1. How many numbers of addresses are usable for addressing in a Class C network?

a. 256

b. 255

c. 254

d. 258

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

 

 

2. How are the data units at Application layer is called?

 

a. Message

b. Datagram

c. User Datagram

d. Signals

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

 

 

3. What protocol is used by DNS name servers? Justify.

a. TCP

b. SNMP

c. UDP d. It can use any routing protocol

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

 

 

4. Which of the following is used to direct a packet inside an internal networks?

a. Routers     

b. Modem   

c. Gateway    

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