Answer: c. 254
The number of addresses usable for addressing specific hosts in each network is always 2 power N – 2 (where N is the number of rest field bits, and the subtraction of 2 adjusts for the use of the all-bits-zero host portion for network address and the all-bits-one host portion as a broadcast address. Thus, for a Class C address with 8 bits available in the host field, the number of hosts is 254
Class A 0.0.0.0 – 127.255.255.255
Class B 128.0.0.0 – 191.255.255.255
Class C 192.0.0.0 – 223.255.255.255
Class D 224.0.0.0 – 239.255.255.255
Class E 240.0.0.0 – 247.255.255.255
Answer:a.Message
The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media
Answer:c. UDP
DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course, transmission reliability suffers with UDP
d None of the above
Answer: a.Routers
Routers are machines that direct a packet through the maze of networks that stand between its source and destination. Normally a router is used for internal networks while a gateway acts a door for the packet to reach the outside of the internal network