CoS Process on Outgoing Packets

The scheduler map and rewrite rules perform the following operations on outgoing packets:

1. Scheduler maps are applied to interfaces and associate the outgoing packets with a scheduler and a forwarding class.
2. The scheduler defines how the packet is treated in the output transmission queue based on the configured transmit rate, buffer size, priority, and drop profile.
   • The buffer size defines the period for which the packet is stored during congestion.
   • The scheduling priority and transmit rate determine the order in which the packet is transmitted.
   • The drop profile defines how aggressively to drop packets that are using a particular scheduler.
3. Output policers meter traffic and might change the forwarding class and loss priority of a packet if a traffic flow exceeds its service level.
4. The rewrite rule writes information to the packet (for example, EXP or DSCP bits) according to the forwarding class and loss priority of the packet.

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