HP MSR Series Configuration Manual page 583

If a matching rule is found and the rule action is inspect, the device forwards the packet to
the DPI engine.
If a matching rule is found and the rule action is drop or pass, the device processes the
packet according to the action.
If no matching rule is found, the device drops the packet.
For more information about the object policy, see Security Configuration Guide.
2. The DPI engine performs protocol parsing for the packet and searches for applicable inspection
rules according to the parsing results.
3. If an applicable inspection rule contains AC patterns, DPI engine performs AC pattern matching.
If an applicable inspection rule does not contain AC patterns, DPI engine directly performs
option matching. The packet matches the rule if it matches the options.
4. If the packet matches an AC pattern in an applicable inspection rule, the DPI engine further
compares the packet against the options in the rule. The packet matches the rule if it matches
the options.
5. If the packet matches an inspection rule, the DPI engine informs the corresponding DPI service
modules to process the packet. If the packet does not match any rule, the DPI engine allows the
packet to pass.
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