Computer Networks — Test 11

Correct Answer: D. D. It manages the routing tables and responsible for routing decisions
Explanation: Routing algorithms manage the routing tables according to the traffic in the network and make changes in them. Router makes routing decisions using routing algorithm. The routing algorithms make use of current routing information and are used to make decisions.

Correct Answer: A. A. Ip address
Explanation: IP address is used by the routers to send packets from source to destination. Each packet has a unique IP address of the destination host. Routers make use of these unique numbers to forward the packets to the correct destination. Remaining addresses are used at different layers.

Correct Answer: C. C. Source quench
Explanation: Source quench is an ICMP message. It is used by the router or destination host when they receive data at a rate that they can not handle. Upon receiving the message, the source host should decrease the load until it no longer receives the same message.

Correct Answer: C. C. Routers do not have memory
Explanation: Routers do have memory. Routers use memory just like any computer for processing. And also routers use memory for storing the routing tables. A router can connect networks which are similar.

Correct Answer: A. A. Physical address of the receiver
Explanation: An ARP query packet contains both the physical address and logical address of the sender(router) and logical address of the receiver. This packet is used to acquire the physical address of the destination host. This physical address of the receiver helps the datagram to pass through physical network.

Correct Answer: B. B. Flow label table
Explanation: A router can contain a flow label table if it is capable of supporting flow labels. Flow label helps the router to find the next hop without consulting the routing table. If the router does not supports the flow label then it simply leaves it aside.

Correct Answer: A. A. Network layer
Explanation: Router belongs to network layer in OSI architecture. Routers are mainly used for packet switching between networks. Bridge and switch are data link layer devices. Repeater and hub are physical layer devices. Application gateway is used in application layer.

Correct Answer: D. D. Source routing
Explanation: Generally, the field of destination address contains the final destination address of the packet, but in the source routing the address field is filled by the address of the router which is going to be visited next.

Correct Answer: A. A. True
Explanation: It is true that congestion avoidance is difficult in datagram network. These networks do not reserve the resources in advance and also the router’s capacity can not be known before transmission. These reasons cause the congestion difficult to avoid in datagram network.

Correct Answer: B. B. Distance vector routing
Explanation: Originally, the ARPANET used distance vector routing in it but later it was replaced by link state routing. This is because of the count-to-infinity problem in distance vector routing. Unlike DVR, routing tables in LS routing contain whole topology of the network.