Consider a long-lived $$TCP$$ session with an end-to-end bandwidth of $$1$$ $$Gbps$$ ($$ = {10^9}\,$$ bits-persecond). The session starts with a sequence number of $$1234.$$ The minimum time (in seconds, rounded to the closest integer) before this sequence number can be used again is _______.

Consider an $$IP$$ packet with a length of $$4,500$$ bytes that includes a $$20$$-byte $$IPv$$$$4$$ header and a $$40$$-byte $$TCP$$ header. The packet is forwarded to an $$IPv4$$ router that supports a Maximum Transmission Unit $$(MTU)$$ of $$600$$ bytes. Assume that the length of the $$IP$$ header in all the outgoing fragments of this packet is $$20$$ bytes. Assume that the fragmentation offset value stored in the first fragment is $$0.$$

The fragmentation offset value stored in the third fragment is _______.

The following are some events that occur after a device controller issues an interrupt while process $$L$$ is under execution.

$$(P)$$ The processor pushes the process status of $$L$$ onto the control stack.
$$(Q)$$ The processor finishes the execution of the current instruction.
$$(R)$$ The processor executes the interrupt service routine.
$$(S)$$ The processor pops the process status of $$L$$ from the control stack.
$$(T)$$ The processor loads the new PC value based on the interrupt.

Which one of the following is the correct order in which the events above occur?

A $$32$$-bit wide main memory unit with a capacity of $$1$$ $$GB$$ is built using $$256M\,\, \times \,\,4$$-bit $$DRAM$$ chips. The number of rows of memory cells in the $$DRAM$$ chip is $${2^{14}}.$$ The time taken to perform one refresh operation is $$50$$ nanoseconds. The refresh period is $$2$$ milliseconds. The percentage (rounded to the closest integer) of the time available for performing the memory read/write operations in the main memory unit is __________.