About Transport Layer -layer 4-

Transcript

1. About Transport Layer
   
   
   - layer 4 -
   Jun 21, 2021 YUMEMI Study Group
   kkeeth @kuwahara_jsri @clown0082
   

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2. About me
   

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3. const my_info = {
   
   
   Name: ‘܂ݪ੟ਔ’,
   
   
   Position: ‘Tech Lead of FET’,
   
   
   Skills: ‘PHP, Node.js, TS, Ruby’,
   
   
   PokemonGO: ‘TL 40’,
   
   
   }
   About me
   

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4. 🙇 Sorry1 … 🙇
   
   
   1. This slide is made in English.
   
   
   2. I’m really bad at infrastructure
   
   
   and networking.
   
   
   Plz feedback for me called
   “Masakari” about my talk !!
   

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5. 🙇 Sorry2 … 🙇
   
   
   NAT, NAPT, Window Control
   will be omitted due to lack of time.
   

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6. 📣 Precondition 📣
   
   
   Physical Layer -> Layer 1
   
   
   Data-Link Layer -> Layer 2
   
   
   Network Layer -> Layer 3
   
   
   Transport Layer -> Layer 4
   

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7. The Role of
   Layer 4
   

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8. Layer 1:
   
   
   Transmission of information to the destination where the
   
   
   cable is connected
   
   
   Layer 2:
   
   
   How data is exchanged within a segment
   
   
   → a state in which signals can be exchanged
   
   
   Layer 3:
   
   
   How data is exchanged between segments(networks)
   
   
   → IP address, Routing
   Previously
   

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9. In other words,
   
   
   The role of actually transferring
   data from computer to computer.
   

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10. The difference between
    
    
    Layers 1-3 and 4-7 💁
    

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11. Layer 4-7
    Differences
    Layer 1-3
    

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12. Layer 4
    Differences
    Layer 1-3
    Data transfer
    (execution unit)
    

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13. Layer 4
    Differences
    Layer 1-3
    Not interested
    
    
    in these
    
    
    ɾData corruption
    
    
    ɾDestination does
    
    
    not exist
    
    
    ɾError occurs
    

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14. Layer 1-3
    Differences
    All I know is that the packets
    reach the destination
    Layer 4-7
    

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15. Layer 1-3
    Differences
    Layer 4
    Perform necessary
    processing for transfer
    or received data
    Layer 4-7
    

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16. About the role of Layer 4 💁
    

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17. The role of layer 4
    Flow Control
    Error Recovery
    (acknowledgement)
    Identifying
    Applications
    
    
    (with Port Number)
    Sequence Number
    

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18. Error Recovery
    
    
    (Acknowledge)
    

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19. Acknowledgement
    A B
    data
    acknowledgement
    

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20. Error Recovery
    A B
    data
    ×
    data
    acknowledgement
    re-send
    

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21. Flow Control
    

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22. Flow Control
    A B
    send lots of data
    now processing…
    

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23. Flow Control
    A B
    send lots of data
    I can't keep up
    with the processing,
    over
    fl
    ow💦
    

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24. Flow Control
    A B
    acknowledgement
    
    
    free space: 2
    

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25. Flow Control
    A B
    acknowledgement
    
    
    free space: 0
    ×
    

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26. Identity Applications
    
    
    (with Port Number)
    

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27. Identifying Applications
    A B
    data
    NIC
    What data is this ?🤔
    

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28. Identifying Applications
    A B
    data
    NIC
    2000 3000 4000
    

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29. Identifying Applications
    A B
    data
    NIC
    2000 3000 4000
    Communication between applications
    
    
    This is called “end-to-end”
    

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30. about “Sequence Number”
    later 💁
    

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31. The role of layer 4
    Flow Control
    Error Recovery
    (acknowledgement)
    Identifying
    Applications
    
    
    (with Port Number)
    Segment
    
    
    (with Sequence Number)
    Reliable transmission 🤝
    
    
    To achieve this, we need …
    

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32. Two Protocols for Control
    TCP UDP
    

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33. TCP
    

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34. Connection, Segment
    

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35. Connection
    The road of data that is exchanged
    between applications is called a connection.
    
    
    The communication path created by TCP
    
    
    is called a virtual communication path.
    

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36. What's the point?🤔
    

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37. Connection
    To communicate reliably and ef
    fi
    ciently
    
    
    To exchange con
    fi
    rmations in advance
    
    
    To make sure that others will con
    fi
    rm
    

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38. Connection
    To communicate reliably and ef
    fi
    ciently
    
    
    To exchange con
    fi
    rmations in advance
    
    
    To make sure that others will con
    fi
    rm
    This is called
    
    
    “Establishing a connection”
    

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39. A kind of “hello ὸ🤙" protocol
    we often use 😆
    

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40. TCP Header
    

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41. TCP Header
    4PVSDFQPSUOVNCFS
    %FTUJOBUJPOQPSUOVNCFS
    
    4FRVFODFOVNCFS
    
    "DLOPXMFEHFNFOUOVNCFS
    
    %BUBP
    ff
    TFU
    3FTFSWF
    $POUSPMCJUT
    XJOEPX
    
    $IFDLTVN
    &NFSHFODZQPJOUFS
    
    0QUJPOT
    ※ numbers are bits
    

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42. TCP Header
    4PVSDFQPSUOVNCFS
    %FTUJOBUJPOQPSUOVNCFS
    
    4FRVFODFOVNCFS
    
    "DLOPXMFEHFNFOUOVNCFS
    
    %BUBP
    ff
    TFU
    3FTFSWF
    $POUSPMCJUT
    XJOEPX
    
    $IFDLTVN
    &NFSHFODZQPJOUFS
    
    0QUJPOT
    ※ numbers are bits
    We can remember it as 20 octets 👍
    

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43. TCP Header
    4PVSDFQPSUOVNCFS
    %FTUJOBUJPOQPSUOVNCFS
    
    4FRVFODFOVNCFS
    
    "DLOPXMFEHFNFOUOVNCFS
    
    %BUBP
    ff
    TFU
    3FTFSWF
    $POUSPMCJUT
    XJOEPX
    
    $IFDLTVN
    &NFSHFODZQPJOUFS
    
    0QUJPOT
    ※ numbers are bits
    

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44. Control bits
    U
    
    
    R
    
    
    G
    A
    
    
    C
    
    
    K
    P
    
    
    S
    
    
    H
    R
    
    
    S
    
    
    T
    S
    
    
    Y
    
    
    N
    F
    
    
    I
    
    
    N
    

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45. 3 Way Handshake
    

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46. 3 Way Handshake
    A B
    SYN
    ACK
    SYN + ACK
    

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47. A kind of “hello ὸ🤙" protocol
    we often use 😆
    

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48. Connection close
    A B
    FIN + ACK
    ACK
    ACK
    FIN + ACK
    

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49. MSS
    

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50. MSS, MTU
    MSS(Max Segment Size)
    
    
    MTU(Max Transmission Unit)
    Ethernet
    Header
    
    
    (14)
    IP Header
    
    
    (20)
    TCP
    Header
    
    
    (20)
    Payload
    
    
    (TCP Segment)
    
    
    (0ʙ1460)
    F
    
    
    C
    
    
    S
    
    
    (4)
    ※ numbers are octets
    MSS
    MTU
    

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51. Sequence Number
    

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52. Sequence Number
    MSS(Max Segment Size)
    
    
    MTU(Max Transmission Unit)
    Ethernet
    Header
    
    
    (14)
    IP Header
    
    
    (20)
    TCP
    Header
    
    
    (20)
    Payload
    
    
    (TCP Segment)
    
    
    (0~1460)
    F
    
    
    C
    
    
    S
    
    
    (4)
    ※ numbers are octets
    MSS
    MTU
    If the data is long,
    
    
    split it up and send it.
    

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53. Sequence Number
    MSS(Max Segment Size)
    
    
    MTU(Max Transmission Unit)
    Ethernet
    Header
    
    
    (14)
    IP Header
    
    
    (20)
    TCP
    Header
    
    
    (20)
    Payload
    
    
    (TCP Segment)
    
    
    (0ʙ1460)
    F
    
    
    C
    
    
    S
    
    
    (4)
    ※ numbers are octets
    MSS
    MTU
    The order of the data is important,
    so assign a number to it.
    
    
    This number is called Sequence Number.
    

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54. 3 Way Handshake
    A B
    SYN
    ACK
    SYN + ACK
    MSS
    
    
    desicion
    

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55. Well Known Port
    

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56. Well Known Port
    A B
    data
    NIC
    2000 3000 4000
    Numbers 1 to 1023 are called
    well known ports.
    
    
    * These numbers cannot be
    used.
    

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57. Well Known Port number
    1PSU
    /VNCFS
    "QQMJDBUJPO
    '51EBUB
    '51DPOUSPM
    5&-/&5
    4.51
    %/4
    %)$1TFSWFS
    %)$1DMJFOU
    1PSU
    /VNCFS
    "QQMJDBUJPO
    5'51
    )551
    101
    4/.1SFRVFTU
    4/.1USBQ
    )5514
    3*1
    

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58. UDP
    

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59. TCP
    A B
    SYN
    ACK
    SYN + ACK
    

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60. UDP
    A B
    

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61. broadcast(TCP)
    A N
    N
    N
    3 Way Handshake
    

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62. broadcast(TCP)
    A N
    N
    N
    segment for each destination,
    
    
    acknowledgement
    

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63. broadcast(TCP)
    A N
    N
    N
    segment for each destination,
    
    
    acknowledgement
    TCP can't send without knowing the destination,
    
    
    so it can't broadcast 😫
    

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64. broadcast(UDP)
    A N
    N
    N
    Just send a single piece
    
    
    of data 👍
    

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65. broadcast(UDP)
    A N
    N
    N
    Since there is no con
    fi
    rmation,
    
    
    it is assumed that high-speed
    

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66. broadcast(UDP)
    A N
    N
    N
    Real-Time communication, Video distribution,
    Broadcasting application, etc.
    

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67. UDP
    A B
    Real-Time communication, Video distribution,
    Broadcasting application, etc.
    

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68. UDP Header
    

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69. UDP Header
    4PVSDFQPSUOVNCFS
    %FTUJOBUJPOQPSUOVNCFS
    
    -FOHUI
    $IFDLTVN
    
    ※ numbers are bits
    

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70. There are many more, so
    check them out 💁
    

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71. View Slide