Source Port Address is a 16-bit field that identifies the source port number of the application
program in the host that is sending the segment.
Answer option A is incorrect. This is a 32-bit field that identifies the byte number that the sender of
the segment is expecting to receive from the receiver.
Answer option C is incorrect. This is a 4-bit field that defines the 4-byte words in the TCP header.
The header length can be between 20 and 60 bytes. Therefore, the value of this field can be
between 5 and 15.
Answer option D is incorrect. This is a 32-bit field that identifies the number assigned to the first
byte of data contained in the segment.

Encrypting confidential data stored on the server and performing regular backup will not make the server fault
tolerant.
Fault tolerance is the ability to continue work when a hardware failure occurs on a system. A fault-tolerant
system is designed from the ground up for reliability by building multiples of all critical components, such as
CPUs, memories, disks and power supplies into the same computer. In the event one component fails, another
takes over without skipping a beat.
Answer options A, C, and D are incorrect. The following steps will make the server fault tolerant:
Adding a second power supply unit
Adding one more same sized disk as a mirror on the server implementing cluster servers facility