Assume a system uses five protocol layers. If the application program creates a message of 100 bytes and each layer (including the fifth and the first) adds a header of 10 bytes to the data unit, what is the efficiency (the ratio of application layer bytes to the number of bytes transmitted) of the system?

66.7 %

Explanation:

If the message created by the application layer, is 100 bytes size, and any of the five protocol layers add 10 bytes to the data unit, when transmitted, the packet will have 150 bytes, from which, 50 bytes are overhead bytes.

So, the efficiency (ratio of application layer bytes (excluding the header) to the number of bytes transmitted) of the system is as follows:

E = 100 / 150 = 66.7 %