Overview of QoS policies on 7210 SAS-T in access-uplink mode

When configured to operate in access-uplink mode, 7210 SAS-T QoS policies are applied on service ingress, access port egress, and access-uplink port ingress and egress. These policies allow users to configure the following:

• classification rules for how traffic is mapped to FCs

• FC association with meters and meter parameters used for policing (rate limiting)

• queuing parameters for shaping and buffer allocation

• QoS marking and interpretation

Several types of QoS policies exist:

• service ingress policies for access SAP ingress

  Service ingress QoS policies are applied to the customer-facing SAPs. Traffic that enters through the SAP is classified to map it to an FC. FCs are associated with a meter or policer on ingress. The mapping of traffic to meters can be based on combinations of customer QoS marking (IEEE 802.1p bits), IP criteria, and MAC criteria. The characteristics of the FC meters are defined within the policy with regard to the number of FC meters for unicast traffic and the meter characteristics (such as CIR, PIR, and so on). Each of the FCs can be associated with different unicast parameters.

  A service ingress QoS policy also defines up to three (3) meters per FC to be used for multipoint traffic for multipoint services. There can be up to 32 meters in total per service ingress QoS policy. In the case of the VPLS, four forwarding types (which is not to be confused with forwarding classes) are supported: unicast, multicast, broadcast, and unknown. Multicast, broadcast, and unknown types are flooded to all destinations within the service, while the unicast forwarding type is handled in a point-to-point manner within the service.

• access egress policies for access port egress

  An access egress policy is analogous to a SAP-egress policy, as defined in the 7x50 SR series of products. The difference is the point of attachment. An access egress policy is applied on the physical port as opposed to the logical port (SAP) for SAP-egress policy. It applies to all the SAPs on the port. An access egress QoS policy maps the traffic egressing the customer facing ports into various queues and marks the traffic accordingly. The FCs are mapped to the queues. There are 8 (eight) queues at the port level. FC-to-queue mapping is not configurable. The number of queues is not user-configurable and software always allocates 8 (eight) queues at the port level. An access egress policy also defines how to remark the FC-to-packet header bits (for example, IEEE 802.1p bits in the Layer 2 VLAN header, and so on).

• network policies for access-uplink port, ingress and egress

  Network queue policies are applied on egress of access-uplink ports when operating in access-uplink mode. The policies define the FC queue characteristics for these entities. The FCs are mapped to the queues. There are 8 (eight) queues at the port level. FC-to-queue mapping is system-defined and not user-configurable. The number of queues is not user-configurable and software always allocates 8 (eight) queues at the port level.

  For devices configured to operate in access-uplink mode, network QoS policies apply to access-uplink ports. Access-uplink ports in access-uplink mode are analogous to network ports in network mode. On ingress, the policy applied to an access-uplink port maps incoming dot1p values to FC and profile state for the traffic received from the core network. On egress, the policy maps FC and profile state to packet header values (for example, IEEE 802.1p value in the Layer 2 header) for traffic to be transmitted into the core network.

• slope policies

  Slope policies are applied to the egress queues on the access, network, and hybrid ports. These policies define the WRED congestion management attributes, such as drop probability and thresholds for high-profile and low-profile traffic.

• network-queue policies for access-uplink port, egress

• port-scheduler policies for access port and access-uplink port egress

Service ingress, access egress, and network QoS policies are defined with a scope of either template or exclusive. Template policies can be applied to multiple entities (such as SAPs and ports); exclusive policies can only be applied to a single entity.

One service ingress QoS policy can be applied to a specific SAP. An access egress policy can be applied to an access port. One access egress QoS policy can be applied to the access port. One network QoS policy can be applied to an access-uplink port when operating in access-uplink mode. A network QoS policy defines both ingress and egress behavior. One network queue policy can be applied to an access-uplink port. If no QoS policy is explicitly applied to a SAP, port, or interface, a default QoS policy is applied.

The following table describes the major functions performed by the QoS policies.