Acknowledgement Number in Selective Repeat protocol.

Question

Consider a sliding window protocol that uses Selective Repeat , the sender sliding window size is 32 .
The sequence number of the frame to be sent after sending 200 frames ______
After receiving first 100 frames the acknowledgement number that is piggybacked by the receiver along with data frame  is _______

Answer 1

In selective Repeat Protocol:
Sender window size = 2^n-1 where n is the number of bits in sequence Number field
now, given that WS = 32
So, 2^n-1 =32
So ,n=6bits
So, we have 64 sequence numbers available(0...to .....63)
Now, to send 200 frames, it has to wrap around because of limited sequence numbers
0 to 63 --->64 frames are sent
again 0...to......63----->64+64=128 frames are sent
0----to-----63 ---->128+64 = 192 frames are
for 193th frame seq number is again 0 hence for 200th frame seq number. will be 7 after this seq number. is 8

2. Now, after sending 100 frames
0 to 63--->for 64 frames
0 to 35 ---> 64 + 36 = 100th frame are sent
so ack number of 100th frame = 36

Comments

no actually i was talking in generic sense...here since nothing is mentioned we can assume for every packet sent we are recieving acknowldegements..so here, there will be no out of order packets!!

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and if u really want to use GBN here then use like SR sending acknowledgements fr every frame not cumultative..then asnwer would remain same...else no use of GBN

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alright..:-)