About Transport Layer -layer 4-

Transcript

1. About Transport Layer - layer 4 - Jun 21, 2021 YUMEMI Study Group kkeeth @kuwahara_jsri @clown0082
2. About me
3. const my_info = { Name: ‘܂ݪ੟ਔ’, Position: ‘Tech Lead of FET’, Skills: ‘PHP, Node.js, TS, Ruby’, PokemonGO: ‘TL 40’, } About me
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 !!
5. 🙇 Sorry2 … 🙇 NAT, NAPT, Window Control will be omitted due to lack of time.
6. 📣 Precondition 📣 Physical Layer -> Layer 1 Data-Link Layer -> Layer 2 Network Layer -> Layer 3 Transport Layer -> Layer 4
7. The Role of Layer 4
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
9. In other words, The role of actually transferring data from computer to computer.
10. The difference between Layers 1-3 and 4-7 💁
11. Layer 4-7 Differences Layer 1-3
12. Layer 4 Differences Layer 1-3 Data transfer (execution unit)
13. Layer 4 Differences Layer 1-3 Not interested in these ɾData corruption ɾDestination does not exist ɾError occurs
14. Layer 1-3 Differences All I know is that the packets reach the destination Layer 4-7
15. Layer 1-3 Differences Layer 4 Perform necessary processing for transfer or received data Layer 4-7
16. About the role of Layer 4 💁
17. The role of layer 4 Flow Control Error Recovery (acknowledgement) Identifying Applications (with Port Number) Sequence Number
18. Error Recovery (Acknowledge)
19. Acknowledgement A B data acknowledgement
20. Error Recovery A B data × data acknowledgement re-send
21. Flow Control
22. Flow Control A B send lots of data now processing…
23. Flow Control A B send lots of data I can't keep up with the processing, over fl ow💦
24. Flow Control A B acknowledgement free space: 2
25. Flow Control A B acknowledgement free space: 0 ×
26. Identity Applications (with Port Number)
27. Identifying Applications A B data NIC What data is this ?🤔
28. Identifying Applications A B data NIC 2000 3000 4000
29. Identifying Applications A B data NIC 2000 3000 4000 Communication between applications This is called “end-to-end”
30. about “Sequence Number” later 💁
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 …
32. Two Protocols for Control TCP UDP
33. TCP
34. Connection, Segment
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.
36. What's the point?🤔
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
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”
39. A kind of “hello ὸ🤙" protocol we often use 😆
40. TCP Header
41. TCP Header 4PVSDF
    QPSU
    OVNCFS  %FTUJOBUJPO
    QPSU
    OVNCFS  4FRVFODF
    OVNCFS  "DLOPXMFEHFNFOU
    OVNCFS  %BUB
    P ff TFU  3FTFSWF  $POUSPM
    CJUT  XJOEPX  $IFDLTVN  &NFSHFODZ
    QPJOUFS  0QUJPOT ※ numbers are bits
42. TCP Header 4PVSDF
    QPSU
    OVNCFS  %FTUJOBUJPO
    QPSU
    OVNCFS  4FRVFODF
    OVNCFS  "DLOPXMFEHFNFOU
    OVNCFS  %BUB
    P ff TFU  3FTFSWF  $POUSPM
    CJUT  XJOEPX  $IFDLTVN  &NFSHFODZ
    QPJOUFS  0QUJPOT ※ numbers are bits We can remember it as 20 octets 👍
43. TCP Header 4PVSDF
    QPSU
    OVNCFS  %FTUJOBUJPO
    QPSU
    OVNCFS  4FRVFODF
    OVNCFS  "DLOPXMFEHFNFOU
    OVNCFS  %BUB
    P ff TFU  3FTFSWF  $POUSPM
    CJUT  XJOEPX  $IFDLTVN  &NFSHFODZ
    QPJOUFS  0QUJPOT ※ numbers are bits
44. Control bits U R G A C K P S H R S T S Y N F I N
45. 3 Way Handshake
46. 3 Way Handshake A B SYN ACK SYN + ACK
47. A kind of “hello ὸ🤙" protocol we often use 😆
48. Connection close A B FIN + ACK ACK ACK FIN + ACK
49. MSS
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
51. Sequence Number
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.
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.
54. 3 Way Handshake A B SYN ACK SYN + ACK MSS desicion
55. Well Known Port
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.
57. Well Known Port number 1PSU
    /VNCFS "QQMJDBUJPO  '51
    EBUB  '51
    DPOUSPM  5&-/&5  4.51  %/4  %)$1
    TFSWFS  %)$1
    DMJFOU 1PSU
    /VNCFS "QQMJDBUJPO  5'51  )551  101  4/.1
    SFRVFTU  4/.1
    USBQ  )5514  3*1
58. UDP
59. TCP A B SYN ACK SYN + ACK
60. UDP A B
61. broadcast(TCP) A N N N 3 Way Handshake
62. broadcast(TCP) A N N N segment for each destination, acknowledgement
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 😫
64. broadcast(UDP) A N N N Just send a single piece of data 👍
65. broadcast(UDP) A N N N Since there is no con fi rmation, it is assumed that high-speed
66. broadcast(UDP) A N N N Real-Time communication, Video distribution, Broadcasting application, etc.
67. UDP A B Real-Time communication, Video distribution, Broadcasting application, etc.
68. UDP Header
69. UDP Header 4PVSDF
    QPSU
    OVNCFS  %FTUJOBUJPO
    QPSU
    OVNCFS  -FOHUI  $IFDLTVN  ※ numbers are bits
70. There are many more, so check them out 💁