Section 3.5

Question 1

This field contains the port number associated with the sending socket for this TCP segment.

Answer 1

Source port number

Question 2

This field contains application data that was written into a socket by the sender of this TCP segment.

Answer 2

Data (or payload).

Question 3

This field contains the index in the sender-to-receiver byte stream of the first byte of that data in the payload carried in this segment.

Answer 3

Sequence number

Question 4

This field contains the index in the byte stream of the next in-order byte expected at the receiver

Answer 4

ACK number field

Question 5

If set, this segment cumulatively ACKs all data bytes up to, but not including, the byte index in the ACK value field of this segment.

Answer 5

ACK bit

Question 6

This field contains the number of available bytes in the TCP receiver’s buffer

Answer 6

Receiver advertised window

Question 7

This field contains the Internet checksum of the TCP segment and selected fields in the IP datagram header

Answer 7

Checksum

Question 8

This field contains the number of bytes in the TCP header.

Answer 8

Header length field

Question 9

Why is it that the receiver sends an ACK that is one larger than the sequence number in the received datagram?

Answer 9

Because the send-to receiver segment carries only one byte of data, and after that segment is received, the next expected byte of data is just the next byte (i.e., has an index that is one larger) in the data stream