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Per-Priority Shaping on MPC7E, MPC8E, and MPC9E Interfaces Overview

Per-priority shaping enables you to configure a separate shaping rate for each of the five priority levels supported by MIC and MPC interfaces. The main use of per-priority shaping rates is to ensure that higher priority services such as voice and video do not starve lower priority services such as data. On MPC7E (MPC7E-MRATE and MPC7E-10G), MPC8E (MX2K-MPC8E), and MPC9E(MX2K-MPC9E), when you enable the enhanced priority mode feature, additional scheduler priorities and shaping rates are supported. For more information on the enhanced priority mode, see enhanced-priority-mode.

There are 5 scheduler priorities:

Guaranteed high (GH)
Guaranteed medium (GM)
Guaranteed low (GL)
Excess high (EH)
Excess low (EL)

Each of the scheduler priorities support a shaping rate for each priority:

Shaping rate priority high (GH)
Shaping rate priority strict high (GHL)
Shaping rate priority medium (GM)
Shaping rate priority medium low (GML)
Shaping rate priority low (GL)
Shaping rate excess high (EH)
Shaping rate excess medium high (EMH)
Shaping rate excess medium low (EML)
Shaping rate excess low (EL)

If each service is represented by a forwarding class queued at a separate priority, then assigning a per-priority shaping rate to higher priority services accomplishes the goal of preventing the starvation of lower priority services.

To configure per-priority shaping rates, include the shaping-rate-excess-high rate <burst-size burst>, at the [edit class-of-service traffic-control-profiles tcp-name] hierarchy level and apply the traffic control profile at the [edit interfaces] hierarchy level. You can specify the rate in absolute values, or by using k (kilo-), m (mega-) or g (giga-) units.

When you enable the enhanced priority mode feature, the queue priorities are mapped to the priorities for the MPCEs as follows:

Table 1: MPCE Priority and Default Excess Priority Values

Configured Priority	Priority Supported on the MPCE	Default Excess Priority
Strict-High	GH	EH
High	GHL	EH
Medium-High	GM	EL
Medium-Low	GML	EL
Low	GL	EM

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Per-Priority Shaping on MPC7E, MPC8E, and MPC9E Interfaces Overview

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Modified: 2016-12-06