Filters -- Filters can be created for the Pipeline products to customize operation with specific types of packets or packet addresses. Filters can be used to restrict access to or from defined destinations, or to identify which packets will cause a connection (call) to be made. Filter conditions can be set up to cover a wide variety of different requirements and restrictions.

Filters are setup in the Filters tab. Filters look for certain values in defined segments of a packet. The filter checks each packet that comes into the Pipeline from the WAN, or it checks each packet that leaves the Pipeline from the LAN or PC. If a packet if found that matches the value in the filter, the packet is either discarded or allowed to continue to its destination (or further checked by another filter), depending the rules setup in the filter. In the illustration above, packets with a matching value at the designated segment are discarded.

The illustration below shows a portion of a UDP packet. The UDP header segment is an 8-byte segment (the detail is not shown here) containing a 16-bit application source port, followed by a 16-bit application destination port, plus other information about packet length, checksums, and the UDP data. If you wanted to filter out packets whose application source port or destination port is an FTP service, you would discard packets whose source or destination port is equal to 21.

The following table shows the value for common network applications:

ID (or port)	Name	Protocol
20	FTP-DATA	File Transfer Data
21	FTP	File Transfer Control
23	TELNET	Terminal Services
25	SMTP	Simple Mail Transfer Protocol
42	NAMESERV	Host Name Server
43	NICKNAME	Who is
53	DOMAIN	Domain Name Server
69	TFTP	Trivial File Transfer Protocol
79	FINGER	Finger
161	SNMP	SNMP Net Monitor
162	SNMP-TRAP	SNMP Traps
514	SYSLOG	Syslog
520	RIP	UDP Routing Info Protocol