networking queestions
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Category: GATE Technical Discussions
Forum Name: GATE CS
Forum Discription: General Technical Discussions, Queries, doubts etc. for GATE in CS.
URL: http://forum.onestopgate.com/forum_posts.asp?TID=192
Printed Date: 07Feb2025 at 11:51pm
Topic: networking queestions
Posted By: Yogesh
Subject: networking queestions
Date Posted: 02Feb2007 at 6:41pm
1) Suppose you are designing a sliding window protocol for a 1 Mbps point-to-point link to a stationary satellite revolving around the earth at 3 * 10000 Km attitude. Assuming that each frame carries 1 Kb of data, what is the minimum number of bits you need for the sequence number when RWS = 1 (RWS = receiver window size) .
a) 20 bits b) 32 bits c) 5 bits d) 16 bits
2) Compute approximate optimal window size when packet size is 53 bytes, propagation delay is 30 msec and bandwidth is 155 Mbps.
a) 32,000 packets b) 12,000 packets c) 22,000 packets d) 42,000 packets
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Replies:
Posted By: Subhash
Date Posted: 02Feb2007 at 6:46pm
1)
Transmission time : 1Kb / 1Mbps
= 2^10 / 10^6
Now propagation delay is : distance / signal speed
here since sattelite communication is used signal speed is same as speed of light = 3 * 10^8 m/s
Thus the RTT(round trip time) = 2 * propagation delay
Thus total time it takes to complete transmission of one packet is
TotalTime = Transmission time + RTT
Since Sliding window protocol is used number of packets that can be transmitted in TotalTime=
TotalTime / transmission time
from the number of packets you can easily make out the number of bits required in sequence number
2^n >= Number of packets
The same method can be used for second Question.
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