Excess RatioDOCSIS Traffic Priority
163
204
245
286
327
Custom DOCSIS Priority to Excess Ratio Mappings
This option is introduced to configure custom priority to excess ratio mappings for downstream service flows
that override the default mappings listed in the above Table.
The configured values are used only for new service flows that are created after the configuration has been
applied. All the existing service flows maintain their previous excess ratio values.
Note
The option to configure priority to excess ratio mappings is available on a per downstream forwarding interface
basis and is applicable to legacy cable, wideband and modular cable, and integrated cable interfaces.
The cable downstream qos wfq weights command is used to configure the mappings.
Maximum Sustained Traffic Rate
The maximum sustained traffic rate (MSR) specifies the peak information rate of a service flow. The MSR
of a service flow is mapped to the shape rate of the packet queue. When the maximum sustained traffic rate
is not specified or set to zero, its traffic rate becomes limited only by the physical channel capacity set by
DOCSIS specifications.
Minimum Reserved Traffic Rate
The minimum reserved traffic rate (MRR) specifies the minimum rate reserved for a service flow. The MRR
of a service flow is mapped to the CIR of the packet queue, which ensures the minimum amount of bandwidth
a queue gets under congestion. When the MRR is not specified, the CIR is set to zero as per DOCSIS
specifications.
High Priority Traffic
High priority traffic flows are mapped to a Low Latency Queue (LLQ) on the data forwarding interface. The
packets in LLQ are serviced with absolute priority over other queues on the same interface.
The following service flows require high priority service:
•
Service flows with DOCSIS downstream latency TLV set to a value above zero. For example, PacketCable
Multimedia Specification (PCMM) voice calls.
Cisco cBR Series Converged Broadband Routers Quality of Services Configuration Guide for Cisco IOS XE
Fuji 16.7.x
84
DOCSIS WFQ Scheduler on the Cisco CMTS Routers
High Priority Traffic
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