Juniper Networks G10 CMTS manual Cable Modem is Dropped, HFC Plant Related Issues

HFC Plant Related Issues

•	! 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-controlcommand 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
•
•
•
•
•
•
•
•
•
•
•
•

156 JUNOSg 3.0 G10 CMTS Hardware Guide