<>UDP

UDP Is a simplified , There are no redundant agreements .
We can find any one UDP Package analysis :

Including active port number , Destination port number , length , Checksum (Checksum), These four are occupied 32 position , in other words UDP Your head has 32 position
One more Pay Load Refers to the UDP Load data carried .

<>TCP

Then analyze it again TCP Specific content of :

The above is the data packet of three handshakes .
Take a closer look ,sequence number and acknowledgment number Number from 0,0—> 0,1 -------> 1,1 .
for the first time :
Transmission Control Protocol, Src Port: 57361, Dst Port: 443, Seq: 0, Len: 0
Source Port:57361 Destination Port: 443 Sequence Number: 0 (relative sequence
number) Sequence Number (raw): 2840399127 Acknowledgment Number: 0
Acknowledgment number(raw): 0 1000 .... = Header Length: 32 bytes (8) Flags:
0x002(SYN) Window: 64240 Checksum: 0x64da [unverified] Urgent Pointer: 0
Options:(12 bytes), Maximum segment size, No-Operation (NOP), Window scale,
No-Operation(NOP), No-Operation (NOP), SACK permitted
The second time :
Transmission Control Protocol, Src Port: 443, Dst Port: 57360, Seq: 0, Ack: 1,
Len:0 Source Port: 443 Destination Port: 57360 Sequence Number: 0 Sequence
Number(raw): 3164801645 Acknowledgment Number: 1 Acknowledgment number (raw):
371797491 1000 .... = Header Length: 32 bytes (8) Flags: 0x012 (SYN, ACK)
Window:64240 Checksum: 0x22c8 Urgent Pointer: 0 Options: (12 bytes), Maximum
segment size, No-Operation(NOP), No-Operation (NOP), SACK permitted,
No-Operation(NOP), Window scale
third time :
Transmission Control Protocol, Src Port: 57360, Dst Port: 443, Seq: 1, Ack: 1,
Len:0 Source Port: 57360 Destination Port: 443 Sequence Number: 1 Sequence
Number(raw): 371797491 Acknowledgment Number: 1 Acknowledgment number (raw):
3164801646 0101 .... = Header Length: 20 bytes (5) Flags: 0x010 (ACK) Window:
260 Checksum: 0x64ce Urgent Pointer: 0
TCP The header information carried is Source port number (Source Port,16 position ), Destination port number (Destination Port,16 position ) , serial number ( Sequence
Number,32 position ), Confirmation number (Acknowledgment Number, It refers to the serial number value you want to receive next time ,32 position ), Head length (Header
Length,4 position ,5 In bytes ), Flag bit (Flags,6 position ), Window size (Window,16 position ), Checksum (Checksum,16 position ), Emergency pointer (Urgent
Pointer,16 position ), option (Options, maximum 40 byte )

Note that the serial number and confirmation number here are relative , Because the actual serial number and confirmation number are generated randomly , Back band (raw) Is the serial number value actually transmitted

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