Objctive 6.3: Select from a list, common firewall features that might interfere with the normal operation of a given protocol

A firewall is a system to prevent unauthorised access to/from a private network. Typically close ports for unauthorised access. However port 80 for HTTP will be open so can use tunnelling ( SOAP and RMI can avoid firewall configuration issues by piggy backing (tunnelling) on HTTP). However, is firewall avoidance a good thing if effectively you are allowing requests through to your systems? Other protocols required ports to be opened explicitly.