User manual

8-8 Packet Filter

Protocol Rules

You can define protocol rules within each protocol section in the

filter file. Protocol rules determine which packets may and may

not access the network.

The rule syntax is:

The combination of keyword, operator, and value forms the

condition which, when combined with the verb, determines

whether the packet is accepted or rejected.

When a packet is filtered, for example an IP packet, the

NETServer parses each rule defined in the IP protocol section

sequentially according to the line number. Filtering is

performed based on the first match that occurs. If there is no

match, by default the packet is accepted. For this reason, you

should order your protocol rules so that the rules you expect to

be most frequently matched are in the beginning of the section.

This reduces the amount of parsing time that occurs during

filtering.