D-Link DFL-260E User Manual for DFL-260E - Page 492
Precedences, The Default Precedence is Zero, There are 8 Possible Precedence Levels
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10.1.6. Precedences Chapter 10. Traffic Management 10.1.6. Precedences The Default Precedence is Zero All packets that pass through NetDefendOS traffic shaping pipes have a Precedence. In the examples so far, precedences have not been explicitly set and so all packets have had the same default precedence which is 0. There are 8 Possible Precedence Levels Eight precedences exist which are numbered from 0 to 7. Precedence 0 is the least important (lowest priority) precedence and 7 is the most important (highest priority) precedence. A precedence can be viewed as a separate traffic queue; traffic in precedence 2 will be forwarded before traffic in precedence 0, precedence 4 forwarded before 2. Figure 10.4. The Eight Pipe Precedences Precedence Priority is Relative The priority of a precedence comes from the fact that it is either higher or lower than another precedence and not from the number itself. For example, if two precedences are used in a traffic shaping scenario, choosing precedences 4 and 6 instead of 0 and 3 will makes no difference to the end result. Allocating Precedence to Traffic The way precedence is assigned to traffic is specified in the triggering pipe rule and can be done in one of three ways: • Use the precedence of the first pipe Each pipe has a Default Precedence and packets take the default precedence of the first pipe they pass through. • Use a fixed precedence The triggering pipe rule explicitly allocates a fixed precedence. • Use the DSCP bits Take the precedence from the DSCP bits in the packet. DSCP is a subset of the Diffserv architecture where the Type of Service (ToS) bits are included in the IP packet header. 492