QUESTION 19 How do stations using a random access protocol for multi-access channels generally recover from a collision? O They implement a randomized backoff period before trying to retransmit. O They use TDMA, FDMA, or CDMA so that collisions never actually happen. O A central access point will take over and specify which station may transmit first. Two stations involved in a collision open a TCP connection so they can align on who transmits next. QUESTION 20 Which of the following is not a true statement regarding MAC addresses? O MAC addresses are used to send data from one node to another within a single subnet. O A link-layer hardware device (e.g., NIC) has a permanent and constant MAC address irrespective of which network it attaches to. There are more possible unique MAC addresses than there are unique IP(V4) addresses; however there are more unique IPV6 addresses than unique MAC addresses. O When sending data to a host in an external network, we can use either the IP address or the MAC address to specify that host in our request. QUESTION 21 Suppose host X wants to send data to host Y and hosts X and Y are located in the same subnet and are only separated by a handful of switches. Further suppose that host X only has the IP address of host Y... how can host X figure out the MAC address of Y so that it can transmit the frame? O The switches regularly broadcasts the mapping of IP addresses to MAC address to all nodes. O X will broadcast an ARP request with Y's IP address to all hosts connected to the switches. Only the host owning that IP address (i.e., Y) will send an ARP response with the MAC address. O It is impossible for X to learn Y's MAC address using only the IP address. For X to send data to Y, it must know Y's IP address and MAC address ahead of time. O The switches maintain a set of IP forwarding tables based on a routing algorithm (either distributed or SDN) - this will help route X's data to Y and X will learn Y's MAC address from the ACK.