Cisco SR2016T-NA Reference Manual page 153

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Chapter 2
Cisco CMTS Configuration Commands
Note
The Cisco CMTS also continues to enforce the load threshold value to perform static load balancing
as well. Therefore, the threshold percentage should be equal to or greater than the percentage
specified with the load load-value option.
For example, if you specify load 10 enforce 15, the Cisco CMTS monitors the load usage between
cable interfaces in the load-balance group. If upstream 1 reaches 33 percent and upstream 2 reaches
45 percent, the Cisco CMTS begins static load-balancing operations by assigning new cable
modems to upstream 1 when they register. If the difference still continues to grow, and upstream 2
reaches 50 percent, the Cisco CMTS also begins dynamic load-balancing operations by moving
online cable modems, until the difference in load usage falls below 15 percent. The Cisco CMTS
then continues static load-balancing operations until the difference falls below 10 percent.
Tip
load minimum—Specifies that cable modems should be moved only if the load between the two
interfaces is greater than the specified number of cable modems or service flows. This option is valid
only when you have configured the load-balance group using either the method modem or
method service-flows options with the
command. It is not used with the utilization method.
stability—Specifies the minimum percentage of ranging requests that are successful before the
Cisco CMTS determines that the interface or channel is unstable. When the channel has fewer than
this percentage of cable modems responding to periodic ranging requests over a one-minute period,
the Cisco CMTS begins moving modems to other channels in the load-balance group. For example,
when set to 75 percent, the Cisco CMTS begins moving modems when fewer than 75 percent of
modems are replying to ranging requests.
ugs—Specifies a threshold for when the Cisco CMTS should move cable modems that have active
UGS service flows, which are typically used for active voice calls. This option goes into force only
when dynamic load balancing has been enabled (using the enforce option), and the Cisco CMTS has
been allowed to move cable modems with active UGS service flows (using the
group policy ugs
service flows that should exist before the Cisco CMTS begins moving calls.
For example, if the band-value threshold is at its default of 70 percent, the Cisco CMTS does not
begin moving cable modems with active UGS service flows until UGS usage on an upstream or
downstream reaches 70 percent of the total available bandwidth. The Cisco CMTS continues
moving cable modems that are online with active UGS service flows until the UGS usage on the
interface falls below 70 percent.
Certain conditions can cause a system instability that could result in the Cisco CMTS endlessly
Note
attempting to load balance the interfaces. For example, this situation could occur in noisy environments,
where cable modems drop offline on a regular basis, or when cable modems are repeatedly trying to
OL-1581-08
In Cisco IOS Release 12.2(15)BC1, the dynamic load balancing method results in cable
modems going offline and having to reregister whenever the modems are moved between
downstreams. This is because the DOCSIS 1.0 specification requires cable modems to
reregister whenever the downstream is changed using the Downstream Frequency Override
message. Cable modems should not go offline when moved between upstreams.
The enforce threshold is not displayed in the configuration file if it is the same as the load
threshold. For example, if you enter the "cable load-balance group 1 threshold load 50
enforce 50" command, it appears as "cable load-balance group 1 threshold load 50 enforce"
in the configuration file.
command). The band-value threshold specifies the maximum usage of UGS
cable load-balance group (global configuration)
Cisco Broadband Cable Command Reference Guide
cable load-balance group threshold
cable load-balance
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