ccna 640-802 s3-12/13@27/791

QUESTION NO: 12
Refer to the following exhibit:

What data structure is described in the exhibit shown above?
A. IP datagram
B. TCP segment
C. Ethernet frame
D. UDP datagram
E. FDDI frame
F. Token Ring frame
G. None of the above
Answer: B
Explanation:
The Figure below illustrates the fields and overall format of a TCP packet.
Twelve fields comprise a TCP packet.

The following descriptions summarize the TCP packet fields illustrated above.
1. SourcePort and DestinationPort-Identifies points at which upper-layer source and
destination processes receive TCP services.
2.
3. Sequence Number-Usually specifies the number assigned to the first byte of data in the
current message. In the connection-establishment phase, this field also can be used to
identify an initial sequence number to be used in an upcoming transmission.
4.
5. Acknowledgment Number-Contains the sequence number of the next byte of data the
sender of the packet expects to receive.
6.
7. Data Offset-Indicates the number of 32-bit words in the TCP header.
8.
9. Reserved-Remains reserved for future use.
10.
11. Flags-Carries a
variety of control information, including the SYN and ACK bits used for connection
establishment, and the FIN bit used for connection termination.
12.
13. Window-Specifies the size of the sender's receive window (that is, the buffer space
available for incoming data).
14.
15. Checksum-Indicates whether the header was damaged in transit.
16.
17. Urgent Pointer-Points to the first urgent data byte in the packet.
18.
19. Options-Specifies various TCP options.
Data-Contains upper-layer information.