Computer Networks — Test 30

Correct Answer: C. C. Router
Explanation: The discarding policy adopted by the routers mainly states that the routers discard sensitive or corrupted packets that it receives, thus controlling the integrity of the packet flow. The discarding policy is adopted as an open loop congestion control technique.

Correct Answer: A. A. Remove after congestion occurs
Explanation: In closed loop congestion control, methods are implemented to remove congestion after it occurs. Some of the methods used are backpressure and choke packet.

Correct Answer: B. B. Backpressure
Explanation: In this closed loop congestion control technique, the congested node propagates in the opposite direction of the data flow to inform the predecessor node to reduce the flow of packets. This is why this technique is called a node-to-node congestion control technique.

Correct Answer: D. D. Virtual circuit networks
Explanation: In Virtual circuit networks, each node knows the upstream node from which a flow data is coming. So, it makes possible for the congested node to track the source of the congestion and then inform that node to reduce the flow to remove congestion.

Correct Answer: C. C. Choke
Explanation: Choke packet is sent by a node to the source to inform it of congestion. Two choke packet techniques can be used for the operation called hop-by-hop choke packet and source choke packet.

Correct Answer: A. A. Exponentially
Explanation: In slow-start algorithm, the size of the congestion window increases exponentially until it reaches a threshold. When it reaches the threshold, it stops increasing and continues sending packets through the threshold window thus preventing congestion.

Correct Answer: B. B. Additively
Explanation: In the congestion avoidance algorithm, the size of the congestion window increases additively until congestion is detected. Once congestion is detected, the size of congestion window is decreased once and then the packets are transmitted to achieve congestion avoidance.

Correct Answer: A. A. Broadcast
Explanation: There is no concept of broadcast address in IPv6. Instead, there is an anycast address in IPv6 which allows sending messages to a group of devices but not all devices in a network. Anycast address is not standardized in IPv4.

Correct Answer: D. D. Anycast address
Explanation: There is an anycast address in IPv6 which allows sending messages to a group of devices but not all devices in a network. Anycast address is not standardized in IPv4.

Correct Answer: A. A. Hop limit
Explanation: The Hop limit value is decremented by one by a router when the datagram is forwarded by the router. When the value becomes zero the datagram is discarded. The field is 8-bits wide, so an IPv6 packet can live up to 255 router hops only.