The TCP sequence numbers used during the data transfer - [CNP3] Computer Networking : Principles, Protocols and Practice | INGInious

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Author(s)	Olivier Bonaventure
Deadline	No deadline
Submission limit	No limitation
Category tags	tcp

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The TCP sequence numbers used during the data transfer

The TCP header, shown in the TCP chapter of Computer Networking: Principles, Protocols and Practice contains a sequence number. The segments below correspond to the beginning of a TCP connection.

Paste this command into your terminal:

The password to connect is

Sequence numbers

Can you infer the sequence numbers of the two segments that transfer data in the trace below ?

#	Length	Summary	Status
0	24 bytes	`Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: 925123579, Len: 0`
1	24 bytes	`Transmission Control Protocol, Src Port: 1234, Dst Port: 53706, Seq: 3658695655, Ack: 925123580, Len: 0`
2	20 bytes	`Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: 925123580, Ack: 3658695656, Len: 0`
3	22 bytes	`Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: ????, Ack: 3658695656, Len: 2`
4	20 bytes	`Transmission Control Protocol, Src Port: 1234, Dst Port: 53706, Seq: 3658695656, Ack: 925123582, Len: 0`
5	23 bytes	`Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: ????, Ack: 3658695656, Len: 3`
6	20 bytes	`Transmission Control Protocol, Src Port: 1234, Dst Port: 53706, Seq: 3658695656, Ack: 925123585, Len: 0`

0000 d1ca04d2372443fb 0000000060027080
0010 00000000020405a0

0000 ÑÊ.Ò7$Cû....`.p.
0010 ........

Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: 925123579, Len: 0
- Source Port: 53706
- Destination Port: 1234
- Sequence number: 925123579
- Acknowledgment number: 0
- 0110 .... = Header Length: 24 bytes (6)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...0 .... = Acknowledgment: Not set
  - .... .... 0... = Push: Not set
  - .... .... .0.. = Reset: Not set
  - .... .... ..1. = Syn: Set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0
- Options: (4 bytes), Maximum segment size
  - TCP Option - Maximum segment size: 1440 bytes
    - Kind: Maximum Segment Size (2)
    - Length: 4
    - MSS Value: 1440

0000 04d2d1cada1343e7 372443fc60127080
0010 00000000020405a0

0000 .ÒÑÊÚ.Cç7$Cü`.p.
0010 ........

Transmission Control Protocol, Src Port: 1234, Dst Port: 53706, Seq: 3658695655, Ack: 925123580, Len: 0
- Source Port: 1234
- Destination Port: 53706
- Sequence number: 3658695655
- Acknowledgment number: 925123580
- 0110 .... = Header Length: 24 bytes (6)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 0... = Push: Not set
  - .... .... .0.. = Reset: Not set
  - .... .... ..1. = Syn: Set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0
- Options: (4 bytes), Maximum segment size
  - TCP Option - Maximum segment size: 1440 bytes
    - Kind: Maximum Segment Size (2)
    - Length: 4
    - MSS Value: 1440

0000 d1ca04d2372443fc da1343e850107080
0010 00000000

0000 ÑÊ.Ò7$CüÚ.CèP.p.
0010 ....

Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: 925123580, Ack: 3658695656, Len: 0
- Source Port: 53706
- Destination Port: 1234
- Sequence number: 925123580
- Acknowledgment number: 3658695656
- 0101 .... = Header Length: 20 bytes (5)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 0... = Push: Not set
  - .... .... .0.. = Reset: Not set
  - .... .... ..0. = Syn: Not set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0

0000 d1ca04d2???????? da1343e850187080
0010 00000000610a

0000 ÑÊ.Ò????Ú.CèP.p.
0010 ....a.

Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: ????, Ack: 3658695656, Len: 2
- Source Port: 53706
- Destination Port: 1234
- Sequence number: ?
- Acknowledgment number: 3658695656
- 0101 .... = Header Length: 20 bytes (5)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 1... = Push: Set
  - .... .... .0.. = Reset: Not set
  - .... .... ..0. = Syn: Not set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0
- TCP payload (2 bytes)

0000 04d2d1cada1343e8 372443fe50107080
0010 00000000

0000 .ÒÑÊÚ.Cè7$CþP.p.
0010 ....

Transmission Control Protocol, Src Port: 1234, Dst Port: 53706, Seq: 3658695656, Ack: 925123582, Len: 0
- Source Port: 1234
- Destination Port: 53706
- Sequence number: 3658695656
- Acknowledgment number: 925123582
- 0101 .... = Header Length: 20 bytes (5)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 0... = Push: Not set
  - .... .... .0.. = Reset: Not set
  - .... .... ..0. = Syn: Not set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0

0000 d1ca04d2???????? da1343e850187080
0010 0000000061620a

0000 ÑÊ.Ò????Ú.CèP.p.
0010 ....ab.

Transmission Control Protocol, Src Port: 53706, Dst Port: 1234, Seq: ????, Ack: 3658695656, Len: 3
- Source Port: 53706
- Destination Port: 1234
- Sequence number: ?
- Acknowledgment number: 3658695656
- 0101 .... = Header Length: 20 bytes (5)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 1... = Push: Set
  - .... .... .0.. = Reset: Not set
  - .... .... ..0. = Syn: Not set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0
- TCP payload (3 bytes)

0000 04d2d1cada1343e8 3724440150107080
0010 00000000

0000 .ÒÑÊÚ.Cè7$D.P.p.
0010 ....

Transmission Control Protocol, Src Port: 1234, Dst Port: 53706, Seq: 3658695656, Ack: 925123585, Len: 0
- Source Port: 1234
- Destination Port: 53706
- Sequence number: 3658695656
- Acknowledgment number: 925123585
- 0101 .... = Header Length: 20 bytes (5)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 0... = Push: Not set
  - .... .... .0.. = Reset: Not set
  - .... .... ..0. = Syn: Not set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0