TCP acknowledgements

The TCP header, shown in the TCP chapter of Computer Networking: Principles, Protocols and Practice contains an acknowledgement number.


Sequence numbers

A data transfer has started with a three-way handshake that is not shown in this trace. Can you infer the acknowledgements numbers of the two missing segments in the trace below ?

# Length Resumé Status
0 68 bytes <TCP: ACK, PSH, SEQ: 3378592493, ACK: 2477434132>
1 60 bytes <TCP: ACK, SEQ: 2477434132, ACK: 3378592501>
2 67 bytes <TCP: ACK, PSH, SEQ: 3378592501, ACK: 2477434132>
3 60 bytes <TCP: ACK, SEQ: 2477434132, ACK: ??>  
4 69 bytes <TCP: ACK, PSH, SEQ: 3378592508, ACK: 2477434132>
5 60 bytes <TCP: ACK, SEQ: 2477434132, ACK: 3378592517>
6 69 bytes <TCP: ACK, PSH, SEQ: 3378592517, ACK: 2477434132>
7 60 bytes <TCP: ACK, SEQ: 2477434132, ACK: ??>  

0000  600843ca001c063d  200107ab00010000  
0010  000000000000000a  200107ab00030000  
0020  000000000000000c  d1ce04d2c9613aed  
0030  93aaa51450187080  4f94000073647173  
0040  6473710a                            

0000  `.CÊ...= ..«....
0010  ........ ..«....
0020  ........ÑÎ.ÒÉa:í
0030  .ª¥.P.p.O...sdqs
0040  dsq.            
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 8
    • Flow Label LB: 17354
    • Payload Length: 28
    • Next Header: 6
    • Hop Limit: 61
    • Source Address: 2001:7ab:1::a
    • Destination Address: 2001:7ab:3::c
    • Payload: TCP
      • Source Port: 53710
      • Destination Port: 1234
      • Sequence Number: 3378592493
      • Acknowledgment Number: 2477434132
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 1
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20372
      • Urgent Pointer: 0
      • Data: bytearray(b'sdqsdsq\n')
0000  600a94d700140640  200107ab00030000  
0010  000000000000000c  200107ab00010000  
0020  000000000000000a  04d2d1ce93aaa514  
0030  c9613af550107080  4f8c0000          

0000  `..×...@ ..«....
0010  ........ ..«....
0020  .........ÒÑÎ.ª¥.
0030  Éa:õP.p.O...    
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 10
    • Flow Label LB: 38103
    • Payload Length: 20
    • Next Header: 6
    • Hop Limit: 64
    • Source Address: 2001:7ab:3::c
    • Destination Address: 2001:7ab:1::a
    • Payload: TCP
      • Source Port: 1234
      • Destination Port: 53710
      • Sequence Number: 2477434132
      • Acknowledgment Number: 3378592501
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 0
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20364
      • Urgent Pointer: 0
0000  600843ca001b063d  200107ab00010000  
0010  000000000000000a  200107ab00030000  
0020  000000000000000c  d1ce04d2c9613af5  
0030  93aaa51450187080  4f93000073716471  
0040  73640a                              

0000  `.CÊ...= ..«....
0010  ........ ..«....
0020  ........ÑÎ.ÒÉa:õ
0030  .ª¥.P.p.O...sqdq
0040  sd.             
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 8
    • Flow Label LB: 17354
    • Payload Length: 27
    • Next Header: 6
    • Hop Limit: 61
    • Source Address: 2001:7ab:1::a
    • Destination Address: 2001:7ab:3::c
    • Payload: TCP
      • Source Port: 53710
      • Destination Port: 1234
      • Sequence Number: 3378592501
      • Acknowledgment Number: 2477434132
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 1
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20371
      • Urgent Pointer: 0
      • Data: bytearray(b'sqdqsd\n')
0000  600a94d700140640  200107ab00030000  
0010  000000000000000c  200107ab00010000  
0020  000000000000000a  04d2d1ce93aaa514  
0030  ????????50107080  4f8c0000          

0000  `..×...@ ..«....
0010  ........ ..«....
0020  .........ÒÑÎ.ª¥.
0030  ????P.p.O...    
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 10
    • Flow Label LB: 38103
    • Payload Length: 20
    • Next Header: 6
    • Hop Limit: 64
    • Source Address: 2001:7ab:3::c
    • Destination Address: 2001:7ab:1::a
    • Payload: TCP
      • Source Port: 1234
      • Destination Port: 53710
      • Sequence Number: 2477434132
      • Acknowledgment Number:
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 0
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20364
      • Urgent Pointer: 0
0000  600843ca001d063d  200107ab00010000  
0010  000000000000000a  200107ab00030000  
0020  000000000000000c  d1ce04d2c9613afc  
0030  93aaa51450187080  4f95000073716471  
0040  736473710a                          

0000  `.CÊ...= ..«....
0010  ........ ..«....
0020  ........ÑÎ.ÒÉa:ü
0030  .ª¥.P.p.O...sqdq
0040  sdsq.           
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 8
    • Flow Label LB: 17354
    • Payload Length: 29
    • Next Header: 6
    • Hop Limit: 61
    • Source Address: 2001:7ab:1::a
    • Destination Address: 2001:7ab:3::c
    • Payload: TCP
      • Source Port: 53710
      • Destination Port: 1234
      • Sequence Number: 3378592508
      • Acknowledgment Number: 2477434132
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 1
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20373
      • Urgent Pointer: 0
      • Data: bytearray(b'sqdqsdsq\n')
0000  600a94d700140640  200107ab00030000  
0010  000000000000000c  200107ab00010000  
0020  000000000000000a  04d2d1ce93aaa514  
0030  c9613b0550107080  4f8c0000          

0000  `..×...@ ..«....
0010  ........ ..«....
0020  .........ÒÑÎ.ª¥.
0030  Éa;.P.p.O...    
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 10
    • Flow Label LB: 38103
    • Payload Length: 20
    • Next Header: 6
    • Hop Limit: 64
    • Source Address: 2001:7ab:3::c
    • Destination Address: 2001:7ab:1::a
    • Payload: TCP
      • Source Port: 1234
      • Destination Port: 53710
      • Sequence Number: 2477434132
      • Acknowledgment Number: 3378592517
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 0
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20364
      • Urgent Pointer: 0
0000  600843ca001d063d  200107ab00010000  
0010  000000000000000a  200107ab00030000  
0020  000000000000000c  d1ce04d2c9613b05  
0030  93aaa51450187080  4f95000073716473  
0040  716473710a                          

0000  `.CÊ...= ..«....
0010  ........ ..«....
0020  ........ÑÎ.ÒÉa;.
0030  .ª¥.P.p.O...sqds
0040  qdsq.           
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 8
    • Flow Label LB: 17354
    • Payload Length: 29
    • Next Header: 6
    • Hop Limit: 61
    • Source Address: 2001:7ab:1::a
    • Destination Address: 2001:7ab:3::c
    • Payload: TCP
      • Source Port: 53710
      • Destination Port: 1234
      • Sequence Number: 3378592517
      • Acknowledgment Number: 2477434132
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 1
      • RST: 0
      • SYN: 0
      • FIN: 0
      • Window: 28800
      • Checksum: 20373
      • Urgent Pointer: 0
      • Data: bytearray(b'sqdsqdsq\n')
0000  600a94d700140640  200107ab00030000  
0010  000000000000000c  200107ab00010000  
0020  000000000000000a  04d2d1ce93aaa514  
0030  ????????50107080  4f8c0000          

0000  `..×...@ ..«....
0010  ........ ..«....
0020  .........ÒÑÎ.ª¥.
0030  ????P.p.O...    
  • IPv6:
    • Version: 6
    • Traffic Class UB: 0
    • Traffic Class LB: 0
    • Flow Label UB: 10
    • Flow Label LB: 38103
    • Payload Length: 20
    • Next Header: 6
    • Hop Limit: 64
    • Source Address: 2001:7ab:3::c
    • Destination Address: 2001:7ab:1::a
    • Payload: TCP
      • Source Port: 1234
      • Destination Port: 53710
      • Sequence Number: 2477434132
      • Acknowledgment Number:
      • Data Offset: 5
      • Reserved: 0
      • NS: 0
      • CWR: 0
      • ECE: 0
      • URG: 0
      • ACK: 1
      • PSH: 0
      • RST: 0
      • SYN: 0
      • 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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