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Junos® OS For Dummies®, 2nd Edition by Michael Bushong, Cathy Gadecki, Walter Goralski

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Controlling Outbound Traffic

After you've effectively identified the inbound traffic on your router and classified it into one of your forwarding classes, you then want to control the outbound flow of that traffic.

Traffic enters the router, and based on a packet's DSCP value, it's assigned to a forwarding class, which identifies the outbound queue into which it's sent. (Oh, yeah, it's routed to the proper next hop too — sometimes you overlook the basics when you discuss a new feature.)

You may want to control various properties of the outbound queue, including

  • Total bandwidth assigned to the queue
  • Total buffer memory assigned to the queue for storing outbound packets
  • Priority of the queue (the order in which the queue is serviced)

Scheduler configuration

Before you can get into tweaking the various operating parameters of the outbound traffic, you have to understand the underlying mechanism used to configure these parameters.

There are two major components to the scheduler configuration:

  • Schedulers: Define the properties of the outbound queues. Once they're tied to individual interfaces and forwarding classes, all traffic matching a particular forwarding class is treated as per the definitions in the scheduler.
  • Scheduler maps: Associate a forwarding class with a scheduler. Scheduler maps are then tied to interfaces, thereby configuring the hardware queues, packet schedulers, and RED processes that operate according to the mapping.

In other words, schedulers and their maps ...

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