Utilisation of the SYN and ACK flags during the three-way-handshake used by TCP

The TCP header, shown in the TCP chapter of Computer Networking: Principles, Protocols and Practice contains several flags, including the SYN and the ACK flags. These two flags play an important role during the establishment of a connection. The three segments below correspond to the three-way handshake that is used to establish a TCP connection.


Acknowledgement numbers

Can you infer the value of the SYN and ACK flags in the three segments below ?

# Length Resumé Status
0 24 bytes <TCP: SEQ: 2250678587, ACK: 0, MSS>  
1 24 bytes <TCP: SEQ: 3164923748, ACK: 2250678588, MSS>  
2 20 bytes <TCP: SEQ: 2250678588, ACK: 3164923749>  

0000  d1cc04d28626a13b  0000000060??7080  
0010  4f900000020405a0                    

0000  ÑÌ.Ò.&¡;....`?p.
0010  O.......        
  • TCP:
    • Source Port: 53708
    • Destination Port: 1234
    • Sequence Number: 2250678587
    • Acknowledgment Number: 0
    • Data Offset: 6
    • Reserved: 0
    • NS: 0
    • CWR: 0
    • ECE: 0
    • URG: 0
    • ACK:
    • PSH: 0
    • RST: 0
    • SYN:
    • FIN: 0
    • Window: 28800
    • Checksum: 20368
    • Urgent Pointer: 0
    • Options: Maximum Segment Size
      • Kind: 2
      • Length: 4
      • Max Seg Size: 1440
0000  04d2d1ccbca4e764  8626a13c60??7080  
0010  4f900000020405a0                    

0000  .ÒÑ̼¤çd.&¡<`?p.
0010  O.......        
  • TCP:
    • Source Port: 1234
    • Destination Port: 53708
    • Sequence Number: 3164923748
    • Acknowledgment Number: 2250678588
    • Data Offset: 6
    • Reserved: 0
    • NS: 0
    • CWR: 0
    • ECE: 0
    • URG: 0
    • ACK:
    • PSH: 0
    • RST: 0
    • SYN:
    • FIN: 0
    • Window: 28800
    • Checksum: 20368
    • Urgent Pointer: 0
    • Options: Maximum Segment Size
      • Kind: 2
      • Length: 4
      • Max Seg Size: 1440
0000  d1cc04d28626a13c  bca4e76550??7080  
0010  4f8c0000                            

0000  ÑÌ.Ò.&¡<¼¤çeP?p.
0010  O...            
  • TCP:
    • Source Port: 53708
    • Destination Port: 1234
    • Sequence Number: 2250678588
    • Acknowledgment Number: 3164923749
    • Data Offset: 5
    • Reserved: 0
    • NS: 0
    • CWR: 0
    • ECE: 0
    • URG: 0
    • ACK:
    • PSH: 0
    • RST: 0
    • SYN:
    • FIN: 0
    • Window: 28800
    • Checksum: 20364
    • Urgent Pointer: 0

Information

Author(s) Olivier Bonaventure
Deadline No deadline
Submission limit No limitation
Category Tags TCP

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