# Using Protocol Agents for connection handling

When related new connections are opened based on information exchanged in an initial connection, Protocol Agents might be needed.

Protocol Agents are provided to handle the following protocols:

- FTP with related active and passive data connections
- H.323 conferencing protocol communications
- Microsoft RPC (MSRPC) for Microsoft Exchange and Outlook communications
- NetBIOS for the Windows NetBIOS datagram services
- Oracle TNS protocol communications
- Remote Shell protocol communications
- Session Initiation Protocol (SIP) communications
- Sun RPC Portmapper communications
- TFTP file transfers

## File transfer protocol (FTP)

FTP uses two related connections: a control connection and a separately established data connection. If the control connection is allowed without the Protocol Agent, the firewall does not recognize that the data connection is part of an existing connection. The connection is handles as a new connection, which usually leads to the data transfer failing.