Cisco ASR 9000 Series Configuration Manual page 132

QoS Features Supported on BNG
Policing and Queuing Support
BNG provides ingress and egress traffic policers. BNG also supports pre-existing traffic policing mechanisms
per subscriber session. 1R2C and 2R3C policers with marking actions is supported at parent-level in subscriber
policies. Only absolute police rates are supported at the parent-level of subscriber policies. 1R2C and 2R3C
policers with marking actions are supported at the child-level in subscriber policies. Both absolute and
percentage based police rates are supported at child-level of subscriber policies.
BNG supports traffic shaping at the physical port level, at the subscriber session level, at the class level, and
at the VLAN level only in egress direction. The system supports all pre-existing queuing actions for subscriber
sessions. The configuration of minimum-bandwidth at the parent-level in subscriber policies is blocked. If
subscriber policies do not have a queuing action, the traffic on those subscribers is still subjected to S-VLAN
shaping and the traffic goes out through S-VLAN policy queues if those are present; if not, the traffic goes
through the interface default-queue. The shaping or bandwidth-remaining queuing action is mandatory in flat
S-VLAN policies. Only absolute shape rates is supported in S-VLAN flat policies and the parent-level of
subscriber policies. However, only shaping and bandwidth-remaining queuing actions are supported in the
parent-level of subscriber policies and all queuing actions are supported in the child-level of subscriber policies.
These additional queuing features are supported in egress policies applied on subscribers:
• A policy can have 1 P1, 1 P2, 1 P3 and 5 normal priority queues.
• A policy can have 1 P1, 2 P2 and 5 normal priority queues. P1 and P3 queues can be shared by multiple
classes whereas P2 queues are never shared.
Default Marking
BNG supports all pre-existing classification and marking options supported for L3 interfaces for use with
subscriber sessions. BNG also supports L3 marking to L2 marking mapping. BNG also supports ToS to CoS
mapping at LAC for downstream PPPoE frames and provides mechanisms to mark 802.1p and IP TOS fields.
The system allows flexible IP TOS marking for L2TP packets based on ingress subscriber qos policy. Marking
is supported at the parent-level in subscriber policies and at the child-level in subscriber policies.
QoS Policy Modification
BNG supports in-service QoS policy-modification. Modification of subscriber-policy (through Radius),
S-VLAN policy (through CLI) and port sub-rate policy (through CLI) are also supported.
L2 Encapsulation
For PPPoE subscribers, the L2 encapsulation size used in QoS rate calculations must be adjustable based on
the last mile encapsulation (DSLAM to subscriber home) signaled in the PPPoE tags.
Classification
The BNG supports all pre-existing classification and marking options supported for L3 interfaces for use with
subscriber sessions. BNG also supports ingress classification based on 802.1P values for single and double
tagged COS, classification based on DSCP in either direction, classification based on L3/L4 ACLs in either
direction, and classification of L2TPv2 traffic based on the outer DSCP marking.
The classification of an incoming L2TP packet on the ingress core side interface is always based on the outer
IP fields even if the packet arrives with an MPLS tag stack.
Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,
Release 4.2.x
122
Deploying the Quality of Service (QoS)
OL-26148-02