An FTP server ( DMZ ) on the existing network of the enterprise provides FTP services to the outside ( Untrust ), and a USG firewall is deployed on the external network port.
The following information is obtained by capturing packets on the FTP server:
Sequence Number Source Address Destination Address Protocol Packet Summary
1 1.1.1.1 192.168.1.2 TCP 3318>21 [SYN] Seq=0 Len=0 MSS=1460
2 192.168.1.2 1.1.1.1 TCP 21>3318 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460
3 1.1.1.1 192.168.1.2 TCP 3318>21[SYN] Seq=1 Ack=1 Win=65535 Len=0
......
13 1.1.1.1 192.168.1.2 FTP Request: PASV
14 192.168.1.2 1.1.1.1 FTP Response: 227 Entering Passive Mode (192, 168, 1, 2, 4, 162)
15 1.1.1.1 192.168.1.2 TCP 3319>1186 [SYN] Seq=0 Len=0 MSS=1460
16 192.168.1.2 1.1.1.1 TCP 1186>3319 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460
17 1.1.1.1 192.168.1.2 TCP 3319>1186 [SYN] Seq=1 Ack=1 Win=65535 Len=0
.....
The following descriptions are correct: