Hosts A and B are communicating over a TCP connection, and Host B has already received

from A all bytes up through byte $126.$ Suppose Host A then sends two segments to Host B

back$-$to$-$back. The first and second segments contain $80$ and $40$ bytes of data, respectively. In

the first segment, the sequence number is $127,$ the source port number is $302,$ and the

destination port number is $80.$ Host B sends an acknowledgement whenever it receives a

segment from Host A$.$

a$.$ In the second segment sent from Host A to B$,$ what are the sequence number, source

port number, and destination port number?

b$.$ If the first segment arrives before the second segment, in the acknowledgement of the

first arriving segment, what is the acknowledgement number, the source port number,

and the destination port number?

c$.$ If the second segment arrives before the first segment, in the acknowledgement of the

first arriving segment, what is the acknowledgement number?

d$.$ Suppose the two segments sent by A arrive in order at B$.$ The first acknowledgement is

lost and the second acknowledgement arrives after the first timeout interval. Draw a

timing diagram, showing these segments and all other segments and acknowledgements

sent. $($Assume that there is no additional packet loss.$)$ For each segment in your figure,

provide the sequence number and the number of bytes of data; for each

acknowledgement that you add, provide the acknowledgement number.