TCPの接続終了フェーズでは、なぜFINパケットでなくFIN/ACKパケットを最初に送るのですか？ # TCP TCPFIN/ACK TCP A TCP B 1. ESTABLISHED ESTABLISHED 2. (Close) FIN-WAIT-1 --> <SEQ=100><ACK=300><CTL=FIN,ACK> --> CLOSE-WAIT 3. FIN-WAIT-2 <-- <SEQ=300><ACK=101><CTL=ACK> <-- CLOSE-WAIT 4. (Close) TIME-WAIT <-- <SEQ=300><ACK=101><CTL=FIN,ACK> <-- LAST-ACK 5. TIME-WAIT --> <SEQ=101><ACK=301><CTL=ACK> --> CLOSED 6. (2 MSL) CLOSED Normal Close Sequence Figure 13. < # FINFIN/ACK TCPSYNFIN # < # ACK ACK Transmission Control Protocol - WikipediaACK > SYN

> FINFIN/ACK

FIN/ACK, ,
, FIN => FIN/ACK => ACK
(FIN RST OS ())

> TCPSYNFIN

3,

* , connection ACK
(ACK, (), )
* connection(), FIN/ACK, ()