Consider a distributed denial of service (DDOS) attack, Assume the attacker has compromised a number of broadband connected computers to use as zombie systems. If the ISP provides a maximum uplink data rate of 512 Kbps in ADSL, what is the maximum number of 512-byte ICMP echo request (ping) packets a single zombie computer can send per second? How many such zombie systems would the attacker need to flood a target server in an organization that has a. A Fast Ethernet.
b. A Gigabit Ethernet.

A ) 200 Zombie systems

B ) 200 Zombie systems

Explanation:

maximum uplink data rate : 512 kbps = 512 * 1000 * 8  = 4096000 bits/sec

Determine the number of 512 byte  ICMP echo packets = 512 * 8 = 4096 bits

hence the maximum number of 512-byte ICMP echo request (ping) packets a single zombie computer can send per second = 400 packets/sec

i.e. for 512kbps = 400 packets/sec

Determine the number of Zombie systems that the attacker will need to flood a target server

A) For a fast ethernet

A fast ethernet = 100 mbps

The number of Zombie systems needed = 1 zombie system * 200

and 1 zombie system = 512 kbps

therefore for a Fast ethernet the number of zombies systems needed = 200

B) For A Gigabit Ethernet

same as a fast ethernet system i.e. = 200