Guidelines for Configuring CoS Shaping-Rate Adjustments for
Subscriber Local Loops
These guidelines apply to configuring an MX Series Ethernet
Services Router installed as an edge router to adjust the configured
shaping rates on scheduler nodes for subscriber interfaces that represent
subscriber local loops. This shaping-rate feature uses the topology
discovery and traffic-monitoring features of the ANCP.
Keep the following points in mind
when you enhance hierarchical CoS policy by configuring ANCP-driven
shaping-rate adjustments:
Shaping-rate adjustments are supported only for subscriber
local loops that terminate at DSLAMs that you have configured as ANCP
neighbors of the MX Series router.
Shaping-rate adjustments are supported only for scheduler
nodes for which you have configured an initial shaping rate by including
the shaping-rate statement in a traffic-control profile applied
to the scheduler node. Specify the initial shaping rate as a peak
rate, in bits per second (bps), and not as a percentage. Other methods
of configuring a shaping rate are not supported with this feature.
Shaping-rate adjustments are supported only for scheduler
nodes that are static logical interface sets that you have configured
to operate at Level 3 of the scheduler hierarchy on the router. If
an interface set is configured with a logical interface (such as unit
0) and queue, then the interface-set is an internal scheduler node
(as opposed to a root node or a leaf node) at Level 2 of the hierarchy.
However, if there are no traffic control profiles configured on logical
interfaces in an interface set, then the interface set is an internal
scheduler node at Level 3 of the hierarchy.
Shaping-rate adjustments are supported only for subscriber
interfaces over physical interfaces that you have configured to operate
in hierarchical scheduler mode. Only ports on EQ DPCs in MX Series
routers support hierarchical scheduler mode.
After shaping-rate adjustments are enabled and the router
has performed shaping-rate adjustments on a scheduler node, you can
configure a new shaping rate by including the shaping-rate statement in a traffic-control profile and then applying that profile
to that scheduler node. However, this new shaping-rate value does
not immediately result in shaping traffic at the new rate. The scheduler
node continues to be shaped at rate set by ANCP. Only when the ANCP
shaping-rate adjustment feature is disabled is the scheduler node
shaped at the newly configured shaping-rate.
The Layer 2 Tunneling Protocol (L2TP) is often used to
carry traffic securely between an L2TP Network Server (LNS) and an
L2TP Access Concentrator (LAC). The QoS adjustment feature supports
the shaping overhead options that you can use to add a specified number
of bytes to the actual packet length when determining shaped session
packet length. ANCP shaping-rate adjustments are not supported for
ingress traffic, only for egress traffic. To configure the number
of bytes to add to the packet at the egress side of the tunnel, include
the egress-shaping-overhead and mode statements
at the [edit chassis fpc slot-number pic pic-number traffic-manager] hierarchy level. Use
the shaping overhead options if you need to account for encapsulation
overhead.