Subscriber Queuing Differences
786 Quality of Service Guide
Another modification is the ability to define egress HSMDA counter override criteria which
relies on an egress TCAM lookup based on IP flow criteria match entries. Egress IP flow
based HSMDA counter overrides are ignored when applied to a SAP not on an HSMDA.
Egress counter overrides are ignored when a SAP is a member of an efficient multicast group.
Subscriber Queuing Differences
Standard service queues are instantiated on a SAP or subscriber sla-profile basis. Each SAP
or subscriber sla-profile instance within a SAP has its own set of queues which are managed
into an aggregate SLA by a software based virtual scheduler. Due to its internal architecture,
subscriber queues on the HSMDA are handled differently. The subscriber aggregate rate limit
is represented by the queue group shaper. Since the queue group shaper only manages the
eight queues within the group, all subscriber hosts within a subscriber context must share the
same eight queues. Each subscriber SLA-profile (the object that allows different groups hosts
for a single subscriber) must classify packets to the subscriber level queues and not to queues
specific to the SLA-profile instance. While each SLA-profile instance does not maintain its
own set of queues on the HSMDA, the packet classification rules are still maintained per sla-
profile instance and not restricted to the subscriber level.
To allow provisioning of the sla-profile QoS classification rules and also provide the ability
to specify the queuing behavior at the subscriber profile level, the SAP ingress and SAP
egress QoS policies are reused in each case. At the sla-profile level, the SAP QoS policies
packet forwarding class classification rules and forwarding class to queue ID mappings are
in-effect (the queue definitions are ignored on the sla-profile instances for HSMDA
subscribers). At the subscriber profile level, the queue-id definitions are in-effect while the
packet classification rules and mappings are ignored.
HSMDA Features
HSMDA LAG
The addition of the HSMDA affects Ethernet Link Aggregation Groups (LAGs). Due to the
different behavior between a SAP created on a standard Ethernet MDA and a SAP created on
an HSMDA, it is important to know the expected behavior at the time the SAP is created. A
SAP can be created on a LAG that has no port members which is clear, that at the time of
creation, the type of SAP may be unknown.
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