Sliding Window Protocol

Question

Assume that SWP is designed for a 1mbps point to point link to the moon which has 1 way latency(delay) of 1.25sec Assuming that each frame carry 1KB of data, find

1. number of sequence number required 

2. number of bits required to represent sequence number.

for 1st question i got ans 306.17, is it accepted or we have to round it as 307

plz clarify 

Comments

i got 312.5 so, 313 and for that 9 bit req ??

Answer 1

no of seq no = no of window size = n

n = tx+2tp / tx

tx = 8 * 10^-3 / 10^-6 = 8 ms

tp = 1250 ms

so, n = (2500+8) / 8 = 313.5 so,314 0r 313

no of bits = ceil(log 313) = 9 .

Answer 2

Optimal window size=((1.25*2)*10^6)/10^3 = 312.5

10 bits for selective repeat protocol  since window size here is

2^n-1 .[ 2^(n-1)=312.5   n=log₂[2*312.5] = 10 bits]

9 bits for Go back n protocol.

[2^n - 1 = 312.5   ,2^n  = 313.5   ,n =ceil(log₂313.5)]