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Stop & Wait, Go Back N and Selective repeat

NOTE:Coming to packet loss both Go Back N and SR will discard silently  but if the packet is corrupted ,GO BackN discard silently but SR is going to produce NAK.

lucky @luckysunda
29 Dec 2016 07:54 pm

I read somewhere that GBN supports both cumulative and individual ack. Am I wrong??

Shraddha @shraddhagami
29 Dec 2016 09:09 pm

GBN supports cumulative acknowledgemet(not exactly cumulative but cumulative with some modification)

Whenever receiver receive a packet a timer called acknowledgement timer(At receiver side) start and expire. By the time it expire how many ever packet are received in that gap going to send 1 acknowledgement

Time out timer(at sender side)>Ack timer(at receiver side

And Ack timer is not too big or not too small.

lucky @luckysunda
29 Dec 2016 08:53 pm

ya..i agree...SO we can say na that it supports both.

Shivesh Kumar Roy @shiveshroy
30 Dec 2016 05:01 pm

Yes GBN supprts both cumulative as well as Independent Acknowledgement. GBN with independent ACK is different than Stop & Wait protocol as in case of GBN(Even for individual ACK) We use the concept of pipelining. Only different in case of cumulative ACK is that it creates less traffic.

Ashish Kumar Goyal @dashish
21 Jan 2017 12:38 pm

@luckysunda @shraddhagami @shiveshroy

GBN always uses cummulative acknowledgement...

But if the ACK timer is too small then it would have to send a ack for each packet....

so, it uses cummulative ack only but may behave as independent if ACK timer is too small.

Check this for further clarification...

https://youtu.be/ZLtkhsgQp8U?list=PLEbnTDJUr_IegfoqO4iPnPYQui46QqT0j&t=1416

Pls correct if i am wrong...