject..

[@JacobSchrum]

Either: en.wikipedia.org/wiki/Selective_Repeat_ARQ