work（ ）,systems that effectively isolate an organization"s internal network structure from an （ ） network, such as the INTERNET is becoming increasingly popular. These firewall systems typically act as application-layer（ ）between networks, usually offering controlled TELNET, FTP, and SMTP access. With the emergence of more sophisticated（请作答此空）layer protocols designed to facilitate global information discovery , there exists a need to provide a general （ ）for these protocols to transparently and securely traverse a firewall.

work（ ）,systems that effectively isolate an organization"s internal network structure from an （ ） network, such as the INTERNET is becoming increasingly popular. These firewall systems typically act as application-layer（ ）between networks, usually offering controlled TELNET, FTP, and SMTP access. With the emergence of more sophisticated（请作答此空）layer protocols designed to facilitate global information discovery , there exists a need to provide a general （ ）for these protocols to transparently and securely traverse a firewall.