The TCP Timestamp option

The TCP Timestamp option, defined in RFC1323 and described in the TCP chapter of Computer Networking: Principles, Protocols and Practice allows endhosts to exchange timestamp information.


Negotiation of the TCP Timestamp option

Assuming that the server supports the timestamp option, can you predict the value of the TS Echo Reply field in both segments ?

# Length Resumé Status
0 36 bytes <TCP: SYN, SEQ: 2810389303, ACK: 0, MSS, TS>  
1 36 bytes <TCP: ACK, SYN, SEQ: 2100570798, ACK: 2810389304, MSS, TS>  

0000  d20004d2a7832337  0000000090027080  
0010  4f9c0000020405a0  0101080a0004759c  
0020  ????????                            

0000  Ò..Ò§.#7......p.
0010  O.............u.
0020  ????            
  • TCP:
    • Source Port: 53760
    • Destination Port: 1234
    • Sequence Number: 2810389303
    • Acknowledgment Number: 0
    • Data Offset: 9
    • Reserved: 0
    • NS: 0
    • CWR: 0
    • ECE: 0
    • URG: 0
    • ACK: 0
    • PSH: 0
    • RST: 0
    • SYN: 1
    • FIN: 0
    • Window: 28800
    • Checksum: 20380
    • Urgent Pointer: 0
    • Options: Maximum Segment Size
      • Kind: 2
      • Length: 4
      • Max Seg Size: 1440
    • Options: No-Operation
      • Kind: 1
    • Options: No-Operation
      • Kind: 1
    • Options: Timestamps Option
      • Kind: 8
      • Length: 10
      • TS Value: 292252
      • TS Echo Reply:
0000  04d2d2007d342aae  a783233890126f90  
0010  4f9c0000020405a0  0101080a0004759d  
0020  ????????                            

0000  .ÒÒ.}4*®§.#8..o.
0010  O.............u.
0020  ????            
  • TCP:
    • Source Port: 1234
    • Destination Port: 53760
    • Sequence Number: 2100570798
    • Acknowledgment Number: 2810389304
    • Data Offset: 9
    • Reserved: 0
    • NS: 0
    • CWR: 0
    • ECE: 0
    • URG: 0
    • ACK: 1
    • PSH: 0
    • RST: 0
    • SYN: 1
    • FIN: 0
    • Window: 28560
    • Checksum: 20380
    • Urgent Pointer: 0
    • Options: Maximum Segment Size
      • Kind: 2
      • Length: 4
      • Max Seg Size: 1440
    • Options: No-Operation
      • Kind: 1
    • Options: No-Operation
      • Kind: 1
    • Options: Timestamps Option
      • Kind: 8
      • Length: 10
      • TS Value: 292253
      • TS Echo Reply:

Information

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

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