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Simon Leinen •
DSCP=8 doesn't necessarily mean "higher priority". In fact, some networks such as GÉANT use it (or at least did so in the past) for "Lower than Best-Effort" (LBE) service. Some ISPs also use DSCPs other than zero to mark certain kinds of traffic for accounting. For example, one can mark all traffic coming in over expensive links with some DSCP on a transit router, and then use that to measure this traffic further downstream, e.g. at a customer access router, to bill the customer specially for this expensively-routed traffic. Or even if it is not billed separately, the ISP may still want to measure this e.g. for traffic planning/management.