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QUESTION 19 1 points Save Awe How do stations using a random access protocol for multi-access channels generally recover from a collision? OTwo 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 TOMA, FDMA or CDMA so that collisions never actually happen QUESTION 20 1 points Save A Which of the following is not a true statement regarding MAC addresses? 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 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 A link-layer hardware device (eg. NIC) has a permanent and constant MAC address irrespective of which network it attaches to MAC addresses are used to send data from one node to another within a single subnet

QUESTION 21 1 points Save Awe 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? The switches maintain a set of IP forwarding tables based on a routing algorithm (either distributed or SON) - this will help route X data to Y and X will learn Ys MAC address from the ACK The switches regularly broadcasts the mapping of IP addresses to MAC address to all nodes. X will broadcast an ARP request with Y's IP address to all hosts connected to the swiches. Only the host owning that IP address (ie., Y) will send an ARP response with the MAC address It is impossible for X to leam Y's MAC address using only the IP address. For X to send data to Y, it must know YIP address and MAC address ahead of time