A Pipe Defined With Minimum Precedence And Maximum Precedence - D-Link NetDefend DFL-210 User Manual

10.1.5. Priorities and Guarantees
In order to determine what precedence network traffic belongs to, each packet buffer is assigned a
precedence number before it is sent into a pipe. The precedence assigned is controlled by the Rules
section. This way, you can prioritize traffic by IP span, protocol number, port number, etc, the same
way you normally filter traffic. This is described in greater detail later in this chapter.
When the pipe is configured, the number of precedences in the pipe can be defined by specifying a
Minimum precedence and a Maximum precedence. The pipe will automatically adjust incoming
packets to comply with these limits: a packet with a too low precedence is moved up to the minim-
um precedence. A packet with too high precedence is moved down to the maximum precedence. If a
packet has no precedence, it is assigned the Default precedence.
The actual limiting of bandwidth is performed inside each precedence; separate bandwidth limits
may be specified for each precedence. These limits may be specified in kilobits per second and/or
packets per second.
The precedence defined as the minimum precedence has a special functionality within the pipe: it
acts as a best effort precedence.
Figure 10.3. A Pipe defined with minimum precedence and maximum
precedence.
In addition to the limit per precedence, a limit for the pipe as a whole may also be specified, as
you've seen in the previous example. When the total bandwidth through the pipe reaches the total
limit, traffic will be prioritized depending on what precedence it belongs to. Higher precedences
have a greater chance of making it through the pipe without queuing. However, if you are only using
two precedences, choosing 4 and 6 rather than 0 and 2, or 0 and 6 if you like, will, of course, make
no difference. The meaning of a precedence is only relative to traffic that passes in the other preced-
ences, not to some external factor like, for instance, what is actually going on in the LAN outside
the firewall, or on the other side of your Internet connection.
Note
The respective precedences are not "special" in any way. Their meaning is only
defined by the limits and guarantees that you configure. The difference is only in relat-
ive importance: traffic in precedence 2 will be passed on before traffic in precedence
0, traffic in precedence 4 before 2 and 0, and so on.
Note
Traffic that exceeds the limit of a higher precedence will automatically be transferred
into the best effort precedence, as long as there is room in the best effort precedence.
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Chapter 10. Traffic Management