Question

Suppose a host has a 5-MB file that is to be sent to another host. The file takes 1 second of CPU time to compress 50%, or 2 seconds to compress 60%. • Calculate the bandwidth at which each compression option takes the same total compression + transmission time. • Explain why latency does not affect your answer.

Answer 1

a) If we don't have ant compression then obviously the total time will be = 5MB/bandwidth as the size of the file is 5MB.

Now, bandwidth is given by = reduced sized of the file after compression/ time taken for the compression.

Now, if we do 50% compression then the size of the file becomes = 2.5 MB

Therefore, bandwidth = 2.5/1 sec = 2.5 MB/sec

Now, if we do 60% compression then the size of the file becomes = 3 MB

Therefore, bandwidth = 3/2 sec = 1.5 MB/sec

b) Latency doesn't affect the answers as if we take the uncompressed version of the file then the transmission will be equal to the compressed version of the file.