# Question (a) (5 pt.) The Ethernet (CSMA/CD) alternates between contention intervals and successful transmissions. Assume a 100 Mbps Ethernet over 1 km cable with signal speed of 200,000 km/sec. • What is the worst-case collision detection time? If the average number of contention slots before a successful transmission is 4, then what should be the average frame size to achieve an efficiency of 50%. (b) (15 pts.) ALOHA. Assume for simplicity that each transmitted packet in a slotted Aloha system is successful with some fixed probability p. New packets are assumed to arrive at the beginning of a slot and are transmitted immediately. If a packet is unsuccessful, it is retransmitted with probability qr in each successive slot until successfully received. Find the expected delay T from the arrival of the packet until the completion of its successful transmission. (c) (5 pt.) Suppose nodes A, B, and C each attach to the same broadcast LAN (through their adapters). If A sends thousands of IP datagrams to B with each encapsulated frame addressed to the MAC address of B, will C's adapter process these frames? If so, will C's adapter pass the IP datagrams in these frames to the network layer C? How would your answers change if A sends frames with the MAC broadcast address? (d) (5 pt.) Consider Ethernet CSMA/CD algorithm. After the fifth collision, what is the probability that a node chooses K=4? The result K=4 corresponds to a delay of how many seconds on a 10Mbps Ethernet? Hint: NIC waits K:512 bit times.

AAIU6W The Asker · Computer Science

Transcribed Image Text: (a) (5 pt.) The Ethernet (CSMA/CD) alternates between contention intervals and successful transmissions. Assume a 100 Mbps Ethernet over 1 km cable with signal speed of 200,000 km/sec. • What is the worst-case collision detection time? If the average number of contention slots before a successful transmission is 4, then what should be the average frame size to achieve an efficiency of 50%. (b) (15 pts.) ALOHA. Assume for simplicity that each transmitted packet in a slotted Aloha system is successful with some fixed probability p. New packets are assumed to arrive at the beginning of a slot and are transmitted immediately. If a packet is unsuccessful, it is retransmitted with probability qr in each successive slot until successfully received. Find the expected delay T from the arrival of the packet until the completion of its successful transmission. (c) (5 pt.) Suppose nodes A, B, and C each attach to the same broadcast LAN (through their adapters). If A sends thousands of IP datagrams to B with each encapsulated frame addressed to the MAC address of B, will C's adapter process these frames? If so, will C's adapter pass the IP datagrams in these frames to the network layer C? How would your answers change if A sends frames with the MAC broadcast address? (d) (5 pt.) Consider Ethernet CSMA/CD algorithm. After the fifth collision, what is the probability that a node chooses K=4? The result K=4 corresponds to a delay of how many seconds on a 10Mbps Ethernet? Hint: NIC waits K:512 bit times.
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Transcribed Image Text: (a) (5 pt.) The Ethernet (CSMA/CD) alternates between contention intervals and successful transmissions. Assume a 100 Mbps Ethernet over 1 km cable with signal speed of 200,000 km/sec. • What is the worst-case collision detection time? If the average number of contention slots before a successful transmission is 4, then what should be the average frame size to achieve an efficiency of 50%. (b) (15 pts.) ALOHA. Assume for simplicity that each transmitted packet in a slotted Aloha system is successful with some fixed probability p. New packets are assumed to arrive at the beginning of a slot and are transmitted immediately. If a packet is unsuccessful, it is retransmitted with probability qr in each successive slot until successfully received. Find the expected delay T from the arrival of the packet until the completion of its successful transmission. (c) (5 pt.) Suppose nodes A, B, and C each attach to the same broadcast LAN (through their adapters). If A sends thousands of IP datagrams to B with each encapsulated frame addressed to the MAC address of B, will C's adapter process these frames? If so, will C's adapter pass the IP datagrams in these frames to the network layer C? How would your answers change if A sends frames with the MAC broadcast address? (d) (5 pt.) Consider Ethernet CSMA/CD algorithm. After the fifth collision, what is the probability that a node chooses K=4? The result K=4 corresponds to a delay of how many seconds on a 10Mbps Ethernet? Hint: NIC waits K:512 bit times.