The nerve roots pass through these joints to go from the spinal cord to the arms, legs and other parts of the body. These joints also allow the spine to bend and twist, and they keep the back from slipping too far forward or twisting without limits.
A forward ftp proxy is used to allow internal LAN clients to connect to Internet ftp servers when connecting through a PF firewall. All control and data connection rules are made by the ftp-proxy daemon and inserted into PF using anchors.
How the TCP Port 21 Works With FTP. The File Transfer Protocol Uses Port 20 and 21. The File Transfer Protocol (FTP) provides a means to transfer information online, much like how the Hypertext Transfer Protocol (HTTP) is used through a web browser. FTP, however, operates on two different TCP ports: 20 and 21.