Netopia R910 Manuel d'utilisateur télécharger pdf (Page 127)

Security 13-127

Each inspector has a speciﬁc task. One inspector’s task may be to examine the destination address of all

outgoing packages. That inspector looks for a certain destination—which could be as speciﬁc as a street

address or as broad as an entire country—and checks each package’s destination address to see if it matches

that destination.

A ﬁlter inspects data packets like a customs inspector scrutinizing packages.

Filter priority

Continuing the customs inspectors analogy, imagine the inspectors lined up to examine a package. If the

package matches the ﬁrst inspector’s criteria, the package is either rejected or passed on to its destination,

depending on the ﬁrst inspector’s particular orders. In this case, the package is never seen by the remaining

inspectors.

INSPECTOR

FROM:

TO:

FROM:

TO:

FROM:

TO:

APPROVED

packet

first

filter

match?

yes

pass or

discard?

to network

discard

(delete)

pass

to next

filter

send

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Netopia R910 Manuel d'utilisateur Page 127