Which of the following protocol pairs can be used to send and retrieve e-mails (in that order)?

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 _______.

Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are FALSE with respect to the TCP connection?

I. If the sequence number of a segment is m, then the sequence number of the subsequent segment is always m + 1.
II. If the estimated round trip time at any given point of time is t sec, the value of the retransmission timeout is always set to greater than or equal to t sec.
III. The size of the advertised window never changes during the course of the TCP connection.
IV. The number of unacknowledged bytes at the sender is always less than or equal to the advertised window

Consider the following statements.

I. TCP connections are full duplex
II. TCP has no option for selective acknowledgment
III. TCP connections are message streams