Answer Happy

QUESTION 14 Which of the following best describes the information that one AS communicates to other AS's via the BGP protocol? It broadcasts a set of policies that neighboring AS's must follow when handling datagrams originating within its own AS. It transmits a data structure that describes the network topology of its AS so that neighboring AS's can use this data to feed to their routing algorithms (e.g. Dijkstra) Olt queries neighboring AS's to see if they can route to a particular destination host once the gateway router receives a datagram destined for that host. It advertises a list of hosts to which it can route datagrams. QUESTION 15 In Software Defined Networking (SDN), how does the remote controller leam about the state of the routing network within its scope? O It doesn't.. SDN uses distributed routing algorithms such as Bellman-Ford. It injects a significant volume of test datagrams between the constituent routers to measure network latencies and congestion. O It synthesizes the network congestions costs reported to it by the individual routers to paint a complete picture. It sniffs datagrams traveling through the network to extract destination IP addresses and then pings those destinations to report when they receive their payloads. . QUESTION 16 Within a single AS, what is meant by hot potato routing? A situation where a router or SDN controller with two gateway options for a datagram leaving the AS will plan a route to the nearest gateway with respect to costs within the AS and without considering subsequent inter-AS costs. The round robin pinging of routers within an AS to determine which ones have gateway access. A situation in which inefficiencies in routing causes a datagram to enter a cycle and revisit routers that it already passed through during the same trip. Oscillations in optimal routing that are introduced when optimal routes get saturated with traffic, causing them to become sub-optimal in future routing calculations. QUESTION 17 At the link layer, what is the purpose of a cyclic redundancy check (CRC)? To help deduplicate frames that are accidentally received twice (e.g., due to no ACK, collision, or multi-path interference) To be used as a hash value to associate an ACK response with a successfully received frame. To help determine whether there are any bit errors in a received frame. To help establish the authenticity of the data in a frame, which helps thwart IP spoofing attacks. QUESTION 18 In what scenario is TDMA (with 10 time slots per round) a more efficient and fair protocol than ALOHA in a multi-access communication channel? Only when there is a single station transmitting O When there are 9 or 10 stations transmitting simultaneously. When there are 2 or 3 stations transmitting simultaneously. When there are significantly more than 10 stations transmitting simultaneously. QUESTION 19 How do stations using a random access protocol for multi-access channels generally recover from a collision? Two stations involved in a collision open a TCP connection so they can align on who transmits next. O A central access point will take over and specify which station may transmit first They implement a randomized backoff period before trying to retransmit. They use TDMA, FDMA or CDMA so that collisions never actually happen.