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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
















    Modified: 2016-12-06