176 views

We have three stations $P, Q, R$ connected in serial manner. $P$ is connected to $Q$ through a $3Gbps$ fibre optic link and length is $500Km$. $Q$ is connected to $R$ through $60Mbps$ link and length is $15Km$.All the links are full duplex in nature. A file is sent from station $A$ to $C$. Packet size is $1Kb$.We use sliding window protocol such that $\text{SWS=RWS}$. Find the optimal $\text{SWS}$.

• $30$ packets
• $32$ packets
• $28$ packets
• $29$ packets
retagged | 176 views
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what is propagation speed ?
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nothing given in the question about pd.......can u tell by assuming it
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we can find propagation delay .length is given and propagation speed of fiber optic is approx 3*10^8
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Tp for P -> Q and Q->R is same ?
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shivanisrivarshini nothing mentioned in question

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Packet Size must be 1KB
I'm getting 38 though
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@gauravkc even I am getting 38 packets

1Kb = 1 * 1024 * 8 bits = 8192 Bits

SWS (Sender Window Size) = 1+2a or Number of bits in transmission channel (RTT * bandwidth )

Using second

RTT  = transmission time + 2* propgaiton delay

= 8192 / 3 * 10^9 + 8192 / 60 * 10^6 + 2* ( 5* 10^5/ 2*10^8 + 15*10^3/2*10^8)

= 5.29 ms

FIber Optic Velocity ~ 2 * 10^8. ~ 75-80%

SWS = RTT * Bandiwidth ( Taking Min(3Gbps, 50Mbps) )

= 5.29 * 60Mbps = 31.74

~~ 32 Packets.

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I am getting 38 packets using 1+2a

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