1. Tcpudp
 TCPUDPOSITCPUDP


 TCPUDP
 TCPUDP
 TCPUDP
 TCP;UDP
 TCP20;UDP8
 TCPUDP

UDPqqqq
TCP

2. Tcp34TIME_WAITTIME_WAIT2MSLCLOSE_WAITTIME_WAIT


 
SYN 1,sequence NumberxSYN_SENT
SYNSYNAcknowledgmentNumber x+1(Sequence Number+1)SYNSYN1, Sequence NumberySYN+ACKSYN_RCVD
SYN_ACKAcknowledgment Numbery+1ACK
ESTABLISHEDTCP


 
(FIN=1seq=x)
1seq=x2FIN1FIN_WAIT_112

(ACK=1ACKnum=x+1)
21FIN1ACKAcknum=x+11FIN_WAIT_22CLOSE_WAIT21

(FIN=1seq=y)
21FIN2LAST_ACK 

(ACK=1ACKnum=y+1)
12FIN2ACK1TIME_WAIT21ACK12MSLServer1 CLOSED 

 1 2MSL2 Maximum Segment Lifetime ACK  CLOSED 

 


  

clientserverserverclientclientserverclientserverserverserverclientserverclientserverserverclient
  

  
ACK SYNSYNSYN
https://www.jianshu.com/p/cf1bed23f7fb

 34
 FIN
 FINACKFIN TCP 
 ACKFINServerClientSYNSYN+ACKACKSYN

 TIME_WAIT
CLOSEACKTIME_WAITACKACK

 TIME_WAIT2MSL
MSLMaximum Segment LifetimeTime_wait  FIN  ACK  TIME-WAIT  ACK  FIN  2MSL 

2MSLACK ACK  Fin  FIN ACK 2  MSL + FIN

TIME_WAIT2MSL
 TCPACK
 TCP2MSLTCPTIME_WAITTIME_WAIT2MSLTCP

 CLOSE_WAIT
CLOSE_WAITFINFINCLOSE_WAITacksokcetBugFINsocketNettyBugBugI/OI/OTaskI/O
CLOSE_WAIT502CLOSE_WAITRecv_Q0DOSRecv_Q5

 TIME_WAIT
 TIME_WAIT  TCP  socket  TIME_WAIT Linux TIME_WAIT = 60
 TIME_WAIT
/etc/sysctl.conf
net.ipv4.tcp_syncookies = 1 SYN CookiesSYNcookiesSYN0
net.ipv4.tcp_tw_reuse = 1 TIME-WAIT socketsTCP0
net.ipv4.tcp_tw_recycle = 1TCPTIME-WAIT sockets0
net.ipv4.tcp_fin_timeout = 30 TIMEOUT 
 /sbin/sysctl -p 

 CLOSE_WAITTIME_WAIT
AHttpClientBapacheAATIME_WAITBBAAHttpClientCLOSE_WAIT
CLOSE_WAIT

3. Tcp
 TCP
 16 TCP

 +: TCP
TCPIPIPTCPTCP

TCPACKACK

 TCP
ACK
a
bACK
ACKACK

500ms0.5500ms2*500ms4*500msTCP

 TCPTCPTCP

 :

 
TCP

TCP16ACKACKACK0

TCP



 TCP 

TCPACK

 
 TCP TCP

congestion window
TCP  **(cwnd) **
cwnd
 cwnd 
 cwnd 


 
;cwnd1 ACKcwnd
 
 >=  ssthresh
 
ssthresh  cwnd ssthresh ==cwnd/2cwnd=1
   
 
 3  ACK  cwnd  ssthresh cwnd=cwnd/2ssthresh=cwnd
cwnd=ssthresh+33  3 ;

 ACK cwnd  1
 ACK  cwnd  ssthresh  ACK  duplicated ACK 

https://www.jianshu.com/p/cf1bed23f7fb

 1


https://blog.csdn.net/cbjcry/article/details/84925028

+


 


4. Tcp
TCPTCPTCPTCP
TCP204nnTCP20


TCP
 2
 Sequence number402^32 - 12^32 2^32-1 0TCPTCP301100301400401401;
 Acknowledge number4BA501200BA700BA701BA701
 4TCPTCP
 60
 URGURGentURG=1
 ACKACKnowledgmentACK=1TCPACK1
 PSHPuSH PSH=1
 RSTReSeTRST=1TCP
 SYNSYNchronizationSYN=1ACK=0SYN=1ACK=1
 FINFINisFIN=1
 2
 2
 2
 
TCPip

 



5. TCPTCP /
 x

 TCPTCP

6. TCP
1TCP + 
2 
3
4 CRCIP

 +  +  + 0 + 16

IPIPTCPTCPTCP


 
 160

5
 16
 1600


1IPTCPUDP
2IPUDPTCPTCP
3UDPTCP
https://blog.csdn.net/insistgogo/article/details/10296167