computer network

Question

An upper layer packet is split into 8 frames each of which has 40% chance of arriving damaged.also assume that no error control at Data Link Layer.How many times the message is sent on an average to get the entire message through

a)  24.65   b)13.33 c)59.54   d)20

Answer 1

probability of loss=40%

No transmission = 8 + 0.4 *8 + 0.4 * 0.4 *8 + 0.4* 0.4 * 0.4 *8 +...+infinity

                            =8(1+0.4 + 0.4² + 0.4³ + ....)

                            =8 (1/(1-0.4))

                            =13.33 should be the ans.

Comments

what is the reason of the first 8 in the equation?

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First attempt we send 8 frames  second attempt 0.4 *8 and so on..hope it helps...