Juniper G10 CMTS, Hardware Manual

Page: 172 / 210

HFC Plant Related Issues
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JUNOSg 3.0 G10 CMTS Hardware Guide 156
!
If the cable modem is a CCCM (CPE controlled cable modem), the performance of the
CPE is affecting the performance of the cable modem. The CPE performance can be
affected by one or more of the following:
! A slow microprocessor.
! Not enough RAM.
! Not enough disk space.
! Running too many applications.
! Improper network configuration.
Cable Modem is Dropped
A cable modem might be dropped from the CMTS for the following reasons:
!
The cable modem belongs to a downstream or upstream interface on which a call
admission control (CAC) policy is assigned. If the ratio of the aggregate best-effort
minimum reserved traffic rate (MRTR) for all admitted service flows to the channel
bandwidth exceeds the ratio configured in the CAC policy, cable modems are dropped
based on the traffic priority of their service flow until the ratio is not exceeded. Issue the
show cable policy admission-control command to display configured CAC policies.
!
You have changed the configuration for an interface that was previously configured with
QoS parameters for admitted service flows based on the original interface configuration.
For example, assume a CAC policy is configured with the maximum allowable ratio of
the aggregate best-effort MRTR for all admitted service flows to the channel bandwidth
at 50 percent. If the original channel bandwidth was 10 Mbps, but is reconfigured to
5 Mbps, the aggregate MRTR above which cable modems are dropped is reduced from
5 Mbps (50 percent of 10 Mbps) to 2.5 Mbps (50 percent of 5 Mbps).
HFC Plant Related Issues
This section assumes that the HFC plant is potentially contributing to issues associated with
the cable modems. Following is a list of potential issues along with suggestions to resolve
them.
This section includes the following topics:
!
Cable Modem Cannot Successfully Range on page 157
!
Cable Modem Throughput is Slow on page 158