A. Givetwo reasons for using layered protocols. (I point) B. A system has an n-layer protocol hierarchy. Applications generate messages of M bytes. At each layer, a header of h bytes is added. What portion of the bandwidth is filled with these headers? (1 point) C. When a file is transferred between two computers, two acknowledgement strategies are possible after the file has been split into packets. In the first one, the packets are individually acknowledged by the receiver, but not the entire file. In the second one, the eatir file is acknowledged when it arives, but not the packets ndividually. Compare the two approaches. (1 point) D. Ethemet and wireless networks (Wi-Fi) have some similanties and some differences. One property of Ethemet is that only one frame at a time can be transmited. Does the 802.11 standard (Wi-Fi) share this property with Ethermet? Justify your answer, 1 point) E. Explain the specifications (or characterstics) of P addresses (length, classes, subnet mask IP address typesetting...).(1 point) F. Consider some subnets with class C addresses Each of them consists of 50 nodes. By optimzing the number of subnets, what subnet mask will be used and what is the mumber of available subnets? (1 point) G. In the OSI layered model. which level do you associate with a switch? Jusify why a switch is related to this layer (1 point)