The Gateway to Computer Science Excellence
First time here? Checkout the FAQ!
x
+1 vote
586 views
If the Sender Window size is 128 using selective repeat ARQ. Then the sequence number of frame to be send after sending 400 th frame is ?
asked in Computer Networks by Loyal (6.6k points) | 586 views
0

In case of GBN

in GBN there is n bits sequence number

then senders window size = 2 n - 1

and receiver windows size  = 1

total sequence number = 2n - 1 + 1   = 2(0 to 2 n- 1 sequences we use)

0
Here in this case available sequence number = 128 + 128 = 256 that's why (0 to 255)

for goback n Available sequence number = 128 + 1 = 129 so (0 to 128)

because sender WS = 2^k - 1 and receiver is 1.

Am i correct ?
0

Na462  yes you are right

+1
in slective repeat : #sequence number = sender ws + receiver ws

                                                             = 128 +128 (since sws=rws)

 total size of sequence number = 256(0-255)

therefore for 4oo frame , we have 400mod 256 =144 answer
+1

 arvin  why not  be 143 ?? as seq no start from "0"

0

sequence number of the frame to be send after sending 400thframes

check the question once.. @magma 

0
got it :p
0
@magma please can you solve it for GBN and tell the answer. using same data!
+1
yeah sure ,

In GBN

No of sequence number = Sender's window size + 1 (receiver window size)

                                          = 128 +1

                                           = 129  [sequences  0 to 128]

No of sequence number consumed after sending the 400 frames  = 400 % 129 = 13

it means  0 to 12 sequences  we used already

after this we send a frame with sequence no : 13

understood ??
0
Yes magma! Perfect, thank you! :)

1 Answer

+3 votes

For selective repeat ARQ, we know that sender window size=receiver window size

and total no number of sequence numbers=2N (where N is the sender window size)

Hence 0-255 would be consumed for sending 256 frames.Next 0-143 would be consumed for sending 144 frames hence total number of frames sent=256+144=400.Hence the sequence number for next frame should be 144.

the sequence no of 400th frame will be 143 

but they are asking 

sequence number of frame to be send after sending 400 th frame is ?

so answer will be 144
 

answered by Loyal (9.4k points)
edited by

Related questions

Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true
49,576 questions
54,182 answers
187,502 comments
71,142 users