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CoS for L2TP Tunnels on Ethernet Interface Overview

For effective packet tunneling, CoS is implemented over L2TP tunnels. For Ethernet interfaces, CoS is supported for L2TP session traffic to a LAC on platforms configured as an LNS that include egress IQ2 or IQ2E PICs.

This feature is supported on the following platforms:

  • EX Series switches

  • M7i and M10i routers

  • M120 routers

To enable session-aware CoS on an L2TP interface, include the per-session-scheduler statement at the [edit interfaces unit logical-unit-number] hierarchy level.

After CoS is configured on an L2TP tunnel, Junos OS dynamically creates a traffic shaper for the traffic-shaping-profile and the L2TP tunnel based on the tunnel identification number. This ensures that the packets are monitored at the LAC and classified to allow the traffic flow to be adjusted on congested networks.

This feature has the following limitations:

  • Only 991 shapers are supported on each IQ2 or IQ2E PIC.

  • For a 4-port IQ2E PIC, you can configure up to 1976 shapers for an 8-queue session and 3952 shapers for a 4-queue session.

  • For an 8-port IQ2E PIC, you can configure up to 1912 shapers for an 8-queue session and up to 3824 shapers for a 4-queue session.

  • Sessions in excess of the maximum supported values specified for the PICs cannot be shaped (but they can be policed).

  • There is no support for PPP multilinks.

  • The overall traffic rate cannot exceed the L2TP traffic rate, or else random drops result.

  • There is no support for logical interface scheduling and shaping at the ingress because all schedulers are now reserved for L2TP.

  • There is no support for physical interface rate shaping at the ingress.

  • You cannot delete or deactivate the primary Ethernet interface on which the tunnel is established.

You can provide policing support for sessions with more than the maximum supported value on each IQ2 or IQ2E PIC. Each session can have four or eight different classes of traffic (queues). Each class needs its own policer; for example, one for voice and one for data traffic.