SAP access egress policies

General Information

SAP access egress policies are applied to access egress interfaces and specify QoS on egress.

SAP access egress policies define egress service queues and map forwarding class flows to queues. In the simplest access egress policy, all forwarding classes are treated like a single flow and mapped to a single queue.

The required SAP access egress policy elements include:

The optional SAP access egress policy elements include:

Each queue in a policy is associated with one or more of the supported forwarding classes. Each queue can have its individual queue parameters allowing individual rate shaping of the forwarding classes mapped to the queue. More complex service queuing models are supported, where each forwarding class is associated with a dedicated queue.

The forwarding class determination per service egress packet is determined at ingress. If the packet ingresses the service on the same managed device, the service ingress classification rules determine the forwarding class of the packet. If the packet was received over a service tunnel, the forwarding class is marked in the tunnel transport encapsulation.

There is one default SAP access egress policy. The default policy gives all traffic equal priority with the same chance of being sent or dropped during periods of congestion.

Policy override

You can override some or all settings associated with an access egress policy on an L2 or L3 access interface, SLA profile, or subscriber profile. See To configure QoS policy overrides on an L2 or L3 access interface for more information.

Note: You can override SAP access egress policies that have the Scope parameter set to template. See To configure a SAP access egress policy for more information.

Policers

You can add a policer to an access egress policy to provide traffic flow limiting. Policers are associated with the forwarding classes defined in the access ingress policy. Policers can also be linked to a policer control policy, which maintains a hierarchy of multiple policer objects in the NFM-P system. Policers are linked to policer control policies by means of an arbiter. For more information, see Policer control policies.

When policers are configured in an access egress policy, they can be used to generate statistics. The type of statistics generated depends on the Stats Mode. Table 50-2, Stats Mode options lists the options for counter allocation when generating statistics.

Traffic mapping

You can specify the mapping between the egress traffic and the egress queue. Mapping is optional and can be based on combinations of customer QoS marking (dot1p, DSCP and precedence), IP/IPv6 criteria, or MAC criteria, as shown in the following table.

Table 50-4: SAP access egress policy traffic mapping

Tab

Function

Dot1p

Maps the dot1p value of the egress traffic to the egress queue ID

DSCP

Maps the DSCP value of the egress traffic to the egress queue ID

Precedence

Maps the precedence value of the egress traffic to the egress queue ID

IP Match Criteria

Maps the IP Match Criteria of the egress traffic to the egress queue ID

IPv6 Match Criteria

Maps the IP Match Criteria of the egress traffic to the egress queue ID

Adding an LspExp rule to a policy forces packets that match the specified MPLS LSP EXP criteria to override the existing forwarding class and enqueuing priority, based on the parameters specified in the LspExp rule. This functionality allows geographically distributed ISP sites to establish site-to-site interconnection service through a backbone network using VPLS/VLL. Each ISP site PE router connects to a 7x50 Ethernet L2 SAP in the backbone network, and traffic is encapsulated in a VPLS/VLL service tunnel. A maximum of eight LspExp rules are allowed on a single access ingress policy.