suppose A 10 Mbps point-to-point link being set up between the Earth and a new l
ID: 3624303 • Letter: S
Question
suppose A 10 Mbps point-to-point link being set up between the Earth and a new lunar colony. The distance from the moon to the Earth is approximately 242,000 miles, and data travels over the link at the speed of light---186,000 miles per second. The RTT for the link is 2.6 sec. The delay X bandwidth = 26 Mb=3.2 MB.Suppose each image is transferred as a sequence of packets using the sliding window algorithm. Assuming each packet carries 4 KB of data
a. How many packets are outstanding in the link?
b. How many bits would be required for the packet-based sequence number for an optimal sliding widow protocol implementation?
c. How many bits would be required for a byte-offset sequence number like TCP’s?
d. Suppose the link ran at 10 Gbps, would TCP work? Would it fill the pipe? What if the file were 4 GB?
Explanation / Answer
Given data: Point-to-point link capacity =10Mbps The distance from the moon to the Earth= 242,000 miles Data travels over the link at the speed of light =186,000miles per second The RTT of the link =2.6sec Delay*bandwidth=26Mbits =3.2MB Each packet carries data=4KB a) Number of packets is outstanding in the link = (Delay*bandwidth)/ packet data =26Mbits/ (4*1024*8bits/packet) =793.4packets b) Number of bits required for packet-based sequence number using sliding window protocol =793.4*2 =1586.9 2^11 =2048.so, number of bits =11
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