Netopia 435 Reference Manual page 146

Internet service
FTP
Telnet
SMTP (mail)
Gopher
Finger
Parts of a filter
A filter consists of criteria based on packet attributes. A typical filter
can match a packet on any one of the following attributes:
The source IP address (where the packet was sent from)
The destination IP address (where the packet is going)
The type of higher-layer Internet protocol the packet is carrying,
such as TCP or UDP
Port numbers
A filter can also match a packet's port number attributes, but only if
the filter's protocol type is set to TCP or UDP, since only those
protocols use port numbers. The filter can be configured to match
the following:
The source port number (the port on the sending host that
originated the packet)
The destination port number (the port on the receiving host
that the packet is destined for)
By matching on a port number, a filter can be applied to selected
TCP or UDP services, such as Telnet, FTP, and World Wide Web. The
tables below show a few common services and their associated
port numbers.
TCP port
20/21
23
25
70
79
Internet service
Who Is
World Wide Web
SNMP
TFTP
AppleTalk Routing
Maintenance (at-rtmp)
Security 7-13
UDP port
43
80
161
69
201